ACUS01 KWNS 311241
SWODY1
SPC AC 311240

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 AM CDT Sat Aug 31 2024

Valid 311300Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY...

...SUMMARY...
Severe thunderstorms capable of producing mainly damaging winds will
be possible today from parts of the central Appalachians into the
Ohio and Tennessee Valleys. Isolated severe wind gusts may also
occur across parts of the northern Great Lakes.

...Mid-Atlantic into the Ohio and Tennessee Valleys...
A mid/upper-level trough will make slow eastward progress today
across Ontario/Quebec and the Great Lakes while amplifying further.
Ahead of this feature, a surface front should continue to lose
definition and weaken through the day as it moves eastward over
parts of the Northeast/Mid-Atlantic, and southeastward over the OH
Valley before eventually stalling. Recent visible satellite imagery
shows cloud cover remains prevalent over much of the Northeast and
Mid-Atlantic. This will hinder daytime heating and delay
destabilization, especially east of the Blue Ridge Mountains. Still,
area 12Z soundings and recent surface observations indicate a moist
low-level airmass remains in place ahead of the weak cold front.
Generally less cloud cover with westward and southward extent into
the upper OH Valley and TN Valley should allow for greater
instability to develop this afternoon across these regions.

The stronger mid-level flow associated the upper trough is expected
to remain generally displaced to the north/west of the surface warm
sector. Even so, modestly increasing west-southwesterly winds with
height through mid levels should support around 20-30 kt of
deep-layer shear across parts of the central Appalachians and upper
OH Valley vicinity. This shear will be sufficient for loosely
organized multicell clusters to develop and subsequently spread
east-southeastward through this afternoon. Isolated to scattered
damaging winds should be the main threat with this convection,
although some hail may also occur with the strongest cores. Activity
should weaken with eastward extent late this afternoon and evening
across the Mid-Atlantic as it encounters a less unstable airmass.
Weaker deep-layer shear with southward extent into the lower OH
Valley and TN Valley will likely limit overall thunderstorm
organization. But, occasional damaging winds may still occur with
thunderstorms along/south of the front as low-level lapse rates
steepen with diurnal heating.

...Northern Great Lakes...
Strong west-northwesterly mid-level flow will be present today over
the Upper Midwest and northern Great Lakes, in association with a
shortwave trough embedded within a larger upper trough moving
east-southeastward across these regions. While low-level moisture
and related instability are both expected to remain limited,
large-scale ascent and strong deep-layer shear may support the
development low-topped convection this afternoon. If these
thunderstorms can form and be sustained, then isolated strong to
severe winds may occur given the forecast strength of the low to
mid-level flow amid steepened low-level lapse rates.

..Gleason/Leitman.. 08/31/2024

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