(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 061411
SPC AC 061411
Day 4-8 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0811 AM CST Mon Jan 06 2020
Valid 091200Z - 141200Z
CORRECTED TO ADD LABEL TO DAY 8 GRAPHIC
...DISCUSSION...
A multi-day severe weather episode is expected across portions of
the Arklatex into the Deep South vicinity on D5/Fri and D6/Sat. The
ingredients for severe thunderstorms will begin to fall into place
Day 4/Thu as an upper ridge spreads eastward across the eastern U.S.
and a large-scale trough intensifies across the western states. At
the surface, a strong surface pressure gradient will develop from
the Midwest to the western Gulf Coast, allowing rich Gulf moisture
to begin streaming northward across east TX and the lower MS Valley
vicinity on Thursday.
The warm sector will expand through the day on Friday from eastern
OK/TX eastward across much of the TN Valley and Gulf Coast states.
Surface dewpoints are expected to be impressive for this time of
year, climbing into the mid 60s to low 70s as a deepening surface
low shifts eastward across OK/TX on Friday. This will occur as the
western trough ejects eastward into the southern Plains and an
intense southerly low level jet overspreads the region. Forecast
guidance also shows a weak EML emanating from the Mexican Plateau
spreading over parts of the region, providing a weak cap that should
limit warm sector convection initially. Confidence has increased
that a strong vertical shear parameter-space will overlay a
high-quality warm sector ahead of the ejecting trough and a
southeastward-advancing cold front Friday afternoon through Friday
night. As such, a 30% severe delineation has been included for parts
of the Arklatex within the broader 15% severe probability area.
On Day 6/Sat, severe thunderstorm potential is expected to continue
into portions of the TN Valley and the northern Gulf Coast vicinity.
Similar to Friday, intense shear parameters and adequate instability
will exist across the region as the upper trough becomes more
compact and lifts northeast across the mid/lower MS Valley to the OH
Valley. 15% severe probabilities will be maintained at this time as
questions remain with respect to how pristine the warm sector will
remain over MS/AL and vicinity, as well as timing/location of key
surface features. That being said, the overall pattern will support
severe thunderstorms into Saturday evening across much of the Deep
South vicinity.
Confidence in severe potential beyond Day 6/Sat is low, though
guidance suggests stormy conditions could return to parts of the
Southeast on Monday/Monday night.
..Leitman.. 01/06/2020
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