Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Sep 04 2023 05:52:33

AWUS01 KWNH 040552
FFGMPD
MTZ000-IDZ000-041150-

Mesoscale Precipitation Discussion 1034
NWS Weather Prediction Center College Park MD
152 AM EDT Mon Sep 04 2023

Areas affected...central ID into southwestern MT

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

Valid 040551Z - 041150Z

Summary...A slow moving axis of moderate to heavy rain is expected
to set up over portions of central ID into southwestern MT
overnight. Peak rainfall rates of 0.5 to 1.0 in/hr may lead to 1
to 2+ inches in 3-6 hours along with localized flash flooding.

Discussion...GOES West water vapor and infrared imagery showed a
well-defined vorticity max in the mid to upper levels over
south-central ID along with a region of colder cloud tops
extending from central ID into southwestern MT. GLM data has been
limited with only one region highlighted with lightning activity
over Custer County, ID over the past hour. Instability across this
region was rather limited with 05Z SPC mesoanalysis data only
showing up to ~500 J/kg MUCAPE. However, moisture was highly
anomalous across this region of the West with 00Z soundings from
BOI, TFX and RIW indicating precipitable water values in the
90-95th percentile.

Expectations are for a deformation axis to become better defined
to the northwest of the slow moving mid-level vorticity max/low,
focusing from the Sawtooth Range of central ID into the Bitterroot
and surrounding northern Rocky Mountains of southwestern MT. While
instability is forecast to remain weak, and likely decrease with
time, strong forcing for ascent will support a slow moving axis of
moderate to heavy rain for 3-6 hours across the ID/MT border.
Coupled entrance and exit regions of the upper level jet,
diffluent flow aloft and lower level convergence/deformation with
relatively slow moving cores of heavy rain will promote 0.25 to
0.50 in/hr rainfall rates with occasional rates over 0.5 in/hr.
Resulting rainfall of 1 to 2+ inches can be expected across
portions of central ID into southwestern MT through 12Z, which may
result in some localized areas of flash flooding.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6-nPgtP4nRuaVc1azCQN9in6yYaGmH1pJ-NvOJ79-Q8tmr_9qPjOxGaixz3k8mBir7O2=
haPpgcNjRvxfehUAE7GyX1g$  for graphic product...

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

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

LAT...LON   46411198 46371090 46241038 45881018 45461037=20
            45061134 44241237 43661312 43441415 43741514=20
            45031477 46061315=20

=3D =3D =3D
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