ACUS03 KWNS 271917
SWODY3
SPC AC 271916

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0216 PM CDT Tue Aug 27 2024

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
MINNESOTA...WESTERN/CENTRAL IOWA...AND FAR EASTERN NEBRASKA...

...SUMMARY...
Severe thunderstorms are possible on Thursday across portions of the
Upper/Middle Mississippi Valley and the central Plains. A few strong
storms also will be possible over portions of southern West
Virginia, Virginia and North Carolina.

...Upper Midwest into the central Plains...

An upper trough will progress eastward from the northern/central
Plains to the Upper Midwest/Great Lakes vicinity on Thursday. Strong
deep-layer southwesterly flow will remain near/north of the
International border closer to the compacted closed low over the
Canadian Prairies/western Ontario, but modestly enhanced
southwesterly flow will extend over portions of the region. At the
surface, a cold front will develop east/southeast across the Upper
Midwest and central Plains through the period. South/southeasterly
low-level flow will maintain 60s F dewpoints, with a corridor of 70s
F dewpoints across southern MN to the mid-MS Valley. Strong heating
and low-level warm advection ahead of the front should allow for a
corridor of strong surface-based instability across parts of the
Mid/Upper MS Valley into eastern portions of the central Plains.
Thunderstorms are expected along the front during the day and into
the evening hours.

Vertical shear will remain somewhat modest, and decrease with
southward extent. Forecast soundings suggest supercells may be
possible, especially across parts of MN/WI/IA where effective shear
magnitudes around 30 kt will be present amid vertically veering
low-level wind profiles. Linear forcing along the front and marginal
shear may favor more rapidly developing line segments however.
Regardless, a risk for all severe hazards may accompany this
activity.

With southward extent into the central Plains, forecast soundings
show weaker deep-layer southwesterly flow. Nevertheless, strong
instability and inverted-v sub-cloud thermodynamic profiles/steep
low-level lapse rates ahead of the southeast-advancing front suggest
strong wind gust potential.

...Mid-Atlantic vicinity...

Weak deep-layer flow is expected across the region in the wake of a
departing upper trough over the Northeast and Canadian Maritimes.
However, a very moist and hot airmass is forecast, support moderate
to strong destabilization during the day. As a cold front sags south
across the region, isolated thunderstorms producing locally
strong/damaging gusts will be possible. This risk should quickly
diminish with loss of daytime heating.

..Leitman.. 08/27/2024

$$