U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

000 
acus02 kwns 210532 
swody2 
Storm Prediction Center ac 210531 


Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1231 am CDT Sat Apr 21 2018 


Valid 221200z - 231200z 


..there is a marginal risk of severe thunderstorms across southeast 
la...much of MS...southwest/southern Alabama...and Florida Panhandle... 


... 
Isolated severe thunderstorms are possible across portions of the 
southeast states and Florida Panhandle. 


... 
Upper low, centered over eastern OK at the beginning of the period, 
is expected to move gradually southeastward, reaching northern Alabama by 
the end of the period. Associated surface low will take a similar 
track with the overall system becoming increasingly vertically 
stacked throughout the day. Widespread showers and thunderstorms are 
anticipated across the Tennessee Valley, southeast states, and Florida as the 
system moves eastward. 


..eastern la into Florida Panhandle/Big Bend... 
Widespread showers and thunderstorms will likely be ongoing at the 
beginning of the period across portions of the lower MS valley and 
mid-south. This activity may impede the moisture return across the 
southeast states. Current expectation is for modest moisture 
advection (i.E. Dewpoints in the low 60s) to occur ahead of the 
surface low (and attendant surface trough) across much of MS and Alabama 
but the better moisture (i.E. Dewpoints in the upper 60s) will 
remain confined to the coastal areas. Strong low-level jet 
accompanying the cyclone will support widespread elevated 
thunderstorms north of the warm front and ahead of the surface low. 


Greater likelihood for surface-based convection is expected along 
the surface trough as it moves across southern MS/Alabama and Florida 
Panhandle. Instability will be limited but strong wind field may 
support occasional updrafts organized enough to produce isolated 
damaging wind gusts and perhaps a tornado or two. Farther northwest 
(in central ms), clearing between the surface trough and cold front 
may result in enough insolation for destabilization and another 
round of thunderstorms. Limited low-level moisture is anticipated 
across the region but cold temperatures aloft (associated with the 
approaching upper low) will still support modest instability. 
Additionally, generally weak low-level wind fields are expected but 
mid-level flow will still be strong enough to support enough bulk 
shear for transient storm organization. Marginal severe 
probabilities were extended back northwestward to account for this 
scenario. Overall severe potential remains too low for anything but 
marginal severe probabilities. 


.Mosier.. 04/21/2018 


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