Day 1 Severe Weather Outlook

Valid 301200Z – 311200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
CHESAPEAKE BAY…DELMARVA PENINSULA…AND INTO FAR SOUTHEAST
PA/SOUTHERN NJ…

…SUMMARY…
A couple of strong thunderstorms may impact portions of the
Mid-Atlantic region Monday afternoon, possibly accompanied by
local/low-end severe risk.

…Synopsis…
A large upper low initially over the Midwest is forecast to drift
slowly east-northeastward into the Upper Great Lakes region today,
as an associated area of mid-level height falls spreads across the
eastern U.S. with time. Farther west, an upper low off the southern
California coast is progged to dig south-southeastward, reaching a
position west of Baja California through early Tuesday morning.

At the surface, an occluded low is expected to linger over the Upper
Great Lakes region, while a trailing cold front — east of the
Appalachian crest by the start of the period — shifts eastward
through the day, and offshore overnight. By midday, a secondary low
is progged to begin developing near the triple point over the
Chesapeake Bay region. The low should shift off the coast around
sunset, and then continue northeastward toward Cape Cod overnight.
Elsewhere across the U.S., high pressure will prevail.

…Mid-Atlantic region…
As a triple-point surface low develops across the Bay area by
midday, and then shifts northeastward toward/off the southern New
Jersey coast by evening, a minimally unstable warm sector will
spread across the risk area during the afternoon, just ahead of the
advancing cold front. While greater/elevated convective development
is forecast northward across eastern PA, which will then spread
northeastward, instability appears too limited for any appreciable
hail risk. Still, a stronger storm or two may evolve from southern
New Jersey/far southeast PA southward across the Delmarva region and
Chesapeake Bay. With shear supportive of organized/rotating
updrafts, very limited/local risk for a stronger wind gust or brief
tornado is apparent, warranting maintenance of MRGL/5% risk, until
the front moves offshore during the evening.

..Goss/Bentley.. 12/30/2019

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