Convective Outlook

U.S. Severe Weather Forecast

acus01 kwns 221612 
Storm Prediction Center ac 221611 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1111 am CDT sun Apr 22 2018 

Valid 221630z - 231200z 

..there is a marginal risk of severe thunderstorms over much of the 
central Gulf Coast states... 

Isolated severe thunderstorms are possible across much of 
Mississippi and Alabama, and from southeastern Louisiana eastward to 
the Florida Panhandle. 

..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. 

.Hart/guyer.. 04/22/2018 


Mesoscale Discussion

acus11 kwns 221537 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 221537 

Mesoscale discussion 0281 
National Weather Service Storm Prediction Center Norman OK 
1037 am CDT sun Apr 22 2018 

Areas affected...southeast Louisiana...southern 
Mississippi...southwest Alabama...far western Florida Panhandle 

Concerning...severe unlikely 

Valid 221537z - 221800z 

Probability of watch issuance...20 percent 

Summary...a marginal tornado and wind damage threat will persist 
into the early afternoon across parts of southeast Louisiana, 
southern Mississippi. The threats will likely affect southwest 
Alabama and the far western Florida Panhandle later today. No 
weather watch is expected due to the marginal setup. 

Discussion...the latest surface analysis shows a 1011 mb low over 
southeast Louisiana with a warm front extending eastward across 
south-central Mississippi. A moist airmass was located south of the 
front with surface dewpoints in the mid to upper 60s f. Water vapor 
imagery showed a shortwave trough over the lower Mississippi Valley. 
Large-scale ascent associated with this feature will continue to 
support thunderstorm development along the warm front into the 
afternoon where a marginal wind damage threat will persist. 

Further south across far southern Mississippi and southeast 
Louisiana, surface dewpoints are near 70 f and instability is 
considerably stronger. The rap suggests that SBCAPE is estimated to 
be near 1000 j/kg right along the Mississippi coast. The Mobile 
WSR-88D vwp does show enough speed and directional shear in the 
lowest 2 km above ground level for a marginal tornado threat. However, due to 
widespread clouds and precipitation ahead of the activity, most of 
the instability is offshore suggesting that any tornado threat will 
remain marginal. 

.Broyles/Hart.. 04/22/2018 

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


Latitude...Lon 32228846 31898933 31658983 31339026 31009034 30769035 
30079004 29338980 29108918 29878854 30398728 32108749 

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