Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed May 31 2023 20:48:12

AWUS01 KWNH 312048
FFGMPD
MTZ000-IDZ000-ORZ000-010246-

Mesoscale Precipitation Discussion 0396
NWS Weather Prediction Center College Park MD
447 PM EDT Wed May 31 2023

Areas affected...portions of the northern Rockies

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

Valid 312046Z - 010246Z

Summary...Rainfall rates with scattered thunderstorms across the
region have increased especially over the past hour or so.  These
rates could cause occasional, yet isolated instances of flash
flooding.

Discussion...Thunderstorms have continued to deepen amid strong
surface heating within the discussion area.  Ascent associated
with orography and very weak vorticity maxima aloft appear to also
be fostering the ongoing convective development as well.  The
storms are in a fairly unstable environment characterized by
nearly 1000 J/kg MLCAPE (highest across Idaho and eastern
Montana), with 0.9 inch PW values and weak steering flow aloft
also promoting efficient local rain rates.  These rates were
estimated to be as high as 1-2 inches/hr - especially within
clusters between Havre and Great Falls in Montana and just south
of Boise, Idaho.  The rates were also exceeding FFG thresholds
across the region, which generally hold in the 0.5-1.0 inch/hr
range.

The ongoing convective trends should continue through the
remainder of the afternoon, with peak heating continuing to
support surface-based instability for convective storms.=20
Eventually, nocturnal boundary layer cooling will result in a
gradual weakening of updrafts and conincident lessening of the
flash flood risk.  This process should begin in earnest after
around 03Z or so.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-_02jFAlktATTLippNgO1cxgMYiN9QFhWX7A-5R-qSbqM5COKUtkYaHu_Iqm7E_vev06=
U-YSvC_h8uSWnWL_ANTbVuA$  for graphic product...

ATTN...WFO...BOI...BYZ...GGW...MSO...PDT...PIH...TFX...

ATTN...RFC...CNRFC...MBRFC...NWRFC...NWC...

LAT...LON   48870942 48500803 47760739 46510761 45900988=20
            44731268 43211493 42251659 42261818 44291772=20
            45131702 47041453 48531176=20

=3D =3D =3D
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