Category: General Weather

Heavy Rain in the Plains and Mississippi Valley Tuesday

 

After Sunday’s cold front ushers in cooler and drier air for Monday in the Northern Plains, a warm front will push north Tuesday. This warm front is attached to a low pressure system that will be moving northeast through the Rockies and into the Northern Plains. Areas in between the northward moving warm front and the southeastward moving cold front could see some strong to severe thunderstorms on Tuesday. This would mainly occur in the eastern Central Plains and portions of the Middle Mississippi Valley where convective energy, CAPE, and turning of the winds, shear, overlap to be able to support these storms.

Cooler and drier air (green colors) moving into the Northern Plains behind a cold front.
Cooler and drier air (green colors) moving into the Northern Plains behind a cold front. Courtesy of College of Dupage.
A warm front nestled between North and South Dakota.
A warm front nestled between North and South Dakota. Courtesy of College of DuPage.
Showalter Index showing possible instability in the Northern Plains, but higher values occur in the Eastern Central Plains and Middle Mississippi Valley.
Showalter Index showing possible instability with negative values in the Northern Plains, but even lower negative values occur in the Eastern Central Plains and Middle Mississippi Valley. Courtesy of AccuWeather.
Severe weather categorical outlook for Tuesday showing the highest probability of severe weather in the Central Plains and Middle Mississippi Valley.
Severe weather categorical outlook for Tuesday showing the highest probability of severe weather in the Central Plains and Middle Mississippi Valley. Courtesy of the Storm Prediction Center.

Farther north along the warm front in the Northern Plains, factors like limited sun exposure, saturated atmospheric columns and a lack of a shear/CAPE overlap may preclude strong to severe thunderstorms all together. There is some question as to how far north the warm front will be able to push into North Dakota so if it is able to push farther north and allow more sun, some strong to possibly severe thunderstorms may occur. At the very least, some thunderstorms may be embedded in what does appear to be a heavy rain event as a result of a vigorous upper level disturbance that appears to go negatively tilted in the upper levels of the atmosphere. This negative tilt allows for a strong draw of moisture into the system as a result of a strong low level jet stream. At the same time, very moist low levels and total column precipitable water values between 1.5 and 2 inches get wrapped around the northeastward moving low pressure system bringing the potential for a heavy rain event into the Northern Plains. Furthermore, large scale lift as a result of a collocated upper level jet stream will help to support the event. All told, 1 to 2.5 inches of precipitation in 24 hours from morning Tuesday to morning Wednesday seems reasonable for this event, but could be higher in any embedded thunderstorm.

The vigorous possibly negatively tilted energy moving into the Central and Northern Plains.
The vigorous possibly negatively tilted energy moving into the Central and Northern Plains. Courtesy of College of DuPage
Strong low level jet in the Northern Plains along with the Central Plains and Middle Mississippi Valley helping fuel heavy rain and strong to severe thunderstorms respectively.
Strong low level jet in the Northern Plains along with the Central Plains and Middle Mississippi Valley helping fuel heavy rain and strong to severe thunderstorms respectively. Courtesy of College of DuPage.
Forecast rainfall totaling 1 to 3 inches. Possibly higher in any thunderstorms from Tuesday morning to Wednesday morning.
Forecast rainfall totaling 1 to 2.5 inches. Possibly higher in any thunderstorms from Tuesday morning to Wednesday morning. Courtesy of the Weather Prediction Center of NWS.

 

It is also interesting to note that the ECMWF model contains around an inch less of precipitation than the GFS model, with the NAM model being closer to the mean of the two models despite the ECMWF model reaching the above parameters. With this in mind, it appears any flooding risk would be low, but could still occur if the higher end of the precipitation range is realized.

 

The low pressure system is forecast to move away from the Northern Plains allowing for drier air to come in for Wednesday and Thursday. However, clouds are forecast to return as another low pressure system ejects off the Rockies for Friday allowing for some more rain.

 

 

 

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.
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.

Tropical Depression Two Develops – Threat to the Carolinas?

The second tropical depression of the 2016 Hurricane Season has developed in the Western Atlantic Ocean.

As of 8pm EDT Friday, Tropical Depression Two was centered approximately 400 miles southeast of Charleston, South Carolina, and was moving towards the west-northwest at 13 mph. Maximum sustained winds are near 35 mph, and additional strengthening is expected.

Infrared satellite loop of Tropical Depression Two. Loop provided by NOAA.
Infrared satellite loop of Tropical Depression Two. Loop provided by NOAA.

The storm is expected to continue on a general west-northwest track into Saturday, with some modest strengthening possible. If the system attains maximum sustained winds of 39 mph or more, it would be named Tropical Storm Bonnie. This may occur on Saturday. However, many of the forecast models are indicating that the system may not strengthen much over the next few days, due to a combination of, wind shear aloft, and sea surface temperatures that are only marginally warm enough to sustain a tropical cyclone. Most of these models do show a track towards South Carolina over the next 24-48 hours.

Model forecasts for the strength of Tropical Depression Two. Image provided by tropicaltidbits.com
Model forecasts for the strength of Tropical Depression Two. Image provided by tropicaltidbits.com
Model forecasts for the track of Tropical Depression Two. Image provided by tropicaltidbits.com
Model forecasts for the track of Tropical Depression Two. Image provided by tropicaltidbits.com

A tropical storm warning has been posted for most of the South Carolina coastline, from the Savannah River to Little River Inlet. Showers and thunderstorms should begin to move into the region later on Saturday, with some locally heavy rainfall totals expected. Wind gusts to tropical storm force will likely be confined to the immediate coast.

As the storm nears the coastline it will start to slow down as the upper-level steering currents start to weaken. A turn towards the north is possible, but if the turn occurs too early, it would prevent the storm from making landfall in South Carolina, but would make a landfall in southeastern North Carolina a bit more likely. Residents along the coast from Georgia to North Carolina should keep an eye on the storm’s progress, as it will likely have a significant impact on the holiday weekend forecast.

The storm will also have an indirect impact on the weekend forecast for much of the remainder of the East Coast. As the upper-level flow becomes south-to-north along the East Coast, it will take moisture from the storm and send it northward, ahead of a cold front. This will result in periods of heavy rain for the Mid-Atlantic states later on Sunday, and the Northeast on Monday. Rainfall totals of 1-2 inches or more are expected, and while it will ruin plans for barbecues and beach days, the region has not received much rain this Spring, so any moisture that does fall is needed.

Rainfall forecast from the GFS model for the weekend. Image provided by Pivotal Weather
Rainfall forecast from the GFS model for Sunday and Monday Image provided by Pivotal Weather

The 2016 Hurricane Season got off to an extraordinarily early start when Hurricane Alex formed back in January. Alex became the first January tropical system in the Atlantic when it acquired subtropical characteristics south of the Azores on January 13. It became a full-fledged hurricane on January 14, the first January hurricane in the Atlantic since Alice in 1955. Alex crossed the Azores on January 15, before weakening to a tropical storm and then becoming extratropical later that day as it headed out in the open Atlantic.

Hurricane Season in the Atlantic Starts on June 1

June is a little more than a week away, and while that marks the start of meteorological summer, it also marks the start of Hurricane season in the Atlantic Basin (North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico).

Hurricane season in the Atlantic runs from June 1 through November 30, but it got off to an extraordinarily early start in 2016 when Hurricane Alex formed back in January. Alex became the first January tropical system in the Atlantic when it acquired subtropical characteristics south of the Azores on January 13. It became a full-fledged hurricane on January 14, the first January hurricane in the Atlantic since Alice in 1955. Alex crossed the Azores as a strong tropical storm on January 15, and eventually head out in the open Atlantic transitioning to an extratropical cyclone on January 17. The next storm that forms will be given the name Bonnie.

Name list and pronunciation for the 2016 Atlantic Hurricane Season
Name list and pronunciation for the 2016 Atlantic Hurricane Season

Is the early start a harbinger for an active hurricane season? Not necessarily. What will be more of a factor is the developing La Nina in the Pacific Ocean. In an El Nino, such as the one we had in 2015, the subtropical jet stream is stronger, which inhibits storm development as the jet stream effectively cuts the tops off of storms before they can develop. In a La Nina, the subtropical jet is weaker, allowing easterly winds to dominate, which allows the storms to develop.

Map showing all tropical systems across the Atlantic Basin from the 2015 Hurricane Season. Image provided by the National Hurricane Center.
Map showing all tropical systems across the Atlantic Basin from the 2015 Hurricane Season. Image provided by the National Hurricane Center.

The presence of El Nino or La Nina is just one of many factors that go into whether a hurricane season is active or quiet, but most predictions are for activity to be more common than in 2015 and above normal. In a normal season, the Atlantic Basin sees 12 named storms, of which 6 become hurricanes and 3 become major hurricanes (Category 3 or higher on the Saffir-Simpson Scale). While there are plenty of hurricane forecasts out there, these were pioneered by Dr. William Gray, who recently passed away after over 50 years in the field. His research team at Colorado State University continues his work, and for this season is calling for 14 named storms, of which 8 could become hurricane, and 3 major hurricanes.

An active season doesn’t guarantee that a storm will make landfall in the United States though. In 2010, there were 19 named storms, 12 hurricanes, and 5 major hurricanes. Only 1 storm, Tropical Storm Bonnie, made landfall in the United States. On the flip side, 1992 was a quiet season, with just 7 named storms, 4 hurricanes, and 1 major hurricane, with the first named storm not forming until August 16. Of course, that first storm was Andrew, which slammed into South Florida on August 24 as a Category 5 hurricane, one of just 3 Category 5 storms to ever make landfall in the United States.

The peak of the season usually occurs from mid-August through late September, but an early start isn’t unusual. On average, the first name storm of the season occurs on July 9, with the first hurricane forming around August 10. In 2015, there were two tropical storms during May and June (Ana and Bill), while 2012 saw 4 named systems (Alberto, Beryl, Chris, and Debby) with 1 hurricane (Chris) forming before the end of June.

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
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.

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.
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.
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.
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.
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.
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.

Sunday’s Pacific Northwest System to Affect Northeast By Midweek

A strong surge of warm air will move east from the Northern and Central Plains into the Mid to Upper Mississippi Valley, Great Lakes, and Ohio River Valley on Sunday. Surface temperatures were forecast to be 15 to 30 degrees above normal for Saturday in the Plains and will be 10 to 20 degrees above normal in the Mid to Upper Mississippi Valley, Great Lakes and Ohio River Valley areas on Sunday. The normal setup for warm air into a region is a pattern of high pressure to the south and low pressure to the north. This allows warm air to come in on the back of high pressure and ahead of a cold front from the low pressure system. Also, with warm air moving into a region, the distance from the ground to a layer with a pressure of 500 mb increases to an above normal height. Above normal heights are forecast for the Mid to Upper Mississippi Valley, Great Lakes and Ohio River Valley areas on Sunday.

Above normal temperatures over the Plains and Pacific Northwest. Notice the below temperature anomalies in the Cadcades mountain range in Northwest Washington.
Above normal temperatures over the Plains and Pacific Northwest. Notice the below temperature anomalies in the Cadcades mountain range in Northwest Washington.
Above normal heights indicating warm air is nearby.
Above normal heights in the west and east indicating warm air is nearby.

 

Farther west, a cold front moves ashore in the Pacific Northwest as a low pressure system moves ashore in Western Canada. The aforementioned warmer temperatures were in the Pacific Northwest 24 hours ago, so many places will receive rain from this front, but higher elevations will receive snowfall. Northern portions of the Cascades may receive near 1 foot of snowfall from this frontal system. In addition, the northern portion of the Rockies within Western Montana and Western Wyoming are forecast to receive 2 to 4 inches of snowfall from this system.

Forecast snowfall over the Cascades and Northern Rockies via WPC.
Forecast snowfall over the Cascades and Northern Rockies via WPC.
European model depiction of a more northerly track and less colder air for snow or freezing rain.
European model depiction of a more northerly track and less colder air for less snow or freezing rain.
GFS model depiction of overnight snowfall or freezing rain.
GFS model depiction of overnight snowfall or freezing rain.
Current snow pack as of Friday night.
Current snow pack as of Friday night. Via the National Operational Hydrological Remote Sensing Center.

 

As the energy for the frontal system in the Pacific Northwest moves ashore, an upper level low pressure system in Central Canada will help to steer the energy towards the Northeast. The energy will eject from the Rockies dive south into the Ohio River Valley region. The track of the system after its movement toward the Ohio Valley region is key for the Northeast. Longer range models initialized Friday night show two possible track options for the storm after the track through the Ohio River Valley. A movement across Southern New England (the American GFS model) will allow more cold air to flow into the region. With more cold air and some moisture around the region, an onset of snow or freezing rain is possible along a cold front that would be across portions of New England at that time, especially north of Route 2 in Massachusetts and into Central and portions of Northern New England. However, a shift to more of a northern track (the European model) would allow for less snow, if any, at the onset overnight Tuesday night as the cooler air wouldn’t be able to come into the region as well as the more southern track. With the current snowpack only in the Berkshires and all the way into Central to Northern New England, a push northward of the warm front overnight, as the European model is hinting at may be possible, but temperatures on Tuesday and Tuesday night will have to be assessed to see how far south the below-freezing air will be able to come into Southern New England. If the colder air is able to come far enough south, the front will probably struggle to move northward and some snow or freezing rain would be possible Tuesday night before changing to rain during the day Wednesday and as the low pressure system approaches from the west.

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.
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.
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.

 

Blizzard of 2016 Recap

This post will go back over some of the highlights of the Blizzard of 2016 with a brief summary of why it happened, some of the reasons why plenty of snow fell where it did and some of the cool visuals that came out of the storm.

Snow totals along the Eastern US.
Snow totals along the Eastern US.

 

The storm had many interesting features that helped it become what it was. It started out over the Pacific Ocean and came onto the United States. As the energy energy ejected out of the Rockies, another low pressure system was entering the West Coast and causing a wave break. This would cause the high pressure ridge to develop behind the storm allowing plenty of cold air to wrap in behind the storm and rapidly develop the storm into a cutoff low even before it exited the East Coast.

Energy (reds and oranges) over the Eastern Pacific before entering the Western US.
Energy (reds and oranges) over the Eastern Pacific before entering the Western US.
The ridge building as a result of a wave break from the storm entering the Western US. The eventual Blizzard of 2016 was in the Eastern US at this point.
The ridge building (green arrow) as a result of a wave break from the storm entering the Western US. The eventual Blizzard of 2016 was in the Eastern US at this point.
Storm position as it affected the Northeast. The blue colors indicate the bent back warm front and frontogensis signature.
Storm position as it affected the Northeast. The blue colors indicate the instability within the bent back warm front and frontogensis signature.

 

Well forecasted position of the coastal front. The front would have heavier snow along it as a result of air colliding along it.
Well forecasted position of the coastal front. The front would have heavier snow along it as a result of air colliding along it.

 

In fact, there was plenty of “wait for the energy to come on shore” phrases being dropped in the meteorological community because the models had the storm on the map for such a long time. However, the snow maps being generated by the models didn’t really give meteorologists much confidence along the way because there were plenty of differences in how far north the snow would come into the Northeast. It was a given that the storm would drop plenty of snow in the Mid-Atlantic since one of the most similar analogs or similar storms to this storm was the January 1996 Blizzard. This storm had areas of 20+ inches in the Mid-Atlantic, but had way too much snowfall in the Northeast. Meteorologists needed to pin point where the banding would set up. This occurred in a coastal front and another band system called a bent back warm front or TROWAL signature. It had plenty of moisture within it and as the storm was cycling and the moisture was wrapping into the storm, the bent back warm front would slowly pivot from a west to east signature to a northeast to southwest signature and then pivot out to sea as the storm passed by New England to the southeast. One wrinkle leading up to the storm had the model that is easy to disregard, the NAM, adjusted moisture way up for the New York region and many final snow maps didn’t include it because it was such an outlier. In fact, many areas over performed as a result of the bent back warm front band along the South Coast of Southern New England and the Coastal front over Southeastern Southern New England. So taking the NAM into consideration in some way may have actually helped.

Blizzard of 1996 is similar for the DC area in snowfall output, but not so similar to the Northeast.
Blizzard of 1996 is similar for the DC area in snowfall output, but not so similar to the Northeast.

 

Coastal flooding would be a huge problem along the East Coast:

 

Some pictures and interesting photos:

Winterized radar image showing snow in the Mid-Atlantic and portions of the Northeast. Image courtesy of Intellicast.com

 

Astronaut Scott Kelly’s photograph from space of thundersnow.

It was a case of the haves and have-nots as relatively small distances separated high and low snowfall totals.

After a while, you’ve gotta have fun with it.

 

The morning after’s visible satellite imagery distinctly showing the snowline.

 

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