U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 141944 
Storm Prediction Center ac 141942 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0142 PM CST Thu Dec 14 2017 

Valid 142000z - 151200z 

..no thunderstorm areas forecast... 

thunderstorm areas are not forecast across the contiguous U.S. 

No changes to the ongoing forecast appear necessary this update. 
While a lightning strike has recently occurred just south of the 
U.S./Mexico border near the southwest corner of New Mexico, 
potential for thunder over adjacent areas of the Southern Plains the 
remainder of the period appears to low/sparse to add a 10% thunder 

.Goss.. 12/14/2017 

Previous discussion... /issued 1026 am CST Thu Dec 14 2017/ 

..synopsis and discussion... 
A shortwave trough over the southwest this morning will move 
southeastward towards the Southern Plains and merge with a nearly 
closed upper low now over Baja California by late tonight. At the 
surface, a reinforcing cold front will likewise develop 
southeastward across Texas today, and then off the Texas Gulf Coast 
tonight. Post-frontal precipitation will likely occur across deep 
south Texas and adjacent coastal waters late this evening into early 
Friday morning as large-scale ascent associated with the upper 
trough overspreads the Southern Plains. While meager low-level 
instability (mucape around 100-200 j/kg) may be present across this 
region, forecast soundings show very poor mid-level lapse rates, and 
the likelihood for charge separation and resultant isolated 
lightning strikes over land appears too low to include a general 
thunderstorm area. 


Mesoscale Discussion

acus11 kwns 120330 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 120330 

Mesoscale discussion 1795 
National Weather Service Storm Prediction Center Norman OK 
0930 PM CST Mon Dec 11 2017 

Areas affected...central New York 

Concerning...heavy snow 

Valid 120330z - 120930z 

Summary...snowfall rates will increase gradually through 06-09z, 
with peak rates likely to exceed 1 inch per hour from about 07-12z. 

Discussion...in association with a midlevel shortwave trough 
approaching the upper Ohio Valley, a deformation snow band has been 
developing eastward over Lake Erie. Low-midlevel warm 
advection/ascent in advance of the trough, as well as weak 
frontogenesis, will support additional eastward expansion of the 
snow band across central New York through the early morning hours. 
Top-down saturation of the column is just beginning across western 
into central NY, and snowfall rates will increase as column 
saturation develops eastward and forcing for ascent increases 
through the early morning hours. Peak snowfall rates should 
approach or exceed 1 inch per hour, and may persist for 3-6 hours at 
locations within the expected corridor of the snow band. 

.Thompson.. 12/12/2017 

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


Latitude...Lon 43217361 43007412 42747497 42497608 42457687 42517744 
42667771 43037760 43837544 44037419 43947361 43617347