Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Jun 05 2023 18:57:56

AWUS01 KWNH 051857
FFGMPD
MTZ000-IDZ000-060100-

Mesoscale Precipitation Discussion 0432
NWS Weather Prediction Center College Park MD
256 PM EDT Mon Jun 05 2023

Areas affected...Northern Rockies

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

Valid 051900Z - 060100Z

SUMMARY...Thunderstorms revolving around a slow moving upper low
may lead to flash flooding in areas with overly saturated soils.

DISCUSSION...GOES 16 water vapor imagery showed a cut off 500mb
low slowly moving northeast through the northern Rockies today.
The unusually cooler temperatures aloft and steeper lapse rates
have already triggered a large footprint of thunderstorms. MLCAPE
is already around 500 J/kg and could approach 750-1,000 J/kg in
western Montana. One of the more anomalous variables at these
storms disposal is moisture. The 12Z BOI sounding contained PWATs
and 0-3km mixing ratios that were hovering around the max moving
average and well above the 90th climatological percentile.

The combination of available instability and anomalous moisture is
sufficient for thunderstorms to contain heavy downpours. The 12Z
HREF shows 6-hr QPF > 10-yr ARI probabilities as high as 40-60% in
parts of the Bitterroots and western Montana. Soil moisture is
also on the rise after another day of storms yesterday, bringing
the AHPS 7-day precipitation of normal totals to 300-400% in some
areas. This includes some cities such as Helena and Great Falls.
Rainfall rates could top 1"/hr in the most intense storms, which
would also challenge 1-hr FFGs in many of these areas. Locations
most prone to flash flooding are where soils are most sensitive
from recent heavy rainfall, as well as along rugged and complex
terrain. Rapid rises in creeks and streams are also possible.

Mullinax

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4BfuzNt2Q4eAgAcea33rocYsx4CTLfW1fHS45dx5NQkVdXgwBi4FrIQ8glIsT58CNNGS=
hRPiyXBXCMKQ-GLTRX5psco$  for graphic product...

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

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

LAT...LON   48711214 48061122 45771120 45361221 44731302=20
            44141345 43821433 43921546 44881599 46281548=20
            47441400 48621295=20

=3D =3D =3D
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