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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1124 AM CDT Sat Aug 13 2022

Valid 131630Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATER THIS
AFTERNOON/EVENING ACROSS PARTS OF MT/WESTERN ND...AND ACROSS EASTERN
IA/SOUTHERN WI/NORTHERN IL...

...SUMMARY...
Isolated severe thunderstorms are possible across portions of the
northern High Plains and Midwest late this afternoon and evening.

...Eastern IA/southern WI/northern IL this afternoon/evening...
A midlevel high persists over the central High Plains, with a
downstream trough over the Northeast, and an upstream trough over
the Pacific Northwest.  Around the northeast periphery of the
midlevel high, an embedded speed maximum will move southeastward
from southeast MN toward southern WI/northeastern IL, in conjunction
with a weak surface cyclone and cold front.  The front is demarcated
by persistent stratus spreading southward across IA, with a warm
sector south of the front characterized by boundary-layer dewpoints
in the mid 60s and surface temperatures warming into the 80s.  Some
elevated convection is ongoing over southwest WI in a zone of warm
advection ahead of the midlevel speed max and weak surface cyclone.

Continued warming/destabilization through the afternoon from
west-to-east will result in MLCAPE of 1000-1500 J/kg in a narrow
corridor ahead of the cold front across eastern IA/northwestern
IL/southwestern WI.  The stronger forcing for ascent will be in the
warm advection zone just east of the surface warm sector, where a
few elevated storms will pose a low-end hail threat.  Low-level
ascent near the surface cyclone and cold front, close to the
northeast edge of the surface warm sector, could support isolated
thunderstorm development this afternoon/evening.  There will be a
fairly narrow zone of overlapping buoyancy and hodograph
length/curvature to support supercells, but confidence is low in
storms forming and remaining in this favorable zone.  Thus, will
maintain 5% wind/hail (MRGL) probabilities. 

...MT to western ND this afternoon/evening...
Subtle speed maxima will rotate around the north/northwest periphery
of the midlevel high over the central High Plains, within the
monsoonal moisture plume from NV/UT into MT.  Modest low-level
moisture (boundary-layer dewpoints in the mid 50s to mid 60s now)
will tend to mix some with strong afternoon heating, which will
result in profiles with weak-moderate buoyancy (MLCAPE of 500-1000
J/kg) and inverted-v thermodynamic profiles.  Aside from heating
over the higher terrain of southwest/south central MT, the sources
for storm initiation are nebulous this afternoon.  Therefore, there
are some questions about storm coverage, though deep-layer vertical
shear will be sufficient for some storm organization.  Overall, MRGL
with 5% wind appears to be a reasonable reflection of the severe
threat with high-based storms/small clusters that will spread
east-northeastward from the higher terrain toward central/eastern MT
later this afternoon into this evening.

There will be a low-end threat for surface-based storm development
this afternoon along a surface warm front across western ND.  If a
storm can form along this boundary, the environment will favor some
potential for supercells.

..Thompson/Bentley.. 08/13/2022