Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1106 PM CST Mon Nov 27 2023
Valid 281200Z - 291200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk of thunderstorms appears negligible across much of the
U.S., today through tonight.
...Synopsis...
Split westerlies emanating from the mid-latitude Pacific will
continue to converge into broad, deep troughing east of the Great
Plains into the western Atlantic. Within this regime, models
indicate that one significant short wave perturbation, crossing the
lower Great Lakes/upper Ohio Valley at the outset of the period,
will fairly rapidly pivot across the northern Atlantic Seaboard by
early this evening. However, broadly cyclonic northwesterly
mid-level flow appears likely to linger across and east of the
Mississippi Valley. Cool to cold, dry and stable conditions will
generally be maintained beneath this regime, while downslope warming
contributes to moderating temperatures across much of the Great
Plains.
Upstream, within a branch of westerlies across the southern
mid-latitude eastern Pacific into the Southwest, mid-level troughing
is forecast to dig across the California coast, with an embedded
weakening low and associated occluding surface cyclone approaching
the San Francisco Bay area by 12Z Wednesday. A modest plume of
moisture will generally remain focused along the occluding boundary
near/offshore of California coastal areas through the period, but
the mid-level cold core may begin to spread inland across northern
through central California coastal areas by the end of the period.
...Lower Great Lakes region...
Steep lapse rates beneath the lower/mid-tropospheric cold core will
be maintained beyond 12Z this morning. Forecast soundings, mainly
over/near the relatively warm lake waters (particularly near
southeastern Lake Ontario coastal areas), suggest that this may
continue to contribute to thermodynamic profiles potentially
conducive to low-topped convection capable of producing lightning,
possibly into the midday or early afternoon hours.
...California coast...
Due to the occluding and weakening nature of the approaching surface
cyclone, and its offshore forecast track, the potential for
appreciable boundary-layer destabilization inland of coastal areas
near San Francisco Bay appears quite low. While mid-level cooling
ahead of the modest mid-level cold core (including 500 mb
temperatures of -22 to -24C) may contribute to convective
development capable of producing lightning offshore of coastal
areas, lightning production with the convection may tend to wane as
it reaches central California coastal areas late tonight into early
Wednesday.
..Kerr.. 11/28/2023
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