SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1218 PM CDT Sat Sep 24 2022
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS
PARTS OF THE UPPER OHIO VALLEY INTO THE NORTHERN MID ATLANTIC
REGION...
...SUMMARY...
Strong thunderstorms may impact parts of the upper Ohio Valley into
the northern Mid Atlantic coast vicinity Sunday, posing at least
some risk for severe weather.
...Synopsis...
Mid/upper flow is in the process of amplifying across the
mid-latitude Pacific into North America. This includes prominent
ridging building across the Pacific coast through the Rockies and,
by late Sunday into Sunday night, a significant short wave trough
digging downstream, across the Upper Midwest into Ohio Valley. A
preceding short wave trough is forecast to accelerate east of the
lower Ohio Valley, before turning northeastward across the northern
Mid Atlantic states and New England, within larger-scale troughing
evolving across the Mississippi Valley through the Atlantic
Seaboard.
Models suggest that this evolving regime will be accompanied by the
development of a broad surface low across parts of the lower Great
Lakes into St. Lawrence Valley vicinity, and a reinforcing intrusion
of cooler and/or drier air across much of the nation east of the
Rockies Sunday through Sunday night. However, this is occurring in
the wake of a substantive prior intrusion of cool/dry air, and in
the wake of the Fiona, which is forecast to migrate north of the
Canadian Maritimes into the Labrador Sea. As a result, it appears
that low-level forcing for ascent and moisture return within the
warm sector of the developing low will remain limited, which may
tend to suppress the potential for vigorous thunderstorm development
during this period.
...Mid/upper Ohio Valley into northern Mid Atlantic...
The mid-level cold pool, and forcing for ascent in the exit region
of the strong mid-level jet streak accompanying the lead short wave
perturbation, seem likely to become the primary focus for any strong
thunderstorm development Sunday. As the wave shifts east of the
mid/upper Ohio Valley by midday, toward the northern Mid Atlantic
coast through early evening, it appears that boundary-layer
destabilization will remain rather modest. CAPE is generally
forecast to peak around or below 500 J/kg along a developing warm
frontal zone across parts of central and eastern Pennsylvania into
Long Island/southern New England, and below 1000 J/kg ahead of the
developing cold front across the Allegheny Plateau vicinity.
However, this could be sufficient to support scattered thunderstorm
development and, in the presence of strong shear (beneath 30-70+ kt
flow in the 850-500 mb layer), at least some potential for organized
severe thunderstorm development. This may include isolated to
widely scattered supercells, particularly along the warm frontal
zone, where various model output suggests that low-level hodographs
might become supportive of the risk for a tornado or two, before
convection wanes by Sunday evening.
..Kerr.. 09/24/2022
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