U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 201718 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1218 PM CDT Monday Oct 20 2014 

Valid 211200z - 221200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are possible over parts of the interior 
west...western and southern Texas...southern portions of the Florida 
Peninsula...and perhaps over a portion of the northeastern states. 


Upper trough over the eastern U.S. Is forecast to evolve into a closed 
low as it moves eastward...reaching the middle Atlantic coast by the end 
of day 2. Cutoff upper low circulation over northern Mexico should drift 
slowly east toward western Texas during the day. Meanwhile...upper trough 
now approaching the western U.S. Coast will continue through the central 
and northern rockies. 

At the surface a Lee trough will become established over the northern and 
Central High plains...while a cold front accompanies western U.S. Upper 
trough through the northern rockies. An occluded low will move through 
the middle Atlantic and off the eastern U.S. Seaboard in association 
with the evolving upper low over the eastern states. 

..srn through central rockies area... 

Plume of subtropical moisture will continue to advect northward ahead of 
the progressive upper trough and in association with closed upper 
low circulation over northern Mexico. Weak instability is expected as the 
boundary layer warms and will promote scattered convection including 
isolated thunderstorms over the higher terrain Tuesday and Tuesday 

..nern states... 

Cold air aloft accompanying the evolving upper low and ascent 
associated with vorticity maxima rotating through this feature 
should promote the development of weak instability and scattered 
showers over the northestern states. Though instability will remain very 
weak /generally at or below 300 j/kg/ it might become sufficient for 
isolated thunderstorms within a more general area of scattered 
showers during the afternoon. 

..srn Florida... 

Scattered showers and thunderstorms will likely develop within plume 
of deep subtropical moisture and marginal instability that should 
characterize the southern Florida pre-frontal warm sector Tuesday. 

.Dial.. 10/20/2014