Libby, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

307
FXUS65 KMSO 102042
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
142 PM MST Sun Nov 10 2024

.DISCUSSION...

KEY MESSAGES:

- Light snow today and tonight above about 5500 feet.

- Strong winds for the Camas Prairie of Idaho on Monday afternoon

- Ongoing unsettled weather beginning again on Monday night
  bringing snow accumulations to mountain passes

Satellite imagery this afternoon is showing a fast-moving
shortwave trough approaching the Idaho Panhandle, with observing
sites reporting rain in the lower elevations. As this system
approaches the ID-MT border, snow will begin. Accumulations will
be light. However, a slightly more impressive circulation is also
visible on satellite imagery over the Gulf of Alaska. This system
is pushing Pacific moisture, along with a well-defined cold front,
into the northeastern Pacific off Washington-Oregon coast.
Precipitation will return to the Northern Rockies with the front
by Monday night. The colder air will bring snow levels down, but
not quite enough for valley snow by Tuesday morning, when winter
weather will impact the mountain passes along the ID-MT border, as
well as Marias Pass in northwest Montana. Moderate to strong
south and southwesterly winds will increase across Idaho and Lemhi
Counties in ID, as well as southwest MT, with the frontal passage
on Monday. Expect about 35-45 mph gusts along Highway 95 from the
Idaho-Adams County line through Grangeville around midday. There
is about a 20 percent chance that gusts will exceed 50 mph in
Grangeville

We will stick with the previous forecast of about a 70% chance of
4 inches or more of snow at Lookout and Lolo Passes, and a 20%
chance at Lost Trail and Marias Passes by Tuesday morning. The
current thinking is to hold off on Winter Weather Advisories in
these areas due to the very specific areas of impacts as snow
levels keep above about 4000 feet. Be prepared for winter weather
if you will be accessing the backcountry on Tuesday. The
Clearwaters, Bitterroots, Cabinets all look to get about 6-12
inches, while the mountains east of about Highway 93 will see
slightly less.

As the closed low in the Gulf of Alaska shifts south along the
Canadian coast Tuesday through Wednesday, it will continue to send
Pacific moisture onshore south of the low pressure center, keeping
the Northern Rockies under moist southwesterly flow. Warmer air
associated with southwesterly flow will bring snow levels back up,
so snow will stay confined to elevations above about 4500 feet on
Thursday. While the longer range ensemble solutions are not in
great agreement, all point to unsettled, wet weather through next
weekend.


&&

.AVIATION...
Radar returns are increasing in coverage this afternoon, but
precipitation has been slow to reach the ground in most places
due to a dry layer below around 8000 feet. Radar projections agree
on light precipitation developing by this evening. Snow levels
will remain above 5,500 feet throughout the afternoon and evening,
with valley areas experiencing periodic light rain showers.
Expect terrain obscurations by this evening, especially along the
Idaho/Montana border, where showers will be more widespread.
Statistical models again forecast stratus and fog returning at
KGPI overnight. The NBM probabilities for KGPI are around a 50%
for MVFR or below and 30% for IFR or below conditions during
Monday morning.


&&

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

$$