596
FXUS65 KMSO 300825
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
225 AM MDT Tue Apr 30 2024

.DISCUSSION...The unsettled and showery pattern continues through
at least late next week (May 10th).

An upper trough remains overhead with a few snow showers
continuing early this morning. Brief snow accumulations have been
noted on some pass level roadways. Shower activity will increase
with daytime heating leading to greater instability. Watch for
brief heavy snow or graupel (rain/snow mix in valleys) with more
intense showers. It will breezy with gusts of 20-30 mph but higher
gusts to near 40 mph will occur near showers.

Wednesday through early Thursday, an upper low will be getting
wound up east of the Continental Divide, wrapping moisture from
the northeast into Glacier National Park. Snow levels will be
3000-4000 feet, so expect the precipitation type from the Flathead
Valley and eastward to be in the form of wet snow. Given that
road temperatures will remain warm enough at lower elevations,
travel impacts will be limited to road surfaces above 5000 feet,
or basically just at Marias Pass. The probability of at least 4
inches of snow at Marias Pass is 45%, so quite similar to early
NBM projections. Across the rest of the Northern Rockies another
round of widespread showers is anticipated on Wednesday. Valleys
may see a dusting of snow but once again limited impact.

Scattered daily showers are expected Thursday and Friday under a
general trough. Currently, most models take the main forcing of a
secondary low from eastern Oregon into southern Idaho. This
leaves the Northern Rockies with mainly instability driven
showers, most widespread in the afternoon/evening hours.

At this point, Saturday morning/afternoon is a mostly shower-free
period with daytime temperatures back to seasonable levels (60s in
the valleys).

Ensemble clusters support an active weather pattern under a
general upper level trough with intermittent showers expected
Sunday (May 5th) through the first full week of May.

&&

.AVIATION...Scattered convective shower activity will increase
into this afternoon, with graupel and/or a rain- snow mix being
the main threats to aviation. Heavier showers could be intense at
times, bringing with them periodically lowered visibility and
ceilings, and localized gusty winds of 30 to 40 mph directly
under the passing showers. Showers will linger overnight with
another round of showers for Wednesday, while gusty winds will
temporarily ease after 01/0200Z, but are expected to increase once
more after 01/1600Z.


&&

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

$$