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Severe Weather Outbreak Likely on East Coast on Monday

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Monday will feature a variety of severe weather. On the first panel on the left, the threat level is depicted, with thunderstorms possible in the shaded regions. There is a heightened risk of severe storms in the dark green area, a higher risk in the yellow zone, an even higher risk in the orange zone, and the highest risk in the red zone. In the second panel, the shaded areas reflect the risk of damaging, severe winds; here the highest risk area is shaded in purple; the third panel reflects the risk for large, destructive hail, with the yellow shaded area representing the greatest risk for that; the last panel shows the overall risk of tornadic activity, with all colors representing risk, with increasing risk from green to brown, brown to yellow, and yellow to red. Image: NWS SPC
Monday will feature a variety of severe weather. On the first panel on the left, the threat level is depicted, with thunderstorms possible in the shaded regions. There is a heightened risk of severe storms in the dark green area, a higher risk in the yellow zone, an even higher risk in the orange zone, and the highest risk in the red zone. In the second panel, the shaded areas reflect the risk of damaging, severe winds; here the highest risk area is shaded in purple; the third panel reflects the risk for large, destructive hail, with the yellow shaded area representing the greatest risk for that; the last panel shows the overall risk of tornadic activity, with all colors representing risk, with increasing risk from green to brown, brown to yellow, and yellow to red. Image: NWS SPC

 

A severe weather outbreak is likely to unfold across a large portion of the U.S. East Coast on Monday. Severe thunderstorms with flooding rains, frequent lightning, damaging wind gusts, large hail, and tornadoes are all possible in this outbreak, with the most severe weather likely to strike from central Pennsylvania south into central Georgia. Tornadoes, some strong, and particularly damaging winds are most likely from parts of South Carolina to Maryland during the afternoon.

An expansive upper trough from Wisconsin  to the Ark-La-Tex will further amplify as the surface low pivots rapidly northeastward towards the Appalachians. A deep surface cyclone over Lower Michigan will progress into Quebec, with an occluded front arcing southward to a minor low over western to central New York  by Monday afternoon. A sharp cold front will extend south of this low across the Southeast into the northeast Gulf, sweeping east across the entire Atlantic Seaboard early Tuesday morning.

Tornado Watches and Warnings may be issued as severe weather unfolds. Image: NWS
Tornado Watches and Warnings may be issued as severe weather unfolds. Image: NWS

This type of meteorological set-up lends itself to three distinct periods of poor weather. The first part will be heavy rain moving north tonight into early tomorrow, threatening cities with the risk of urban flooding.  As the farm front moves to the north, some sunshine should come out which will help destabilize the atmosphere in portions of the Mid Atlantic. With the atmosphere destabilized from afternoon heating from that sunshine, thunderstorms will be able to rapidly grow and intensity, setting the stage for frequent lightning, flash flooding rains, and the threat of damaging wind gusts and tornadoes.  The third distinct part of this storm should be a well defined squall line that should sweep to the coast as a cold front advances east. While this cold front will bring an end to the precipitation once it clears, it could be quite rough as it passes through with a squall line of intense thunderstorms, destructive straight-line winds, and the risk of hail.

“The downstream environment will already be favorable for supercells including strong tornado potential,” the Storm Prediction Center at NOAA warns. “Any semi-discrete supercells in this environment will have the potential to produce a strong tornado and large hail through early afternoon before large-scale outflow likely shifts offshore of the Georgia/north Florida coast.

The cold frontal passage will be significant, with much colder air arriving behind it. While accumulations aren’t expected, snow flurries and snow showers are possible as far east as eastern Pennsylvania, northwestern New Jersey, and eastern Upstate New York.