Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0747 AM CDT Mon Jul 03 2023

Valid 031300Z - 041200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
THROUGH EARLY TONIGHT FROM NORTHEAST WY INTO SD...AND THIS
AFTERNOON/EVENING ACROSS THE MID-ATLANTIC AND CAROLINAS...

...SUMMARY...
Scattered damaging winds and large hail are expected across the
Mid-Atlantic Region and portions of the northern Great Plains this
afternoon into tonight.

...Northern Plains to northern Rockies/Great Basin...
A surface cold front across MN/SD and gradual height falls with an
approaching midlevel trough will support scattered thunderstorm
development, mainly this afternoon into early tonight from northern
UT/WY to SD and vicinity.  The environment centered on
western/central SD will be the most favorable for severe storms
based on steep lapse rates, MLCAPE of 1500-2500 J/kg and effective
bulk shear of 30-40 kt.  The initial storms will likely be
supercells this afternoon in SD, and another cluster or two could
spread into western SD from WY late this evening into tonight.  The
primary threats will be isolated very large hail (up to 2.5 inches
in diameter) with the initial supercells, and severe outflow gusts
of 60-75 mph with both the supercells and later storm clusters. 
Low-level shear will not be particularly strong and
temperature-dewpoint spreads will be relatively large, though an
isolated tornado or two could occur with supercells along the front.

Farther west into western WY and northern UT/southeast ID,
high-based thunderstorm development is expected this afternoon. 
Inverted-V profiles with modest CAPE and large DCAPE, in combination
with 25-40 kt midlevel flow, will support the potential for at least
isolated strong-severe outflow gusts of 55-70 mph.

...Mid-Atlantic into the Southeast this afternoon/evening...
A slowly weakening midlevel trough and associated surface
cyclone/cold front will move eastward over the Appalachians to the
Mid-Atlantic and southern New England by tonight.  A moist boundary
layer with dewpoints in the lower 70s precedes the front, and
surface heating in cloud breaks will boost MLCAPE to 1500-2000 J/kg
prior to convective initiation around early-mid afternoon.  The
moderate buoyancy and effective bulk shear of 25-35 kt will favor a
mix of multicell clusters and some supercells capable of producing
damaging outflow gusts and isolated large hail.  Flow will weaken
gradually with southward extent, though this will be offset some by
hotter surface temperatures and a deeper layer of steep low-level
lapse rates into the Carolinas.  

Moderate-large buoyancy (MLCAPE 2000-3000 J/kg) will extend farther
west along/south of the cold front into MS/AL/GA, and as far west as
a remnant MCV in OK.  Despite weak vertical shear, water-loaded
downdrafts in an environment with DCAPE near 1000 J/kg will support
the potential for isolated damaging winds this afternoon/evening.

..Thompson/Gleason.. 07/03/2023