LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 AM CDT Wed Aug 23 2023
Valid 231200Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE GREAT LAKES AND UPPER OHIO VALLEY...
...SUMMARY...
Thunderstorms associated with damaging wind gusts and hail are
expected to develop tonight across parts of the lower Great Lakes
region and upper Ohio Valley. Marginally severe wind gusts and hail
will also be possible in parts of the northern Plains late this
afternoon and evening.
...Great Lakes/Upper Ohio Valley...
A mid-level anticyclone will be located across the central U.S.
today. On the northeastern periphery of this feature, mid-level flow
will be from the west and northwest across the Great Lakes region.
Thunderstorms will likely be ongoing across parts of Lower Michigan
at the start of the period. This activity is expected to weaken by
late morning. A moist airmass will advect eastward across Lower
Michigan today, with surface dewpoints increasing into the lower to
mid 70s F. Within northwest mid-level flow, a shortwave trough is
forecast to move southeast across the eastern Great Lakes. Ahead of
this feature, model forecasts consistently develop scattered
thunderstorms late this evening. This activity is forecast to
organize into an MCS and move southeastward across eastern Lower
Michigan, and into northern Ohio and northwest Pennsylvania during
the overnight period. RAP forecast soundings near the track of the
MCS around midnight suggest that the storms will be surface-based
with strong instability (MUCAPE above 4000 J/kg), and moderate
deep-layer shear. This should support a wind-damage threat as the
MCS develops into a bowing line segment. The MCS could impact areas
as far south as southeast Ohio and western Pennsylvania later in the
period.
...Northern Plains...
Mid-level flow is forecast to be from the west-southwest across the
north-central U.S. today, over the top of a mid-level anticyclone in
the central U.S. At the surface, a quasi-stationary front will
remain from central South Dakota into southern Minnesota. Low-level
moisture will be maximized to the north of this boundary from
northeastern South Dakota into central and eastern North Dakota,
where an axis of instability will likely develop. Isolated
thunderstorms may form across parts of North Dakota near this axis
of instability from late afternoon into evening. The storms will
most likely develop along the leading edge of a band of large-scale
ascent ahead of an approaching shortwave trough, with most of the
convection remaining elevated. In spite of this, effective shear
near 40 knots and somewhat steep lapse rates above 700 mb may be
enough for a marginal hail threat. A few strong wind gusts will also
be possible.
..Broyles/Weinman.. 08/23/2023
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