ACUS02 KWNS 180558
SWODY2
SPC AC 180557

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Thu Jul 18 2024

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
THE NORTHERN/CENTRAL HIGH PLAINS INTO THE NORTHERN/CENTRAL PLAINS...

...SUMMARY...
Isolated strong to severe thunderstorms are possible across portions
of the northern/central High Plains into the northern/central Plains
on Friday.

...Synopsis...
Expansive upper ridging is expected to be in place from the
Southwest into western Canada early Friday morning, with upper
troughing anticipated east of this ridging across the central/
eastern CONUS and much of eastern Canada. A shortwave trough
embedded within this eastern troughing is forecast to progress
eastward across Ontario and adjacent portions of the St. Lawrence
Valley and northern New England. Another shortwave trough is
forecast to progress through the northeastern periphery of the
western ridge, moving from eastern MT southeastward across the
northern High Plains and reaching the central Plains by early
Saturday.

Surface pattern early Friday will be dominated by a strong high over
the OH Valley, with a weak stationary front along its southern
periphery stretching from SC into the TX Hill Country. Warm and
moist conditions are expected along this boundary, helping to
support afternoon thunderstorms amid modest low-level convergence
along the front as well as in the vicinity of a convectively
generated vorticity maximum expected to move across the Lower MS
Valley and MS/AL. Storm severity should be mitigated by weak shear
and largely disorganized storm mode.

...Northern/Central High Plains into the northern/central Plains...
Surface lee troughing is anticipated across the High Plains, with
moderate low-level moisture east of this lee troughing across the
majority of the Plains. Afternoon thunderstorm development appears
probable along the lee trough as well as farther east into more of
SD and NE as the previously mentioned shortwave trough moves into
the region. Moderate northwesterly flow aloft will support a
southeasterly storm motion, taking any development into areas with
more favorable low-level moisture and stronger buoyancy.

Additionally, this moderate northwesterly flow aloft atop low-level
southerlies will help support moderate deep-layer vertical shear.
This shear could help organize initially high-based,
outflow-dominant storms into one or more coherent bowing segments
capable of damaging gusts. While this overall convective evolution
appears probable, where it occurs is less certain. Furthermore,
there is uncertainty regarding just how strong the gusts with this
line (or lines) will be. Uncertainties merit delaying the inclusion
of higher probabilities to later outlooks when these more mesoscale
details become predictable.

..Mosier.. 07/18/2024

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