Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 171001
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
401 AM MDT Thu Apr 17 2014

...WIND AND SNOW IMPACT FOR NORTHWEST MONTANA ON FRIDAY...

.DISCUSSION...

Model guidance weather characterization for the next week has
shifted significantly during the past day. As a result, there are
some weather impacts to discuss for this forecast period.

IMPACT - Friday - wind/snow - west central and northwest Montana

Most models agree that a vigorous Pacific storm system will
intensify further along the border with Canada on Friday. Winds
ahead and behind a surface cold front will likely be gusty,
impacting motorists and boaters on Flathead Lake. The wind impact
upon Flathead Lake will be most noteworthy, with gusts 30-40 mph
possible and waves reaching 3-5 feet across the open water.

Considering the intensification and closed low pressure
circulation anticipated to develop with this Pacific system as it
reaches the Continental Divide, the snowfall over mountain passes
may become significant for this time of year. 3-6 inches snow
accumulation over Marias Pass, including some blowing snow, will
create hazardous travel conditions Friday morning through Friday
evening.

Breezy conditions will redevelop on Saturday and Sunday across the
Northern Rockies, as another fast-moving Pacific storm system
grazes northwest Montana. Wind gusts will be somewhat weaker than
those on Friday, however still plenty strong to increase wave
activity on Flathead Lake. Most of the precipitation with the
weekend system will remain over the mountains of northwest
Montana, however a few sprinkles at low elevations are not
completely out of the question.

Relatively dry and warm conditions appear to prevail Sunday
evening through Monday evening, with high pressure returning to
the region.

Forecast confidence goes off a cliff from Tuesday through Thursday
next week. All global weather models are depicting a broad and
far-reaching low pressure circulation developing over the Northern
Rockies and then intensifying east of the Continental Divide. The
weather scenario itself is not necessary unbelievable, however the
anomalously cold air depicted over much of the western US appears
much more extreme than a mere day ago. The current forecast
reflects the trend of this extreme forecast, however not nearly as
extreme in terms of cold or precipitation chances. Mountain passes
are likely to be impacted with snow covered roads at some point
during the latter half of next week, however specific timing is
unclear at this time.

&&

.AVIATION...Current water vapor loops clearly depict the next
weather system moving onto the west coast. Cloud cover ahead of this
system will continue to obscure terrain and rain will further lower
the ceilings through the Idaho panhandle and into northwest
Montana. Precipitation will expand through north central Idaho and
western Montana this evening and overnight as a cold front
approaches and passes. Gusty west winds can be expected with the
frontal passage mainly overnight and early Friday morning. The
main trough will reside over the region on Friday, so showers and
terrain obscurations are going to remain common through Friday
afternoon.

&&

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

$$

Zumpfe/Kitsmiller
Aviation...Kitsmiller

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