352
FXUS65 KMSO 132009
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
209 PM MDT Thu Jun 13 2024

.DISCUSSION...Our streak of gorgeous late spring days continues,
expect 80s to low 90s (Hells Canyon, Idaho) for temperatures
today. Add in bountiful sunshine with light breezes and hopefully
you can enjoy some time outside. Friday will be quite similar
with an uptick in westerly winds as an open wave slides onshore
the Pacific Northwest.

Friday afternoon an isolated shower or thunderstorm will be
possible in southwest Montana and Lemhi County Idaho.

Saturday will be very breezy with gusts in the valleys up to 40
mph and in the mountains 40 mph or greater. Temperatures will
also cool, in some cases 15 to 20 degrees compared to Friday. For
those recreating on area lakes please exercise caution as choppy
conditions will be possible. Chances for showers increase region
wide but north of I-90 will have the best chance for measurable
precipitation, with a greater than 40% of at least 0.10 of an
inch.

Sunday remains cooler and breezy with shower activity confined
along the Canadian border and Glacier National Park. Snow levels
which will become very important by Monday, will have already
lowered to around 6000 feet. Dress accordingly for outdoor
activities that take you into the mountains, hypothermia can
happen even in June.

Monday the models are in high agreement for a closed low, winter-
like system to begin to affect the Northern Rockies. Although
there remains differences in timing and exact placement of the
low pressure.

Expect widespread wet conditions with very cool conditions, winds
will turn northeasterly. Heavy, wet accumulating snow is expected
above 5000 feet, throughout southern Idaho County and most of
western Montana. In western Montana, above 6000 feet a trace to 14
inches is possible, while in the Bitterroot, Anaconda, and Pintler
Mountains, Bob Marshal Wilderness, and Glacier National Park
Region the highest terrain has a 25% chance of receiving 14 to 20
inches of snow. This amount snow accumulating on trees with
foliage could cause branches to go down on back country roads, be
prepared. Due to the high impact potential above 6000 feet and
moderate confidence of the event actually happening, winter storm
watches have been issued along Continental Divide from the
Canadian border through MacDonald Pass on I-90, including
Georgetown Lake and the Anaconda and Pintler Mountains. The main
snow event will be overnight Monday through Tuesday.

Similar events to this one, in June 2008 and 2001, produced a
small area of valley snow down to 2800 feet. There is insufficient
confidence in either low pressure track or intensity currently,
but you are encouraged to follow future forecasts as 1 to 2
inches of heavy, wet snow on trees with leaves could easily cause
broken branches leading to localized power outages with winter
driving conditions in area mountain passes.



&&

.AVIATION...High pressure currently over the region is bringing
generally sunny skies and light, terrain driven winds. By Friday,
winds aloft will increase significantly from the southwest ahead
of an approaching weather system. These winds will be able to mix
down into the valleys by Friday afternoon, with gusts to 25kts
common across all of western Montana and north central Idaho.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from Monday afternoon through Tuesday evening
     for West Glacier Region.

     Winter Storm Watch from Monday evening through Tuesday evening
     for Butte/Blackfoot Region...Potomac/Seeley Lake Region.

ID...None.
&&

$$