(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 240847
SPC AC 240847
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CDT Thu Apr 24 2025
Valid 271200Z - 021200Z
...DISCUSSION...
...Day 4/Sun - Great Plains...
An upper trough over the southwestern U.S. early Sunday will develop
east, becoming oriented from the central Rockies to the Lower CO
Valley by Monday morning. As the trough develops east, a band of
enhanced southwesterly mid/upper flow will overspread NM northeast
to the Dakotas. A lee surface cyclone will deepen over western
SD/NE, eventually shifting east into eastern SD by early Monday.
Southerly low-level flow will transport Gulf moisture northward
across the Plains as a dryline sharpens over western portions of the
Plains. An EML should limit diurnal thunderstorm activity, though an
isolated supercell can not be ruled out somewhere along the dryline
from western SD southward into west TX. As a 50-60 kt low-level jet
develops overnight, elevated convection may develop near the surface
low over parts of SD/ND. This activity could pose a risk for hail,
but uncertainty precludes 15 percent probabilities at this time.
...Day 5/Mon - Southern Plains to Upper Midwest...
A shortwave trough embedded within the larger-scale western U.S.
upper trough will eject from the central Rockies to the Upper
Midwest on Monday. The southern branch of the western upper trough
will stall over the Four Corners vicinity, but a broad swath of
50-80 kt 500 mb southwesterly flow will extend from the southern
Plains to the upper Great Lakes. A surface low will shift east
across the Upper MS Valley, with a trailing cold front moving across
the northern/central Plains into WI/IA during the afternoon and
overnight hours. A dryline also will extend southwest from
northeast/central KS into western OK/northwest TX.
Rich Gulf moisture will be transported northward on increasing
southerly low-level flow ahead of the aforementioned surface
features. Moderate to strong destabilization is forecast from OK
northeast into IA and adjacent parts of southern MN/southwest WI.
Supercell wind profiles amid this very moist/unstable airmass will
support an all-hazards severe risk. The greatest risk should be
centered on IA and adjacent areas from extreme northeast KS into
southeast MN/southwest WI, where an intense low-level jet is
expected to develop by late afternoon/early evening.
With southwest extent across eastern KS into OK, and northwest TX,
convective coverage is less certain as capping my limit severe
thunderstorm development. Current model trends hanging back the
southern branch of the upper trough also suggests large-scale ascent
will be weaker across the region, resulting in a more difficult time
overcoming capping. Higher probabilities may be needed in subsequent
outlooks if trends suggest capping will be less of a hindrance.
...Day 6/Tue - North TX into southern Lower MI and OH...
Severe potential will continue into Tuesday, especially from the
Mid-MS Valley into Lower MI/OH where the surface cold front is
expected to continue pushing east/southeast through the period.
While the upper shortwave trough over the Great Lakes will deamplify
through the day, enhanced southwesterly flow atop the frontal
boundary and a moist/unstable airmass should continue to support
severe thunderstorm organization in the form of clusters and line
segments.
With southwest extent into AR/eastern OK/north TX, large-scale
ascent will become weaker. However, persistent warm advection in the
vicinity of a stalled boundary, and potential secondary surface low
development should foster strong/severe thunderstorm activity.
...Days 7-8/Wed-Thu... OK/TX into the Lower MS Valley...
Forecast guidance shows the southwestern U.S. upper trough ejecting
across the southern Plains and Lower MS Valley by the end of the
forecast period. This could bring severe thunderstorm potential to
these regions (OK/TX on Wed, ArkLaTex/Lower MS Valley on Thu).
However, several periods of thunderstorm activity leading into
Wednesday and large surface pattern differences among medium range
guidance precludes introduction of severe probabilities at this
time.
..Leitman.. 04/24/2025
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