(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 130845
SPC AC 130845
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Sun Oct 13 2024
Valid 161200Z - 211200Z
...DISCUSSION...
Initially amplified mid-level troughing near the Atlantic Seaboard
is forecast to shift offshore and lose amplitude across the western
Atlantic during the middle to latter portion of the coming work
week. In its wake, medium-range guidance indicates at least a
couple of significant short wave perturbations will emerge from a
somewhat more progressive regime across the mid-latitude latitude
Pacific.
It still appears that the lead perturbation may provide support for
strong surface cyclogenesis to the lee of the Canadian and northern
U.S. Rockies during the latter portion of this week. While there is
variance among the models concerning early evolution south of the
international border, primary cyclone development is appearing most
probable across the Canadian Prairies into higher latitudes of
interior Canada. As this occurs, a trailing cold front may overtake
modestly deep surface troughing across the northern into central
U.S. Great Plains Thursday into Friday. This could become a focus
for a corridor of increasing thunderstorm development. However, it
still appears that rather modest to weak low-level moisture return,
in the wake of a prior cool/dry intrusion as far south as the
northern Gulf of Mexico, will tend to limit destabilization and
minimize the risk for severe storms.
Models indicate that the second impulse, quickly progressing inland
behind the lead wave, will tend to split off toward the southern
mid-latitudes. However, the differences between the ECENS/ECMWF and
GEFS/GFS remain quite large concerning the amplification and
progressiveness of this perturbation across the central/southern
U.S. late this week into next weekend. Even so, with low-level
moisture return off the Gulf of Mexico initially limited, and then
perhaps impeded by the progression of the lead system, it is not
clear whether these differences will have much impact on the overall
convective potential.
..Kerr.. 10/13/2024
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