U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 240049 
Storm Prediction Center ac 240048 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0748 PM CDT sun Apr 23 2017 

Valid 240100z - 241200z 

..there is a slight risk of severe thunderstorms centered over 

..there is a marginal risk of severe thunderstorms from portions of 
southern Georgia to extreme southern NC... 

Strong thunderstorms may still impact parts of Georgia and the 
Carolinas tonight, accompanied by at least some risk for severe 
weather. This includes a possibility for a couple of tornadoes near 
a frontal zone across the Piedmont and coastal plain of South 


Early evening water vapor imagery depicts the center of a pronounced 
upper low over the northwestern tip of Alabama in line with latest 
short-range model guidance. This feature will dig into Georgia late 
tonight as strongest flow aloft has yet to round the base of the 
trough. 00z soundings from jax and chs depict modest mid-level 
lapse rates/deep-layer shear and ongoing convection supports this 
being somewhat disorganized and not particularly strong. As the 
trough approaches Georgia/SC late tonight, shear profiles should increase 
such that organized sustained updrafts will be more likely, 
especially within stronger low-level warm advection where low level jet is 
focused. Will maintain slight risk for severe storms centered over SC 
where a few tornadoes may develop if sustained supercells evolve. 

.Darrow.. 04/24/2017 


Mesoscale Discussion

acus11 kwns 231825 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 231824 

Mesoscale discussion 0551 
National Weather Service Storm Prediction Center Norman OK 
0124 PM CDT sun Apr 23 2017 

Areas affected...portions of SC and far east-central Georgia 

Concerning...severe potential...watch unlikely 

Valid 231824z - 232100z 

Probability of watch issuance...20 percent 

Summary...an isolated strong/gusty wind and perhaps brief tornado 
threat may exist this afternoon with thunderstorms developing along 
a front. Watch issuance is unlikely in the short term. 

Discussion...a stalled front is draped east-west across SC into far 
east-central Georgia as of 18z per recent visible satellite imagery and 
surface observations. Although large-scale ascent associated with an 
upper low over Tennessee remains displaced to the west, low-level 
convergence along the front has proven sufficient for the initiation 
of isolated showers and thunderstorms in SC over the past hour or 
so. The airmass along and south of the boundary is weakly unstable 
(mlcape up to 750 j/kg), with surface temperatures generally in the 
low to mid 80s and dewpoints in the low to mid 60s. Mid-level lapse 
rates remain poor across this region, around 6 c/km. 

Both low and mid-level flow are generally modest (30 kt or less), 
although strongly backed winds in the 0-1 km layer along and just 
north of the front are contributing to 0-1 km srh around 200-250 
m2/s2 per recent vwps from kcae. A veering wind profile with height 
is supporting 30-35 kt of effective bulk shear, locally higher right 
along the front. The combination of weak instability and shear along 
may allow for some updraft organization with the strongest storms, 
and isolated instances of strong/gusty winds may occur. In addition, 
a brief tornado cannot be ruled out with any storm which crosses the 
boundary and encounters greater effective srh along/just north of 
the front. The overall severe weather threat is expected to remain 
isolated through the afternoon, and watch issuance is unlikely. 

.Gleason/Weiss.. 04/23/2017 

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


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