(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 300859
SPC AC 300859
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Sun Mar 30 2025
Valid 021200Z - 071200Z
...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/WED...
...DISCUSSION...
Medium-range models appear to be in good agreement with overall
evolution of the synoptic-scale pattern into the Day 7 (Saturday
April 5) time period, when divergence in solutions increases.
Earlier in the period however, model consistency lends fairly high
confidence that a widespread/potentially substantial outbreak of
severe weather will evolve Wednesday/Day 4, from Lower Michigan and
the Ohio Valley, southwestward across the Middle and Lower
Mississippi Valleys, and into eastern portions of Texas and
Oklahoma. Convection will likely be ongoing or developing early in
the day, over western portions of the risk area -- from Wisconsin
southwestward to Oklahoma/North Texas. As an upper low shifts
northeastward across the northern Plains toward the upper
Mississippi Valley through the day, and the cold front crosses
Iowa/Missouri/eastern Oklahoma, steep lapse rates atop a
moist/diurnally heating warm sector will support widespread
convective development.
With ascent along the front somewhat modest as stronger large-scale
ascent focuses northward into the western Upper Great Lakes and into
Ontario, storm mode may tend toward isolated storms, as opposed to
more linear development. This, combined with flow that is forecast
to weakly veer but dramatically strengthen with height, suggests a
primarily supercell storm mode. In additional to very large hail
(particularly with southward extent), widespread damaging winds and
several tornadoes are expected, some possibly significant. Risk is
expected to continue well into the evening and likely overnight,
shifting slowly eastward across the Midwest and mid/lower
Mississippi Valley through the end of the period.
Day 5/Thursday, trailing portions of the cold front should become
aligned east-northeast to west-southwest across the Ohio and mid
Mississippi Valleys and into the southern Plains, as the upper
system shifts quickly across eastern Canada. While weak short-wave
ridging will evolve atop the surface frontal zone in the wake of the
departing system, daytime heating of a very moist boundary layer
along and south of the front combined with strong flow aloft will
support reinvigorated convection through the afternoon and evening
hours, along with attendant severe-weather risk.
Day 6/Friday, the surface front should remain quasi-stationary, but
short-wave ridging should increase as a cut-off low evolves across
the West. As such, much of the Day 6 convection may occur to the
cool side of the surface front, in the zone of warm
advection/isentropic ascent. While some severe risk will likely
evolve, mainly in the form of hail, uncertainty overall (given the
ridging aloft) precludes inclusion of a Day 6 risk area.
By the weekend, deviation in model solutions increases, due to
uncertain evolution of the low/trough over the West. As such, no
risk areas will be included.
..Goss.. 03/30/2025
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