Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Sat Jul 19 2025
Valid 191630Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN/CENTRAL PLAINS...MIDWEST/GREAT LAKES...AND
VIRGINIA/NORTH CAROLINA...
...SUMMARY...
Scattered damaging winds are possible today across parts of the
Midwest/Great Lakes and southern Mid-Atlantic. Scattered large to
very large hail and severe gusts are possible, along with a
potential tornado threat, across the northern/central Plains during
the late afternoon and evening.
...Midwest/Great Lakes...
An ongoing sub-severe MCS continues east-southeast across IL with an
attendant warm advection cluster of thunderstorms downstream over
the lower Wabash Valley. Considerable convective overturning
coupled with convective cloud debris have acted to limit
destabilization thus far across IL into western IN and northward
into the southwest Great Lakes. Have reduced severe probabilities
this outlook update for northern IL into WI due to limited
destabilization, and models converging on limited storm coverage
through the remainder of the day and their depiction of primary
thunderstorm activity tonight occurring farther south/southwest over
IA into central IL towards daybreak.
However, downstream of the ongoing thunderstorm clusters over IL/IN,
gradual heating will probably support some intensification of storms
into the afternoon. Isolated to perhaps scattered damaging winds in
small clusters appear to be the primary severe hazard. Other
thunderstorm development is possible over Lower MI where a
wind-damage threat may materialize with the stronger storms that
develop this afternoon. Later this afternoon but more likely into
tonight, additional storms are forecast to develop on the trailing
outflow with an attendant risk for mainly hail/wind.
...Virginia/North Carolina...
A west-east draped frontal zone resides over southern PA to the
north of this region. However, a very moist low-level airmass
featuring lower to mid 70s dewpoints will continue to
heat/destabilize through mid-late afternoon and promote the
development of moderate buoyancy. Despite weak mid-level lapse
rates, high PW (around 2 inches) will promote water-loaded
downdrafts capable of strong to severe gusts and scattered wind
damage with the more organized cluster(s). Around 15-25 kt of
mid-level westerly flow will favor eastward-moving storm activity.
The severe risk is expected to concentrate during the 20-01 UTC
period as storms move towards central VA and into eastern VA by this
evening.
...Northern/Central Plains...
Water-vapor imagery shows a mid-level impulse moving eastward across
the northwest quarter of MT this morning. This will continue
eastward towards eastern MT and the western Dakotas by early
evening. Weaker mid-level westerly flow will remain farther south
into the central High Plains. At the surface, a lee trough will
extend southward from eastern MT to eastern CO. Generally low to mid
60s surface dewpoints should exist this afternoon along/east of the
lee trough, with upper 60s to lower 70s F dewpoints present near a
remnant front/boundary in NE.
Scattered thunderstorms will likely develop initially over the
higher terrain of the northern/central Rockies this afternoon, with
additional development farther east along the lee trough. As this
convection spreads eastward into a moderately to strongly unstable
airmass across the northern/central High Plains, it should
strengthen. Weak low-level winds are forecast to veer and increase
with height through mid/upper levels, supporting strong deep-layer
shear and the potential for supercells. Scattered large hail will be
possible with any supercells that can persist, with most guidance
indicating a greater concentration of severe thunderstorms across
eastern MT into western ND, and separately across western/central
NE. Given the presence of steep mid-level lapse rates and 40-50+ kt
of deep-layer shear, isolated very large hail appears possible.
Recent model guidance indicates a few supercells may develop across
west-central NE late this afternoon into the evening. Some
enlargement of the hodograph during the evening combined with moist
low levels may support a couple hour window for a locally higher
tornado risk compared to within this broader region.
..Smith/Weinman.. 07/19/2025
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