784
FXUS65 KMSO 310745
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
145 AM MDT Fri May 31 2024

.DISCUSSION...It will be a chilly start to the day with upper 20s
to mid 30s for many valleys leading to areas of frost. Pleasant
conditions will occur today with daytime highs returning to
seasonable levels (valleys in the upper 60s to 70s) as a weak
ridge passes through the Northern Rockies.

The flow becomes zonal over the weekend with seasonable
temperatures continuing. A weak disturbance on Saturday afternoon
and evening leads to scattered showers and a few rumbles of
thunder but precipitation amounts appear light.

The first inkling of the atmospheric river arrives Sunday evening
as upslope areas begin to experience light precipitation. The
heaviest precipitation is expected during the day on Monday with
widespread rainfall (snow levels over 9000 feet) across the
Northern Rockies. Precipitation amounts have trended upward
slightly with the overall mean from 0.75"-1.5" in the terrain of
north- central Idaho through Tuesday. Less rainfall is
anticipated in western Montana valleys with the mean indicating
between 0.25"-0.50". While the probabilities are low (15% to 25%),
2 inches of rain isn`t out of the question for the higher terrain
near Highway 12 from Lowell to Lolo Pass. The expected rainfall
may pose a risk for isolated locations to experience minor impacts
due to rock and mudslides, along with a noticeable increase in
water levels in area streams and creeks.

The latter part of next week, most (85%) of ensemble clusters
show a strong ridge building over the western U.S. leading to an
extended period of warmer temperatures. Highs are expected to be
the warmest we have seen so far this year with 80s to lower 90s
for valleys. There is still considerable uncertainty with the
orientation of the ridge, thus with a day or two of thunderstorms
may be mixed in.


&&

.AVIATION...Other than patchy morning fog, VFR conditions will be
common into Saturday morning as a brief ridge passes through the
Northern Rockies. Winds will be light and diurnally driven with a
few gusts to 20 kts in the afternoon.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Frost Advisory from 3 AM to 8 AM MDT Friday for Flathead/Mission
     Valleys...Kootenai/Cabinet Region...Lower Clark Fork
     Region...Missoula/Bitterroot Valleys.

ID...Frost Advisory from 3 AM MDT /2 AM PDT/ to 8 AM MDT /7 AM PDT/
     Friday for Eastern Lemhi County...Northern Clearwater
     Mountains...Orofino/Grangeville Region...Western Lemhi
     County.

&&

$$