Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat May 27 2023 03:45:16

AWUS01 KWNH 270345
FFGMPD
MTZ000-270915-

Mesoscale Precipitation Discussion 0352
NWS Weather Prediction Center College Park MD
1144 PM EDT Fri May 26 2023

Areas affected...central to east-central MT

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

Valid 270341Z - 270915Z

SUMMARY...Areas of heavy rain with rates of 1-2 in/hr are expected
to impact portions of central/east-central MT over the next
several hours. Additional totals of 2-4 inches are expected which
could result in flash flooding.

DISCUSSION...03Z regional radar imagery over eastern MT showed a
mature MCS with a well-defined MCV located roughly 60 miles east
of BIL. The MCV was tracking northward with new convective
development occurring to its north within an environment
characterized by 500-1000 J/kg MLCAPE via the 03Z SPC mesoanalysis
and the 00Z sounding from GGW. MRMS-derived rainfall rates were
1-3 in/hr, but given the presence of hail embedded within some of
the stronger cells and their distance from the nearest radar
(KBLX) within the melting layer, 1-2 in/hr is believed to be a
more reliable estimate for what's occurring at the surface.

A segment of the low level jet located over the central/northern
Plains was noted to branch off toward the northwest into MT, with
850-700 mb winds of an easterly/upslope component in east-central
MT within a zone of warm air advection and low level confluence
partially due to a ridge centered over southern Alberta and
Saskatchewan. The zone of confluence and upslope winds is expected
to translate northward ahead of the MCV over the next few hours.
Additionally, upper level winds are forecast to become increasing
diffluent and divergent over the eastern half of MT ahead of an
approaching upper level shortwave located in southwestern WY. A 60
kt jet streak near 250 mb currently in east-central WY (identified
via GOES East DMVs) is forecast by the RAP to strengthen to 70 kt
as it translates into west-central MT through 09Z, supporting
increased divergence aloft within its right entrance region. Areas
of slow moving cells and brief training should support rainfall
rates of 1-2 in/hr in a few locations over central to east-central
MT, prior to instability depleting later in the night. Additional
rainfall totals of 2-4 inches are expected which may result in
flash flooding.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7YI6_JXXmANUdK1oq4Gm-JJhM5iftRueSFxQ65YQnVhEgWAQNXNwkx-iKuOCv8Vzl7G5=
wi-hrF06RAAAvRPEn0O914U$  for graphic product...

ATTN...WFO...BYZ...GGW...TFX...

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

LAT...LON   48500643 48410523 48010475 47550482 46480617=20
            46240668 45980767 46050908 46501047 46861106=20
            47691117 48361037 48430816=20

=3D =3D =3D
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