U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 180053 
Storm Prediction Center ac 180052 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0652 PM CST Thu Jan 17 2019 

Valid 180100z - 181200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms will continue across parts of the Great Basin 
into the central rockies, and along the coast of Oregon and northern 
California, this evening and overnight. 

..01z update... 
The loss of daytime heating across eastern Nevada and western Utah will 
further reduce the already meager surface-based instability noted on 
the 00z sounding from Elko, Nevada. With the potential for strong to 
damaging wind gusts from ongoing convective showers and 
thunderstorms also lessening, have removed the marginal risk from 
this region. Isolated thunderstorms will continue to be possible 
across the eastern Great Basin into parts of the central rockies 
this evening and overnight as an upper trough moves over these 
areas. Very isolated lightning strikes may also occur mainly this 
evening along/near the coast of or and northern California. 

.Gleason.. 01/18/2019 


Mesoscale Discussion

acus11 kwns 130855 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 130854 

Mesoscale discussion 0019 
National Weather Service Storm Prediction Center Norman OK 
0254 am CST sun Jan 13 2019 

Areas affected...central Virginia and Maryland...including southern 
portions of the Washington D.C./Baltimore Metro area 

Concerning...heavy snow 

Valid 130854z - 131300z 

Summary...moderate to heavy snow now developing across parts of 
central Virginia and Maryland is expected to persist through mid to 
late morning, with rates (around or in excess of 1 inch per hour) 
likely maximizing in the 6-10 am EST time frame. 

Discussion...a broadly cyclonic 50-70+ kt 500 mb jet streak 
continues to gradually develop eastward across the northern Gulf 
Coast states, with its exit region now beginning to nose to the Lee 
of the southern Appalachians, toward the southern mid Atlantic coast 
through mid to late morning. It appears an associated broad area of 
strong upward vertical motion will include a period of strengthening 
lower/mid-tropospheric frontogenesis across Virginia and adjacent 
portions of the mid Atlantic. 

Across central Virginia into adjacent portions of central Maryland, 
where temperature profiles are expected to remain entirely below 
freezing, models indicate that lift may begin to become maximized 
within the favorable mixed-phase layer for dendritic ice Crystal 
growth by daybreak, and continue through mid to late morning. Aided 
by relatively high precipitable water content (up to around .70 
inches), one or more bands of heavy snow, at rates around or in 
excess of 1 inch per hour, appear possible. Forecast soundings 
suggest that this may persist for a 3-4 hour period at any 
particular location, generally in a narrow corridor from the 
vicinity of the Blue Ridge, north of Roanoke VA, east/northeastward 
through southern portions of the greater Washington D.C./Baltimore 
metropolitan area. 

.Kerr.. 01/13/2019 

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


Latitude...Lon 38287888 38517861 38657841 38977644 38497624 37937809 
37697891 37767939 38087930 38287888