ACUS01 KWNS 161234
SWODY1
SPC AC 161233

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0733 AM CDT Tue Sep 16 2025

Valid 161300Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR
NORTHEAST CO...WESTERN/CENTRAL NE...AND EXTREME NORTHWEST KS...

...SUMMARY...
Scattered severe thunderstorms are possible this afternoon into
early evening across a portion of the central Great Plains. Large
hail, severe gusts, and a tornado or two may occur.

...Synopsis...
Early morning satellite imagery shows a fairly amplified upper
pattern across CONUS, consisting of two ridge/trough pairs. The
westernmost pair features ridging that extends from just off the
central CA coast north through southern BC and a shortwave trough
that extends from central MT into northeast NV/northwest UT. The
eastern most pair features ridging from the southern Plains through
the Upper Great Lakes and a modest cyclone centered over central NC.
Despite this amplified upper pattern, flow is generally modest, with
the strongest flow extending through the base of the western
shortwave from northern UT into eastern WY.

The surface analysis reveals a relatively nondescript surface
pattern free of any sharp gradients or notable features, aside from
a weak low just off the northeast NC coast. Moderate moisture (i.e.
mid/upper 60s dewpoints) does extend from the southern Plains
through the Lower MO Valley into southern IA.

...Central High Plains into the Central Plains ...
The western shortwave trough mentioned in the synopsis is forecast
to progress slowly eastward throughout the day, evolving towards a
more closed mid/upper level circulation as it does. Eastern
periphery of ascent associated with this shortwave will impinge on
the western periphery of the better low-level moisture and buoyancy,
resulting in scattered to numerous thunderstorms from eastern WY/CO
into western NE/KS. The best buoyancy across the region will likely
reside from far northeast CO into central NE where low to mid 60s
dewpoints beneath steep mid-level lapse rates will support MLCAPE
around 2000-2500 J/kg. Low-level convergence along a weak cold front
is anticipated in this area as well. The resulting combination of
lift, instability, and modest shear (i.e. around 35 kt of effective
bulk shear) will support strong to severe storms. Large hail appears
to be the most prominent hazard, but some clustering could lead to a
few strong gusts as well. Presence of a surface low and potential
backed low-level flow will result in a low-probability tornado risk
as well.

...Eastern SD to northeast MN...
Steep lapse rates atop moderate low-level moisture will support
moderate to strong buoyancy along a weak front zone forecast to
extend from eastern SD into north-central MN this afternoon.
Low-level convergence along the front will be modest, with warm low
to mid-level temperatures (and resultant capping) likely keeping
storm coverage isolated. Mid-level flow will be modest across most
of the region, but the strong buoyancy could still result in an
isolated threat for severe hail and damaging winds with any storms
that develop. A relatively higher severe potential exists across
northeast NM, where stronger mid-level flow through southern
peripheral of a shortwave trough moving over far northwest Ontario
will be in place this evening.

...VA Tidewater and far northeast NC...
A weak cyclone east of the Outer Banks is progged to drift
northwestward today, reaching the NC/VA border area by this
afternoon. Low-level flow enhancement through its northwest
periphery will promote potential for strong to marginally severe
gusts with any sustained convection. However, the more buoyant air
is expected to remain offshore and displaced east of this stronger
low-level flow, thermodynamically limiting the spatial extent of any
severe threat. Meager surface-based instability may glance the coast
from later this morning through the afternoon before low-level wind
fields subside and the severe risk becomes negligible.

..Mosier/Bentley.. 09/16/2025

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