U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 180519 
Storm Prediction Center ac 180517 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1117 PM CST sun Feb 17 2019 

Valid 181200z - 191200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms are possible over the Great Basin this 
afternoon. Scattered thunderstorms are expected to develop from East 
Texas into the lower Mississippi Valley tonight. 

..Great Basin... 

Another in a series of vorticity maxima rotating through the broad 
upper trough will move through the 4 corners region near peak 
heating this afternoon. With cold temperatures aloft and steep 
mid-level lapse rates in place, heating of the boundary layer will 
boost MLCAPE to 200-300 j/kg. This destabilization along with 
forcing for ascent accompanying the vorticity maximum should result 
in an increase in convection, with scattered showers likely today as 
well as isolated thunderstorms by mid-late afternoon, continuing 
into early evening. 

..East Texas through the lower Mississippi Valley... 

A large area of surface high pressure will build eastward through 
the Great Lakes and Ohio Valley maintaining offshore flow over the 
Gulf. However, a cold front now moving through the western Gulf will 
likely stall and then move northward as a warm front late this 
period, approaching the la coast by 12z Tuesday. A southerly 
low-level jet is forecast to strengthen from the western Gulf into 
East Texas and the lower MS valley augmenting Theta-E advection above 
the stable surface layer north of the warm front. This will result 
in a corridor of elevated instability overnight with 1000-1500 j/kg 
MUCAPE. Scattered thunderstorms will likely develop within this zone 
of destabilization and isentropic ascent late. Despite the elevated 
nature of the convection, effective bulk shear will be sufficient 
for a few updrafts to acquire modest rotation, which combined with 
moderate instability suggests a few instances of hail cannot be 
ruled out. However, mid-level lapse rates below 7 c/km should 
mitigate overall threat. 

.Dial/squitieri.. 02/18/2019 


Mesoscale Discussion

acus11 kwns 180727 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 180727 

Mesoscale discussion 0107 
National Weather Service Storm Prediction Center Norman OK 
0127 am CST Mon Feb 18 2019 

Areas affected...northern New Jersey...lower Hudson Valley...Long 
Island...much of CT 

Concerning...winter mixed precipitation 

Valid 180727z - 181130z 

Summary...mixed winter precipitation is expected to continue from 
northern New Jersey across the lower Hudson Valley and into CT for the next 
few hours. 

Discussion...recent regional radar imagery has shown a modest 
increase in precipitation intensity across the region. Observations 
continue to show a transition zone from rain to freezing rain to 
snow extending from northern New Jersey across the lower Hudson Valley and 
into eastern CT. Expectation is for light to moderate precipitation 
to persist across this region for the next few hours as 
southwesterly flow aloft continues to support warm-air advection. 

Those areas currently experiencing rain (i.E. Long island) and 
freezing rain (i.E. Northern New Jersey and lower Hudson valley) will likely 
continue to experience those precipitation types as surface 
temperatures remain steady and low to mid-level temperatures 
increase slightly. Areas experiencing snow will likely see a 
transition towards more mixed precipitation as mid-level 
temperatures continue to gradually warm but surface temperatures 
remain unchanged. Freezing rain rates around 0.02"-0.05" per hour 
are possible. 

.Mosier.. 02/18/2019 

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


Latitude...Lon 41647416 41747379 41827331 41887250 41757201 41597176 
41357168 41047203 40677327 40587404 40567444 40587468 
40647490 40797508 41057502 41267483 41647416