Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Mon Apr 28 2025
Valid 282000Z - 291200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT FOR SOUTHEAST MINNESOTA...NORTHERN IOWA AND
WESTERN WISCONSIN...
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR NORTHWEST
TEXAS AND SOUTHWEST/SOUTH-CENTRAL OKLAHOMA LATE THIS AFTERNOON INTO
EARLY TONIGHT...
...SUMMARY...
Multiple corridors of severe thunderstorms are expected across the
Upper Midwest this afternoon into tonight, with a regional severe
weather outbreak possible. The most dangerous period is likely
during the late afternoon and evening when strong tornado potential
should be maximized. Scattered large to very large hail and damaging
winds are likely as well.
...IA/MN/WI through early tonight...
A positive-tilt midlevel trough and associated 70-80 kt jet streak
will eject quickly northeastward from the mid MO Valley to the upper
MS Valley this evening. An associated surface cyclone will likewise
move across MN/WI, while a trailing cold front moves southeastward
into the central Plains, and a dryline mixes eastward into northwest
IA/far eastern NE before stalling this evening. Storms are ongoing
along the front moving across southern MN, where cloud breaks and
moisture advection have resulted in substantial destabilization.
Long, sufficiently curved hodographs will support a threat for large
hail (potential greater than 2 inches) and tornadoes, with the
threat for strong tornadoes maximized for storms that remain
semi-discrete within the broken band. Otherwise, convection will
spread eastward through early tonight into WI, with all hazards
possible.
Farther south, storm development is less certain along the dryline
into western/central IA and northeast KS. Deepening cumulus along
segments of the dryline in eastern NE and central KS could be
precursors to isolated storm development late this afternoon/evening
into western IA and northeast KS, respectively. The storm
environment will conditionally favor supercells capable of producing
very large hail and a few tornadoes.
...TX/OK through early tonight...
Despite a narrow band of thicker mid-high clouds, surface
temperatures continue to warm into the 85-90 F range along the
dryline across west central/northwest TX. As surface heating
removes convective inhibition, flow near 700 mb largely parallel to
the dryline suggests sufficient residence times for storm initiation
near or after 22z across northwest TX. Boundary-layer dewpoints of
65-70 F beneath midlevel lapse rates in excess of 8.5 C/km will
contribute to large buoyancy (MLCAPE near 3500 J/kg), while
deep-layer shear will be favorable for splitting supercells. The
initial, more discrete storms will pose a primary threat of very
large hail of 2.5 to 3+ inches in diameter. Though low-level shear
will be modest this afternoon, some increase in low-level shear this
evening in the zone of richer moisture near the Red River will allow
a window of opportunity for tornadoes. Eventual upscale growth into
an MCS is expected with an accompanying threat for large hail and
damaging winds.
..Thompson.. 04/28/2025
.PREV DISCUSSION... /ISSUED 1123 AM CDT Mon Apr 28 2025/
...Upper MS Valley...
Morning water vapor imagery shows a broad positively tilted upper
trough across the western states, with the band of primary mid-level
winds extending from the central Rockies into the upper MS Valley.
Embedded within the stronger flow, a progressive shortwave trough is
evident over KS/NE that will track into IA/MN/WI this afternoon and
evening. Strong large-scale forcing ahead of this feature will
result in scattered intense thunderstorms.
Strong southerly low-level winds are transporting mid 60s dewpoints
rapidly northward into IA/MN. Cloud cover is limiting daytime
heating, but sufficient destabilization from cooling/ascent aloft
will lead to convective initiation along/ahead of the surface cold
front by mid-afternoon. Storms will be most numerous over central
MN, with increasingly sparse development with southward extent
across IA. Supercells capable of strong tornadoes and very large
hail appear likely. Storms will track into western WI during the
evening with a continued risk of significant severe weather.
...Northern MO...
Several morning CAM solutions suggest a secondary area of concern
for discrete supercell storms over northwest MO and vicinity. While
low and mid-level wind fields are a little weaker in this area
compared to farther north, forecast hodographs remain favorable for
tornadoes. Have therefore extended the 10% SIG tornado
probabilities that far south.
...OK/TX...
Strong heating occurring along a dryline that will extend from
western OK into west TX. Large-scale forcing mechanisms are weak
across this region, but a consensus of CAM solutions show scattered
intense thunderstorm development over southwest OK/northwest TX by
mid-afternoon, and further development southward during the evening.
Very large hail and a few tornadoes are possible across this region.
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TKR3Pr
