ACUS01 KWNS 251243
SWODY1
SPC AC 251242

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Thu Jul 25 2024

Valid 251300Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MONTANA...

...SUMMARY...
Strong to locally severe thunderstorms with wind gusts will be
possible today across Montana and the northern Rockies/Great Basin,
southern Arizona, and Carolinas/Mid-Atlantic States.

...Montana/Northern Rockies to Great Basin...
A prominent upper-level trough will spread eastward from British
Columbia toward Alberta/Saskatchewan, with strengthening cyclonic
westerlies overspreading the northern Rockies/Montana. Scattered
thunderstorm development is forecast to initiate off the higher
terrain this afternoon, and in advance of a cold front, across
central Montana, where a hot and deeply mixed boundary layer may
become characterized by modest instability. Forecast soundings are
suggestive of 40-60 F temperature-dew point spreads by peak heating.
A downward mixing of 30-40+ kt ambient southwesterly to westerly
flow in the 700-500 mb layer may contribute to severe-caliber wind
gusts in consolidating outflows, as convection spreads eastward into
this evening toward eastern Montana and possibly western North
Dakota.

Other high-based storms capable of severe-caliber wind gusts could
occur as far southwest as parts of the Great Basin later this
afternoon and evening, within an unstable air mass ahead of a front
across the northern Intermountain region.

...Arizona...
Lingering early day outflow/cloud cover via yesterday's relatively
active convection should generally abate by afternoon. As the
boundary layer diurnally warms and destabilizes, thunderstorms are
again likely to initiate across the Mogollon Rim and adjacent
mountains of southwest New Mexico this afternoon. Given the position
and movement of the mid-level high, somewhat stronger (around 15 kt)
northeasterly steering flow will remain focused across southeast
into adjacent portions of central Arizona. Localized severe-caliber
wind gusts and blowing dust will again be possible this afternoon
through early/mid-evening as storms progress south-southwestward
onto the desert floor.

...Carolinas/Mid-Atlantic States...
Cloud cover will likely remain prevalent regionally today with
showers/some thunderstorms ongoing this morning to the south of the
primary front that will be shifting south-southeastward across the
northern and central Appalachians. Near the southern periphery of
the larger-scale mid-level troughing, a belt of 30-40 kt
south-southwesterly flow in the 850-500 mb layer may enhance
convective development within a plume of seasonably high moisture
content. While lapse rates and overall buoyancy will be modest,
heavy precipitation loading and downward mixing of momentum may
contribute to a few strong downdrafts with the possibility of
locally damaging surface gusts/tree damage this afternoon.

...Middle/Upper Texas Coast and Southern Louisiana...
Extensive showers and some thunderstorms are ongoing along the Texas
coast early today. Influenced by a weak mid-level disturbance, some
guidance suggests that a strengthening of low-level winds/shear will
occur today. However, mid-level winds will remain weak, while the
aforementioned convection should considerably limit destabilization
inland. These factors seem likely to minimize the potential for
anything beyond a few very weak/transient mesocyclones.

..Guyer/Jewell.. 07/25/2024

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