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
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