ACUS02 KWNS 200456
SWODY2
SPC AC 200455

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1155 PM CDT Sat Jul 19 2025

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MONDAY INTO
MONDAY NIGHT ACROSS PARTS OF THE NORTHERN GREAT PLAINS AND TENNESSEE
VALLEY INTO SOUTH ATLANTIC SEABOARD...

...SUMMARY...
Strong thunderstorm development may pose at least some risk for
severe wind and hail across parts of the northern Great Plains and
parts of the Southeast Monday into Monday night.

...Synopsis...
Models continue to indicate at least some shearing of mid-level
troughing initially across the Pacific Northwest at the outset of
the period, between fairly prominent and persistent lower latitude
ridging encompassing much of the interior U.S. and stronger higher
latitude ridging centered over the northeastern Pacific.  However,
one short wave impulse embedded within the troughing may maintain
fairly vigorous strength while slowly accelerating northeastward
into the mountains of western Montana.  Downstream of this
perturbation, the interior U.S. ridging may tend to build a bit
further northeastward across parts of the northern U.S. Great Plains
and Upper Midwest/adjacent Great Lakes vicinity, in the wake of
significant mid-level troughing progressing offshore of the northern
U.S. and Canadian Atlantic coast.  Another significant trough and
embedded mid-level low emerging from the northwestern Canadian
Arctic latitudes is forecast to slowly turn east of the Northwest
Territories toward Hudson Bay.

In lower levels, it appears that a cold front associated with the
higher latitude perturbation may advance through the Canadian
Prairies, but remain north of the international border through this
period.  A preceding cold front may progress slowly southward
through portions of the southern Mid Atlantic, while stalling across
parts of the lower Ohio into middle Mississippi Valleys and
weakening across the middle Missouri Valley/northern Great Plains.

...Northern Great Plains...
Beneath a plume of warm and capping elevated mixed-layer air, models
indicate that a seasonably moist boundary layer will again become
characterized by moderate to large potential instability across
parts of the middle Missouri Valley and adjacent Great Plains.  The
NAM has been more aggressive in recent runs with boundary-layer
moistening on northeasterly to easterly low-level flow into
deepening surface troughing across central and southeastern Montana.

However, aside from the higher terrain of central Montana,
downstream of the short wave impulse emerging from the Pacific
Northwest, forcing for ascent to support convective development
remains a bit unclear across much of the remainder of the northern
Great Plains, given the inhibition associated with the elevated
mixed-layer air.

There does appear an increasing signal that a subtle short wave
impulse, migrating around the western/northwestern periphery of the
stronger mid-level ridging, may contribute to scattered vigorous
high-based thunderstorm development within the drier and more deeply
mixed environment across parts of eastern Wyoming and northeastern
Colorado.  This activity may pose a risk for severe hail and wind
while tending to advect across and northeast/east of the higher
plains late Monday afternoon and evening.

Otherwise, locally enhanced low-level convergence during and shortly
after peak heating might weaken inhibition sufficiently to support
isolated supercell development within the seasonably moist/higher
CAPE environment, with various model output continuing to indicate
one possible focus across parts of central or north central South Dakota.

...Tennessee Valley into southern Atlantic Seaboard...
Even as the lead cold front continues to advance south of the
stronger westerlies, destabilization along and ahead of it may
become conducive to scattered upscale growing thunderstorm activity
posing a risk for potentially damaging wind gusts by late Monday
afternoon into early evening.  Based on model output, it still
appears possible that this could be aided by a remnant convectively
generated or enhanced perturbation emerging from the lower Ohio Valley.

..Kerr.. 07/20/2025

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