298
ACUS01 KWNS 091254
SWODY1
SPC AC 091253

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Wed Jul 09 2025

Valid 091300Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MID-ATLANTIC STATES/CAROLINAS AND NORTHERN/CENTRAL PLAINS...

...SUMMARY...
Scattered damaging winds are possible this afternoon to early
evening from parts of the Carolinas to the Mid-Atlantic. Large hail
and severe wind gusts are also possible across parts of the
northern/central Plains late this afternoon into evening.

...Mid-Atlantic/Southeast States...
A weak mid-level trough will move slowly eastward today across the
Great Lakes and Ohio Valley. A belt of modestly enhanced
southwesterly mid-level flow will remain over the Mid-Atlantic
through this evening, diminishing with southward extent in the
Southeast. Scattered to numerous thunderstorms are once again
expected to develop this afternoon over the southern Appalachians
and Blue Ridge Mountains, and then spread eastward towards the
coast. Steepening low-level lapse rates and rich low-level moisture
will support MLCAPE generally around 1500-3000 J/kg across lower
elevations.

Loosely organized clusters may eventually develop from parts of
Virginia towards the DelMarVa Peninsula and vicinity owing to
somewhat more favorable deep-layer shear across these regions.
Isolated hail may occur initially with the more cellular/discrete
convection, before scattered severe/damaging winds becomes the
primary risk with eastward extent as multiple clusters potentially
develop.

...Northern/central Plains...
Downstream of a low-amplitude mid-level ridge emanating from an
upper-level anticyclone over the Southwest, most guidance continues
to suggest that isolated to scattered thunderstorms should form by
late this afternoon along a weak surface trough. However, it should
be noted that guidance continues to vary considerably in the
short-term spatial details, likely owing to owing to degree of
elevated mixed layer/warmth aloft. Recent HRRR (and RRFS) runs are
somewhat uncharacteristically more aggressive (given the capping and
modest forcing regime etc.) in terms of overall degree of deep
convective development and the southward extent thereof, as compared
to various global guidance.

A corridor of strong to very strong instability will exist by late
afternoon/early evening from parts of western/central Dakotas to
northern Nebraska, aided by daytime heating and very steep lapse
rates. Despite modest mid-level west-northwesterlies owing to the
proximity of the upper ridge, stronger upper-level westerlies will
support adequate deep-layer shear for a few supercells initially,
with associated threat for large to isolated very large hail.
Outflow-dominated downdrafts should foster clustering
east-southeastward across the Dakotas and parts of Nebraska, with a
risk for severe-caliber wind gusts, some of which could be 75+ mph
on an isolated basis given the rather favorable thermodynamic
environment forecast. Risk-magnitude uncertainty increases southward
across Kansas, but at least isolated severe storms may occur across
western/central/northern parts of Kansas, and possibly into northern
Oklahoma.

...Northern Intermountain West/Rockies and northern Great Basin...
Downstream of a shortwave trough moving eastward toward the northern
Great Basin, an elongated belt of enhanced southwesterly mid-level
flow will exist across the northern Great Basin/Rockies. Within this
favorable flow regime amid steepened low-level lapse rates through
daytime heating, scattered thunderstorms should foster strong to
isolated severe wind gusts from parts of eastern Oregon into
Idaho/Montana and possibly northern Utah.

...Lower Michigan to northwest Ohio...
Isolated/marginally severe hail and locally damaging winds may occur
this afternoon across parts of Lower Michigan and northwest
Ohio. This will be as scattered thunderstorms develop beneath a weak
upper trough, supported by a modest combination of instability and
deep-layer shear.

..Guyer/Dean.. 07/09/2025

$$