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Heavy Rain for New England, Heavy Snow for the Dakotas

Two developing storm systems will impact parts of the nation over the next several days, but that’s where the similarities end.

Two low pressure areas are developing off the East Coast this evening. The northern system is the stronger of the two, but the southern one is being monitored by the National Hurricane Center. It has the potential to develop into a tropical depression or subtropical storm over the next day or two. Whether it does or not, these two low pressure areas will eventually merge and become a rather strong non-tropical system later this week. There is very little in the way of steering currents right now, so the system will just meander around off the coast until Saturday.

As the system drifts northward, it will produce gusty winds along the coast, especially in New England. Tides are astronomically low at the moment, but will be rising later this week, so coastal flooding, while not a major concern, will still be possible in some locations. Rough seas will also be a large concern for marine interests. However, the biggest concern and also the biggest question mark right now is heavy rainfall.

Wind gusts in excess of 50 mph are possible across much of Southern New England. Image provided by WeatherBell.

While the storm will likely spread some heavy rainfall into New England, there is still plenty of uncertainty as to how far north the heavy rain gets, as well as how much rain actually falls. Some of the models are producing extremely heavy rainfall. While these are likely overdone, the fact that most of the models are showing this potential means that some very heavy rain is likely, especially south of Boston, where flood watches have been issued.

Rainfall forecast from the NAM model. The heaviest rain will likely fall across southeastern Massachusetts. Image provided by the College of DuPage.

Thanks to some dry weather over the past couple of months, flash flooding is not likely. However, a prolonged period of heavy rain may still produce flooding in some areas. Strong winds will also start to take some of the leaves off of trees, which may clog up storm drains, resulting in flooding in some areas.

Recent dryness means that flash flooding is not likely in New England with this storm. Image provided the the Northeast River Forecast Center.

While all this is taking place off the East Coast, some of the coldest air so far this fall will settle into the Rockies and Plains states as low pressure starts to develop across the Central Plains. This system will head north-northeastward while strengthening. The system isn’t expected to become that strong, but with a large high pressure area building in behind it, it will produce some strong winds. It will also draw warm and moist air northward from the Gulf of Mexico. As this air runs into the much colder air on the backside of the storm, the first significant snowstorm of the season is expected to develop across the Northern Plains.

Winter Storm Watches and warnings have been posted from parts of Idaho Montana, and Wyoming into parts of northern Nebraska and the Dakotas as well as northwestern Minnesota. across Idaho, Montana, and Wyoming, snowfall totals of 6-12 inches are possible, with some heavier amounts in the higher elevations. The biggest issues are expected across the Dakotas and northwestern Minnesota.

Wind gusts of 40-50 mph or more are expected across the Northern Plains. Image provided by WeatherBell.

The precipitation will start as rain across this area late Wednesday, but strong northerly winds will usher much colder weather in, changing the rain to snow from west to east on Thursday. Like its East Coast counterpart, this storm won’t move at a rapid pace, so snow, possibly heavy at times will continue across this area into early Saturday, with snow showers lingering into Sunday.

This storm also has some questions with it’s precipitation shield. While heavy snow is likely across a large area, how much falls and where the heaviest snow will fall is still a question. Right now, it looks like the heaviest snow will fall from central South Dakota into central and eastern North Dakota, but that still could change. As for amounts, many areas could see more than a foot, with totals in excess of 2 feet possible in many areas. The snow will be accompanied by winds gusting to 40-50 mph, resulting in blizzard conditions, especially late Thursday into Friday.

Snowfall totals of 1-2 feet or more are possible across the Dakotas. Image provided by Pivotal Weather.

While snow in October is not unusual across this region, snowfall amounts of this magnitude this early in the year are very rare. In Grand Forks, ND, the largest October snowstorm on record occurred October 24-26, 2001, and it dropped 10.9″ on the city. In Fargo, ND, the largest October snowstorm on record is only 8.1″ on October 30-31, 1951. For Pierre, SD, the October snowstorm of record occurred October 30-31, 1943, and it only produce 7.2″ of snow. Current model forecasts are forecasting amounts that are 3-4 times the records. These model forecasts are likely too high, but it seems likely that many of these October records are going to be obliterated in the next few days.

Hot in Texas, Humid in the East, Severe Weather in the Midwest

The “Dog Days of Summer” have arrived, with heat and humidity across a large part of the nation. Meanwhile, severe weather is possible across the Midwest on Friday.

A weather pattern that is both typical and atypical of summer at the same time is going to settle into the nation over the next several days. The typical part is that we’ll have a ridge of high pressure off the East Coast, and another one in the Southwest. The ridge off the East Coast will result in heat and humidity up and down the coastline for the next several days. The ridge in the Southwest will bring very hot conditions to the Southwest and especially the Southern Plains, where record highs are expected over the next several days. The Atypical part is across the Midwest. Normally, in between the two ridges of high pressure you’d have a trough of low pressure, but in this case, we actually have a closed upper-level low pressure system. While these are common in the fall, winter, and spring, they usually don’t occur much in the summer. This will bring cooler than normal conditions into the Midwest for the next few days.

The upper-level pattern features ridges of high pressure in the Southwest and off the East Coast, and an upper-level low pressure system in the Great Lakes. Image provided by Pivotal Weather.

While hot weather is expected across Texas and the Southwest during the summer, the ridge of high pressure that is currently setting up across the region will bring in temperatures that are well above normal. In fact, record highs are expected for the next several days across much of Texas, as temperatures soar past 100 across much of the state, with some locations possibly exceeding 110 degrees. The heat won’t be confined to the Lone Star State, with triple-digit highs also expected from parts of the Lower Mississippi Valley into the Southern Plains as well as parts of Colorado and New Mexico. There won’t be much, if any, relief at night either, as low temperatures will stay in the 70s, with many locations, especially urban areas like the Dallas-Fort Worth Metroplex likely not dropping below 80 degrees for low temperatures.

Friday looks to be the hottest day across the Southern Plains and Texas, with many record highs expected to be broken. Image provided by WeatherModels.com

As we head into next week, the heat will ease a bit across Texas and the Southern Plains, but the core of the intense heat will shift westward into the Desert Southwest. High temperatures will top 110 degrees across much of the area for the first half of next week, with the usual hot spots such as Lake Havasu City, Arizona; Laughlin, Nevada; and Death Valley, California likely exceed 120 degrees during some of the afternoons. Highs will also top 100 across much of interior California once again.

Moisture will stream northward from the tropics into much of the East Coast over the next several days. Loop provided by WeatherModels.com

While the Texas and the Southwest deal with extreme heat, the East Coast will get a little bit of relief from what has been a hot start to summer. While temperatures will still be a little above normal this weekend into much of next week, highs will only be in the 80s to lower 90s. While the temperatures won’t be that bad, humidity levels will. With high pressure anchored off the East Coast, a southerly flow will help moisture stream northward from the tropics right up the East Coast this weekend and into much of next week. Dewpoints will be in the upper 60s and 70s across the region, so even though temperatures may not be hot, it will feel oppressive across much of the region.

Heavy showers and thunderstorms are expected across much of the East Coast each afternoon over the next week. Image provided by College of DuPage.

With a warm and humid airmass in place for much of the week, it won’t take much for showers and thunderstorms to develop each day. With plenty of available moisture, some of these storms will end up producing very heavy rainfall. While the map above is a forecast that shows widespread coverage of heavy rain, in many cases, the storms will be very localized. Some locations could get hit by slow-moving thunderstorms over and over, while other spots a few miles away get little to no rainfall. Across the Mid-Atlantic States, where heavy rain led to flooding during the Spring, similar conditions are possible again for the next week. Across the Northeast, things are a little different.

Much of the Spring has been very dry across New England and New York, with drought conditions developing. Image provided by the National Drought Monitor.

Much of the Spring has been very dry across New England and New York. Localized thunderstorms have brought heavy rain to a few spots, especially earlier this week, but overall, rainfall has been well below normal across the area. Some relief will come this weekend. A weak low pressure system will move across the region late Saturday into Sunday as an upper-level low pressure system moves into the Midwest. The surface low will bring heavy rain and some gusty winds to parts of Southern New England and southeastern New York. The heaviest rain is expected late Saturday night into early Sunday morning, so neither day should be a washout. Once that system moves by, a warm and humid airmass will settle in, with a daily chance for showers and thunderstorms this week.

This pattern is expected to remain in place through at least next weekend and possibly even longer. While none of the models are showing development of any systems in the tropics right now, this is the type of pattern that is conducive to storms impacting the East Coast. The tropics have been fairly quiet so far this season, and a relatively quiet season is expected, especially compared to last year. However, should something develop in or near the Bahamas, it wouldn’t take much for it to impact the East Coast with relatively little lead time. In 1991, a tropical depression developed in the Bahamas on August 16, 48 hours later it was a Category 3 Hurricane named Bob brushing the Outer Banks of North Carolina before slamming into Southern New England as a Category 2 storm 12 hours after that.

A severe weather outbreak is possible on Friday across the Ohio and Tennessee Valleys. Image provided by the Storm Prediction Center.

While Texas bakes and the East Coast sweats, an upper-level low pressure area will settle into the Midwest. With the clash in airmasses along a cold front, showers and thunderstorms will develop. Some of these storms will become strong to severe on Friday, especially across the Ohio and Tennessee Valleys. The main threats with any storms that develop will be strong winds, large hail, and torrential rainfall that could trigger flash flooding. Some tornadoes are also possible. The storms may start during the morning closer to the Great Lakes, with the afternoon and evening seeing the most widespread activity across the region. While activity should weaken at night, the threat of severe weather will continue across southern and eastern parts of the region.

Strong to severe thunderstorms are expected across the Midwest on Friday. Loop provided by WeatherModels.com

Here Comes the Heat

As we get into the final days of June and prepare to flip the calendar to July, a heat wave is about to grip a large portion of the nation.

Heat and humidity are already in place across much of the nation’s mid-section. Excessive Heat Warnings and Heat Advisories are in effect across the eastern Plains and much of the Mississippi Valley on Friday. High temperatures will be in the 90s and lower 100s across the region. When you add in dewpoints in the 60s and 70s, heat indices will range from 100-115 degrees across much of the area during the afternoon.

Heat indices will exceed 100 degrees across much of the nation’s mid-section on Friday. Image provided by WeatherBell.

The heat will spread to the East Coast today, with very hot conditions expected for Sunday and Monday. High temperatures will soar well into the 90s across much of the East, with dewpoints slowly creeping up over the next few days. Right now, Sunday looks like the hottest day, with temperatures reaching the middle to upper 90s across the heavily-populated I-95 corridor. Relief will be found right along the coastline, where seabreezes may keep temperatures in the 80s.

Several record high temperatures could be broken across the Northeast on Sunday. Image provided by Weathermodels.com

Some changes start to happen towards late Monday and Tuesday. A cold front will start to approach the Northeast. This may produce a few showers and thunderstorms, especially across parts of New England, with some relief from the heat across Northern New England behind the front. There are questions as to how far south this front will get before it dissipates however. Odds are that it dissipates before reaching the New York City area, but if it washes out across central New England, then the heat will continue across southern New England right through the Fourth of July and possibly the end of the week. Across the Mid-Atlantic states, especially from New York City down to Washington, hot and humid conditions should continue for much of the week.

A ridge of high pressure will expand westward into the Plains and Rockies as we get towards the middle of the week. Image provided by Pivotal Weather.

The ridge of high pressure aloft responsible for the heat across the East will start to spread westward as we head towards the middle of the week. This will have several implications. In the East, it will allow the heat to begin to ease. With winds becoming more northwest aloft, disturbances will be able to drop down from Canada, bringing in some much needed shower and thunderstorm activity, along with some slightly cooler conditions. This will also allow the heat to spread back into the Mississippi Valley and the Plains states. High temperatures will be back into the 90s and lower 100s across the area as the ridge moves back into the area.

Will Summer be a Sizzler?

As meteorological summer knocks on the door and many hit the roads, beaches, and head to mountain hikes we wonder what summer will bring this year. Will rain ruin barbecues and camp-outs or will it be so hot that outdoor activities are dangerous.

Currently ENSO conditions are neutral and are forecast to remain so through the summer and fall. We would not expect much of a contribution from ENSO for the summer weather across the U.S.

Sea surface temperatures remain cooler than normal through the tropical Atlantic (which might contribute to a less active tropical season) but are above normal through the mid latitudes of the Atlantic. This could help promote more of a Bermuda high situation as summer rolls along.

The overall weather pattern during May has favored warmth across much of the nation and sometimes this can be a signal for what summer might offer.

May temperature Anomaly to date provided by Weathermodels.com

Further support for a warmer than average summer continues to come from model forecasts. The EPS long range model from Europe has been maintaining the idea of a dominant ridge across the south-central U.S. for some time and would favor hot weather for a good part of the western and central U.S. Anomalous soil moisture throughout the South and Southeast into the Tennessee Valley may dampen the heat through those areas, but increase humidity levels. The trough noted through the Northeast may allow for episodes of pleasant summer polar air for that region, at least through early summer.

EPS Forecast for Jul 12 2018 courtesy of Weathermodels.com

CFS forecasts from NCEP also provide support for a warmer than average summer across parts of the nation, mostly for the west. The combination of occasional troughing across eastern Canada and high soil moisture levels through the South and Southeast may keep the East from being sizzling hot but for the West and Southwest it appears that the heat threat is high for the summer.

NOAA’s summer outlook is looking for warmer than average temperatures across many parts of the nation. The north-central states are favored to be closer to normal based on cooler than average temperatures forecast for July and August. Elsewhere the heat is on according to NOAA.

Summer Temperature outlook provided by NOAA

Most signs point toward warmer than average temperatures across many parts of the nation this summer. Exceptions may be through the South and Southeast where excess rainfall and soil moisture prevent the atmosphere from heating to its’ potential. Early summer temperatures through the Northeast could also be impacted by cooler air from eastern Canada on occasion but as summer grows older we might see the Bermuda high begin to pump warmer air into the Northeast more persistently. The region that appears to be most prone to summer heat this year will be across the West and into Texas where excessive heat may occur off and on due to a more persistent sub-tropical ridge.

The West bakes while polar air invades the mid-South

Heat wave conditions are likely to build through the far West during the coming days while temperatures more in keeping with early fall settle into the mid-South region. This pattern will be brought about by a strong western ridge and a central U.S. trough. A strong ridge near the West Coast of the U.S. will allow heat to build northward into the Pacific Northwest and southwest Canada. At the same time an anomalously deep trough for mid summer will allow for summer polar air to drain southward from central Canada into the Plains and even the Deep South. The upper air jet stream flow forecast depicted for this coming Friday shows much more amplification than what is normal for this time of year.

500MB Forecast for Fri Aug. 4, 2017 Courtesy of Penn. State University

The accompanying 6-10 day forecast provided by the Climate Prediction Center takes on a look more in keeping for a season other than summer. A wide portion of the central and southern U.S. are forecast to see temperatures below normal if not well below normal. Normal high temperatures for many of these areas are in the low and mid 90s at this time of year but the refreshing push of polar air from southern Canada will keep temperatures in the 80s along with lower levels of humidity. In some cases temperatures may average as much as 10 to 15 degrees below normal for a few days during the first week of August through parts of the mid Mississippi and Tennessee Valleys. On the flip side, temperatures from California northward to Washington State are expected to average from 10-15 degrees above normal during this time with widespread coverage of triple digit high temperatures. This pattern will be prime for development of seasonal wildfires throughout the West some of which may be sparked by high based thunderstorms across the mountains.

6 to 10 day Temperature forecast courtesy of the Climate Prediction Center

As we have seen earlier in this warm season the weather pattern is probably going to undergo changes after a few days of western heat and eastern chill. The summer weather pattern has been mostly transitional across the nation to date with most areas not getting stuck in any one extreme for very long. The forecast on the left side of the chart below is valid for August 16, 2017 and shows a reversal in the weather pattern. The spaghetti plot on the right side shows that most members are in agreement that the western ridge will be replaced by a trough while the idea of a ridge across the southern Plains to the Southeast appears to be most plausible. Assuming this forecast is in the ballpark we can expect western heat to diminish by mid August while heat and humidity return to the central and southeastern U.S.

15-day mean 500MB forecast courtesy of Penn. State University

The Pacific is Not Living Up to It’s Name

The tropics remain quiet in the Atlantic right now, but it’s a different story in the Pacific, where there are currently six active systems, three in the East, and three in the West.

Starting with the Eastern Pacific, Hurricane Hilary is the strongest on the storms as well as the closest to land. At midday Monday, Hillary was centered about 340 miles south of Manzanillo, Mexico, moving towards the west-northwest at 8pm. This track is expected to continue for the next few days, bringing the system away from Mexico. Hilary has maximum sustained winds near 80 mph, but it is in an environment favorable for strengthening, and is expected to become a major hurricane over the next 24-36 hours. After that, a gradual weakening trend is expected.

Forecast track for Hurricane Hilary. Image provided by the National Hurricane Center.

A little farther to the west is Tropical Storm Irwin. Irwin was centered about 750 miles southwest of Cabo San Lucas, Mexico at midday Monday, drifting westward at 3 mph. Irwin has maximum sustained winds of 60 mph, and additional strengthening is expected. Irwin should become a hurricane Monday night or Tuesday. The forecast track for Irwin is highly uncertain at the moment. Several of the computer models show an erratic motion for the storm, as it may interact with Hurricane Hilary. Irwin will remain over open water for the next several days, and is not a threat to any land areas.

Model forecasts for the track of Tropical Storm Irwin. There is plenty of disagreement among the models on its eventual track. Image provided by Tropical Tidbits.

Heading westward again, we come to Tropical Storm Greg. Greg’s top winds peaked at 60 mph on Friday, and has been slowly weakening over the weekend. At midday Monday, Greg had top winds near 45 mph, and additional weakening is expected over the next few days. Greg was centered a little more than 1500 miles east of Hawaii, and was moving towards the west at 12 mph. Greg should dissipate well east of Hawaii later this week.

Forecast track for Tropical Storm Greg. Image provided by the National Hurricane Center.

In the Central Pacific, there are no active storms at the moment. However, what’s left of Hurricane Fernanda is moving across Hawaii today, producing some gusty winds along with locally heavy showers and thunderstorms on Oahu and Kauai. At one point last week, Fernanda was a Category 4 hurricane with top winds of 145 mph over the open waters of the Eastern Pacific.

Satellite photo showing 3 active systems and another potential tropical system in the Western Pacific. Image provided by the Joint Typhoon Warning Center. — Satellite photo showing three active systems and another potential tropical system in the Western Pacific. Image provided by the Joint Typhoon Warning Center.

In the Western Pacific, we also have three active systems, and another area being watched for development.

Forecast track for Typhoon Noru. Image provided by the Japan Meteorological Agency.

The strongest of the storms is Typhoon Noru (07W). Noru has been meandering around in the waters well southeast of Japan for several days, and this erratic motion should continue for another day or so before a general westward motion takes over. Noru currently has maximum sustained winds near 90 mph, and some further strengthening is possible over the next 36 hours. Noru will impact the Bonin Islands over the next few days with heavy rain and gusty winds.

Forecast track for Tropical Storm Kulap. Image provided by the Joint Typhoon Warning Center.

To the east of Noru is Tropical Storm Kulap (09W). Kulap is gradually weakening, and this should continue over the next few days. Kulap currently has top winds near 50 mph, but should weaken to a tropical depression by Tuesday. Kulap should continue moving off to the east, heading into the open waters of the Western Pacific.

Forecast track for Tropical Storm Sonca. Image provided by the Vietnam National Centre for Hydro-Meteorological Forecasting.

The storm that is the biggest threat to populated areas at the moment is Tropical Storm Sonca (08W). Sonca is currently centered about 160 miles east-northeast of Da Nang, Vietnam, moving towards the southwest at 4 mph. A turn more towards the west is expected over the next 24 hours, with landfall in Vietnam expected by early Tuesday. Sonca has maximum sustained winds near 45 mph, and some additional strengthening is possible before landfall. The biggest threat from Sonca is flooding from heavy rains. Sonca could produce rainfall totals of 10-20 inches or more in parts of Vietnam and Laos.

GFS Ensemble forecast for the track and strength of a tropical disturbance in the Western Pacific Ocean. Image provided by Tropical Tidbits.

In addition to all the active systems, an area of disturbed weather about 375 miles northwest of Palau in the Western Pacific Ocean is being monitored for development. Conditions should be favorable for the system to develop over the next few days, and it could become a tropical depression later this week as it moves northward. Current computer model forecasts show the possibility of additional strengthening later this week, with the potential for a threat to the Philippines or Taiwan towards the end of the week.

Summer Outlook Full of Mixed Signals

As spring turns into summer there are mixed signals as to what summer 2017 may bring to the U.S. with respect to temperature and precipitation. Summer for this post is defined as the months of June, July, and August (meteorological summer).

El Nino-Southern Oscillation (ENSO) during the spring season has been categorized as neutral, but forecasts for the summer are for a weak El Nino to begin to evolve. Typically during an El Nino we find temperatures near or a little cooler than normal along with somewhat wetter than normal conditions from the Plains to the East Coast during meteorological summer. To date we are still in neutral ENSO conditions. There is normally a lag time of 60 days or so for the sensible weather to catch up to the ENSO signature. We would not expect a major impact on the summer forecast from ENSO although there may be some contribution, especially since we are currently seeing a weather pattern reflective of El Nino. The chart below from the International Research Institute for Climate and Society (IRI) and the Climate Prediction Center (CPC) shows the most recent forecast for ENSO into next winter. The mean forecast (yellow line) remains under 1.0 which is the classification of El Nino but some models do forecast values over 1.0 later this summer and through the fall.

Sea surface temperature anomalies through the tropical Pacific west of South America are a little above normal but not in the classic looking El Nino signature just yet. The sea surface temperature anomalies have increased a bit during recent weeks along the Equator and indicate that the early stages of a weak El Nino could be taking place.

Sea Surface Temperature Anomaly courtesy of NOAA/NESDIS

Another indicator we can look at is the Madden-Julian Oscillation or the MJO. The MJO is best described as areas of concentrated thunderstorms through the global tropics that propagate eastward in a 30 to 60 day cycle. These areas of moving thunderstorms influence the weather in the mid latitudes. The MJO forecast through the middle of June implies that the mostly cool, wet pattern we’ve seen during May could continue for the eastern half of the U.S. for at least the next couple of weeks.

Lastly, despite the start of meteorological summer we continue to see signs of high latitude blocking in a fashion to favor episodes of cool, sometimes wet weather for the East. Wet weather may continue to produce flooding and severe weather from the Southern Plains through the Deep South through at least mid June.

We’ve outlined three indicators that could keep the eastern half of the nation a little cooler and wetter than normal for at least part of the summer. NOAA’s forecast for official summer, (June, July, August) shows a different scenario with warmth for the South and East while cooler and wet conditions cover the interior mountains of the West. It should be noted that some of the most recent modeled forecasts for June produced by NOAA at the end of May do depict cooler than average temperatures for a majority of the nation, including the East and South.

Summer Temperature forecast courtesy of NOAA

Summer Precipitation forecast courtesy of NOAA

Sea surface temperatures across the western Atlantic and more so through the tropical Atlantic are milder than average as we approach summer’s start. This type of pattern could help elevate temperatures across the eastern and southern U.S. once high latitude blocking and the effects from MJO diminish later in June. It’s possible that the NOAA forecast could have validity to it if one is patient and allows the leftover spring pattern to weaken and fade. Could this be a summer like 1988 which started slow but ended with widespread heat? The South and Plains may be slower to warm with excess soil moisture levels in place but that could add humidity to the equation making for more uncomfortable conditions. There are certainly differing signals for the summer outlook at this time but most of the signs for cooler readings are short term. Once we reach late June and beyond the warmer scenario of NOAA is plausible if El Nino is slow to start and remains weak.

Winter, Spring, and Summer – All at the Same Time

The current weather pattern across the country is one that is fairly typical of Spring. However, the results of that pattern are wintry weather in the Rockies and summer-like weather in the East. In the battlezone between the two there is plenty of severe weather, which is fairly typical of Spring.

500mb analysis map from 8am EDT May 17, shows a ridge of hgh pressure in the East and a trough of low pressure in the West. Image provided by College of DuPage.

An upper-level low pressure area will move out of the Pacific Northwest and into the nation’s midsection over the next few days. While one surface low pressure area moves into the Upper Midwest today, a second one will develop east of the Rockies and move into the Plains states on Thursday. With cold air moving in behind the system, and warm, moist air flowing northward from the Gulf of Mexico ahead of it, strong to severe thunderstorms are likely again today, Thursday, and Friday across the Plains states.

Severe weather has plagued the nation’s midsection for the past few days, with over 500 reports of severe weather between Monday and Tuesday. Nearly 30 tornadoes were reported, along with hail as large as softballs, and hundreds of reports of wind damage from gusts as high as 85 mph.

GFS model snowfall forecast through Saturday morning for the Rockies. Image provided by WeatherBell.

Behind the low pressure area, a late-season snowstorm is expected across the Rocky Mountains. Heavy snow will continue across portions of Montana and Idaho today, spreading into Wyoming and Colorado for Thursday into Friday. Across the higher elevations, totals of 1-3 feet are expected, which will keep the ski season going for a while longer. Snow may also spread into the High Plains of eastern Colorado and western Nebraska, with some minor accumulations possible. In Denver, it looks a couple of slushy inches may fall, though at least 1 model is forecasting much heavier amounts. In a normal year, Denver averages 1.7″ of snow, and the city has seen measurable snow during the month of May in 11 out of the last 16 years, so snow in May is not uncommon, though a heavy snowstorm, if it materializes, would be. Denver has only received 10 or more inches of snow in the month of May 6 times in a 135 years of records, with a record total of 15.5″ set back in May of 1898.

Record high temperatures are expected to be broken across the Northeast on Thursday. Image provided by WeatherBell.

Meanwhile, in the East, an early taste of summer is ongoing, thanks to a ridge of high pressure aloft, and a surface high pressure area off the East Coast. Temperatures soared into the 80s and lower 90s on Wednesday, setting several records, but the hottest day for many locations will be Thursday. High temperatures will climb into the lower to middle 90s in many locations, likely breaking records across much of the region. When you combine the heat with dewpoints well into the 60s, it will definitely feel like a mid-summer afternoon across the region. A cold front will move through the area of Friday, possibly triggering a few showers and thunderstorms, but also sending temperatures back to where they should be in the middle of May.

Heavy Rain Heading for the Northeast

It’s been a very wet spring across much of the Northeast, and it’s going to get a lot wetter over the next few days.

The last 2 months have seen well above normal rainfall across the Northeast. Image provided by Northeast Regional Climate Center.

After experiencing drought conditions for much of the past year, a much wetter pattern has settled in across the Northeast this Spring. Much of the region has received 6-12 inches of rain since the middle of March, which is up to twice the normal amount. As a result, flooding has been observed, especially north of the border into portions of Ontario and Quebec. Persistent heavy rains across these provinces has flooded hundreds of communities in the past few weeks.

Instead of relief, it looks like conditions will worsen this weekend. Low pressure will move into the Carolinas on Friday, then off the East Coast on Saturday, slowly moving northeastward over the weekend. Rain and thunderstorms will move across the Mid-Atlantic states on Friday, spreading northeastward during the day. The rain should reach the New York City area around daybreak Saturday, moving into Southern New England during the afternoon. As the system slows down south of Long Island, heavy rain is likely across portions of the Northeast Saturday night into Sunday. Although the rain will taper off Sunday afternoon, it may not completely end until sometime on Monday as the storm takes it time to depart the region.

GFS model rainfall forecast through Monday evening. Image provided by Pivotal Weather.

While heavy rain and flooding are the main threats with this system, they are not the only threats. As the system intensifies over the North Atlantic, gusty winds are expected, especially along the coastline of New England and Long Island. Sustained winds of 20-30 mph with gusts to 50 mph are likely. These winds will help churn up some rough seas, which may lead to some coastal flooding on Sunday, especially along east-facing shorelines in New England.

An upper-level low pressure area has remained in place across the Northeast for the past several days. Image provided by Pivotal Weather.

Much of the last week to 10 days has been characterized by cool and damp conditions across the Northeast, thanks to an upper-level low pressure area that has been anchored in placed. That pattern is finally changing, and the result will be welcome news across the region. A ridge of high pressure will build in for much of the upcoming week, which means the clouds and below normal temperatures will be replaced by sunshine and near to above normal temperatures.

A ridge of high pressure will settle in across the East this week, bringing sunshine and warmer temperatures in. Image provided by Pivotal Weather.

High temperatures across the Northeast have only been in the 50s and 60s for the past several days across much of the region, which is 5 to 10 degrees below normal. By mid-week, temperatures should reach the 70s and 80s across much of the region, which will be 5 to 10 degrees (or more) above normal.

Severe Weather in the South Today, Bigger Outbreak Friday?

Severe weather is likely across portions of the Gulf Coast and Mississippi Valley today, but another, perhaps more widespread, outbreak is possible at the end of the week.

Surface analysis as of 7am CDT Wednesday April 26. Image provided by NOAA.

A strong cold front is moving into the Mississippi Valley and Texas this afternoon, and it is helping to trigger strong to severe thunderstorms across portions of the region. Ahead of the front, temperatures are into the 70s and lower 80s, with dewpoints in the upper 60s and 70s, so there’s plenty of warm, moist air in place. Behind the front, temperatures quickly drop into the 50s and 60s. Thunderstorms will continue to develop in the unstable airmass ahead of the front, with some of the storms containing large hail, heavy downpours, damaging winds, and possibly some tornadoes. Earlier this morning, some storms produced baseball-sized hail and wind gusts in excess of 70 mph in portions of Missouri, Arkansas, and Oklahoma. The threat should start to diminish across the region as we head into the overnight hours.

A more significant severe weather outbreak is possible later Friday into Saturday from the Southern Plains and Texas into portions of the Mississippi and Tennessee Valleys. Low pressure will move out of Texas and head northward, drawing warm moist air northward from the Gulf of Mexico once again. North and west of the system, much cooler air will be in place (more on that in a moment).

Models are showing that a very unstable airmass will be in place across Texas and the Lower Mississippi Valley Friday afternoon. Image provided by Pivotal Weather.

As low pressure rides along the boundary between the two airmasses, it will help to trigger strong to severe thunderstorms across the region. The threat will continue into the overnight hours Friday night, shifting into the Mississippi and Tennessee Valleys on Saturday as the system continues to progress northeastward. Some of the storms may produce torrential downpours that could trigger flash flooding, large hail, damaging winds, and tornadoes.

Portions of the Mississippi Valley could received 5-10 inches of rain between Wednesday and Sunday. Image provided by WeatherBell.

Behind the storm, as colder air settles into the region, a different threat is evolving – heavy snow. While it’s getting late in the season, heavy snow is not uncommon in the Central and Southern Rockies at this time of year. Some of the higher elevations in Colorado and New Mexico could receive 1-2 feet of snow Friday into Saturday. East of the Continental Divide, especially in the High Plains, snow is also possible, especially from eastern Colorado and western Kansas into portions of the Oklahoma and Texas Panhandles. In Denver, there is still a big question as to whether to precipitation falls mainly as rain, snow, or a wintry mix. Some snow accumulation seems likely at this point, but it’s still a little too early to tell whether there will be heavy snow in the city itself.

GFS models forecast for snowfall through Sunday morning across the Plains and the Rockies. Image provided by WeatherBell. — GFS model forecast for snowfall through Sunday morning across the Plains and the Rockies. Image provided by WeatherBell.

Severe weather outbreaks are not uncommon at this time of year. In fact, from late March into early May is when they are most likely. The largest tornado outbreak on record occurred 6 years ago this week. Between April 25 and 28, 2011, a total of 362 tornadoes were observed from Texas to New York and portions of southern Canada, resulting in 324 fatalities, 317 of them on April 27, the most active day.

Map showing tracks of all 362 tornadoes from the April 2011 "Super Outbreak". Image provided by Encyclopedia Brittanica. — Map showing tracks of all 362 tornadoes from the April 2011 “Super Outbreak”. Image provided by Encyclopedia Brittanica.