Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Sep 29 2023 23:07:57

AWUS01 KWNH 292307
FFGMPD
WIZ000-MNZ000-SDZ000-300505-

Mesoscale Precipitation Discussion 1115
NWS Weather Prediction Center College Park MD
707 PM EDT Fri Sep 29 2023

Areas affected...south-central MN

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

Valid 292305Z - 300505Z

SUMMARY...Thunderstorms are expected to increase across portions
of central/southern MN between 00-03Z with potential for training
and repeating cells from southwest to northeast. Rainfall rates of
1-2 in/hr are likely with possible flash flooding developing
overnight.

DISCUSSION...22Z surface observations placed a surface low along
the southern MN/SD border with a warm front extending eastward
from the low through southern MN and a cold front southwestward
into northeastern NE. Farther north, a diffuse cold front was
analyzed from northern MN into northwestern SD, marked mainly be a
drop in dewpoint in the cold sector. 2245Z radar imagery showed a
small cluster of thunderstorms over southwestern MN, located just
north of the warm front and a few thunderstorms ahead of the cold
front in the vicinity of southeastern SD. SPC mesoanalysis data
from 22Z showed ~500 to 2000 J/kg MUCAPE available just north of
the warm front along with PWAT values of 1.2 to 1.4 inches in
south-central MN.

RAP forecasts have been consistent with an increase in the low
level jet overnight, with southerly 850 mb wind speeds increasing
from their current values of 20-30 kt into the 45-50 kt range by
06Z. At the leading edge of surge in low level wind will be
increasing moisture in the 850-700 mb layer and an axis of
convergence that is expected to align from southwest to northeast,
or parallel to the mean steering flow. Elevated instability up to
~1500 J/kg is forecast to advect across central MN overnight,
coincident with an increase in thunderstorm development and modest
diffluence aloft. Southwest to northeast training and repeating of
cells is expected to increase the threat for localized flash
flooding, especially after 03Z as the low level jet increases.
Flash flood guidance varies across the region but is lowest across
eastern MN with some areas of 1-2 in/hr. Isolated/localized flash
flooding will be possible as a result.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6y-U3rbejdARPv27V5cEaLFho8EYRSQru4l8LRxxoCz0leTt7rhbl-Co4_5CDGrO43nd=
Fe37Xo-9QddvKV8SrhlbRuI$  for graphic product...

ATTN...WFO...ABR...DLH...FGF...FSD...MPX...

ATTN...RFC...MBRFC...NCRFC...NWC...

LAT...LON   46789262 46579219 46239218 45539236 45019282=20
            44519376 44119543 44249657 45519639 46079517=20
            46459402=20

=3D =3D =3D
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