U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 240456 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1156 PM CDT Mon Apr 23 2018 

Valid 251200z - 261200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are expected over a part the Southern Plains 
and lower Mississippi Valley as well as the middle-Atlantic area on 


A couple of shortwave troughs will move through the broad synoptic 
upper trough that will remain situated over the eastern two thirds 
of the country on Wednesday. One such feature is a near-stationary 
closed upper low located over the Tennessee Valley. This low will move 
northeast through the mid-Atlantic as an upstream shortwave trough 
continues southeast through the lower Mississippi and Tennessee Valley 
regions. At the surface a cold front will move southeast through the 
Southern Plains, while farther east an occluded low will lift 
northward along the eastern Seaboard in association with the 
northeast-ejecting shortwave trough. 

..Southern Plains through lower Mississippi Valley... 

Cold front should extend from the Great Lakes region into southwest 
Texas early Wednesday and continue southeast during the day. A recent 
Gulf frontal intrusion and persistent offshore flow resulting from 
circulation around a low pressure area over the southeast states 
suggest only partial Gulf boundary-layer modification and modest 
moisture return through most of the Texas pre-frontal warm sector. 
Modest instability is expected with a corridor of 1000-1500 j/kg 
MUCAPE from southwest through west central Texas where modifying 
Continental-polar air will have returned northwestward beneath 
steeper mid-level lapse rates. Given the marginal thermodynamic 
environment and weak forcing in warm sector, current indications are 
that most storms will remain confined to cool side of the 
southeast-advancing cold front. While a few instances of small to 
marginally severe hail cannot be ruled out from southwest through 
west central Texas where steeper 700-500 mb lapse rates will reside, 
overall severe threat is expected to remain limited. 

..middle Atlantic through a portion of the northeast states... 

Isolated thunderstorms will remain possible where cooler air aloft 
and slightly steeper lapse rates will reside in association with the 
northeast-advancing upper low circulation. Other thunderstorms will 
be possible within zone of isentropic ascent and weak 
destabilization along northeast advancing occluded/warm front. 

.Dial.. 04/24/2018