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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0754 AM CDT Wed Sep 14 2022

Valid 141300Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM WESTERN
NEBRASKA INTO PARTS OF SOUTH DAKOTA...AND OVER PORTIONS OF THE
SOUTHERN HIGH PLAINS...

...SUMMARY...
Storms capable of isolated severe gusts will be possible this
afternoon and evening from western Nebraska into parts of South
Dakota, and over portions of the southern High Plains.

...Synopsis...
The main mid/upper-level feature for this forecast will be a loosely
organized trough -- initially located from western/central MT
roughly southward over central parts of UT/AZ.  Several smaller-
scale perturbations are evident in moisture-channel imagery within
the associated cyclonic flow -- the most prominent being over
southwestern CO to south-central NM, eastern NV, western MT/eastern
ID, and eastern MT.  The basal, CO/NM shortwave trough resides in a
zone of strongly difluent flow aloft, in the left-exit region of a
subtropical-jet segment that extends from south-central CA to
southwestern NM this morning.  This feature will stretch north-south
as it ejects east-northeastward today, reaching eastern parts of
CO/NM by 00Z.  By 12Z, this perturbation should extend from western
NE southward down the High plains to west TX, beco*ing the dominant
portion of the broader-scale trough.

At 11Z, the surface analysis showed a cold front over Downeast ME,
south-southwestward across Atlantic waters to northern FL and
west-southwestward across the northern Gulf.  This front will
proceed eastward out of ME the next several hours and slowly
southward over northern FL today.  General thunderstorms are
expected over FL along and south of the front in a weak-flow/weak-
shear environment.  Farther west, lows were analyzed between SHR-MLS
and between SNY-AKO, along a lee trough that extends farther south
over eastern portions of CO/NM.  Cyclogenesis is expected  through
the day across western SD, consolidating the lows farther northwest
and south, with slight eastward shift of the trailing lee trough
across the central/southern High Plains.

...NE/SD to Southern High Plains...
Isolated to scattered thunderstorms are forecast to develop near the
lee trough, in a long corridor from southern SD to the eastern
NM/west TX north-south border region, with a threat of isolated
severe gusts.  Greater convective coverage may occur in the south,
with more large-scale ascent/support aloft and weaker MLCINH, in
closer proximity to the mid/upper trough.  Better low-level
thermodynamic support, especially in terms of diabatic heating and
convergence in the boundary layer closer to the cyclogenesis, is
expected in the north.  Both areas, however, will be characterized
by deep subcloud layers with steep mid/later afternoon lapse rates
(near dry adiabatic).  Vertical mixing will be counterbalanced
enough by moist advection to keep dewpoints generally in the 50s F,
supporting around 500-1000 J/kg MLCAPE in both areas (somewhat
higher in the north, but with a stronger EML/capping regime).

Kinematically, both areas will be characterized by veering with
height in low to middle levels, well-curved but generally small
hodographs, and modest effective shear due to lack of greater
midlevel speeds.  As such, variably organized, occasionally
clustered, high-based multicells should be the main storm type,
decreasing rapidly in coverage/intensity after dark as the foregoing
boundary layer cools/stabilizes.

At this time, a relative minimum in convective coverage is progged
for the portions of NE/KS between the two severe-outlook areas,
making the intervening area more conditional.  Still, the airmass in
between also will be characterized by a deep/well-mixed boundary
layer, and a strong-severe gust cannot be ruled out from any
sustained convection there as well.

..Edwards/Smith.. 09/14/2022