U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 211624 
Storm Prediction Center ac 211622 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1022 am CST Thu Feb 21 2019 

Valid 211630z - 221200z 

..no severe thunderstorm areas forecast... 

widely scattered thunderstorms are possible across much of the deep 
south today and tonight. Isolated thunderstorms may also affect 
parts of Arizona and Southern California today. 

..deep south including East Texas to the Carolinas... 
A consolidating front will move slowly north/northwest through 
tonight toward the Texas coastal plain, across southern portions of 
la/MS, and across south-central Alabama. Showers and widely scattered 
thunderstorms are expected north of this front with warm/moist 
advection focused atop the sloping frontal zone. A sporadic instance 
of marginally severe hail cannot be conclusively ruled out across a 
broad corridor with MUCAPE exceeding 1000 j/kg in some cases; 
however, the overall potential for sustained/organized severe storms 
will likely remain low. 

Any prospects for near-surface-based convection will be confined to 
the immediate frontal corridor across southeast la and far southern 
MS into south-central portions of al/GA. While a conditionally 
supportive environment for a few strong/locally severe storms may 
materialize in this corridor this afternoon/early evening, the 
likelihood of near-boundary or warm sector convection will be 
limited by persistent cloud cover and weak forcing influences within 
the warm sector amidst gradually rising upper heights. 

..Arizona/Southern California... 
An increasingly low latitude upper trough will continue to 
amplify/dig southeastward over the southwest deserts toward Baja 
California and other parts of northwest Mexico. Related DCVA and the 
left-exit region of a cyclonically curved upper jet will coincide 
with steep lapse rates for the possibility of a few thunderstorms 
across Southern California as well as parts of Arizona. 

.Guyer/Broyles.. 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