Subj : DAY1SVR: Day 1 Convective Outlook
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Dec 03 2023 19:35:23

ACUS01 KWNS 031935
SWODY1
SPC AC 031934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0134 PM CST Sun Dec 03 2023

Valid 032000Z - 041200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
WESTERN PENNSYLVANIA AND VICINITY...

....SUMMARY...
Isolated, marginally severe thunderstorms are possible over western
Pennsylvania and vicinity this afternoon.

....20Z Update...
Low-topped convection is increasing this afternoon from eastern OH
into western PA, in advance of a dynamic mid/upper-level shortwave
trough approaching the upper OH Valley. Uncertainty remains
regarding the potential for stronger storms to mature within the
favorably sheared but weakly unstable environment, but some
potential remains for gusty/locally damaging winds, hail of 0.5-1
inch in diameter, and possibly a brief tornado. See the previous
outlook discussion below for more information, and MCD 2302
regarding the short-term threat across western PA and vicinity.

...Dean.. 12/03/2023

..PREV DISCUSSION... /ISSUED 1018 AM CST Sun Dec 03 2023/

....Upper OH Valley...
Morning water vapor imagery shows a fast-moving intense shortwave
trough over central IL.  This feature will become negatively tilted
this afternoon as it races eastward into parts of OH/PA/NY.  A
strong mid/upper level jet is associated with this system, with 90+
knot winds at 500mb and 150+ knots at 300mb providing significant
mesoscale forcing in the left-front quad of the jet as it tracks
into western PA around peak heating.  Most 12z models show the
development of scattered fast-moving showers and isolated
thunderstorms later today (mainly 20-01z), but luckily
thermodynamics are expected to be quite weak (CAPE values generally
200-500 J/kg and dewpoints only around 50F).  The combination of
very steep mid-level lapse rates, ambient vorticity, and strong lift
could result in funnel clouds or a brief tornado from this
convection, along with small hail and gusty winds.  However, the
overall severe threat appears marginal due to the weak instability.

$$

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