Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 221700
SWODY2
SPC AC 221659

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1159 AM CDT Tue Aug 22 2017

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN MID-ATLANTIC AND EASTERN CAROLINAS...

...SUMMARY...
A few strong/marginally severe storms may impact parts of the
southern Mid-Atlantic and eastern Carolinas Wednesday. Gusty,
damaging winds will be the main threat.

...Synopsis...
Broad cyclonic flow will envelop much of the eastern US on
Wednesday, with a corridor of 40-60 kt mid-level flow from the
Dakotas to the Canadian Maritimes. At the center of this regime, a
closed low will gradually lift northeast across northern Quebec.
Meanwhile, a compact shortwave trough will advance southeast from
the Canadian Prairies towards the northern Plains. The surface
pattern will feature expansive high pressure building southeastward
across much of the Mississippi and Ohio Valleys. Along the leading
edge of this building surface ridge, a cold front will push towards
the Southeast US and Gulf Coasts, while having cleared much of New
England early in the day.

...Southern Mid-Atlantic and Eastern Carolinas...
Along the southern fringe of the synoptic trough, a weak/sheared
impulse, likely in association with the surface front, will approach
the region during the mid-day/afternoon hours. Higher terrain, the
front, and a pre-frontal trough may all serve to focus initiation
through the day. Plentiful boundary-layer moisture and some diurnal
heating will overcome meager mid-level lapse rates for the
generation of moderate mixed-layer buoyancy by afternoon.
Low/mid-level flow appears quite modest, with west/southwesterly
winds around 25 kt or less through 500 mb. Therefore, convection
will likely organize into multicell clusters initially, perhaps
followed by small corridors of upscale growth, as cells propagate
into greater moisture towards the coast. The warm/moist environment
and expected mode evolution suggest isolated pockets of damaging
gusts will be the primary threat with this activity during the
afternoon and evening hours, before convection weakens with a loss
of heating.

..Picca.. 08/22/2017

$$



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