LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Fri Aug 25 2023
Valid 251300Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MIDWEST...
...SUMMARY...
Isolated to scattered thunderstorms associated with strong wind
gusts and hail are possible this afternoon and evening especially
across parts of the the Midwest, and more broadly from the central
Plains eastward to the Ohio Valley and Mid-Atlantic States.
...Midwest...
With the prominent upper high centered over the southern Plains, a
shortwave trough (and related speed max) over northern Minnesota and
nearby Ontario will continue to modestly amplify and spread
southeastward over the Great Lakes through tonight. While forcing
for ascent and stronger winds aloft will exist to the north, some of
these influences will partially overlap a frontal zone across the
Midwest and Middle Mississippi Valley/Lower Ohio Valley, with the
easternmost portion of the front convectively modified and more
southward progressive across the Appalachians/Mid-Atlantic region.
The aforementioned disturbance appears to be influencing widely
scattered thunderstorms across Iowa early today. This forcing for
ascent may interface with the frontal zone later today, where a very
unstable air mass will reside particularly across southeast Iowa
into central Illinois and southern Indiana. Even with some
capping-related uncertainties, concern exists for the possibility of
at least isolated intense thunderstorm development this afternoon
into early evening, with the high degree of instability and ~30 kt
of effective shear potentially supportive of upscale
growing/east-southeastward-moving clusters capable of wind damage.
...Appalachians/Mid-Atlantic States...
A southward-moving MCS continues to spread generally southward
across parts of West Virginia/western Virginia as it has tended to
weaken through the early morning hours. Some later-day thermodynamic
uncertainties exist related to this MCS, but zones of differential
heating/terrain influences and lee trough development should lead to
additional thunderstorm development this afternoon as the boundary
layer recovers/destabilizes. Some strong to severe thunderstorms
capable of wind damage will be possible, even while deep-layer shear
will remain weak.
...Central Plains...
A front will sag southward across the region, with low-level
moisture and buoyancy maximized later today near and north of the
front including eastern Colorado into western/northern Kansas and
southern Nebraska. As the airmass diurnally destabilizes, an
increase in thunderstorms is expected across the region into
mid/late afternoon, with more prevalent thunderstorms this evening.
Steep lapse rates, moderate buoyancy, and modest strength deep-layer
shear will support some severe storms capable of hail and
severe-caliber wind gusts, mostly late this afternoon and evening
across parts of eastern Colorado, western/northern Kansas, and
southern Nebraska.
..Guyer/Goss.. 08/25/2023
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