U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 231619 
Storm Prediction Center ac 231617 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1117 am CDT Mon Apr 23 2018 

Valid 231630z - 241200z 

..there is a marginal risk of severe thunderstorms over parts of 
Georgia and South Carolina... 

..there is a marginal risk of severe thunderstorms over parts of 
southeast Wyoming...northeast Colorado...and the Nebraska 

A few strong to severe storms are possible across parts of Georgia 
and South Carolina, and over the Central High plains. 

A persistent upper low is centered over west TN, with 
west-southwesterly mid level winds across the southeast states. The 
primary occluded surface low is beneath the upper low, with an 
occluded front extending southeastward into Georgia. The primary region 
of concern for a few strong/severe storms today will be in vicinity 
of a warm front extending from its intersection with the occluded 
boundary into SC. 

Visible satellite imagery shows breaks in the clouds along and south 
of the warm front, where dewpoints in the mid 60s will yield 
afternoon MLCAPE values around 1000 j/kg. This should result in 
scattered thunderstorm development this afternoon. Forecast 
soundings suggest that mid-level lapse rates will be rather weak, 
limiting updraft strength and overall severe threat. However, 
sufficient deep layer shear will promote organized storm structures 
capable of hail and/or gusty winds. This threat should diminish a 
few hours after sunset. 

The strongest low-level shear profiles will be in vicinity of the 
warm front over central/eastern SC. Storms in this area would also 
have some potential for isolated/brief tornadoes. Current 
indications are that the overall setup is sufficiently covered by 
the ongoing marginal risk category. 

Water vapor loop shows a progressive shortwave trough moving into 
western Wyoming. Lift associated with this feature will begin affecting 
eastern Wyoming and northern Colorado this afternoon. Surface dewpoints will 
only be in the upper 30s to lower 40s. However, strong heating will 
combine with very steep lapse rates to yield just enough cape for 
thunderstorms later today. Cold temperatures aloft and favorable 
effective shear suggest a few rotating storms or bowing structures 
capable of hail and/or gusty winds. 

.Hart/grams.. 04/23/2018 


Mesoscale Discussion

acus11 kwns 231509 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 231509 

Mesoscale discussion 0285 
National Weather Service Storm Prediction Center Norman OK 
1009 am CDT Mon Apr 23 2018 

Areas affected...parts of coastal South Carolina 

Concerning...severe potential...watch unlikely 

Valid 231509z - 231715z 

Probability of watch issuance...5 percent 

Summary...locally gusty winds and perhaps a brief tornado are 
possible along parts of the South Carolina coast this morning. 

Discussion...radar data this morning depict a likely mesoscale convective vortex lifting 
north across the Savannah, Georgia area. Warm advection/low-level 
confluence attendant to this mesoscale convective vortex is focusing a band of convection 
that extends to the southeast offshore the coast. As the primary 
warm front remains farther south, onshore surface temperatures/dew 
points are only in the lower/mid 60s across coastal South Carolina, 
resulting in meager surface-based buoyancy. Still, a few stronger 
gusts have been reported recently near the Georgia/SC border, likely 
aided by weak low-level rotation in these cells lifting northeast. 
Kclx vwp data show notable veering of winds with height, favorable 
for continued weak rotation. In turn, localized strong, damaging 
gusts and perhaps even a brief tornado may be possible near the 
coast into early afternoon. 

.Picca/Hart.. 04/23/2018 

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


Latitude...Lon 32208132 32908033 33157998 33147970 32937949 32657966 
32288028 31828089 31788118 31938130 32208132