Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1138 AM CDT Tue Sep 16 2025
Valid 161630Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
HIGH PLAINS...
...SUMMARY...
Scattered severe thunderstorms are expected this afternoon into
early evening across a portion of the central Great Plains. Large
hail, severe gusts, and a tornado or two may occur.
...Eastern Colorado/Wyoming and Central Plains...
A semi-closed upper low will continue to spread southeastward today
over Wyoming and nearby parts of southern Montana and northern
Colorado, as a cold front similarly settles southeastward across the
Front Range/central High Plains, while a weak surface wave develops
northeastward along the front. Increasing forcing for
ascent/strengthening flow aloft related to a lead portion of the
upper trough will influence steadily increasing and organized
thunderstorm development into the afternoon, especially within the
immediate post-frontal environment.
Buoyancy will be maximized from far northeast Colorado into central
Nebraska where low to mid 60s F dewpoints beneath steep mid-level
lapse rates will support MLCAPE around 2000-2500 J/kg. The resulting
combination of lift, instability, and moderate shear (generally
around 35 kt of effective bulk shear) will support strong to severe
storms. Large hail appears to be the most prominent hazard
(especially western Nebraska), but some clustering could lead to a
few strong gusts as well. Presence of the surface low/boundary and
backed low-level flow may result in a low-probability tornado risk
as well.
...Iowa/northern Missouri/eastern Nebraska...
Some stronger/locally severe pulse-type storms may occur late this
afternoon through around sunset within the strong instability/weak
deep-layer flow regime.
...Northern Minnesota/Lake Superior...
Severe-weather potential should be limited across this region, but
will retain low-severe probabilities given somewhat stronger
deep-layer shear and a low or conditional-type potential near the
advancing front.
...Virginia Tidewater/far northeast North Carolina...
Surface reflection of a semi-stacked cyclone is just off the far
northeast corner of North Carolina at midday. This low should
continue to drift north-northwest today and tonight, while likely
gradually weakening, although its northern peripheral strong
low-level east/northeasterly winds (reference Wakefield WSR-88D VWP)
will likely persist through the day. Dry northerly continental
trajectories inland will relegate meaningful (albeit limited)
buoyancy to the immediate coasts of the Virginia Tidewater/Maryland
shore, and otherwise offshore. This will similarly relegate any
transient supercell and low-end tornado/wind risk to the immediate
coast, but more likely just offshore.
..Guyer/Thornton.. 09/16/2025
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