U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 111923 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0123 PM CST Mon Dec 11 2017 

Valid 112000z - 121200z 

..no thunderstorm areas forecast... 

no thunderstorm areas are expected today or tonight. 

No changes were made to the previous outlook. 

.Bunting.. 12/11/2017 

Previous discussion... /issued 1010 am CST Mon Dec 11 2017/ 

Dry and stable conditions are expected to preclude thunderstorm 
activity across the nation today. 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 110155 

Mesoscale discussion 1794 
National Weather Service Storm Prediction Center Norman OK 
0755 PM CST sun Dec 10 2017 

Areas affected...Lee of Lake Erie and Lake Ontario 

Concerning...heavy snow 

Valid 110155z - 110700z 

Summary...persistent lake effect snow bands extending west-northwest 
from Lake Erie and Lake Ontario will persist into the overnight. 
Highest snowfall rates from these bands are peaking now (locally in 
excess of 2 inches per hour) and should begin to weaken later 

Discussion...lake effect snow bands have persisted through the 
afternoon across portions of Erie, Wyoming, Genesee, and Orleans 
counties in western New York and Jefferson, Oswego, Lewis, and 
Herkimer counties across northern New York. Observations suggest 
that these bands have intensified over the last few hours and are 
producing snowfall rates in excess of 2" per hour, with locally 
higher rates likely. Given water temperatures in the mid 30s f, 850 
millibar temperatures of -9.5 c (per 00z buf sounding), and westerly 
low-level flow around 35 knots, these lake effect snow bands will 
continue for the next 4-6 hours. In the 06-08z time frame, a surface 
cold front should move through the area resulting in low-level flow 
veering. As such, lake effect snow bands will shift south and west, 
with an overall weakening trend given the shorter fetch over the 

.Marsh/Broyles.. 12/11/2017 

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


Latitude...Lon 42367850 42177920 42277964 42487972 42897950 43427808 
43857711 44347498 44057430 43657452 43457521 43227635 
42847730 42367850