U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 171942 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0142 PM CST Thu Jan 17 2019 

Valid 172000z - 181200z 

..there is a marginal risk of severe thunderstorms across portions 
of the Great Basin... 

Strong to isolated severe wind gusts will be possible with isolated 
thunderstorms across parts of eastern Nevada into western Utah 
during the late afternoon and early evening. 

Current forecast reasoning is well-described within the prior 
outlook; with clearing/modest heating ongoing across Nevada, and 
spreading into western Utah at this time, limited risk for 
gusty/damaging winds locally remains evident. 

.Goss.. 01/17/2019 

Previous discussion... /issued 1029 am CST Thu Jan 17 2019/ 

..eastern Nevada and western Utah... 
Guidance differs greatly with the degree and eastern extent of 
boundary-layer heating with the NAM substantially cooler than the 
rap, given a pervasive swath of ongoing cloudiness. However, 
mid-level drying yielding clearing is evident in satellite imagery 
across western Nevada and this should shift eastward into the afternoon. 
In conjunction with mid-level cold-air advection, the setup should 
Foster increasing destabilization during the afternoon via delayed 
boundary-layer heating and lapse rates aloft becoming very steep. 

Mid-level DCVA associated with the portion of the shortwave trough 
shifting from northern California into the Great Basin and convergence along 
a cold front should yield a broken band of showers with embedded 
thunderstorms by late afternoon from the Nevada/UT/ID border area 
south-southwest into east-central Nevada. 30-40 kt effective shear could 
support modestly organized convective structures. Where inverted-v 
thermodynamic profiles can develop, strong to isolated severe wind 
gusts may occur as activity spreads east before waning this evening. 


Mesoscale Discussion

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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