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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0257 PM CDT Wed Jul 24 2024

Valid 242000Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR
WESTERN/CENTRAL NY INTO NORTHWESTERN PA...AND SOUTHERN ARIZONA...

...SUMMARY...
Strong to severe thunderstorms may produce damaging wind gusts
across western/central New York and vicinity, the northern Rockies,
and across southern Arizona this afternoon/evening.

...20z Update...
The current D1 Outlook remains on track with no changes needed with
this update. 

Several clusters of thunderstorms are ongoing along a cold front
extending from the Great Lakes region northeastward into portions of
New York. In this region, daytime heating has yielded around
1000-1500 J/kg of MLCAPE with 30-40 kts of deep layer shear. In this
regime, some more organized cells have produced wind damage across
portions of New York and Pennsylvania. The threat for strong to
severe gusts will continue through the afternoon and evening,
shifting eastward with the front.

Farther west, two areas of potential continue with a Marginal Risk
across the Northern Rockies and a Slight Risk across southern
Arizona. Within these regions, damaging wind will be possible with
thunderstorm activity this afternoon. See MCD #1701 for more
information on the threat across southern Arizona.

..Thornton/Thompson.. 07/24/2024

.PREV DISCUSSION... /ISSUED 1128 AM CDT Wed Jul 24 2024/

...Western/central NY and northwest PA this afternoon/evening...
A midlevel trough will progress eastward from the upper Great Lakes
toward NY as an associated surface cold front likewise moves
eastward into western NY and southeastward into OH/northwest PA
through this evening.  Surface heating is underway in a corridor
ahead of the cold front from northern OH into western NY where
boundary-layer dewpoints are in the mid-upper 60s with surface
temperatures warming into the lower 80s, and a band of convection
has already developed from Lake Erie to western Lake Ontario.  These
storms may persist into the afternoon while spreading eastward, with
additional development possible along convective outflow, a
pre-frontal confluence zone and/or local lake breeze boundaries. 
Midlevel lapse rates will remain modest (roughly 6.5 C/km), but the
low-level moisture/warming temperatures will drive MLCAPE in the
1000-1500 J/kg range.  Deep-layer vertical shear/hodograph length
will be on the lower margins for organized clusters/cells per local
VWPs now sampling 30-40 kt midlevel flow, while steepening low-level
lapse rates will support the potential for occasional wind damage
with strong thunderstorm outflow in the 50-60 mph range.

...Southern AZ this afternoon/evening...
Strong surface heating is underway near and south of the Rim, and
late afternoon temperatures will peak near or above 110 F across the
lower deserts into southern AZ.  Moisture will be sufficient for
thunderstorm development this afternoon along the Rim and the
mountains in southeast AZ, while northeasterly midlevel flow of
15-20 kt will steer outflows southwestward toward the lower deserts.
 MLCAPE will increase to the 1000-1500 J/kg with deep inverted-V
profiles favoring strong downdrafts and outflow winds of 60-75 mph
capable of producing wind damage and substantial blowing dust.  The
relatively greater severe threat will be with the stronger/deeper
convection driven by outflow mergers.

...Northern Rockies area this afternoon/evening...
A plume of mainly midlevel moisture with PW values of 0.75-1 inch
(per BOI and LKN 12z soundings) will persist around the northern
periphery of a midlevel high over the Great Basin, and southeast of
a midlevel trough approaching WA.  High-based thunderstorms are
expected in a few loosely organized clusters within this plume,
where deep inverted-V profiles will support the potential for a few
strong-severe outflow gusts 50-65 mph.

...Mid-Atlantic into NC this afternoon...
Modest surface heating within small cloud breaks and boundary-layer
dewpoints of 72-74 F will contribute MLCAPE approaching 1500 J/kg to
the east of the Blue Ridge, though midlevel lapse rates will remain
poor.  Still, the southern extent of 30-40 kt midlevel flow will
support a low-end wind damage threat with the stronger storm
clusters this afternoon.