U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 200555 


Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1255 am CDT Mon Aug 20 2018 


Valid 211200z - 221200z 


..there is a slight risk of severe thunderstorms across the 
north-central Appalachians/mid-Atlantic states and the south-Central 
High plains... 


... 
Severe thunderstorms will be possible on Tuesday, especially during 
the afternoon and evening across portions of the 
Appalachians/mid-Atlantic states as well as the south-Central High 
plains. 


..Appalachians/upper Ohio River valley and mid-Atlantic states... 
Although the primary surface cyclogenesis will be focused north of 
the international border, a semi-amplified belt of seasonally 
strong/cyclonically curved westerlies will overspread much of the 
region on Tuesday coincident with an eastward-moving cold front. 
Relatively widespread early-day convection and lingering cloud cover 
limits confidence in appreciable destabilization and may somewhat 
curb the overall magnitude of tuesday's severe risk. 


However, relatively strong low-level shear and upwards of 35-40 kt 
effective shear suggests the potential for sustained multicells and 
some supercells where adequate (even modest) diurnally enhanced 
destabilization occurs Tuesday afternoon. This currently appears 
most probable across far eastern Ohio/western Pennsylvania southward 
into parts of Maryland/Virginia. Elsewhere, at least isolated severe 
storms may occur as far south as the Carolinas/southern Appalachians 
under a more modestly strong flow regime. 


..south-Central High plains... 
Moist low-level upslope flow will be focused on Tuesday to the north 
of a southern High Plains surface low. This will be in conjunction 
with a moderately strong (25-30 kt at 500 mb) belt of westerlies to 
the north of the southern High Plains-centered upper-level ridge. 
While initial storm development Tuesday afternoon is expected over 
the Front Range/foothills vicinities, it appears a sub-regional area 
of more favorable deep-layer shear and buoyancy coincident with 
probable storm development will exist across far southeast Colorado 
and neighboring areas including far southwest Kansas and the western 
Oklahoma Panhandle. Both severe-caliber wind gusts and hail will be 
possible across the region. 


..maximum risk by hazard... 
Tornado: 5% - slight 
wind: 15% - slight 
hail: 15% - slight 


.Guyer.. 08/20/2018 


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