SPC AC 041631
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1031 AM CST Sat Dec 04 2021
Valid 041630Z - 051200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
Isolated thunderstorms are possible across a wide area from north
Texas and southern Oklahoma, through parts of the mid South.
In the mid levels, a split flow regime with moderate to strong
northwesterly flow was observed across the northern third of the
CONUS. Several vorticity maxima and their associated jet streaks
within the mostly zonal flow field will move east with time today,
supporting several areas of wintry precipitation from the Pacific
Northwest/northern Rockies into the Northeast. Within the weaker
southern branch of the mid-level westerlies, an upper low over the
Southwest will linger through the forecast period while a weak
shortwave trough moves east along the Gulf Coast. At the surface, a
stalled front and weak low from eastern Oklahoma and north Texas
into Alabama will support increased ascent and moistening through
the forecast period.
...Southern Plains and portions of the Southeast...
As low-level moisture and weak ascent increase through the period,
Isolated thunderstorms may develop through the forecast period
across several areas. Weak isentropic ascent along the front through
the Gulf coast and central Alabama may support a few thunderstorms
as diurnal warming and moistening contribute to a weakly unstable
(MUcape around 500 J/kg) environment.
The greatest focus for warm and moist ascent appears likely across
portions of north Texas and eastern Oklahoma into southern Arkansas
late in the period, as a low-level jet and upstream shortwave trough
support isolated thunderstorm development overnight. Continued
low-level warm advection should result in low 60s F surface
dewpoints reaching into southern Arkansas by 06z. Cooling
temperatures aloft ahead of the southern branch shortwave should
favor modest lapse rates around 6.5 C/km aiding in weak to moderate
destabilization. With MUCAPE around 500-100 J/kg, and weak mid-level
flow, a few pule type storms with small hail may develop. However,
forecast coverage is expected to remain below thresholds for severe
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