Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 262126

Area Forecast Discussion
National Weather Service Missoula MT
226 PM MST WED NOV 26 2014

.DISCUSSION...Warmer conditions will persist throughout the night
tonight, with many valleys not even reaching freezing in western
Montana and central Idaho. The ample moisture over the last 24
hours, near record rainfall in many locations and record rainfall
in yesterday in Butte, has primed the atmosphere for fog. Cloud
cover and an increasing southerly wind will be working against the
fog, and may cause it to lift to a low stratus cloud deck by
morning. But there is so much moisture with snow on the ground at
least patchy fog is likely.

Glacier National Park and Marias pass will continue to get snow
through this evening. Precipitation is likely to continue there
through Thanksgiving and Friday, though it has lightened and become
less of an impact, so the warning has been cancelled.

Thanksgiving will be warmer with highs in the 40s across much of
the region with continued light rain and snow, mainly over the
mountains and in northwest Montana.

The models are still in agreement with a change in the weather for
this coming holiday weekend. A plume of moisture will be
streaming into the Northern Rockies Friday into Saturday. Snow
levels will be fairly high during the onset of precipitation
causing mainly rain in the valleys and snow being confined to the
higher terrain. An arctic will push into northwest Montana Friday
night over the continental divide. This arctic front will cause
snow levels to crash to valley floors and also enhance snowfall
rates. Areas north of the I-90 corridor could receive significant
snow amounts. The combination of snow and strong easterly winds
could cause areas of blowing snow. The arctic will finish pushing
across western Montana on Saturday, but the interaction with the
moisture does not appear to be as significant. While the arctic
pushes into western Montana, a Pacific cold front will move into
north central Idaho causing snow levels to lower and bring in a
cooler airmass. Areas above 3000 feet should receive accumulating
snow, while lower valleys like Orofino and Riggins will primarily
remain rain.

Saturday night the systems will move out of the area causing
skies to clear. This clearing should allow temperatures to drop
significantly with many valley locations across western Montana
being in the single digits and below zero. North central Idaho
should cool to the 20s and 30s. The combination of rain changing
to snow followed by very cold temperatures could cause hazardous
driving conditions throughout the weekend.

The models are indicating that the Northern Rockies should
transition to a more westerly flow pattern by next week. This
pattern should allow temperatures to slowly moderate with periodic
disturbances causing showers through the week.


.AVIATION...Light rain and snow continue across the area. Ample
moisture with the continuing precipitation and near record amounts
of precipitation over the last 24 hours will make fog a risk
throughout the night. Normally the clouds would prevent
significant fog, but there is so much moisture with rain and snow
on the ground that even a little cooling could cause fog to form.
The risk of fog will actually decrease closer to the morning (12Z)
as a southerly pressure gradient causes winds to increase, making
low stratus more likely. Terminals KMSO and KGPI are most likely
to be affected.


MT...WINTER STORM WARNING until 11 PM MST this evening West Glacier


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