Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1113 PM CST Sat Nov 25 2023
Valid 261200Z - 271200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk of severe thunderstorms appears negligible across the U.S.,
today through tonight.
...Discussion...
Modestly amplified split westerlies near the North American Pacific
coast converge across and east of the Rockies, where a pair of
significant consolidating short wave troughs are forecast to
contribute to the evolution of more prominent larger-scale troughing
in the northern stream, as another short wave impulse digs across
the central Canadian/U.S. border. As subtropical ridging centered
over the Caribbean maintains strength as far north as the
southeastern Gulf of Mexico and southern Florida Peninsula, models
indicate considerable intensification of westerly flow between the
large-scale troughing and ridging today through tonight.
Within this regime, a focused area of strengthening upward vertical
motion (supported by low-level warm advection beneath an
increasingly divergent upper flow field) is forecast to continue to
develop through daybreak today, near and south of Gulf coastal areas
from southeastern Louisiana toward the Florida Big Bend. Coincident
with further gradual modification of the north central and
northeastern Gulf boundary layer, models suggest that
destabilization may become supportive of an upscale growing
convective cluster with embedded thunderstorm activity. It appears
that this generally will become rooted above a residual stable
boundary layer, to the north of a warm front in advance of a modest
developing frontal wave, which likely will persist and overspread
the Big Bend and adjacent portions of northern Florida through mid
to late afternoon.
Thereafter, a relatively compact, but stronger, surface cyclone is
forecast to begin to develop offshore of the southern Mid Atlantic
coast by early this evening, before migrating toward the Cape Cod
vicinity through 12Z Monday. North-northwest of this feature,
various model forecast soundings indicate the development of weak
CAPE rooted within strengthening lower/mid-tropospheric warm
advection. While this may be accompanied by an expanding area of
convection across northern Mid Atlantic into New England coastal
areas late this evening through the overnight hours, the extent to
which this could become capable of producing lightning remains
unclear. Due to at least initially limited low-level moisture
return, and the lack of stronger forecast cooling aloft,
thunderstorm probabilities still appear less than the minimum 10
percent threshold for a categorical thunder area at this time.
...Tampa Bay vicinity...
Within the warm sector of the frontal wave, it is possible that
hodographs could become supportive of potential for supercells with
a risk of tornadoes along coastal areas near/north of Tampa Bay by
late this afternoon. However, given lingering questions concerning
the depth of the moistening boundary layer, and, particularly, a
capping (relatively) warm layer centered around or just below the
500 mb level, unconditional severe probabilities still appear
generally negligible (i.e., less than 2/5 percent for tornado/wind,
respectively).
..Kerr/Weinman.. 11/26/2023
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