U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 210519 
Storm Prediction Center ac 210518 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1118 PM CST Wed Feb 20 2019 

Valid 211200z - 221200z 

..no severe thunderstorm areas forecast... 

scattered thunderstorms are possible across the southeast and 
southern mid-Atlantic states today but the risk of severe 
thunderstorms appears negligible. 

Upper pattern is expected to amplify today as the low currently 
centered over the upper Midwest ejects northeastward and the 
shortwave trough currently off the Pacific northwest coast digs 
southward along the West Coast. By 00z, a deep upper trough will be 
in place west of The Rockies with an embedded low centered over the 
Southern California/Nevada border and a long and broad fetch of southwesterly 
flow extending from southern Arizona. 

..East Texas...Southeast...southern mid-Atlantic... 
a stalled front will likely extend from the central Alabama/Georgia border 
southwestward to the central la coast and into the western Gulf of 
Mexico at the beginning of the period. Strengthening low-level flow 
and resulting isentropic ascent within this frontal zone will 
promote elevated thunderstorm development from East Texas into northern 
al, with thunderstorms likely ongoing early this morning and 
continuing through the evening. Limited instability should temper 
updraft strength, keeping the severe probability low, despite 
favorable shear. 

Additional thunderstorm development is possible farther east (i.E. 
Across southern Alabama and central/southern ga) amidst modest moisture 
advection and low-level confluence. Expectation is for most of these 
storms to be elevated, although reduction of surface-based 
convective inhibition by moisture advection may allow for isolated 
surface-based updrafts. Storm interaction with the stalled front may 
also allow for brief updraft augmentation. Even so, this region is 
displaced east of the stronger mid- and low-level winds, limiting 
vertical shear and the potential for updraft rotation/organization. 

.Mosier/Bentley.. 02/21/2019 


Mesoscale Discussion

acus11 kwns 210315 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 210315 

Mesoscale discussion 0118 
National Weather Service Storm Prediction Center Norman OK 
0915 PM CST Wed Feb 20 2019 

Areas affected...parts of PA/NY/NJ into New England 

Concerning...winter mixed precipitation 

Valid 210315z - 210815z 

Summary...a large area of wintry precipitation -- with mainly snow 
across far northeast NY, much of New Hampshire and VT, and most of ME, and 
transitioning to mainly freezing rain south of this area -- is 
expected to spread across the discussion area overnight. 

Discussion...a widespread band of primarily freezing rain continues 
to shift quickly eastward across central New York/eastern PA, where ice 
accumulation continues. This area of precipitation will spread into 
-- and across -- New England overnight, moving off the southern New 
England coast and diminishing over Maine beginning prior to sunrise. 

At this time, temperatures remain in the low to mid 20s across most 
of eastern New York and southern New England, and in the teens to low 20s 
over much of VT/NH/ME. Gradual warming in the 900 to 700 mb layer 
will continue as low-level warm advection increases and secondary 
surface low pressure develops offshore. 

This increasing warm advection should allow a transition from 
freezing rain to rain to occur across coastal southern New England 
overnight, and likewise a transition from light snow to freezing 
rain over the remainder of southern New England. Indeed, this 
transition from snow to freezing rain is already observed at some 
locales, and this trend will continue over the next few hours as 
warm advection above a shallow/cold boundary layer increases. 

The precipitation area is relatively fast-moving -- owing to the 
fast westerly flow aloft -- and as such, overall snowfall 
accumulations will be limited despite rates of 1" per hour briefly 
possible in a few areas. Meanwhile, freezing rain accumulations of 
over 0.05" to .10" per hour will occur for a couple of hours in some 
locations, potentially resulting in hazardous Road conditions in 
some areas overnight. 

.Goss.. 02/21/2019 

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


Latitude...Lon 41657170 41317340 40707456 40607590 40937692 41747730 
43107713 43907563 44667360 45097032 44546951 42787108 
41817083 41657170