U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 051655 
Storm Prediction Center ac 051654 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1054 am CST Thu Dec 05 2019 

Valid 061200z - 071200z 

..no severe thunderstorm areas forecast... 

the risk for severe thunderstorms appears negligible across the 
U.S., Friday through Friday night. 

Within one branch of split westerlies across the mid-latitude 
eastern Pacific, models indicate that amplified troughing will begin 
to advance inland across the Pacific coast region during this 
period. An initially broad and deep lower/mid tropospheric cyclone 
is embedded within this feature, but it is forecast to weaken 
considerably as it approaches the coast, and may still be centered 
several hundred miles west of the northern California/southern 
Oregon coast at 12z Saturday. 

Downstream of the troughing, there may be some flattening/broadening 
of short wave ridging shifting across The Rockies through the 
Mississippi Valley. As this occurs, the remnants of a mid-level low 
(initially digging into the lower Mississippi Valley at 12z friday) 
are expected to turn eastward and accelerate across the eastern Gulf 
states, into the western Atlantic by late Friday night. 

..Pacific coast region... 
The initially broad -22 to -24 c 500 mb cold core of the approaching 
trough and cyclone may begin to warm during this period, with 
coldest temperatures likely to remain offshore. However, models do 
indicate that -20 to -22 c 500 mb temperatures may gradually begin 
to overspread Washington, Oregon and northern California late Friday 
through Friday night. Destabilization inland of coastal areas seems 
likely to remain weak to negligible, but could become maximized 
across the Shasta/Siskiyou region and northern Sierra Nevada late 
Friday night. This is where a preceding influx of moisture from the 
lower latitude Pacific, coupled with strengthening 
south/southwesterly low-level flow and associated orographic lift 
and warm advection, may contribute to thermodynamic profiles 
sufficient for convection capable of producing occasional lightning. 

..lower Mississippi Valley/central Gulf states... 
Mid-level cooling and forcing for ascent associated with the digging 
southern stream perturbation may be contributing to scattered 
thunderstorm development across southeast Arkansas and adjacent 
portions of the lower Mississippi Valley region at the beginning of 
the period. This will be aided by moistening southerly return flow, 
likely rooted above a stable boundary layer, and may continue into 
the day Friday. How long, and how far east/southeastward across the 
central Gulf states, remains unclear, with weak thunderstorm 
activity expected to diminish as the mid/upper impulse accelerates 
eastward toward the South Atlantic coast and low-level moisture 
return becomes cut off. 

..maximum risk by hazard... 
Tornado: <2% - none 
wind: <5% - none 
hail: <5% - none 

.Kerr.. 12/05/2019