(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 270857
SPC AC 270857
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Thu Mar 27 2025
Valid 301200Z - 041200Z
...DISCUSSION...
Predictability remains a concern during the medium-range period.
Models reveal notable differences even in the Day 4-5 time frame
with respect to strength of the eastern U.S. upper trough, and
associated evolution/development of the surface pattern. As the
initial surface system moves offshore late in the Day 5 period
(Tuesday morning), substantial divergence in solutions is evident
with the next trough moving into/across the western CONUS. Given
these differences, any severe potential beyond Day 5 cannot be
quantified with any degree of confidence.
With that said, a fairly widespread area of severe potential remains
evident Day 4/Sunday, ahead of a cold front moving eastward across
the Mississippi and Ohio and eventually the Tennessee Valleys.
Northward advection of 60s dewpoints is expected ahead of this
front, which will combine with daytime heating to boost mixed-layer
CAPE into the 1000 to 1500 J/kg range, and potentially above 2000
J/kg farther southwestward along the front from East Texas into the
lower Mississippi Valley.
As a belt of strong southwesterly flow aloft overspreads the
moistening/destabilizing pre-frontal boundary layer, development of
strong/severe storms is expected near and ahead of the boundary
during the afternoon -- potentially extending as far southwestward
as East Texas. Along with potential for large hail and damaging
winds, likelihood for supercell storms suggests potential for a few
tornadoes as well. Risk will spread eastward through the evening
across portions of the Midwest/Ohio Valley and Mid/Lower Mississippi
Valley, and southeastward into the Tennessee Valley and central Gulf
Coast states overnight -- likely persisting through the end of the
period.
Day 5/Monday, models begin to differ more substantially with respect
to surface frontal location -- particularly with northern extent.
The GFS depicts the front as extending from New England
southwestward to the Texas Coast Monday morning, while the ECMWF
places it from Lower Michigan to coastal Texas. By late afternoon,
the GFS shows the front reaching the New England coastal area and
Mid-Atlantic region, focusing the primary severe threat from the
Mid-Atlantic area southwestward. Meanwhile, some risk could extend
as far north as the Lower Great Lakes region/central Appalachians
per the ECMWF's deterministic forecast. At this time, will keep the
Day 5 risk area focused from the Mid-Atlantic region to the lower
Mississippi Valley, though adjustments/refinements to the area over
the next several days will likely be required.
..Goss.. 03/27/2025
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