1:45 PM | ***Another threat of heavy rain and severe thunderstorms for the Mid-Atlantic region***

A key ingredient to this newest threat of severe weather and torrential rainfall in the Mid-Atlantic region is a strong upper-level low that will travel from the Upper Midwest earlier today to the northern Mid-Atlantic by later tomorrow. Map courtesy Canadian Met Centre, tropicatidbits.com

Overview

Heavy rain and severe thunderstorms rocked the Mid-Atlantic region last Monday and a somewhat similar overall weather pattern can bring a repeat performance from late today into Tuesday. In a situation like a week ago, several ingredients will come together in the atmosphere that will raise the chance for heavy downpours and severe thunderstorms which can produce damaging wind gusts, hail and even isolated tornadoes. These ingredients include a vigorous upper-level low that is currently pushing eastward across the Upper Mississippi Valley, copious amounts of available moisture, strong jet streaks at multiple levels of the atmosphere, and a strong surface cool front that ultimately crosses the Mid-Atlantic region late Tuesday. The time period for the potential heavy downpours and severe thunderstorms will be from late today into Tuesday night.

An upper-level jet streak across the Northeast US will enhance upward motion in the Mid-Atlantic region and help to destabilize the atmosphere. Other levels of the atmosphere will feature high winds as well and these in combination will produce strong wind shear and raise the chances for severe weather conditions. Map courtesy Canadian Met Centre, tropicaltidbits.com

Details

An active weather pattern across the northern US will bring another chance of heavy downpours and severe thunderstorms to the Mid-Atlantic region in the time period from late today into Tuesday afternoon. The upper-level weather maps this morning feature a vigorous wave of low pressure that is currently located over the Upper Mississippi Valley and it will slide slowly eastward reaching the northern Mid-Atlantic region late tomorrow. At the surface, low pressure and its associated strong cold front will push in the same general eastward direction during the next 24-30 hours and enhance overall upward motion in the Mid-Atlantic region from early tonight into Tuesday night.

A low-level jet streak across the Mid-Atlantic region will enhance upward motion and help to destabilize the atmosphere. Other levels of the atmosphere will feature high winds as well and these in combination will produce strong wind shear and raise the chances for severe weather conditions. Map courtesy Canadian Met Centre, tropicaltidbits.com

As was the case a week ago, strong jet streaks at multiple levels of the atmosphere will play a destabilizing role from late today into Tuesday and increase chances of wind shear which, in turn, increases the chance for severe thunderstorm activity. While the threat for heavy rain and severe thunderstorms will exist in the entire Mid-Atlantic region tonight (and that includes both in the overnight hours as well as the more conventional evening hours), the risk on Tuesday should be highest “along and to the east” of the I-95 corridor region of DC-to-Philly-to-NYC (i.e., less risk on Tuesday for heavy rain and strong storms in the far northern and western suburbs of the big cities as compared with the urban centers and areas to their south and east). Any severe thunderstorm that forms both tonight and during on Tuesday will contain the risk of producing damaging wind gusts, hail, and even isolated tornadoes.

NOAA’s Storm Prediction Center has placed parts of the Mid-Atlantic region and Ohio Valley in a “slight” risk for severe weather on Tuesday and Tuesday night.

In terms of rainfall, the passage of a warm front later today will usher in an increasingly humid air mass with precipitable water amounts rising appreciably by this evening.  As a result of the high levels of available moisture, any shower or thunderstorm that forms from later today into tomorrow afternoon can put down a lot of rainfall in a short period of time. In addition, there is the chance for “training” of thunderstorms during this weather event meaning heavy downpours can occur multiple times in the same area…all of which raises the chance for localized flash flooding; especially, given the already well-saturated grounds of the Mid-Atlantic region.

Showers and thunderstorms are expanding in coverage early this afternoon across the western Mid-Atlantic and eastern Ohio Valley. Numerous showers and thunderstorms will overspread the eastern Mid-Atlantic this evening and continue through the overnight hours. Maps courtesy NOAA, College of DuPage

Following the passage of the strong cool front late tomorrow, the stage may be set for an unusual quiet stretch of weather during the second half of the week – something not seen often in recent weeks. The time period from Wednesday through Saturday should generally feature dry and warm conditions. The weather may then turn pretty hot by the early part of next week with highs at or slightly above the 90 degree mark on Monday afternoon in the DC-to-Philly-to-NYC corridor.    

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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