Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Sep 27 2023 19:08:45

AWUS01 KWNH 271908
FFGMPD
INZ000-ILZ000-280105-

Mesoscale Precipitation Discussion 1106
NWS Weather Prediction Center College Park MD
307 PM EDT Wed Sep 27 2023

Areas affected...northeastern IL into central/northern IN

Concerning...Heavy rainfall...Flash flooding possible

Valid 271906Z - 280105Z

Summary...Slow moving showers and thunderstorms will pose an
isolated flash flood threat over portions of northeastern IL into
central/northern IN through 01Z. Rainfall rates of 1-2 in/hr and 6
hour totals of 2-4 inches will be possible.

Discussion...GOES East water vapor imagery showed a mid-level low
over north-central IL moving slowly toward the east. Precipitable
water values sourced through GPS sensors showed 1.1 to 1.4 inches
(weakly anomalous) across central/northern IL into IN but cloud
cover has been limiting instability. 18Z SPC mesoanalysis data
showed MLCAPE of 500-1000 J/kg from northeastern IL into central
IN and further heating and minor erosion of cloud cover should
allow local expansion/increases in CAPE values but likely
remaining capped near 1000 J/kg.

Slow cell movement of less than 10 kt is expected with
shower/thunderstorm development near the mid-level low from
northeastern IL into northern IN along with potential training
where 850 mb winds match deeper-layer steering flow from the
southeast. However, weak instability and modest moisture should
limit the coverage of any cells that develop. In addition,
surface-based instability should begin to quickly fade with the
loss of daytime heating this evening with the exception of the
warmer waters of southern Lake Michigan. Just ahead of the upper
low, westerly to southwesterly steering flow and southwesterly 850
mb winds of 10-15 kt may support repeating and short term training
of cells in the vicinity of a surface low and related frontal
boundaries.

Both regimes will support rainfall rates of 1-2 in/hr and
localized totals of 2-4 inches over the next 6 hours. While
locally wetter antecedent conditions exist in IL compared to IN,
lowering FFG values to the west, both IL and IN will see a
localized threat for flash and urban flooding. The potential for
2-4 inches is expected through 01Z.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-LTTDIAv95RKFiMhK8ZctSA7oQWMVHdm5yExSMw0ZY-fPr77T56AhqrTwRLvjkYSfyqm=
AsZd1ace16y8KtfsvS8EAlc$  for graphic product...

ATTN...WFO...ILX...IND...IWX...LOT...

ATTN...RFC...NCRFC...OHRFC...NWC...

LAT...LON   42008772 41848728 41768699 41718654 41658602=20
            41548562 41418521 41188489 40778488 40438497=20
            39778567 39588600 39388657 39408721 39758774=20
            40388838 41168870 41858867=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)

.