SPC 0700Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1156 PM CST Tue Jan 05 2021

Valid 071200Z - 081200Z


Thunderstorms are possible Thursday across the Southeast, with a
conditional threat of isolated severe storms from the Mississippi
and Alabama coasts into the Florida Panhandle.

A strong shortwave trough with cyclonically curved jet max will move
east across the southeastern states on Thursday, with upper low
moving from northern LA toward the southern Appalachians by Friday
morning. Of particular note will be the cold temperatures aloft,
with -20 C at 500 mb as far south as Mobile AL. Strong westerly
winds aloft will lengthen hodographs across the region, particularly
the northern Gulf Coast.

At the surface, a low is forecast to move east across southern parts
of MS, AL, and GA, and perhaps across the FL Panhandle as well.
Large-scale lift with this system will conditionally favor a few
strong storms, but boundary-layer details will determine how
productive of an event it is.

Elsewhere, cooling temperatures aloft with an upper trough will
impact the Pacific Northwest, with instability developing overnight
favoring a few lightning flashes.

...MS/AL/FL Panhandle...
A relatively cool and stable surface air mass will be in place over
much of the Southeast during the day ahead of the surface low.
However, southerly winds ahead of the low will bring at least mid
50s F dewpoints onshore across far southern MS, AL, and the FL
Panhandle, possibly resulting in sufficient SBCAPE. Forecast
soundings indicate up to 500 J/kg SBCAPE may develop immediately
ahead of the cold front and dry slot aloft, where cooling aloft will
be rapid. Large values of SRH will be present due to the warm
advection atop the cool boundary layer, and will be reduced rapidly
as the front approaches. There may be a brief window of opportunity
where SBCAPE favor wind gusts or a tornado, and effective SRH
remains strong. If this happens, isolated supercells may form. This
event is highly conditional on the surface air mass and moisture
return. If the air mass remains too cool along the coast, then
little if any severe threat may develop.

...Coastal OR and northern CA...
Increasing moisture may result in elevated CAPE across the region
late in the day, with sporadic thunder possible. However, the
strongest cooling aloft will occur close to 12Z Friday along the
coast, and this is when models indicate non-zero SBCAPE may develop.
Forecast soundings from various models are not in very good
agreement regarding instability, but this area will need to be
watched in subsequent outlooks. Shear will remain strong, and may
conditionally favor a strong storm along the coast should
instability be greater than currently forecast.

..Jewell.. 01/06/2021

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