10:45 AM | ***Active weather pattern to continue into May…multiple storm systems can impact Mid-Atlantic/Northeast US from Friday into Monday***

The upper air pattern may feature a deep low early next week centered over the Ohio Valley with a strong surface storm near the Mid-Atlantic coastline. Map courtesy Pivotal Weather, ECMWF

Overview

Cold air outbreaks continue to work their way from Canada into the US as we wind down the month of April and it appears they will continue to do so right through the early part of May.  As long as this kind of pattern holds, there will be an enhanced threat of severe weather outbreaks in the US and an increased chance for the formation of strong storm systems.  In fact, more severe weather is possible on Wednesday in places like Texas and Oklahoma as cold, dry air advances from the west and clashes with entrenched warm, humid air across the south-central US.  This severe weather threat will then shift eastward to Louisiana, Mississippi and Alabama by Thursday afternoon.

Looking ahead, there are signs for a soaking rain event in the eastern US from Friday into Saturday and then a second and perhaps stronger system may form later in the weekend and produce more significant rain in the Mid-Atlantic/Northeast US. This second storm system may feature some strong-to-severe thunderstorm activity of its own in its warm sector from late Sunday into Monday and perhaps even some wet snow and/or ice on its cold side in some of the higher-elevation, interior spots of the northeastern US…just as we begin the month of May. 

Another cold, dry air mass will push towards Texas on Wednesday and clash with entrenched warm and humid air…the end result may be severe weather to include the possibility of large hail, damaging wind gusts and even isolated tornadoes. Map of severe weather probabilities on Wednesday/Wednesday night courtesy NOAA/Storm Prediction Center

Details

The overall weather pattern for much of the Mid-Atlantic region and Northeast US has been rather dry in recent weeks and soil moisture content has been at rather low levels.  As an example, Philly has been drier-than-normal so far in the month of April with a total precipitation deficit of more than one inch and this is despite a soaking rainfall this past weekend.  In the prior months of February and March, the Philly metro region also experienced drier-than-normal weather with both months running total precipitation deficits of more than one inch…similar findings in Washington, D.C. and New York City as well in the months of February, March and April. This drier-than-normal weather pattern of recent months in the Mid-Atlantic region appears to be in serious jeopardy as numerous storms in the near future are likely to return soil moisture content to much more typical levels as we progress from April into May.

There is the potential for a powerful storm system by early next week centered somewhere near the Mid-Atlantic coastline with heavy rain a possibility (yellow, orange) and this will follow what can be a Friday/Saturday soaking rain event. Map courtesy ECMWF, Pivotal Weather

One of the culprits of this active weather pattern is the continuing influx of colder-than-normal air into the US from Canada and these outbreaks not only enhance chances for severe weather, but also increase chances for the development of strong storm systems. On Wednesday, severe weather is indeed on the table for the south-central states centered primarily on the state of Texas given the expected combination of advancing cold, dry air from the west into a warm, humid air mass in place across the south-central states. This clash of air masses combined with upper-level support will lead to strong-to-severe thunderstorm activity over Texas and Oklahoma with the threat of large hail, damaging wind gusts, and even isolated tornadoes. By Thursday, this threat of severe weather will shift eastward to Louisiana, Mississippi and Alabama and conditions there will have to be closely monitored.

Enough cold air may be around early next week for the possibility of a mix of snow and ice (purple) in some of the higher-elevation, interior locations of he northeastern states. Map courtesy ECMWF, Pivotal Weather

By the time we get to end of the work week and weekend, the upper-air pattern will likely feature multiple lows extending from the middle of the nation into southern Canada. In addition, it looks like there will be a series of surface low pressure systems as well that will impact the eastern states beginning perhaps with a soaking rain event from Friday into Saturday. The wave of energy expected to be in southern Canada by Friday will likely become the most important player over the weekend as it’ll act to “absorb” the other upper-level low pressure systems and intensify. The end result may be one deep upper-level low by late Sunday or Monday centered over the Ohio Valley and likely a strong surface low pressure system near the Mid-Atlantic coastline.  As a result, there can be a second soaking rain event in the Mid-Atlantic/Northeast US from later Sunday into Monday and strong-to-severe thunderstorms can be in the mix as well in the warm sector of this storm system.  On the cold side of the storm, there may even be some wet snow and/or ice in some of the higher-elevation, interior locations of the northeastern states by early Monday…just as we begin the month of May.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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