Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jun 10 2023 18:08:40

AWUS01 KWNH 101808
FFGMPD
MTZ000-110000-

Mesoscale Precipitation Discussion 0458
NWS Weather Prediction Center College Park MD
207 PM EDT Sat Jun 10 2023

Areas affected...Western Montana

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

Valid 101805Z - 110000Z

SUMMARY...Thunderstorms containing rainfall rates around 1"/hr may
lead to flash flooding in areas with overly saturated soils.

DISCUSSION...GOES-16 visible and GLM imagery showed developing
thunderstorms over parts of western MT. Surface analysis shows a
cold front pushing west into the front range of the northern
Rockies, acting as a sufficient trigger for thunderstorms. In
addition to the front, easterly mean 850-500mb flow will support
upslope enhancement and act as a trigger for thunderstorms as
well. The atmosphere continues to sport a hefty amount of
moisture, as indicated by available PWs that range between
0.75-1.0". There is also some instability to work with as RAP
mesoanalysis depicts 250-500 MLCAPE will be available this
afternoon.

HRRR area averaged soundings showed RH values at low-mid levels
>80% in the Lewis Range with mean cloud layer winds topping out
around 10 knots. The biggest factor supporting a potential flash
flood threat, aside from the available moisture and instability,
is the large areal extent of overly saturated soils. Much of
central MT on west towards Helena and along the eastern slopes of
the Lewis Range have picked up as much as 400% of normal rainfall
over the past 7-14 days according to AHPS rainfall analysis.
Rainfall rates could top 1"/hr and 1-hr FFGs in the most sensitive
locations are as low or lower than 1"/hr. Flash flooding is a
possibility once again this afternoon with areas featuring the
most saturated soils and nearby creeks and streams most at-risk.

Mullinax

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!5alZutcmZYSe78WobNbmqY-MoqFXmX_BHm3ef1rLMjfm83vTo5AS7v4PbdPbAvoWBf9g=
1rxF9zpw77P2eo5CXNuXKd8$  for graphic product...

ATTN...WFO...BYZ...MSO...TFX...

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

LAT...LON   49241260 48651073 47350924 46740936 46371003=20
            45851042 46101202 46911342 48361449 49031427=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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