U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190044 
Storm Prediction Center ac 190043 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0643 PM CST Tue Dec 18 2018 

Valid 190100z - 191200z 

..no severe thunderstorm areas forecast... 

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

A vigorous mid-level low/shortwave trough over the Permian Basin 
will move east across much of Texas tonight. A low chance for a few 
thunderstorms is forecast initially over the Edwards Plateau and 
subsequently farther east over east-central Texas later tonight. 
Isolated thunderstorms are possible through at least the late 
evening hours over western Washington south to near the Columbia River. 
Rising mid-level heights later tonight will correspond to 
diminishing convective activity over the Pacific northwest by early 
Wednesday morning. Elsewhere, quiescent conditions will prevail. 

.Smith.. 12/19/2018 


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