362
ACUS01 KWNS 221955
SWODY1
SPC AC 221953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Sat Jun 22 2024

Valid 222000Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
MIDWEST AND SOUTHERN NEW ENGLAND...

...SUMMARY...
Scattered severe thunderstorms are possible through this evening
across parts of the Midwest, mainly posing a risk of damaging winds
and a few tornadoes. Scattered damaging winds are possible over
southern New England through early evening.

...20Z Update...
The severe weather forecast largely appears on-track with only a
couple of adjustments based on latest observational/guidance trends.
Isolated, high-based thunderstorms should develop farther southwest
in southeast MT and northwest SD within a similar moderate westerly
mid-level flow regime to ND. Across east-central Lower MI, a
confined corridor of enhanced low-level SRH persists ahead of a
low-topped convective rain cluster. There is still potential for
this activity to deepen into thunderstorms amid MLCAPE near 500 J/kg
with a low-probability tornado/wind threat, before spreading into
Saginaw Bay. To its south, warm mid-level temperatures/weak lapse
rates yielding meager buoyancy suggest that upstream thunderstorms
across the Upper MS Valley should weaken as they cross southern LK
MI this evening.

Please see MCD 1373 for short-term discussion on the southern New
England severe threat.

..Grams.. 06/22/2024

.PREV DISCUSSION... /ISSUED 1129 AM CDT Sat Jun 22 2024/

...Midwest into Lower MI...
A moderately strong mid-level shortwave trough over the eastern
Dakotas will track into the upper MS valley this afternoon.  The
main synoptic surface boundary extends from northern IA into
southern WI, with strong heating and ample low-level moisture
present to the south.  Present indications are that scattered
thunderstorms will develop along the boundary by mid-afternoon and
sag southward across eastern IA and northern MO/IL through the
evening.  Forecast soundings show moderate CAPE values and favorable
deep-layer shear for convective organization and a few supercells,
capable of damaging winds, hail, and a few tornadoes.  The main
limiting factors for a more significant severe weather event appear
to be the warm temperatures aloft and resulting weak lapse rates,
and CAM solutions indicating a rather quick evolution into more
linear storm-modes.

...Southern New England...
A cluster of thunderstorms currently over eastern NY is expected to
intensify and track southeastward along a surface boundary into
southern New England this afternoon.  This may result in a corridor
of locally damaging wind gusts.  Have therefore added a small SLGT
risk area.  Please refer to MCD #1371 for further details.

...Western FL Peninsula...
Strong heating is resulting in a hot/humid airmass over the western
FL peninsula today, with temperatures in the mid 90s.  Combined with
dewpoints in the mid-upper 70s, steep low-level lapse rates, and
high PWAT values, the environment appears favorable for a few wet
microbursts later today.  Several morning CAM solutions suggest
organized outflow from early storms over eastern FL may further
increase the risk of strong wind gusts.

$$