U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 101258 
Storm Prediction Center ac 101257 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0757 am CDT Sat Oct 10 2015 

Valid 101300z - 111200z 

..no severe thunderstorm areas forecast... 

organized severe storms are not expected over the contiguous United 
States. A few storms may produce gusty winds or small hail over 
parts of South Carolina and Georgia this afternoon. 

Upper-air pattern in and near Continental U.S. This period will be dominated by 
three primary perturbations.. 
1. Lead shortwave trough -- now amplifying and pivoting eastward with 
middle/upper-level vorticity center apparent in moisture-channel 
imagery near cha. Associated 500-mb low is forming at this time and should 
shift east-southeastward across northestern Georgia and western/central SC today...before 
decelerating over SC coastal plain in 06z-12z time frame. 
2. Upstream strong shortwave trough -- located 450-500 nm off Washington/Oregon 
coast at this time and forecast to move ashore during 00z-06z time segment. 
Associated large-scale ascent/cooling aloft is supporting widely 
scattered glaciated convection over Pacific at this time...and destabilization 
aloft should be maintained eastward to coastal areas in support of 
potential for at least a few lightning strikes this evening shortly before 
trough moves inland. 
3. Cut-off cyclone west of Baja California will continue to retrograde...moving 
westward across Pacific waters and only exerting very weak/peripheral 
convective influence near Arizona/mex border. 

At surface...cold front was analyzed at 11z from Atlantic waters well southeast of 
Cape Cod southwestward across NC Outer Banks...through frontal-wave low 
collocated with ongoing convection over central/southwestern SC...to southern 
portions MS/al. Front should move or redevelop offshore through 
period as second low develops over Atlantic waters offshore Georgia/northern Florida. 
By end of period...front should extend from Atlantic low well east of chs 
southwestward across northern Florida to northestern Gulf. 

..sern Continental U.S.... 
band of non-severe thunderstorms is ongoing close to surface low and cold front 
over northern/central SC southwestward to southern Georgia. This activity should proceed 
eastward across SC/Georgia coastal plain next few hours. Break in 
clouds...apparent in infrared imagery between anvil shield of this 
convection and cirrus plume near/off coast...may allow brief/weak 
diurnal heating this morning prior to arrival of 
convection...however organization should remain poor due to weak 
shear and lack of more robust lapse rates. Short-fused/ 
convection-permitting NCEP and esrl hrrr guidance from past few 
hours has been too slow and intense with this activity...which is 
moving into rich moisture but also poor 700-500-mb lapse rates as 
sampled by chs radiosonde observation. 

Additional...widely scattered to scattered thunderstorms should develop 
later today behind morning convection as cold-core/DCVA region of 
midlevel low approaches...and residual moisture becomes overlain by weak 
cinh and cooling temperatures aloft. A few strong thunderstorms with gusty winds or 
small hail may occur. However...amount of destabilization in low 
levels is in doubt following overturning by morning convection...and 
great majority of this second-stage convective regime should remain 
behind surface cold front. Modified forecast soundings suggest that pockets 
of sustained diabatic heating even behind front and/or behind 
morning activity could render surface-based effective inflow for some 
parts of eastern GA/SC. Severe potential at this time appears too small and 
conditional to draw specific categorical area. 

.Edwards/Cook.. 10/10/2015 


Mesoscale Discussion

acus11 kwns 092340 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 092340 

Mesoscale discussion 1850 
National Weather Service Storm Prediction Center Norman OK 
0640 PM CDT Friday Oct 09 2015 

Areas affected...eastern Virginia...Delaware-Maryland-Virginia peninsula 

Concerning...Severe Thunderstorm Watch 513... 

Valid 092340z - 100115z 

The severe weather threat for Severe Thunderstorm Watch 513 

Summary...although locally strong surface gusts may continue to 
accompany a southward advancing squall line across the Chesapeake 
Bay/Delaware-Maryland-Virginia peninsula region another couple of hours...the need for 
an additional severe weather watch is not currently anticipated. 

Discussion...an elongated narrow pre-frontal squall line continues 
to advance southeastward across/east of southern New England and 
northern middle Atlantic coastal areas. A segment of this line to the 
southwest of Severe Thunderstorm Watch 513...now advancing southeast 
of the Baltimore/Washington D.C. Area...probably will continue to 
impact parts of the eastern Virginia and southern 
Chesapeake/Delaware-Maryland-Virginia peninsula region through the 02-04z time frame. 
The environment across this region appears at least weakly 
unstable...and sheared westerly deep layer mean flow only appears to 
drop off from around 40 knots near the Maryland Pennsylvania border to 
around 35 knots across southern Virginia. However...there is little 
evidence to suggest support for appreciable further intensification 
of storms...particularly with boundary layer cooling now well 
underway. Although gusty surface winds may continue to accompany 
the passage of the squall line...potential for severe wind gusts 
currently seems rather limited. 

.Kerr.. 10/09/2015 

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


Latitude...Lon 37597525 37277597 37357677 37787779 38007745 38487639 
38917487 39047421 37597525