Subj : DAY2SVR: Nws Storm Predic
To   : All
From : Mike Powell
Date : Mon Sep 04 2023 07:28:00

ACUS02 KWNS 040553
SWODY2
SPC AC 040552

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Mon Sep 04 2023

Valid 051200Z - 061200Z

....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MISSISSIPPI VALLEY...

....SUMMARY...
Severe storms with isolated large hail and damaging winds will be
possible on Tuesday across parts of the Upper Mississippi Valley.
Marginally severe storms will also be possible in parts of the lower
to mid Mississippi Valley.

....Upper Mississippi Valley...
An upper-level trough will move across the northern Plains on
Tuesday. Ahead of the trough, mid-level flow will be southwesterly
over much of the upper Mississippi Valley. An associated cold front
will move eastward from the northern Plains into the upper
Mississippi Valley, with surface dewpoints in the 60s F ahead of the
front. In response to surface heating, moderate to strong
instability is forecast to develop from Iowa northeastward into
Wisconsin. Thunderstorms appear likely develop along and ahead of
the front around midday, with storms moving eastward into the
stronger instability across the upper Mississippi Valley. The
greatest cell coverage is forecast to develop during the late
afternoon and early evening across Minnesota, Wisconsin and Iowa,
but more isolated storms will also be possible southward into parts
of the mid Mississippi and lower Missouri Valleys.

NAM forecast soundings near the instability axis, in the late
afternoon from Minneapolis south-southwestward to far northern Iowa,
have MLCAPE peaking in the 2000 to 3000 J/kg range. O-6 km shear
along this corridor is forecast to be in the 35 to 45 knot range,
with 700-500 mb lapse rates around 8 C/km. This environment will
likely support supercells with isolated large hail. A wind-damage
threat is also expected with supercells, and with organized
multicells, especially with the faster-moving short line segments.
The severe threat is expected to continue through much of the
evening, as a large cluster or MCS moves eastward toward the western
Great Lakes.

....Lower to Mid Mississippi Valley...
An upper-level trough is forecast to move across the lower to mid
Mississippi Valley on Tuesday, where a moist and unstable airmass
will be in place. As surface temperature warm on Tuesday, MLCAPE is
forecast to peak in the 2000 to 3000 J/kg range. Although deep-layer
shear is expected to remain relatively weak, low-level lapse rates
are forecast to become steep during the mid to late afternoon. This
could be enough for marginally severe wind gusts with the stronger
multicells near peak heating. Hail could also occur with the more
intense cells.

...Broyles.. 09/04/2023

$$
--- SBBSecho 3.14-Linux
 * Origin: Ilink: CCO - capitolcityonline.net (454:1/105)

.