ACUS01 KWNS 030532

SWODY1

SPC AC 030530



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

1230 AM CDT Thu Jul 03 2025



Valid 031200Z - 041200Z



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

THE NORTHEAST AND NORTHERN PLAINS...



...SUMMARY...

Scattered severe thunderstorms capable of producing severe/damaging

winds and large hail are forecast across parts of the Northeast and

northern Plains today.



...Northeast...

An upper trough with an embedded 40-50 kt mid-level speed maximum

will pivot across the Northeast today. A related surface cold front

will likewise develop eastward across this region through the

afternoon/evening. Filtered daytime heating of a seasonably moist

low-level airmass will support the development of moderate

instability along/ahead of the cold front by late morning/early

afternoon. Aided by the enhanced mid-level flow, deep-layer shear

will likely be strong enough to support updraft organization,

including a mix of multicells and perhaps some supercells. Scattered

severe/damaging winds should be the primary severe threat as

low-level lapse rates gradually steepen. But, some large hail may

occur given favorable shear, especially if any supercells can be

sustained. The Slight Risk has been expanded northward to include

more of New England, as recent guidance trends show potential for

organized severe convection along/ahead much of the length of the

front.



...Northern Plains...

An upper ridge will persist over much of the Plains today. Even so,

a weak mid-level disturbance is forecast to advance eastward from MT

across the northern Plains this afternoon/evening on the northern

periphery of the upper ridge. This feature should encourage isolated

to scattered intense thunderstorm development along/near a warm

front extending across parts of ND by late afternoon/early evening.

Moderate to strong instability is expected along/near this boundary,

aided by steep lapse rates aloft. Modest low-level southerly flow is

forecast to gradually veer and strengthen with height through

mid/upper levels. This will support sufficient deep-layer shear

(30-40 kt) for organized convection, including some supercells

initially across western/central ND. These supercells should pose a

threat for scattered large hail, some of which may be 2+ inches in

diameter given a rather favorable thermodynamic environment

forecast. With time this evening, there may be some potential for

upscale growth into a small bowing cluster with eastward extent into

central/eastern ND. If this mode transition occurs, then the

severe/damaging wind threat would likewise increase. Although

low-level flow should remain fairly modest, a tornado or two also

appears possible, particularly along/near the front where effective

SRH should be locally enhanced.



...Upper Midwest...

Compared to the northern Plains, there is generally less confidence

in overall thunderstorm coverage and development across much of the

Upper Midwest through the period. Weak forcing aloft and the

persistence of the upper ridge should tend to limit convective

development in an otherwise moderately to strongly unstable airmass.

Still, any thunderstorms which can develop, perhaps aided by modest

low-level warm advection this evening/tonight, could pose an

isolated severe hail/wind threat. The Marginal Risk area has been

adjusted northward/westward some based on latest guidance trends

showing multiple potential zones of isolated strong/severe

thunderstorms.



..Gleason/Lyons.. 07/03/2025



$$