298
ACUS01 KWNS 242001
SWODY1
SPC AC 242000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Mon Jun 24 2024

Valid 242000Z - 251200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN THE UPPER MS
VALLEY ACROSS SOUTH WI...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY IN EAST
NC...

...SUMMARY...
Scattered severe thunderstorms are expected over parts of the Upper
Midwest late this afternoon into tonight. A corridor of potentially
widespread destructive wind gusts could develop over parts of
Minnesota into Wisconsin.

...20Z Update...
Overall forecast scenario remains valid with potential for an
intense, bowing MCS this evening into tonight. With continued
spatiotemporal differences among recent guidance for initial
supercell development, confidence is below-average for further
increases in severe probabilities along the north-northwest to
south-southeast oriented MLCAPE gradient over the Upper MS Valley.
In addition, the likely orientation of the MCS with respect to the
instability gradient suggest the significant severe wind threat may
be relatively confined owing to abundant warm-moist sector MLCIN to
the west and diminishing instability to the east. The corridor
previously highlighted, that is centered on a portion of the Upper
MS Valley into south WI, remains the most probable zone for
potentially destructive wind gusts.

..Grams.. 06/24/2024

.PREV DISCUSSION... /ISSUED 1131 AM CDT Mon Jun 24 2024/

...Upper Midwest...
A weakening MCS continues to track eastward across central MN,
associated with a shortwave trough over southern Canada.  Extreme
instability will develop along the southern fringe of this MCS and
accompanying cloud shield, with hot/humid conditions leading to
MLCAPE values over 4500 J/kg by late afternoon across southwest MN.
Very warm temperatures aloft will likely suppress convective
development in this volatile air mass, but strengthening
southwesterly low-level winds by early evening will enhance warm
advection and likely lead to thunderstorms over central MN.  Initial
storms will be supercellular, with forecast soundings showing ample
low level and deep-layer shear to support a risk of very large hail,
damaging winds, and a few tornadoes.

As the evening progresses, most morning CAM solutions indicate that
the cluster of supercells will grow upscale into a fast moving
bowing MCS.  However, there is considerable diversity regarding the
track of the most intense storms.  Given the very warm temperatures
aloft, it seems likely the storms will track southeastward along the
thermal gradient - across central/southern WI and into northern IL.
The potential exists for a corridor of widespread and occasionally
significant (exceeding 65 kt) wind damage, so have upgraded to ENH.
The low-level air mass will become increasingly less unstable as the
storms move across Lake Michigan and into northern IN by early Tue
morning, suggesting a weakening trend.

...Central High Plains...
Scattered high-based showers and thunderstorms are expected to
develop over the central Rockies and Black Hills today and spread
eastward into parts of SD/NE/KS.  Hot surface temperatures and
inverted-v profiles will support a risk of gusty/damaging winds with
this activity for a few hours early this evening.

...Eastern NC/SC...
A surface front is sagging southeastward across NC today, with a
very moist and moderately unstable air mass in place ahead of the
front.  Thunderstorms are expected to form in this environment, with
sufficient westerly flow aloft to help organize the storms and
promote a risk of damaging wind gusts.  Given the amount of heating
that is occurring in eastern NC, and morning guidance showing
substantial coverage of storms, have added a SLGT risk for parts of
this area.

$$