U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 211247 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0647 am CST Wed Nov 21 2018 

Valid 211300z - 221200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are possible today from coastal into central 
California, and across parts of southeast Texas. 

No changes to the previous outlook. A weak southern-stream 
shortwave trough will move eastward to the northwest Gulf Coast by 
tonight, in advance of a larger-scale trough that will progress 
inland over California. Steepening low-midlevel lapse rates with the California 
trough, as evidenced by the area of convection and isolated 
lightning strikes near 130 W, will support a threat for isolated 
thunderstorms from about midday into tonight. Along the Texas coast, a 
modifying low-level air mass and a low-level warm advection regime 
will contribute to weak destabilization atop a coastal front. A few 
elevated thunderstorms will be possible from this afternoon into 

.Thompson/Peters.. 11/21/2018 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 211409 

Mesoscale discussion 1653 
National Weather Service Storm Prediction Center Norman OK 
0809 am CST Wed Nov 21 2018 

Areas affected...northern New York into northern Vermont 

Concerning...heavy snow 

Valid 211409z - 211815z 

Summary...the potential exists for snow squalls, producing reduced 
visibilities and snowfall rates approaching 1 inch per hour, to 
develop this morning across northern New York as a cold front 
advances eastward, reaching northern Vermont toward 18z. 

Discussion...a deep, cold closed low will move across southern 
Quebec today, while an accompanying cyclonic flow regime persists 
through the northeast states. Strong 100-110+ kt mid-upper low jets 
will spread into central New York this morning and central/southern Vermont/New Hampshire 
by early afternoon. The discussion area favorable for snow squalls 
will remain on the cyclonic shear side of the 500-mb jet, while 
linear forcing along the cold front should also support an 
environment favorable for snow squalls as this boundary advances 
east. Reduced visibilities and higher snowfall rates will tend to 
be short-lived, limiting overall snow accumulation. 

.Peters.. 11/21/2018 

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


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