Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 12 2023 18:12:07

AWUS01 KWNH 121812
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-130010-

Mesoscale Precipitation Discussion 0912
NWS Weather Prediction Center College Park MD
210 PM EDT Sat Aug 12 2023

Areas affected...Northeast OH...Northwest PA...Western NY

Concerning...Heavy rainfall...Flash flooding likely

Valid 121810Z - 130010Z

SUMMARY...Strong to severe thunderstorms impacting areas with
locally moist to wet antecedent conditions will also be capable of
producing scattered instances of flash flooding this afternoon.

DISCUSSION...Showers and thunderstorms are quickly developing and
growing upscale across the Lower Great Lakes region with an
emphasis on areas of northeast OH, northwest PA and parts of
western NY. The convection is associated with an approaching cold
front and a rather strong upper-level trough crossing the Great
Lakes region and heading for the Northeast. MLCAPE values are
already well over 1500 J/kg with rather strong vertical shear
profiles in place, and this will drive a rather strong level of
convective organization through the afternoon with a combination
of supercell and multi-cell convection developing and expanding in
coverage.

While the convection will have a severe component to it, the
activity is likely to drive heavy rainfall amounts given concerns
for rainfall rates locally reaching upwards of 1.5 to 2
inches/hour. These heavier rainfall rates will be occurring over
areas that have already seen heavy rainfall over the last 24
hours, and especially across northeast OH and western PA. FFG
values are quite low across these areas and the USGS data shows
elevated streamflows ongoing. Therefore, the additional rainfall
will likely lead to locally enhanced runoff concerns. An urban
flash flood threat will exist as well as the activity expands in
coverage this afternoon and advances off to the east into the
Cleveland and eventually Pittsburgh metropolitan areas.

The 12Z HREF guidance shows the potential for locally as much as 3
to 4 inches of rain where some of these convective cells repeat
over the same area, and thus given the sensitive antecedent
conditions on the ground, and urban corridor concerns, at least
scattered instances of flash flooding will be likely.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_2j7vcKJ9aNUK_x_3Vra_TE8fabJAZH5uzxT13ZSe78Ajbm4tQ0ifd9FLE4b1PHFivfy=
rm492MYcelXLlY1GCAmk2-E$  for graphic product...

ATTN...WFO...BGM...BUF...CLE...CTP...ILN...PBZ...RLX...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON   42587852 42477715 41707708 40737895 39748045=20
            39858239 40708345 41388291 41798154 42188020=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to
https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email
Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.14-Linux
 * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

.