285
ACUS01 KWNS 031945
SWODY1
SPC AC 031944

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 PM CDT Wed Jul 03 2024

Valid 032000Z - 041200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN/CENTRAL PLAINS...AND THE OZARKS INTO THE OHIO VALLEY...

...SUMMARY...
Scattered severe thunderstorms appear possible through evening
across parts of the northern/central High Plains, and from the
Ozarks into the Ohio Valley. The most favorable corridor for
isolated very large hail and significant severe wind gusts is
centered on the central High Plains.

...20z Update...

Severe probabilities remain unchanged from the previous outlook.
Severe storms are possible into this evening from portions of the
central High Plains to the Ozarks and lower Ohio Valley. See Severe
Thunderstorm Watch 501 and MCD 1520 regarding short term discussions
on severe potential in the central High Plains, MCD 1522 for the
northern High Plains, and MCD 1521 for the Ozarks vicinity.

..Leitman.. 07/03/2024

.PREV DISCUSSION... /ISSUED 1128 AM CDT Wed Jul 03 2024/

...Synopsis...
An upper trough will continue moving eastward across Ontario and the
Great Lakes today, while an upper high remains centered over the
Southeast. Farther west, a separate mid-level shortwave trough will
advance east-southeastward from the northern Rockies to the
northern/central High Plains through tonight. Multiple convectively
augmented mid-level vorticity maxima will move generally
east-northeastward across the central Plains into the mid MS and OH
Valleys. At the surface, a cold front extends from the OH Valley
southwestward to the southern Plains. Weak lee cyclogenesis is
forecast to occur across the central High Plains through late this
afternoon, and modest low-level moisture return is anticipated to
the north of the front and east of a weak surface lee trough across
parts of the northern/central Plains.

...Northern/Central Plains...
Morning clouds and lingering convection across parts of the central
Plains will hamper the development of instability today, especially
with eastward extent into NE/KS. Even so, pockets of filtered
daytime heating will occur across the northern/central High Plains
along and east of the surface lee trough. With steepened mid-level
lapse rates present over eastern CO/WY into western SD/NE, a narrow
zone of moderate instability is forecast to be in place prior to
robust convective initiation this afternoon. Initial development
should occur along the length of the lee trough from parts of
western NE into eastern CO. A somewhat separate area of convection
may also develop from northeastern WY to the Black Hills, as
large-scale ascent preceding the mid-level shortwave trough
overspreads this region.

Modest low-level east-southeasterly flow will quickly veer to
westerly at mid/upper levels, with some strengthening and hodograph
elongation. Corresponding strong deep-layer shear will support
supercells initially, with attendant threat for large hail. Given
relatively cool temperatures aloft and the presence of steep
mid-level lapse rates, isolated very large hail greater than 2
inches in diameter appears possible. A small zone with favorable
overlap of moderate instability, strong deep-layer shear, and
sufficient low-level shear remains apparent over parts of the NE
Panhandle into northwest NE. This area may have a locally greater
threat for a couple of tornadoes with any supercells that can
persist late this afternoon into the early evening, assuming the
boundary layer does not become too well mixed. Otherwise, upscale
growth/clustering appears probable this evening as convective
outflows aggregate into the central Plains. Severe/damaging winds
should become the main threat as this occurs, with isolated
significant gusts up to 75 mph possible if a more consolidated
bow/MCS can develop. Confidence in this occurring still remains
somewhat low, but the best chance for a more concentrated corridor
of severe winds remains across parts of eastern CO into southwest NE
and northwest KS this evening.

...Ozarks to the Ohio Valley...
A rather moist low-level airmass remains present along/south of the
front today, with surface dewpoints generally in the low to mid 70s,
and precipitable water values around 1.75-2.2 inches. A fair amount
of convective cloud debris is present along/near the front across
the mid MS Valley. This will tend to slow diurnal destabilization to
some extent across this area. Mid-level lapse rates are also
expected to remain poor. Still, moderate to locally strong
instability and steepened low-level lapse rates are forecast to
develop through peak afternoon heating along/south of the front,
which will extend from the Ozarks northeastward into parts of the OH
Valley.

Low-level winds are expected to remain generally weak, but a modest
increase in southwesterly winds at mid levels should foster
sufficient deep-layer shear to support some updraft organization.
Mainly multicell clusters should develop this afternoon, focused
along the front. Some of this activity may produce scattered
damaging winds through early evening before eventually weakening.
Morning guidance shows a greater concentration of thunderstorms with
clustering potential across the Ozarks into the mid MS Valley.

$$