U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 240449 
Storm Prediction Center ac 240448 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1148 PM CDT sun Apr 23 2017 

Valid 241200z - 251200z 

..there is a marginal risk of severe thunderstorms across the 
Carolina coastal plain... 

Thunderstorms accompanied by at least some severe weather potential 
will impact the Carolina coastal plain and portions of the adjacent 


24/00z model guidance is in good agreement regarding the progression 
of upper low from central Georgia to just south of ilm at daybreak 
Tuesday morning. This low-latitude feature will induce forcing for 
ascent across the coastal plain and adjacent coastal waters such 
that widespread convection is expected within a focused warm 
advection zone much of the period. 

Early this morning, a fairly organized squall line is advancing 
across SC and this activity should overturn much of the instability 
that currently resides across the coastal plain. However, exit 
region of 500mb speed Max will spread across Georgia into SC early in the 
period and renewed thunderstorm development is expected along a 
reinforced warm front that should struggle to advance inland due to 
aforementioned widespread precipitation. Given the extensive 
convection expected across this region it appears buoyancy will be 
limited with primary storm Mode being thunderstorm clusters. Even 
so, strengthening shear profiles favor some organization and perhaps 
a few embedded supercell structures. For these reasons will 
maintain marginal risk for damaging winds/hail and perhaps an isolated 
tornado. Severe threat will gradually shift toward the NC coast 
during the latter half of the period where both the NAM and GFS 
allow moisture/instability to return to this portion of NC within a 
zone of focused warm advection. 

.Darrow/leitman.. 04/24/2017 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 240232 

Mesoscale discussion 0552 
National Weather Service Storm Prediction Center Norman OK 
0932 PM CDT sun Apr 23 2017 

Areas affected...southeast Georgia...central/eastern SC 

Concerning...severe potential...watch unlikely 

Valid 240232z - 240500z 

Probability of watch issuance...20 percent 

Summary...thunderstorms are expected to persist into late tonight, 
especially across portions of South Carolina. The strongest cells 
will be capable of locally damaging wind and perhaps a tornado or 
two. Watch issuance is considered unlikely at this time. 

Discussion...thunderstorms have recently increased in coverage and 
intensity across portions of eastern Georgia into west-central SC. This 
increase occurred in conjunction with a collision of the 
westward-moving sea breeze and an eastward-moving outflow boundary 
emanating from earlier convection over Georgia. The resulting composite 
boundary extends southward from a weak surface low over eastern GA, 
with another nearly-stationary boundary extending eastward from the 
low across central SC. 

A few cells have exhibited weak rotation across portions of 
west-central SC in Aiken and Barnwell counties, though these are 
likely slightly elevated and up to now have not appeared to pose an 
appreciable severe risk. Cells further south have shown less 
organization, but as they advance eastward into a somewhat more 
unstable airmass across the coastal plain of SC, some increase in 
intensity is possible with a risk of locally damaging wind in the 
short term. 

Later this evening, a modest increase in the low-level jet is 
anticipated in response to a well-defined upper low that will move 
slowly east-southeastward into Georgia. As this occurs, cells that are 
able to interact with the frontal boundary (which may move slowly 
northward as a warm front with time) may pose a threat of a brief 
tornado or two, though widespread convection and relatively weak 
deep-layer shear will likely keep the severe threat relatively 
limited. While a low-end severe threat will exist for much of the 
night, the magnitude of the threat at any particular location and 
time is currently expected to remain too limited for watch issuance. 

.Dean/guyer.. 04/24/2017 

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


Latitude...Lon 32718163 33238157 33728142 34058052 33997956 33827892 
33227913 32787973 32368044 31878113 31948167 32278171