ACUS02 KWNS 290603
SWODY2
SPC AC 290602

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0102 AM CDT Mon Jul 29 2024

Valid 301200Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
IOWA...WESTERN ILLINOIS...AND FAR NORTHEAST MISSOURI...

...SUMMARY...
Scattered strong to severe storms will be possible across a broad
region from the northern Plains to the Midwest, Ohio Valley, and
Carolinas. A more concentrated severe wind threat is possible across
portions of the Corn Belt.

...Synopsis...
On Tuesday, a mid-level trough across the western CONUS will start
to advance east across the northern Rockies. This will start to
deamplify the mid-level ridge across the northern Plains while
another weak trough will advance east across the central
Appalachians. At the surface, lee troughing will strengthen somewhat
across the Plains with rich moisture extending from the Gulf of
Mexico to the Upper Midwest. This will result in a broad region of
moderate to strong instability along and south of a stationary
boundary which will extend from the Ohio Valley to the Northern
Plains.

...Iowa, Northeast Missouri, and West/Northwest Illinois...
A remnant convective complex from D1/Monday will likely be in the
vicinity of western Iowa at 12Z Tuesday. As the low-level jet
weakens Tuesday morning, the convective complex will likely weaken
with potentially remnant outflow boundaries in the region. Some
guidance indicates a supercell or two persisting along the outflow
boundary through the morning and into the afternoon. This is
possible given forecast soundings show inhibition eroding by late
morning. However, given the lack of greater forcing across the
region, this scenario remains uncertain.

Some weak ascent is expected across northern Iowa late Tuesday
afternoon/evening as a weak shortwave trough approaches from the
west and the low-level jet begins to strengthen. Assuming morning
convection has not grown upscale and augmented the environment, a
very favorable environment should be present with forecast soundings
suggesting 3000 to 4000 J/kg MLCAPE, 40 knots of effective shear,
and 8.5 to 9 C/km mid-level lapse rates. If storms can develop
within this environment, severe weather is likely with rapid growth
upscale into a severe wind producing MCS. Despite a pattern
favorable for a severe MCS, uncertainties remain given the lack of a
clear forcing signal and likely significant impacts from the Day 1
convection. A slight risk has been introduced for the region with
the most favorable environment, but adjustments/upgrades may be
necessary in later outlooks, once the most favorable corridor
becomes more clear.

...Ohio Valley to the Carolinas...
A MCS will likely be ongoing at the beginning of the period across
Kentucky/Tennessee. Forecast soundings indicate only minimal heating
will be needed ahead of this convective complex to erode inhibition
with most guidance showing minimal CINH by 15-16Z. Therefore, it is
possible this MCS will continue east through the day and eventually
reach the Atlantic Coast.

Even if the MCS does not strengthen during the late morning and
maintain itself through the day, additional thunderstorms are
expected (perhaps along a remnant MCV leftover from the MCS) and
within the uncapped airmass. 2500-3000 J/kg MLCAPE and around 25
knots of shear (as forecast by NAM/RAP forecast soundings) will be
sufficient for a few strong to severe storms Tuesday
afternoon/evening.

...Northern Plains...
Weak height falls amid moderate to strong instability may lead to
some thunderstorm development along a surface trough/dryline across
the Dakotas Tuesday afternoon. Given the lack of a consolidated
mid-level speed max, deep-layer shear varies significantly within
model guidance during the afternoon/evening. This will affect storm
organization and intensity. If stronger mid-level flow (30-35+
knots) can overspread the warm sector during the afternoon/evening,
a greater severe weather threat may materialize. However, that
scenario remains uncertain at this time.

..Bentley.. 07/29/2024

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