U.S. Severe Weather Forecast (Konvektīvā prognoze)

Day Three

acus01 kwns 160547 
Storm Prediction Center ac 160545 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1145 PM CST Tue Jan 15 2019 

Valid 161200z - 171200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are likely late Wednesday across parts of 
northern and central California. Gusty winds may accompany this 


00z short-range model guidance is in general agreement that a strong 
short-wave trough will approach the northern California coast by 17/06z with 
substantial height falls expected to spread inland during the 
overnight hours. Large-scale forcing for ascent will likely 
encourage weak elevated convection ahead of the front during the 
early evening but this activity should struggle to attain heights 
necessary for lightning. However, significant mid-level cooling will 
aid destabilization as lapse rates steepen just ahead of a 
pronounced surface front that should move onshore around 06z. 
Forecast soundings along the northern California coast suggest near-surface 
based buoyancy will evolve along the front which will likely result 
in one or more strongly-forced bands of convection. Very strong 
southwesterly flow is forecast just off the surface and there is 
some concern strong winds may mix to the surface with the frontal 
convection. NAM forecast sounding at sfo at 17/06z exhibits SBCAPE 
on the order of 300 j/kg with 50kt southwesterly flow at 1k feet 
above ground level. At this time will not introduce marginal for gusty winds but if 
sufficient instability can materialize a few strong storms may be 
possible with the frontal convection. 

.Darrow/leitman.. 01/16/2019 


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