Subj : DAY1SVR: Day 1 Convective
To   : All
From : Mike Powell
Date : Tue Oct 31 2023 09:37:00

ACUS01 KWNS 311250
SWODY1
SPC AC 311248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Tue Oct 31 2023

Valid 311300Z - 011200Z

....NO SEVERE THUNDERSTORM AREAS FORECAST...

....SUMMARY...
Isolated thunderstorms are possible over parts of the Great Lakes
and immediate vicinity.

....Synopsis...
In the wake of a strong surface cold front -- moving through then
offshore from south FL today -- a large, continental/polar air mass
will reside over much of the CONUS.  Within that, a surface low is
nearly stacked with a compact cyclone's midlevel center -- now
apparent in upper-air analyses and satellite imagery over western
WI.  An accompanying mid/upper-level trough extends to Lake Superior
and to near STJ.  The 500-mb low is forecast to weaken through much
of the period, reaching extreme northern IN by 00Z, but with a
strong, positively tilted shortwave trough still attached, from
Lower MI to near PAH.  Overnight, the deep-layer cyclone will lose
definition, with a strong, open-wave trough at 500-mb from southern
ON across OH to AL by 12Z.

Cold midlevel air (-30 to -35 deg C at 500 mb) is expected to move
across portions of the Upper Great Lakes region (especially Lakes
Michigan/Huron) today, then Lower Great Lakes tonight, in the zone
of strong DCVA immediately preceding the trough aloft.  As that
occurs, over the lakes and areas just downwind/inland in the
boundary layer, low/middle-level lapse rates will steepen rapidly,
with lake moisture and thermal fluxes contributing enough theta-e
for convective plumes (including snow).  MLCAPE of 100-300 J/kg is
possible, some of which can extend into icing layers suitable for
lightning generation.  Greater potential convective coverage and
lightning threat are evident compared to yesterday, given the
stronger deep-layer forcing and low-level lift expected.  However,
overall thunderstorm coverage still may be marginal for a
10%/general-thunderstorm outlook area.

...Edwards/Smith.. 10/31/2023

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