U.S. Severe Weather Forecast (Convective Outlook)

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Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1125 PM CST Sat Dec 07 2019 


Valid 081200z - 091200z 


..no severe thunderstorm areas forecast... 


... 
scattered thunderstorms are expected on Sunday over parts of the 
southwestern states and isolated storms are possible late near the 
Carolina coast. 


..southwestern US... 


Strong upper trough, currently located along the Pacific coast, will 
dig southeast to a position from central Colorado - Southern California by 09/12z. 
As this occurs, strong 500mb jet will sag southeast and vertical 
profiles will cool substantially north of the jet. Latest model 
guidance allows a corridor of weak instability to develop as lapse 
rates steepen, especially during the day when some boundary-layer 
heating is expected. Forecast soundings suggest the 
strongest/deepest convection will attain heights necessary for 
lightning, and for these reasons will maintain at least 10% thunder 
probabilities across much of the southwestern US. 


... 


Weak short-wave trough is forecast to eject across the eastern Gulf 
states late in the period to near the NC coast by 09/12z. This 
feature should induce a surface trough off the Atlantic coast which 
may be drawn inland across eastern NC during the overnight hours. 
Weak warm advection and moistening profiles suggest some threat for 
lighting with the strongest convection, primarily after 06z. 


.Darrow/squitieri.. 12/08/2019 


$$ 

Mesoscale Discussion


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Mesoscale discussion 2189 
National Weather Service Storm Prediction Center Norman OK 
0254 PM CST Sat Dec 07 2019 


Areas affected...northern California 


Concerning...severe potential...watch unlikely 


Valid 072054z - 072330z 


Probability of watch issuance...5 percent 


Summary...isolated strong storms remain possible this afternoon. 


Discussion...surface analysis shows temperatures into the 60s f over 
the valley, with gusty south winds aiding warm air advection 
northward toward the midlevel temperature gradient (from Chico north 
per objective analysis). Batches of precipitation exist in these 
areas, which is minimizing destabilization. Shear remains strong 
with 150-200 m2/s2 effective srh currently, and 200-250 m2/s2 0-1 km 
srh. 


With time, winds just off the surface will veer, reducing low-level 
srh, but enhancing upslope east of the valley. Continued cooling 
aloft along with the diurnal cycle suggest a few strong storms may 
yet develop. If a substantial enough updraft can survive in the 
shear (most likely where convergence is maximized), an isolated 
supercell is possible, with perhaps a brief/weak tornado. Otherwise, 
small hail may occur. 


.Jewell/Hart.. 12/07/2019 


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


Attention...WFO...sto...eka... 


Latitude...Lon 39012180 39032236 39292269 39702285 40072291 40342299 
40672293 40982282 41152245 41162198 40892162 40442127 
39812091 39342089 39122134 39012180