LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1242 AM CDT Fri Aug 25 2023
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS...LOWER TO MID MISSOURI VALLEY...MID MISSISSIPPI
VALLEY...OHIO VALLEY...SOUTHERN AND CENTRAL APPALACHIANS...AND
MID-ATLANTIC...
...SUMMARY...
Isolated to scattered thunderstorms associated with strong wind
gusts and hail will be possible this afternoon and evening from the
central Plains eastward to the Ohio Valley and Mid-Atlantic.
...Mid Mississippi Valley/Ohio Valley/Mid-Atlantic...
A mid-level cyclonic flow pattern will be in place today from the
north-central U.S. east-southeastward into the Great Lakes. At the
surface, a moist airmass will be located across much of the eastern
U.S., with an axis of maximized low-level moisture extending from
southeast Iowa into the Ohio Valley. Some model forecasts develop a
cluster of strong thunderstorms along and near this axis of
instability. Although low-level lapse rates are forecast to become
steep near this axis during the late afternoon, deep-layer shear
will remain weak. For this reason, any wind-damage potential should
remain marginal.
Further to the east into the southern and central Appalachians, and
Mid-Atlantic, mid-level flow will be divergent and from the
northwest. As surface temperatures warm during the day, isolated to
scattered thunderstorms are expected to develop in the central
Appalachians. Although low-level lapse rates will become steep
across much of the region, deep-layer shear will remain weak. This
suggests that any severe threat will be marginal late this afternoon
and early this evening. A few strong wind gusts will be the primary
hazard.
...Central Plains/Lower to Mid Missouri Valley...
A mid-level anticyclone will remain over the south-central U.S.
today as flow remains west-northwesterly across the north-central
and northeastern states. At the surface, a cold front will advance
southeastward into the central plains and mid Missouri Valley. A
narrow corridor of maximized low-level moisture will be in place
near the front, with surface dewpoints generally in the 60s F. This
will contribute to moderate instability by afternoon. As the airmass
destabilizes, scattered thunderstorms are forecast to develop in the
central High Plains, where large-scale ascent will likely be
maximized near and ahead of a shortwave trough. In addition to
moderate instability, RAP forecast soundings at 21Z from eastern
Colorado into northwest Kansas have 0-6 km shear peaking in the 25
to 30 knot range. This, combined with 700-500 mb lapse rates near 7
C/km could be enough for a few severe storms. Marginally severe wind
gusts and hail will be the primary threats.
Further east into the lower to mid Missouri Valley, isolated
thunderstorm development will be possible during the late afternoon
and early evening. However, large-scale ascent and deep-layer shear
will remain weak. This suggests any severe threat that develops
should be marginal and isolated. Hail and a few strong wind gusts
will be the primary threats.
..Broyles/Thornton.. 08/25/2023
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