807
FXUS65 KMSO 040823
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
223 AM MDT Mon Aug 4 2025

.DISCUSSION...

KEY MESSAGES:

-  The KMSX Radar (Missoula, MT local weather radar) will remain
   offline due to scheduled maintenance through the first week of
   August.

-  Southwest flow continues with thunderstorms this week.

-  Pattern change coming this weekend to northwest flow.

A trough over the west coast is leaving the northern Rockies under
southwest flow. That flow will help precipitable water, which is
the amount of water in the atmosphere available for rain, to
increase today. Along with the increased precipitable water a
shortwave is moving through the region today. This will cause much
more wide spread thunderstorms with heavy rain. There is an 80 to
100 percent chance (depending on location) that if you get hit by
the core of a thunderstorm you`ll pick up a quarter of an inch of
rain, probably in less than half an hour. For high elevations
there`s a 30-40 percent chance of picking up half an inch or more
in the same time.

Recently we`ve seen quite a few wash outs, or debris flows
associated with these storms. Some of those washouts are
associated with burn scars from last year, but not all. If you`re
in any area with heavy rain and steep terrain, stay alert for
these debris flows!

Then on Thursday the west coast trough moves over our region
causing another round of thunderstorms, and much cooler
temperatures for Friday and the weekend. This shift will also
cause a pattern change to northwest flow.

The change to northwest flow will cause precipitable water to
decrease, so any storms we get in that pattern won`t be as wet.
Ensembles are struggling with how strong to build the ridge over
the west coast that gives us northwest flow, so a lot of
uncertainty in temperatures remains, but in general they should
rebound to above average pretty quick after the cold weekend.

&&

.AVIATION...A shortwave approaching the region in southwest flow
will cause widespread thunderstorms affecting all area terminals
today. These storms will bring heavy rain, small hail, gusty
winds, and a lot of lightning. Currently, high resolution models
show maximum potential wind gusts around 55 mph, though the HREF
indicates a 20 percent chance or less of getting wind gusts over
40 mph for any location including terminals.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$