Subj : DAY1SVR: Day 1 Convective Outlook
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Oct 16 2023 12:33:03

ACUS01 KWNS 161232
SWODY1
SPC AC 161231

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0731 AM CDT Mon Oct 16 2023

Valid 161300Z - 171200Z

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

....SUMMARY...
Severe thunderstorms are not expected.

....Synopsis/Discussion...
The positively tilted, mid/upper-level longwave covering much of the
CONUS and central/eastern Canada will lose some amplitude through
the period, especially on the western/ridging side.  This will occur
as a pair of strong shortwave troughs traverse the northern tier of
states and southern Canada:
1.  A leading perturbation -- initially just west of the mean ridge
over portions of SK/MB.  This feature is forecast to penetrate
deeper into the large-scale ridging as it moves to northwestern ON,
the MN Arrowhead, western Lake Superior, and WI by 12Z tomorrow.
However, its effects will be too far from moisture sufficient to
support a thunderstorm area.
2.  A trailing perturbation -- now embedded within cyclonic flow
near the base of a larger, synoptic trough over the northeastern
Pacific from the Gulf of Alaska to west of CA.  The shortwave trough
component will separate eastward -- likely strengthening to include
a closed 500-mb cyclone as it crosses the coast of WA and BC between
00Z-06Z.  By 12Z, the low should be over the southernmost Canadian
Rockies -- with a slightly positively tilted trough across ID and
northwestern NV.

As the Pacific trough approaches the coast and moves ashore, cooling
aloft superimposed on maritime boundary-layer moisture will yield a
minimally inhibited boundary layer topped by 50-300 J/kg MUCAPE,
sometimes surface-based, and sometimes reaching vertically into
icing layers suitable for lightning generation.  Expected
thunderstorm coverage appears marginal for a general-thunder area,
given the barely supportive thermodynamic profiles forecast, but the
thunder area will be maintained for this outlook cycle. Otherwise,
despite dry lower-elevation dewpoints mixing into the upper 30s F,
surface heating and lack of substantial stable layers aloft should
support isolated to widely scattered showers and perhaps a transient
thunderstorm or two this afternoon over portions of southeastern AZ.
Overall coverage there appears too isolated to outline a 15%/general
thunder area for now.

...Edwards/Broyles.. 10/16/2023

$$

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