U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 171232 
Storm Prediction Center ac 171230 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0630 am CST Mon Dec 17 2018 

Valid 171300z - 181200z 

..no severe thunderstorm areas forecast... 

severe thunderstorms are not forecast across the contiguous United 
States today and tonight. 


A dry, stable airmass remains in place across most areas east of the 
Rocky Mountains. This airmass will act to limit thunderstorm 
potential through Tuesday morning. West of the Rocky Mountains, a 
lightning strike or two will be possible across interior portions of 
central/Southern California as ascent associated with a strong 
mid-level trough progresses through the area and supports scattered 
weak convection. Late Monday into Tuesday morning, a few lightning 
strikes may also occur along coastal areas of the Pacific northwest 
as the exit region of a mid-level jet, associated with the next 
mid-level trough, approaches the region. 

.Marsh.. 12/17/2018 


Mesoscale Discussion

acus11 kwns 170704 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 170703 

Mesoscale discussion 1714 
National Weather Service Storm Prediction Center Norman OK 
0103 am CST Mon Dec 17 2018 

Areas affected...southern and eastern Maine 

Concerning...winter mixed precipitation 

Valid 170703z - 171300z 

Summary...snow, perhaps mixed with freezing rain or sleet, will 
remain possible through the overnight hours. 

Discussion...frontogenesis in the 850-700-millibar layer within the 
warm-conveyor belt has resulted in a band of heavy precipitation 
along the southeast coast of Maine. This band will continue to pivot 
northwest through the overnight hours. In the vicinity of this band, 
surface temperatures have fallen below 32f, despite rap forecasts 
suggesting temperatures would remain near or above 32f. Modifying 
the rap soundings for the observed colder surface temperatures, wet 
snow is likely, but given the strength of the warm-air advection 
within the warm-conveyor belt, temperatures within the 
850-700-millibar layer may approach, or even exceed, 0c. As such, 
precipitation may mix with, or change to, freezing rain or sleet 

.Marsh/Goss.. 12/17/2018 

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


Latitude...Lon 44197086 45246936 45826711 44936676 44246739 43256962 
43007082 44197086