U.S. Severe Weather Forecast (Convective Outlook)

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acus01 kwns 221934 
swody1 
Storm Prediction Center ac 221933 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0233 PM CDT sun Apr 22 2018 


Valid 222000z - 231200z 


..there is a slight risk of severe thunderstorms across portions of 
the central/eastern Gulf Coast... 


..there is a marginal risk of severe thunderstorms across portions 
of the southeast... 


... 
Isolated severe thunderstorms, capable of damaging winds and a few 
tornadoes, are possible across parts of Alabama, the Florida 
Panhandle, and southwest Georgia into this evening. 


... 
Recent single-radar and mrms data have displayed an organizational 
uptick in shallow supercellular activity across the region. In fact, 
a tornadic debris signature was recently observed with a cell over 
Crenshaw co, al, suggesting some increase in tornado potential is 
being realized this afternoon. Kevx data display a wind profile 
favorable for the sustenance of low-level mesocyclones, and 
boundary-layer moisture is certainly adequate for tornadogenesis 
with these isolated cells, as well as new development moving onshore 
from the northern Gulf. Therefore, a slight risk has been introduced 
from southeast Alabama to southwest Georgia and the Florida 
Panhandle. 


.Picca.. 04/22/2018 


Previous discussion... /issued 1111 am CDT sun Apr 22 2018/ 


..central Gulf Coast... 
Water vapor imagery shows a well-defined shortwave trough rotating 
eastward across la. A surface low associated with this feature will 
occlude and lift northward across MS today. Widespread clouds and 
precipitation in the warm sector of the low will limit 
destabilization and the resultant overall severe threat. Therefore, 
will maintain the ongoing marginal risk category. However, local VAD 
profiles and forecast soundings show substantial low-level vertical 
shear over the central Gulf Coast states. Radar signatures this 
morning have shown occasional rotating cells over southeast la, and 
this general trend may continue through the day. Isolated cells 
will be capable of brief tornadoes or locally gusty/damaging wind 
gusts throughout the day, but the isolated and brief nature of the 
threat does not warrant an upgrade at this time. 


$$ 

Mesoscale Discussion


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acus11 kwns 222059 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 222058 
alz000-msz000-222330- 


Mesoscale discussion 0283 
National Weather Service Storm Prediction Center Norman OK 
0358 PM CDT sun Apr 22 2018 


Areas affected...west-central Alabama 


Concerning...severe potential...watch unlikely 


Valid 222058z - 222330z 


Probability of watch issuance...20 percent 


Summary...a marginal tornado threat and a few strong wind gusts will 
be possible across parts of west-central Alabama late this 
afternoon. The threat is expected to remain localized and weather 
watch issuance appears unlikely. 


Discussion...the latest surface analysis shows a deepening 1008 mb 
low across eastern Mississippi. Winds are backed at the surface to 
the east of the surface low across most of Alabama. A moist airmass 
extends northward into central Alabama where surface dewpoints are 
in the mid to upper 60s f. Although little surface heating has taken 
place in central Alabama, the rap suggests that weak instability is 
present. This combined with strong large-scale ascent associated 
with a shortwave trough evident on water vapor imagery, will support 
surface-based thunderstorm development over the next couple of 
hours. The WSR-88D vwp at Birmingham shows a looped hodograph with 
0-6 km shear at 55 kt and 0-1 km shear near 40 kt. This should be 
sufficient for storm rotation within the stronger discrete cells. As 
a result, a marginal tornado threat will be possible late this 
afternoon. A few strong wind gusts may also occur. 


.Broyles/Hart.. 04/22/2018 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...bmx...mob...Jan... 


Latitude...Lon 33978773 33918712 33268644 32458645 31948672 31678738 
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