SPC Jul 1, 2025 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1228 PM CDT Tue Jul 01 2025

Valid 021200Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE NORTHERN ROCKIES AND UPPER MIDWEST INTO THE GREAT LAKES...

...SUMMARY...
At least scattered storms are possible across a large portion of the
continental U.S. on Wednesday. Isolated severe gusts may accompany
the stronger storms over portions of the Northern Rockies and the
Upper Midwest to central Michigan region.

...Synopsis...
A mid-level trough will amplify while tracking toward New England,
with an upper ridge poised to build over the central U.S. as another
mid-level trough impinges on the Pacific Northwest tomorrow
(Wednesday). Widespread, rich low-level moisture will encourage at
least scattered thunderstorm development across much of the CONUS.
However, the best chance for strong to isolated severe thunderstorms
will be over parts of the Northern Rockies and the Upper
Midwest/Great Lakes regions. Here, low-level moisture and
instability will best overlap with modest mid-level westerly flow
along the periphery of the upper ridge, where some vertical wind
shear will be present to encourage storm organization.

...Portions of the Northern Rockies...
Through the day, surface heating will support mixing of a dry
boundary layer, which may deepen to 500 mb in spots. Tropospheric
lapse rates will steepen to around 9 C/km, boosting SBCAPE into the
500-1500 J/kg range. High-based thunderstorms should develop by
afternoon peak heating. Modest mid-level flow along the periphery of
the ridge will overspread the dry boundary layer, resulting in
elongated, straight hodographs and 30 kts of effective bulk shear.
Multicell structures or perhaps a transient supercell will be the
likely storm modes. Given the dry boundary layer, the stronger storm
cores may produce a few severe gusts.

...Upper Midwest into the Great Lakes...
Along the eastern periphery of the upper ridge, broad northwesterly
mid/upper flow will overspread the Upper Midwest and Great Lakes
region during the afternoon. Modest low-level moisture and mid-level
lapse rates will contribute to 1000-2000 J/kg MLCAPE by afternoon
peak heating. A belt of stronger northwesterly 500 mb flow will
overspread the Great Lakes as the eastern trough deepens in the
18-00Z time frame, contributing to vertical speed shear and
elongated, straight hodographs. Over 30 kts of unidirectional
effective bulk shear will support multicells capable of producing a
few instances of severe wind and/or hail.

..Squitieri.. 07/01/2025

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