ACUS03 KWNS 131901
SWODY3
SPC AC 131900
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 PM CST Thu Nov 13 2025
Valid 151200Z - 161200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE SATURDAY
AFTERNOON AND EVENING ACROSS PARTS OF EASTERN OHIO...WESTERN
PENNSYLVANIA AND NORTHERN WEST VIRGINIA...
...SUMMARY...
Showers and a few thunderstorms may be accompanied by strong wind
gusts across parts of the upper Ohio Valley late Saturday afternoon
and evening.
...Discussion...
Saturday into Saturday night, it appears that the more progressive
flow emanating from the northern mid-latitude Pacific will begin to
impinge on the blocking regime now evolving across parts of eastern
North America into the Atlantic. While an initially prominent
cyclone on the leading edge of this regime is forecast to undergo
considerable deformation and weakening, models continue to indicate
that a notable perturbation emerging from it will dig across the
upper through lower Great Lakes, accompanied by secondary surface
cyclogenesis.
Upstream, the westerlies may undergo notable amplification,
including digging mid/upper troughing offshore of the British
Columbia and northern Pacific coast and building ridging across and
east of the Canadian/northern U.S. Rockies. As this occurs, an
initially cut-off low offshore of the southern California/northern
Baja coast is forecast to accelerate into the Southwest late
Saturday through Saturday night.
...Upper Ohio Valley...
Within the warm sector of the developing surface low, NAM forecast
soundings indicate that modest low-level moisture return may become
supportive of the development of thermodynamic profiles
characterized by weak conditional and convective instability in the
lowest 5-6 km AGL. It appears that this environment could become at
least marginally conducive to boundary-layer based convection
capable of producing lightning by late Saturday afternoon, mainly
near the southern periphery of the colder mid-level air, across
parts of northeastern Ohio into the western slopes of the Allegheny
Mountains.
In the presence of strengthening lower/mid-tropospheric wind fields
(including 40-50+ kt west-northwesterly mean flow in the lowest 6 km
AGL), the development of a relatively compact band of stronger
showers and thunderstorms appears possible. This activity, perhaps
aided by latent cooling in downdrafts associated with melting small
hail, may contribute to the downward transfer of stronger winds to
the surface, before convection weakens while crossing the Allegheny
Mountains Saturday evening.
...Southwest...
Models suggest that a mid-level cold core, characterized by 500 mb
temperatures as cold as near or just below -20 C, will finally shift
inland late Saturday through Saturday night. These temperatures
appear on the relatively warm side compared to cool season
environments typically conducive to low-topped convection capable of
producing lighting across and inland of Pacific coastal areas.
However, it is possible that low-level moisture return emanating
from the lower-latitude eastern Pacific and Gulf of California may
compensate.
Otherwise, it might not be out of the question that preceding
elevated moisture return contributes to layers of weak conditional
instability minimally supportive of convection capable of producing
lightning across parts of the Mojave Desert/lower Colorado Valley
vicinity.
..Kerr.. 11/13/2025
$$
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