SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1158 PM CST Tue Feb 16 2021

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHEAST LOUISIANA...FAR SOUTHERN MISSISSIPPI AND FAR SOUTHERN
ALABAMA...

...SUMMARY...
Isolated severe thunderstorms may occur from this evening into
tonight across portions of the central Gulf Coast. A couple
tornadoes, damaging wind gusts, and perhaps some hail will be
possible.

...Central Gulf Coast...
An upper-level trough will move across the Great Plains today as
southwest mid-level flow remains in place from the southern Plains
to the Eastern Seaboard. At low-levels, the northern edge of a moist
airmass in the Gulf of Mexico will advect northward into the central
Gulf Coast area as a jet near 850 mb moves eastward across the
region. Isolated thunderstorms may develop early this evening near
the axis of the low-level jet, in the vicinity of the mouth of the
Mississippi River. The chance for thunderstorm development will
increase during the evening as low-level moisture increases across
the central Gulf Coast. The potential for thunderstorm development
may become maximized during the late evening and early overnight
period as instability finally develops across the central Gulf
Coast.

Forecast soundings across the central Gulf Coast this evening
gradually increase surface dewpoints in the 50s and lower 60s F. The
strongest instability is forecast to remain across far southeast
Louisiana in the early evening, where isolated severe thunderstorm
development will be possible. Further to the north in the vicinity
of Biloxi, Mississippi and Mobile, Alabama, instability is forecast
to increase by mid to late evening. At that time, forecast soundings
near Mobile show strong speed shear in the lowest 3 Km above ground
level with 60 to 70 kt of southwest flow in the mid-levels. This
shear environment will be enough to overcome the weak instability
across far southern Alabama and the western Florida Panhandle.
Supercell development may occur on the northern edge of the stronger
instability and to the west of the low-level jet, where shear will
be maximized. Supercells may occur with a potential for wind damage
and tornadoes. This severe threat is expected to gradually shift
eastward across southern Alabama into the western Florida Panhandle
during the overnight period. If a line of storms can organize, then
a wind damage threat would be possible through late in the period.

..Broyles/Wendt.. 02/17/2021

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