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Severe Weather In the Northeast on Saturday?

For the second weekend in a row, there is a threat for severe weather across parts of the Northeast. Unlike last weekend, when the threat was centered on areas from the Delmarva Peninsula southward to the Carolinas, the threat on Saturday is focused on the Northeast.

Strong to severe thunderstorms moved across the Midwest Friday evening. Loop provided by College of DuPage NexLab.

Low pressure is moving across Lake Superior this evening, with a warm front extending east and southeast from the system across the eastern Great Lakes and into Virginia. A cold front trails the system into the Dakotas and Wyoming. South of these two fronts a very warm and humid airmass is in place, with temperatures well into the 80s and 90s on Friday. Dewpoints were in the 60s to lower 70s across much of the region as well. As the cold front moved into the Upper Midwest, it helped ignite a line of strong to severe thunderstorms. These storms produce golfball-sized hail and wind gusts as high as 76 mph as they cross Minnesota and Wisconsin Friday afternoon and evening.

Usually, strong to severe thunderstorms diminish during the evening hours as they lose the heating of the sun. However, with the warm and humid air in place across the Midwest, these storms will likely continue to march eastward overnight ahead of the cold front.

Radar loop predicted by the NAM model from Friday night into Sunday night. Loop provided by College of DuPage NexLab

Forecast models indicate that this line of thunderstorms will move across portions of New York and Pennsylvania Saturday morning and afternoon before moving into portions of New England. How far north and east the warm front moves will help determine where the best chance for severe weather will be located.

High temperature forecast for Saturday afternoon based on the WRF model. Image provided by WeatherBell. — High temperature forecast for Saturday afternoon based on the NAM model. Image provided by WeatherBell.

Dewpoint forecast for Saturday afternoon based on the WRF model. Image provided by WeatherBell. — Dewpoint forecast for Saturday afternoon based on the NAM model. Image provided by WeatherBell.

Right now, it looks like the warm front will only make it into New York and southwestern New England before the cluster of showers and thunderstorms arrives. Some of the stronger storms could produce downpours, strong winds, and hail across portions of New York, Pennsylvania, and New Jersey.

Across New England, the threat for the afternoon seems less, with more typical showers and thunderstorms expected. However, this does not mean that the threat is zero. If the warm front were to make progress farther northward, the threat would increase. The bigger threat in this region could come at night. The warm front should eventually push through during the evening, allowing the warm and humid air to move into Southern New England. As the cold front continues it eastward march, another round of showers and thunderstorms will likely develop along and ahead of it. As these storms move across New England overnight, some of those storms could produce heavy downpours and strong winds.

Forecast for 500mb heights and winds based on the WRF model. Image provided by Pivotal Weather. — Forecast for 500mb heights and winds based on the NAM model. Image provided by Pivotal Weather.

After the cold front moves through Saturday night, skies should become partly to mostly sunny across the Northeast on Sunday with near-to-below normal temperatures expected. An upper-level low will slowly move across the Gulf of Maine early next week, keep temperatures near or below seasonal normals while heat and humidity dominate the remainder of the eastern two-thirds of the nation.

The Heat is On Across the Plains

A large ridge of high pressure will shift from the West coast into the Nation’s midsection over the next few days, bringing with it some of the hottest weather so far this year to the Plains states.

Temperature anomalies for the past 30 days across the nation. Image provided by WeatherBell.

A persistent ridge of high pressure has been anchored across the West for the past few weeks, keeping temperatures well above normal for much of May and early June. Numerous records were set across the region, even in normally hot locations like the Desert Southwest, where temperatures exceeded 110 degrees several times. In Death Valley, California, which is frequently the nation’s hotspot, the first 8 days of June have averaged 10.6 degrees above normal, with high temperatures exceeding 115 degrees each day.

While the West has been baking, temperatures across the Plains states have been 1 to 3 degrees below normal for the past month. That is about to change as the ridge slides eastward. By the end of the week and the weekend, the ridge will be centered across the Plains and doesn’t look to move that much right through next week.

Map showing heights at the 500mb level across the United states on Friday June 8. Image provided by Pivotal Weather. — Map showing heights at the 500mb level across the United states on Sunday June 12. Image provided by Pivotal Weather.

Map showing heights at the 500mb level across the United states on Friday June 15. Image provided by Pivotal Weather. — Map showing heights at the 500mb level across the United states on Friday June 17. Image provided by Pivotal Weather.

With the ridge of high pressure in place, temperatures will soar well into the 90s across the Plains states and adjacent portions of the Mississippi Valley for much of the remainder of the week, with some triple-digit heat possible across parts of the Dakotas, especially Friday and Saturday.

High temperature forecast based off of the GFS model for Friday June 10. Image provided by WeatherBell — High temperature forecast based off of the GFS model for Saturday June 11. Image provided by WeatherBell

Some relief will settle into the Northern Plains in the form of a cold front early next week, but the heat will continue from the Southern Plains and Texas eastward into the Southeast. Across these areas, humidity levels will be higher, with dewpoints rising into the 60s and 70s. The result will be heat index values well over 100 degrees across parts of these areas.

The ridge will also act to suppress thunderstorm activity across the Plains states for much of the remainder of the week. Cluster of thunderstorms may develop across the Northern Rockies and ride over the Ridge and into the Great Lakes and eventually the Northeast later in the week. One of these clusters could produce some severe weather across the Eastern Great Lakes and Mid-Atlantic states on Saturday.

Severe Outbreak Possible in the East, Tropical Trouble in the Gulf?

The weather will become quite active across both the East and the Gulf later this weekend and into early next week.

A strong cold front will slowly make its way eastward this weekend, likely reaching the East Coast Sunday night. Ahead of the front, with a warm, humid airmass in place, showers and thunderstorms will develop, some of which will become strong to severe. Widespread severe weather isn’t expected on Saturday, but there is a risk for some strong to severe storms from the Great Lakes into the Ohio Valley. Sunday will be a different story. The ingredients will be in place for a severe weather outbreak from the Mid-Atlantic states into the Carolinas.

GFS forecast of Lifted Index values for Sunday afternoon. Image provided by Pivotal Weather

GFS forecast of CAPE values for Sunday afternoon. Image provided by Pivotal Weather

As temperatures rise into the 80s to lower 90s, the airmass will become increasingly unstable. CAPE, which is short for Convective Available Potential Energy, is a measure of instability through the atmosphere. CAPE values of 1000-3000 J/kg are expected from the Delmarva Peninsula into the Carolinas Sunday afternoon. These values are indicative of moderate instability in the atmosphere. The “Lifted Index” is the difference in temperature between the atmosphere at 500mb (about 18,000 feet) and a parcel of air from the surface that is lifted to 500mb. A negative value is indicative of unstable conditions. On Sunday, forecast models are showing values between -4 and -9 across the Mid-Atlantic states.

While Sunday may start off cloudy with showers across parts of the region, breaks of sunshine should develop by early afternoon, with showers and thunderstorms developing along the eastern slopes of the Appalachians. Thunderstorm activity will likely organize into a line that will march eastward, reaching the Washington/Baltimore area by late afternoon, and the Richmond/Norfolk area towards evening. The main threats with any storms that do develop are strong winds, hail, and heavy downpours, with a few tornadoes also possible.

Meanwhile, Tropical Storm Bonnie has redeveloped east of North Carolina this evening. As of 5pm Friday, Bonnie was centered about 285 miles east of Cape Hatteras, NC, moving towards the east at 13 mph. Maximum sustained winds are near 40 mph. Bonnie is expected to head out into the open waters of the Atlantic over the weekend while steadily weakening.

Satellite loop of Tropical Storm Bonnie from Friday afternoon. Loop provided by NOAA.

While June is usually quiet in the tropics, another area of disturbed weather in the western Caribbean is being monitored for development this weekend. A cluster of showers and thunderstorms will head towards the Yucatan Peninsula this weekend and then turn more towards the north and head into the Gulf of Mexico. For several days now, forecast models have been indicating that this system could become a tropical depression or tropical storm over the Gulf early next week.

Computer model forecasts for the strength of a potential tropical system in the Gulf of Mexico. Image provided by Tropical Tidbits

Computer model forecasts for the track of a potential tropical system in the Gulf of Mexico. Image provided by Tropical Tidbits

Most forecasts are for the storm to turn more toward the northeast early next week and cross the Florida Peninsula as a tropical depression or weak tropical storm. While winds aren’t expected to be strong, the main impact will be heavy rainfall. The storm could drop as much as 4-8 inches of rain on the Sunshine State next week, especially the southern half of the state. Heavy rain fell on portions of the region during May, so additional heavy rain could lead to flooding in parts of the area.

Severe Weather Outbreak Across the Southern Plains on Tuesday

While the attention has been on heavy rain and flooding across portions of southern and eastern Texas recently, areas to the north of there will be in the spotlight early next week.

Severe Weather Outlook for Tuesday from the Storm Prediction Center

All of the ingredients appear to be coming together for a severe weather outbreak from Kansas into northern Texas on Tuesday. Low pressure, both at the surface and aloft will move out of the Rockies and across the Central Plains on Tuesday. Ahead of the storm, warm, moist air will flow northward from the Gulf of Mexico into Texas and the Southern Plains. A cold front trailing the system will provide the lift needed to initiate thunderstorm development during the afternoon hours across the region.

Forecasted CAPE (Convectice Available Potential Energy) for Tuesday evening. Image courtest of WeatherBell. — Expected CAPE (Convective Available Potential Energy) for Tuesday evening. Image courtesy of WeatherBell.

As the storms move into south-central Kansas, central Oklahoma, and north-central Texas, they will encounter a very unstable airmass. The above map shows the forecast of Convective Available Potential Energy (CAPE) across the Southern Plains for Tuesday evening. CAPE is a measure of instability through the depth of the atmosphere, and is related to updraft strength in thunderstorms and is measured in Joules of energy per kilogram of air. A CAPE value of 1000 or less is considered “weak” instability, a value of 1000-2500 is “moderate” instability, a value of 2500-4000 is “strong” instability, and over 4000 is “extreme” instability. Areas shaded in purple on the map have values over 4000 Joules/kg, with some of the lighter purple shading in excess of 4500 Joules/kg. With this much instability in place, it won’t take much for storms to quickly become severe, with strong winds, large hail, torrential downpours, and tornadoes all possible.

Late April and early May are a time when severe outbreaks can be common across the Central and Southern Plains. If this outbreak does pan out, it will fall on the 25th anniversary of another outbreak across parts of the same area. On April 26, 1991, a total of 54 tornadoes were observed from Iowa and eastern Nebraska into portions of Missouri, Kansas, Oklahoma, and northeastern Texas, resulting in 21 deaths.

Plot of all 55 tornadoes that were reported on April 26, 1991 across the Central and Southern Plains. Image courtesy of the Storm Prediction Center — Plot of all 54 tornadoes that were reported on April 26, 1991 across the Central and Southern Plains. Image courtesy of the Storm Prediction Center

There was one F5 tornado reported that day – the one that moved across portions of Wichita, Kansas, including McConnell Air Force Base, before devastating the town of Andover, Kansas.

Residents of this region should pay attention to the forecast over the next few days and keep an eye to the sky if they have outdoor plans for Tuesday.

Flooding Possible in the Southern Plains

Heavy rain will move across the Southern and Central Plains through Monday night as a result of an upper level low pressure system west of the region. What is a dry line and pre frontal trough of instability Saturday into the overnight hours will turn into a cold front early Sunday. This will provide a center for showers and thunderstorms with the threat of heavy rain as warm/moist flow comes in from the south. Parameters for this event indicate heavy rain with precipitable waters (a measure of the amount of moisture in a column of the atmosphere that could fall as rain) above normal by 2 to 3 standard deviations and low level jet stream winds reaching 1 to 2 standard deviations above normal from the south indicating strong inflow of warm/moist air. This is also collocated with a strong area of large scale ascent indicated by upper level divergence of winds that also translate east through the time period.

Departures from normal of Precipitable Water forecast by the NAEFS ensemble system for Sunday morning.

2 week departure from normal of precipitation over the Southern and Central Plains. Notice the higher amounts in Texas and Oklahoma.

Placement of midlevel theta-e (a measure of warmth and moisture) and midlevel vertical velocity indicate the placement of heavy rain will move from a line between western Nebraska to western Texas later Saturday to a line between eastern Nebraska and eastern Texas by daybreak Monday along the aforementioned eventual cold front. Many times, overnight convection and thunderstorms die off as instability fades, but a self-sustaining area of heavy rainfall (called a mesoscale convective system, MCS) results. A similar process looks to form an MCS at the southern end of the cold front in southwestern/south-central Texas. This will move east slowly toward southeastern Texas by daybreak Tuesday.

Moderate to Severe drought conditions have formed in portions of the Central and Southern Plains.

Forecast precipitation over the Plains region. Notice the 4 to 8+ inches of rainfall forecast.

Flooding is very likely with this event especially in Oklahoma and Kansas where areas of Moderate to Severe drought conditions have developed. Remember that after a long dry spell and drought conditions, drier ground is harder to penetrate with water and so it remains standing on the surface allowing for flooding quickly. In addition, above normal rainfall has fallen over the past 2 weeks especially around Abilene and San Angelo, Texas and into Southwestern Oklahoma, which would allow for already swollen bodies of water to overflow quickly. In addition to the influence of the current ground conditions, the shear amount of moisture that is forecast to fall further exacerbates the flooding situation. 4 to 8 inches of rainfall is forecast to fall over portions of the Southern and Central Plains through Tuesday morning with the potential for higher amounts in thunderstorms. As a result, the National Weather Service has issued flash flood watches on a line from southwestern Nebraska to southwestern Texas ahead of the convection and heavy rain. This is very likely to translate east along with and ahead of the line of convection that is forecast to form.

Severe Weather Possible in the Plains This Week

The Storm Prediction Center has highlighted the Southern Plains with the potential for severe weather on Monday and Tuesday with Monday’s main hazard being marginally severe hail and Tuesday containing all of the main hazards including wind, hail and tornadoes.

Storm Prediction Center forecast of severe weather risk for Monday (left) and Tuesday (right). Hazards for Monday: marginally severe hail. Hazards for Tuesday: all hazard types including tornadoes are possible.

CIPS analogs based on the NAM (left) for Monday and GFS (right) for Tuesday. Notice that the analogs for Monday are contoured for 5 reports in an area and analogs for Tuesday are contoured for 1 report in an area.

This is a result of a strong low level jet flowing in from the Gulf of Mexico bringing in plenty of warm and moist air. Air with a dew point of 60F or greater moves into eastern Texas toward the end of the day Monday and dew points into the upper 50s exist in parts of the Central Plains. Plenty of turning in the wind, shear, exists in the atmosphere along with plenty of upward motion, CAPE. An area of very dry air exists in the mid levels of the atmosphere, which will act to inhibit weaker storm growth, but in areas where the upward motion is strong, the storms may have the chance to create hail, especially in any supercells that form. Analogs based on the Saturday night run of the short range forecast model, the NAM, have an area from the Panhandle of Texas into central Kansas where at least 5 previous severe weather reports occurred, which is close, but not the same as the SPC forecast severe weather risk, which has its severe area from southern Texas into south-central Kansas. Short range model simulations from the NAM as well as the NCAR ensemble forecast show convection firing in central Texas and eastern Oklahoma and moving into eastern Oklahoma and eastern Kansas as the day turns to night.

Height anomalies showing the general high and low pressure placements. Low anomalies (blue) indicate low pressure. — Height anomalies showing the general high and low pressure placements. Low anomalies (blue) indicate low pressure and vice versa. Via PivotalWeather.

For Tuesday, the strong energy that helped to force along the heavy flooding rain along the West Coast will move south into Mexico. This energy will help to drive more moisture and warm air into Southern Plains on Tuesday. Dew points will be into the 60s in eastern Texas and plenty of CAPE and shear will exist in that region. Plenty more energy around the region will help to spark more storms. With the copious amounts of CAPE and shear, all types of severe hazards will be in play including tornadoes. Towards the end of the day, when the sun’s heating turns off, storms tend to form into a convective line with strong winds or into a large complex with heavy rain and thunderstorms, called an MCS. The Storm Prediction Center hints that an MCS may form towards the end of the day in southern and Eastern Texas. Analogs based on the Saturday night run of the long range forecast, the GFS, have an area from central into northeast Texas where at least 1 previous severe weather report occurred. This is a smaller area of than the Monday setup, perhaps indicating a lesser event or because of the general bias of the shorter range NAM model to having more moisture to enhance storms. The SPC has a slight risk, which is the same severe risk category given for Monday covering eastern Texas and portions of the States bordering Texas. The SPC risk includes the analog risk area. Shorter range model projections have convection in Oklahoma and Missouri.

The severe weather risk continues into the middle and possibly the end of the work week in Southern United States.

Strong Storm to Impact the Midwest and Southeast Early Next Week

Two pieces of energy will be phasing or combining this weekend off the West Coast. This will allow for a low pressure system to develop and intensify as the energy digs across southwestern United States. The storm is developing early enough that the storm should take a general northeast track after the storm ejects off the Rocky Mountains.

The two pieces of energy offshore before phasing over the weekend.

After the pieces of energy have phased and storm begins intensifying and turning northeast. — After the pieces of energy have phased and storm begins intensifying and turning northeast early Monday.

It will have all of the precipitation types that winter normally features with snow north of the low pressure system’s track as well as a mixed bag of snow/sleet/freezing rain near the warm front as the warm and moist air runs into the cold air aloft. This cold air begins settling south from Canada early Tuesday, which is when the snow should fall north of the track. It’s way too early to looking at snowfall accumulation maps so outlooks are best at this point for the system. Strong winds are often associated with developing low pressure systems. This system is no different with forecast analogs based on the GFS forecast (America long range forecast model) showing a possibility of blizzard conditions over Iowa. Remember, blizzard conditions are more about wind and visibility than snowfall so that even just light blowing snow could still be designation as a blizzard as long as visibility is reduced.

Appreciable snowfall/sleet highlighted on day 4. Via the Weather Prediction Center.

In addition to the wintry precipitation types, this system will also produce some severe weather. Severe weather is forecast to begin occurring Monday Night across the Southern Plains and continue moving eastward as the cold front and warm sector (area where warm air resides) move east. The limiting factor in this case will be the instability, but there may be enough shear (turning of the wind with height or change in speed with height) to overcome any shortcomings that instability might have. With that in mind, a look at forecast analogs based on the GFS show the potential for severe weather to occur Tuesday in the Lower Mississippi Valley. The winds are strong aloft so wind damage and a few tornadoes are possible from this event as well as some hail. Flash flooding may also be possible under any thunderstorm.

Snapshot of the cold air(north and west of the low) and warm sector (south and east of the low). Notice the stronger winds (barbs with triangles indicating 50+ knot winds) in the area within the packed contours. — Snapshot of the cold air(north and west of the low) and warm sector (south and east of the low). Notice the stronger winds (barbs with triangles indicating 50+ knot winds) in the area within the packed contours just southeast of the pressure system indicating stronger shear. This is at a level where air is at a pressure of 700mb. Via the College of DuPage.

Analog guidance based on the GFS models highlighting severe weather in the Lower Mississippi Valley for Tuesday. — Analog guidance based on the GFS models highlighting the placement of severe weather in the Lower Mississippi Valley for Tuesday. Via the Cooperative Institute for Precipitation Systems.

Tuesday's probability of severe weather over the Lower Mississippi Valley. This seems to correlate well with the CIPS analog guidance's placement of severe weather. Via the Storm Prediction Center. — Tuesday’s probability of severe weather over the Lower Mississippi Valley. This seems to correlate well with the CIPS analog guidance’s placement of severe weather. Via the Storm Prediction Center.

Snow, Rain and Severe Weather in the Central US, Record Warmth in the East

A low pressure system that formed on Saturday and will intensify into Monday as it moves from the Southern Plains into the Great Lakes and eventually into the Northeast by Monday night. Saturday night will see showers and thunderstorms in the Southern Plains ahead of, and especially along, a cold front extending southward from the system. That cold front will move from the Southern Plains and into the Tennessee River Valley and parts of the Southeast with strong winds and possibly a tornado being the main threats, along with flooding rainfall. As much as 2 to 5 inches of rainfall is forecast to fall by Monday morning in Northeast Texas and Eastern Oklahoma. The main limiting factor for the thunderstorms in the Southern Plains will be instability, especially with the morning cloud cover expected to remain around the region through the day. For the most part, this storm is expected to be mostly rainfall, but the outermost edges to the north and west of the storm may have a chance to change to snow, from Northern New Mexico and southeastern Colorado northeastward into Northern Minnesota. Some of the higher elevations in Colorado could see a foot or more of snow while the lower elevations could see 2 to 6 inches, especially in southern Colorado and northeastern New Mexico.

48 hour rainfall forecast. Note the higher amounts in northeast, Texas and western Oklahoma.Via WPC. — 48 hour rainfall forecast. Note the higher amounts in northeast, Texas and western Oklahoma. Map provided by the National Weather Service’s Weather Prediction Center

Snowfall forecast. note the higher amounts in Colorado and New Mexico. Via WPC. — Snowfall forecast. note the higher amounts in Colorado and New Mexico. Map provided by the National Weather Service’s Weather Prediction Center.

As the low pressure system intensifies, it will have quite a pull of warm and moist air from the south into the eastern half of the United States. This could result in dozens of record high temperatures and record high minimum temperatures being set across the region. In many places, the forecasts would exceed the current records by 5 to 10 degrees or more.

Record high minimum temperatures on Saturday night denoted by white circles. Map provided by WeatherBell.

Record high temperatures circled in white especially over the eastern half of the US. — Record high temperatures expected for Sunday circled in white, especially over the eastern half of the US. Map provided by WeatherBell.

Record high minimum temperatures on Sunday night denoted by white circles. Map provided by WeatherBell.

This pattern is almost the complete opposite of what we had at this time last year when anomalously warm temperatures were draped across most of western and central United States with below normal temperatures residing over most of Eastern United States.

Another Round of Severe Weather for the Nation’s Midsection

In a similar setup to last week, a cold front dropping south from the Pacific Northwest to the Southwestern United States signifies the upper level jet from the polar regions dropping south. At the same time, another upper level jet resides in the subtropics. These two will combine or phase and create enough energy to develop a low pressure system just east of the Rockies. As the storm gets going it will be able to wrap in cooler air especially on its western side and snow will be able to develop in the Southern Rockies. A general 1 to 4 inches are possible from Nevada to Western Nebraska and Kansas with higher amounts possible in the higher elevations. Wind gusts should be around 45 mph, but could be as high as 65 mph along in the higher terrain.

Snowfall forecast through early Wednesday. (Note this isn't quite the mean, but it is the 50th percentile). Via WPC. — Snowfall forecast through early Wednesday. (Note this isn’t quite the mean, but there are equal chances that the final outcome is larger or smaller than this total.) Via WPC.

Meanwhile, on the eastern side of the low pressure system, warm and moist flow will be able to create enough instability and very strong wind energy and low level moisture should be available for thunderstorm development. On Monday, the area with the greatest threat is within the Southern Plains. The day’s storm mode will probably include supercells, but should eventually evolve into a squall line type as the night overtakes the day. Tornadoes along with strong winds will be very possible with a few areas of hail with the day’s storms and very strong winds and heavy rain will be possible with the nighttime squall line as the earlier discussed phased jets allow for strong winds that can get brought to the surface in the intense vertical motion within rainfall and thunderstorms. For Tuesday, the area with the strongest storms shifts east as the low pressure system moves northeast and its attendant cold front slowly moves east. The cold front will be the main driver of the thunderstorms for this time period and while the squall line will be the main story for Tuesday, some supercells ahead of the cold front can’t be ruled out.

Severe weather outlook for Monday via SPC.

Monday helicity (top) and shear (bottom) forecast. 200 m2/s2 of helicity is enough for tornadoes. 30 kts of shear is enough for tornadoes.

Monday shear (top) and helicity (bottom) forecast. 200 m2/s2 of helicity is enough for tornadoes. 30 kts of shear is enough for tornadoes.

In addition to the severe weather and snow, rain is also possible near the low pressure system and both the warm front and cold front during this time period, especially in any thunderstorms. Because of the way the combined jet stream is situated and the added energy of the phased jet streams, the heavy rain will be situated in the lower Plains and lower Mississippi Valley regions. Over 5 inches is forecasted especially in the lower Mississippi Valley region, but that rainfall total could be higher in any thunderstorm. Furthermore, previous consistent rainfall over northeast Texas allowed rivers within the headwater basins of the Neches and Sabine Rivers to remain swollen so the National Weather Service and River Forecast Center in the Northeast Texas area have indicated that those rivers in that basin could flood during this upcoming event.

Areas to watch for flooding during upcoming rain storm. Via the West Gulf River Forecast Center.

Strong Storm May Produce Severe Weather, Blizzard Conditions, and Lake-Effect Snow

A strong storm system moving out of the West will bring heavy snow to the Rockies, severe weather to the Mississippi Valley, and maybe even some lake-effect snow to parts of the Great Lakes before the week is over.

A developing low pressure area will move across the Rockies and into the Central Plains today. Over the weekend this storm brought beneficial rainfall to California, with snowfall across the higher elevations of the Cascades and Sierra Nevada. Up to an inch of rainfall fell across the San Francisco Bay area, with locally heavier amounts of 1-2 inches in Santa Clara and Santa Cruz Counties. Farther inland, 1-2 inches of rain was reported across much of the Central Valley. Strong thunderstorms were also reported across the area, with a tornado warning issued Monday evening for the suburbs of Sacramento, though no tornado was ever confirmed to have touched down. In the Sierra Nevada, as much as 6-12 inches of snow was reported as of Tuesday morning. At the National Weather Service office in Reno, Nevada, four inches was reported in one hour Monday evening.

As the system moves eastward, snow is expected across much of the Intermountain West today into Wednesday. The heaviest snow is expected across the mountains of Utah and Colorado, where 8-16 inches may accumulate. Rain will change over to snow across the western Plains as colder air filters in behind the system. Snowfall totals of 3-5 inches are expected across western portions of Nebraska and Kansas as well as eastern Colorado, including the Denver Metropolitan Area. The snow will be accompanied by northerly winds of 20-40 mph, gusting to 60 mph at times. As a result, blizzard warnings are in effect for much of this region, with high wind warnings for much of the remainder of the Central and Southern Plains.

Watches and Warnings in effect for the Central US as of Midday Tuesday November 10. Blizzard Warnings are in Red, Winter Storm Warnings are in Pink, Winter Storm Watches in Dark Blue, Winter Weather Advisories are in Purple, High Wind Warnings are in Light Brown, and High Wind Watches in Dark Brown.

Southerly winds ahead of the storm will continue to draw warm, moist air northward from the Gulf of Mexico. With the clash of airmasses, strong to severe thunderstorms will likely develop ahead of the cold front on Wednesday from northeastern Texas into much of the Mississippi Valley. Strong winds, hail, and tornadoes are the main threats with any storms that do develop. The best chance for tornadoes looks to be across portions of Iowa, Illinois, and Missouri, where a few strong tornadoes are possible. Just to the north of this area, heavy rain is likely from eastern Nebraska and northern Iowa into southern Minnesota and much of Wisconsin. Rainfall totals of 1-2 inches are possible across this area.

Severe Weather Outlook for Wednesday November 11 from the Storm Prediction Center.

By Thursday, the storm will move into southern Canada, dragging a cold front across the East. This will produce showers across much of the Northeast and Mid-Atlantic states, with gusty westerly winds ushering in cooler air behind the front. As these westerly winds blow over the relatively warmer Great Lakes, some lake-effect rain or snow showers will likely develop on Friday and Saturday. Some snowfall accumulation is possible, mainly over the Tug Hill Plateau of northern New York and parts of the Southern Tier in western New York. A few inches of accumulation are possible, with heavier amounts in the normally favored locations.

Snowfall forecast for Friday and Saturday from the GFS model. Image courtest of WeatherBell. — Snowfall forecast for Friday and Saturday (November 13-14) from the GFS model. Image courtest of WeatherBell.