U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 161632 
Storm Prediction Center ac 161630 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1030 am CST Sat Feb 16 2019 

Valid 161630z - 171200z 

..no severe thunderstorm areas forecast... 

showers with occasional/embedded lightning will be possible from 
portions of Oregon and California into the Great Basin today. 
Showers and a few thunderstorms may also evolve late in the period 
over parts of the Tennessee Valley area. 

As an upper trough over the northeast pivots northeastward 
into/across the Canadian Maritimes, a second/large trough over the 
western states will gradually expand with time, with cyclonic flow 
to encompass the entire western and central U.S. By the end of the 

At the surface, a baroclinic zone will linger west-to-east from the 
southeast to the Southern Plains. A frontal wave is progged to 
shift eastward out of the Southern Plains and into the 
mid-Mississippi Valley region during the second half of the period, 
with warm advection ahead of the wave, and a cold air surge into the 
Southern Plains in its wake. 

Widespread showers, and occasional/embedded lightning in some areas, 
is expected across a large portion of the western U.S. Today, as 
cold air aloft/steep mid-level lapse rates reside across the area 
within the broadening upper trough. The greatest lightning risk 
appears to exist from portions of California and Oregon into the 
Great Basin. 

Late tonight, increasing low-level warm advection across the 
mid-Mississippi/Tennessee Valley region should result in elevated 
convective development, and possibly a few embedded thunderstorms. 

No severe weather is expected. 

.Goss.. 02/16/2019 


Mesoscale Discussion

acus11 kwns 141850 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 141850 

Mesoscale discussion 0104 
National Weather Service Storm Prediction Center Norman OK 
1250 PM CST Thu Feb 14 2019 

Areas affected...central California - particularly within the San 
Joaquin Valley 

Concerning...severe potential...watch unlikely 

Valid 141850z - 142045z 

Probability of watch issuance...5 percent 

Summary...isolated/briefly severe convection may occur through the 
afternoon across the discussion area. A ww issuance is currently 
not anticipated. 

Discussion...a band of relatively persistent convection has 
developed across portions of Calaveras and Tuolumne counties in 
California over the past hour. Within the pre-convective 
environment, sunshine has allowed for surface warming, with 60s f 
surface temperatures and mid 50s f dewpoints boosting MUCAPE values 
into the 500 j/kg range. Additionally, terrain-related backing of 
low-level flow beneath strong southwesterly mid-level winds aloft 
have boosted 0-3 km srh values to around 225 m2/s2 (based on latest 
VAD data at hnx). The cape/shear combination suggests some 
potential for convection in the discussion area to briefly rotate, 
which may result in a very isolated threat for wind damage and 
perhaps a brief tornado through at least 00z. This threat will be 
too localized/marginal for a ww issuance, although trends will 
continue to be monitored throughout the afternoon. 

.Cook/Hart.. 02/14/2019 

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


Latitude...Lon 37932104 38282090 38532041 38251990 37511934 37011918 
36891908 36511916 36281936 36241979 36412026 36832081 
37642108 37932104