U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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acus03 kwns 240619 
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Storm Prediction Center ac 240618 


Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0118 am CDT Tue Apr 24 2018 


Valid 261200z - 271200z 


..no severe thunderstorm areas forecast... 


... 
a few thunderstorms are possible from the Sierra Nevada region into 
the Pacific northwest. Isolated thunderstorms might also occur from 
a part of the southern and Central Plains to the middle Mississippi 
Valley as well as over a portion of the southeast states. 


... 


Several vorticity maxima will move through a broad synoptic trough 
situated over the eastern two thirds of the U.S. Thursday. Farther 
west a closed upper low will move into northern California and the Pacific 
northwest region. Shortwave trough expected to be over the lower MS 
valley early Thursday will continue through the southeast states 
accompanied by a weak surface low and cold front that will move 
through the northern Gulf. Farther west an upstream trough will 
advance southeast through the central and Southern Plains as well as 
the MS valley region accompanied by another frontal surge. 


..southeast states... 


With limited moisture return inland and weak lapse rates, 
instability will remain very marginal with MUCAPE well below 500 
j/kg. However, forcing for ascent accompanying the shortwave trough 
and its attendant boundaries will promote shallow and weak 
convection advancing through the Gulf Coast states during the day. 
Isolated lightning strikes cannot be ruled out with this activity. 


..southern and Central Plains through middle Mississippi Valley... 


Very limited low-level moisture will reside in pre-frontal warm 
sector, but mid-level lapse rates and boundary-layer warming in 
conjunction with frontal ascent might be sufficient to initiate 
shallow convection. Some of this activity might become deep enough 
for a few lightning strikes. Other elevated convection will be 
possible into the overnight within band of ascent accompanying the 
shortwave trough, and some of this activity might also produce 
isolated lightning strikes. 


... Sierra Nevada through the Pacific northwest... 


Steep mid-level lapse rates will reside in this region in advance of 
the approaching upper trough. Isolated thunderstorms cannot be ruled 
out over the Sierra Nevada during the afternoon and early evening. 
However, greater thunderstorm chances (with updraft bases rooted 
above 700 mb) are expected overnight from northern California into western 
or when ascent accompanying a vorticity maximum rotates through the 
upper low circulation and onshore. 


.Dial.. 04/24/2018 


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