Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Thu Sep 04 2025
Valid 041200Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
EAST...
...SUMMARY...
Isolated damaging winds are possible across parts of the Northeast
to the southern Appalachians and Tennessee Valley from late morning
through the afternoon.
...Synopsis...
A vertically stacked cyclone will drift north in northern ON, as an
intense mid-level jetlet and shortwave trough amplifies from the
southern Canadian Prairies across the Upper Midwest/Great Lakes. A
leading cold front will progress east into the Northeast to TN
Valley by this afternoon, with a separate lee trough diurnally
sharpening from VA into NY.
...Southern Appalachians/TN Valley to the Northeast...
Convection will likely be ongoing at 12Z along parts of the
aforementioned cold front from the Lake Erie to northern KY
vicinity. Despite weak mid-level lapse rates, diabatic surface
heating ahead of this activity should yield diurnal increases in
convective coverage/intensity by late morning across parts of the
Cumberland Plateau. This will overlap the northern extent of
moderate buoyancy across the TN Valley where low-level moisture is
richer. Combined with a more westerly component to mid-level flow
near the basal portion of the broad trough, a few semi-discrete and
loosely organized cells should develop southward during the
afternoon. Locally damaging winds and marginally severe hail are
possible, centered on the eastern TN vicinity.
Isolated to scattered multicell clusters and short-line segments may
also evolve in the afternoon from convection along/ahead of the cold
front and lee trough. Weak MLCAPE and poor mid-level lapse rates
will temper convective vigor, with damaging wind potential locally
augmented where pockets of deeper boundary-layer heating occur.
...Mid-MO Valley...
The aforementioned shortwave trough and intense mid-level jetlet
amplifying into the Upper Midwest could support a couple brief
strong storms in the early evening. A narrow corridor of meager
surface-based buoyancy may develop ahead of a sharpening cold front
by late afternoon. Modified moisture return in the wake of a prior
frontal passage will be limited and convection should remain
low-topped given the flimsy buoyancy. Still, the background wind
fields and strengthening forcing for ascent render concern for a few
locally strong gusts and small hail.
...KS...
An accelerating and sharpening cold front will sweep south across
the central High/Great Plains tonight. Undercut/elevated convection
should form to the cold side of this boundary early Friday morning.
Locally strong surface gusts may accompany this activity amid robust
low-level northerlies.
..Grams/Thornton.. 09/04/2025
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