ACUS02 KWNS 140556
SWODY2
SPC AC 140555

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Wed May 14 2025

Valid 151200Z - 161200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PARTS OF THE
UPPER MISSISSIPPI RIVER VALLEY AND WESTERN GREAT LAKES...

...SUMMARY...
Scattered severe thunderstorms are expected across parts of the
upper Mississippi River Valley and western Great Lakes region
Thursday afternoon and evening. More isolated severe thunderstorms
are expected through the lower Ohio River Valley, Ozarks Plateau,
and parts of the Mid-Atlantic.

...Synopsis...
The upper-level trough currently over the Intermountain
West/northern Rockies is forecast to eject into the upper MS River
Valley over the next 48 hours. As this occurs, a Pacific cold front
will rapidly push east into the MS Valley and Midwest as an intense
surface cyclone begins to occlude over the eastern Dakotas/western
MN. Scattered thunderstorms are expected to develop along the front
by early-afternoon with increasing coverage across the upper MS
Valley through early evening. Increasingly sparse, but severe,
thunderstorms are anticipated along the front across the Midwest
into the lower OH Valley and Ozarks/Texarkana regions through the
evening and overnight hours.

...Upper MS Valley and western Great Lakes...
04 UTC surface observations show upper 50s to low 60s dewpoints
already spreading northwest into the upper MS Valley as a surface
low begins to organized across the northern Plains. Confidence
remains high that dewpoints in the mid 60s should overspread much of
the region by mid-day Thursday and will contribute to regional
MLCAPE values upwards of 2000-2500 J/kg. Strong forcing for ascent
along the approaching front and within the left-exit region of a
50-60 knot mid-level jet will erode capping at the base of a stout
EML and promote thunderstorm development by early afternoon across
parts of central to southern MN. Elongated hodographs with
cross-boundary mean winds will promote organized, initially
discrete/semi-discrete cells with an attendant severe wind and hail
(potentially as large as 2 inches) threat. Veering winds through the
lowest 2 km will also support a tornado threat with early convection.

With time, persistent strong forcing along the front should promote
some degree of upscale growth/clustering, though supercells will
remain likely on the southern fringe of the line where capping will
remain stronger and favor more isolated convection. The potential
for somewhat longer-lived supercells may be maximized across
southeast WI into adjacent portions of IL, northern IN, and
southwest lower MI. Forecast soundings depict ESRH values on the
order of 200-300 m2/s2, suggesting a significant tornado threat
could materialize. Confidence in the coverage of such cells remains
limited, but trends will be monitored for the need for increased
tornado risk probabilities.

...Midwest and Ohio Valley...
Forecast guidance continues to show the best moisture return across
parts of IL, IN, and northern KY by Thursday afternoon. Dewpoints in
the upper 60s to low 70s under nearly 8 C/km mid-level lapse rates
will support a very unstable air mass with MLCAPE values approaching
4000 J/kg. Despite the very favorable buoyancy, capping at the base
of the EML is expected to limit storm coverage across this region.
Recent guidance has trended towards perhaps a slightly increased
coverage of thunderstorms compared to previous runs, but the overall
consensus among deterministic and CAM ensemble guidance is that
storm coverage should be sparse. Nonetheless, effective bulk shear
values on the order of 40-50 knots will promote supercells during
the late afternoon/evening hours with all hazards possible,
including the potential for significant hail/tornadoes.
Consideration was given for an expansion of the Enhanced risk area,
but limited confidence in convective coverage precluded such expansion.

...Texarkana to the Ozark Plateau...
Weaker forcing along the front and strong capping will likely limit
thunderstorm coverage from the Texarkana region into the Ozark
Plateau during the afternoon/evening. Heading into the overnight
hours, increasing low-level isentropic ascent over the frontal
boundary will support thunderstorm development - especially across
the Ozarks into the mid-MS Valley. Strong deep-layer shear will
promote initial supercells, but storm propagation along the front
will likely promote clustering with time. Nonetheless, a severe
hail/wind threat will likely materialize within this corridor.

...Mid-Atlantic...
A moist, weakly capped air mass is expected to remain in place
across the Mid-Atlantic through Thursday afternoon. While lapse
rates will be modest after several days of convective overturning,
temperatures warming into the upper 70s/low 80s will promote
sufficient buoyancy for thunderstorm development. Upper ridging
moving into the region will likely limit thunderstorm coverage, but
convection developing along the Blue Ridge Mountains will mature in
an environment with increasing deep-layer shear. A few organized
cells appear possible with an attendant severe hail/wind threat.

..Moore.. 05/14/2025

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