090
FXUS65 KMSO 171854
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1254 PM MDT Tue Sep 17 2024

.DISCUSSION...A cut-off low pressure system will continue to spin
over east-central Idaho through the evening today, that will bring
widespread wetting rains across much of western Montana and
north-central Idaho through early Wednesday. In the more immediate
time-frame, locally heavy rainfall will be possible on the
northern periphery of the low across northwest and west-central
Montana this afternoon and evening. Currently, there is a 40%
probability locations along and east of Highway 93 could see rain
rates up to, or exceeding 0.50"/hr. Flood prone areas, such as
steep terrain and burn scars will be the primary areas of concern
for rock and mudslides (Glacier National Park for example).

The low pressure system will move into western Wyoming and central
Montana overnight, that will transition most of the precipitation
to locations along the Continental Divide, where probabilities for
24hr rainfall amounts totaling 1.00", range from 60-70%. The
probabilities quickly drop off to 30-40% for areas along highway
93. Locations in north-central Idaho, west of the Bitterroot Crest,
will miss out on the higher amounts, where probabilities for even
0.25" are as low as 10-20%.

Some clearing is expected Wednesday night with high valley
locations cooling down into the 30s, and upper 20s in the Dixie,
Idaho area. Patchy fog Thursday morning will give way to a
gorgeous day across the Northern Rockies with temperatures warming
into the 60s and 70s. Breezy westerly winds 10 to 20 mph will
develop in the afternoon and evening.

Ensemble guidance continues to trend away from the colder system
over the weekend, with roughly 80% of the ensembles showing a
west-northwest flow pattern. This translates to partly cloudy
conditions, with temperatures in the upper 60s/low 70s in western
Montana and upper 70s/low 80s in north-central Idaho.


&&

.AVIATION...Shower and embedded thunderstorm activity will increase in
coverage by 17/2000Z(mid-afternoon) and continue through 18/0400Z
(10 pm MDT this evening). Locally heavy rain, lower ceilings/visibility,
lightning and gusty winds to 30 knots are possible, especially
from Clearwater County, Idaho to areas north and east into
northwest Montana. A departing low pressure area will keep
persistent showers going through Wednesday with mountain
obscurations and lowered ceilings at times.



&&

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

$$