(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 270836
SPC AC 270836
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0336 AM CDT Mon Mar 27 2023
Valid 301200Z - 041200Z
...DISCUSSION...
An upper trough will shift east across the western U.S. to the
central/southern Rockies on Day 4/Thu. Forecast guidance has come
into better agreement with a slower eastward ejection of the trough.
As such, the 15 percent severe area for Thursday has been shrunk
compared to previous days. Some severe potential, albeit more
conditional, will still exist as strong surface cyclogenesis occurs
over the central High Plains. In response to this developing low,
strengthening southern low-level flow across the southern/central
Plains will transport upper 50s to mid 60s F dewpoints across
TX/OK/KS to the east of a dryline. Large-scale ascent is expected to
be modest as the main trough remains too far west. However, strong
vertical shear will overlap a moderately unstable airmass. If
thunderstorms can develop/overcome capping, isolated supercells
capable of all hazards will be possible in the vicinity of the
dryline from late afternoon into Thursday night.
By Day 5/Fri, all-hazards severe potential will expand across a
large portion of the central U.S. There is still some uncertainty in
timing and intensity of the ejecting upper trough. Nevertheless, a
broad warm sector is expected to develop from eastern portions of
the southern Plains toward the Mid/Lower MS Valley through the
afternoon, and eastward to the Lower OH/TN Valley vicinity by
evening/overnight. Intense southwesterly mid/upper flow will overlap
the warm sector as a cold front tracks east/southeast. The severe
threat could end up taking a bi-modal character, with an area of
enhanced potential focused near a strong surface low over the IA/IL
vicinity, and another area focused further south toward the
Mid-South where large-scale ascent will be weak, but a better
thermodynamic environment will overlap with strong shear. However,
enough differences exist in forecast guidance regarding the location
of the surface low track and amplitude of the ejecting upper trough
that a broad 15 and 30 percent severe delineation has been
introduced. These areas will likely change some in the coming days
as forecast details become better resolved.
Severe potential could continue eastward toward the Mid-Atlantic and
Southeast on Day 6/Saturday. A moist boundary-layer will exist
across these areas ahead of the east/south advancing cold front.
However, timing and location of the surface low and focus of strong
shear/large-scale ascent is uncertain, and predictability is too low
to delineate any areas at this time.
Large spread in forecast guidance continues/increases during the end
of the forecast period, and predictability remains low on Days
7-8/Sun-Mon.
..Leitman.. 03/27/2023
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