(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 071007
SPC AC 071007
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0407 AM CST Wed Dec 07 2022
Valid 101200Z - 151200Z
...DISCUSSION...
A increase in divergence of solutions amongst medium-range models,
and an increase in ensemble spread, is noted as compared to 24 hours
prior, along with a general slowing of the advance of the western
U.S. trough.
In general, models forecast a very gradual amplification of the flow
field Days 4-5 and into Day 6, as short-wave energy digs
south-southeastward in the vicinity of the western North America
Coast Day 4/Saturday, and then begins to pivot a bit more
southeastward into the western U.S. Day 5/Sunday.
On Day 6/Monday, a more eastward advance of a large closed low will
commence, with pronounced height falls reaching the central and
southern Plains -- particularly through the evening/overnight hours.
This eastward advance appears likely to be accompanied by strong
central High Plains cyclogenesis, with a cold front to advance into
(GFS) or across (ECMWF) the southern Plains region through the
second half of the period. Based on this current pace of advance of
the synoptic features, most of the severe risk Monday would appear
to exist after dark, spreading across parts of eastern Oklahoma and
North Texas, and possibly (per the ECMWF) into western Arkansas.
Given favorable northward advection of high theta-e air, and very
strong deep-layer shear, all-hazards severe potential would be
expected.
Continued advance, and additional deepening, of the upper low is
expected Tuesday/Day 7, with the surface low progged to occlude over
the central Plains and a cold front to sweep eastward to the Mid
Mississippi Valley region after dark. With a moist warm sector
likely to reside across East Texas/Arkansas/Louisiana in this
scenario, and given the very strong wind field accompanying the
intensifying synoptic features, all-hazards severe risk including
tornado potential would exist.
By Day 8, model differences increase, casting additional uncertainty
into the forecast. With that said, it does appear that much more
limited moisture/instability will exist ahead of the system -- in
part due to a strong antecedent ridge of surface high pressure. As
such, a diminished severe risk would appear to exist for Day 8.
..Goss.. 12/07/2022
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