Fire Weather Watch 11, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
814 AM MDT Wed Aug 22 2012

.UPDATE...Issued a Fire Weather Watch for the Bitterroot...
Deerlodge/Beaverhead National Forests for winds and low relative
humidities Thursday afternoon and evening.

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.DISCUSSION...Due to the expected increase in westerly winds and
lowering of relative humidities ahead and with a cool front, we
have issued a Fire Weather Watch to highlight these conditions
while considering surface fuels and the number of existing fires.
Cooler, more moist air will invade northern Idaho and western
Montana Thursday night for improving conditions fire weather-wise.

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.AVIATION...Scattered showers and thunderstorms remain across
northwestern Montana this morning which will continue to affect
areas around KGPI. Showers will quickly dissipate and move out of
western Montana as sunrise approaches. Today will be a nicer day
with mostly sunny skies as high pressure builds back into the
region. Breezy afternoon west winds will begin to pick up for all
aviation sites after 22/2000Z and begin to diminish around sunset
tonight.

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.PREV DISCUSSION... /ISSUED 405 AM MDT Wed Aug 22 2012/

DISCUSSION...The upper trough continues to weaken as it swings
through northwest Montana this hour. Still have some scattered
showers and isolated thunderstorms across portions of western
Montana but these should weaken and be east of the area by mid
morning. Behind the trough a cool day can be expected with some
increased afternoon west winds. A weak upper level ridge will
build over the region tonight into Thursday in advance of the next
Pacific weather system. Clear and calm conditions tonight will be
conducive to some decent radiational cooling for Thursday morning
readings below average. Thursday, expect warming and drying
conditions with increased afternoon and evening winds.

Thursday night through Saturday...The ridge of high pressure will be
short lived with the next storm system approaching from the
northwest. This system will be relatively dry, with most of the
moisture being confined to the extreme northwest portion of
Montana, including Glacier National Park. The main concern with
this system will be the increased dry west winds affecting area
fires. West winds will begin to pick up Thursday night and be at
their peak Friday afternoon and evening. Winds could gust as high as
30 mph in the valleys Friday with the higher terrain along the
Continental Divide seeing occasional gust approaching 40 mph. Area
lakes, especially Flathead Lake, will see increased choppy
conditions Friday. Backpackers and outdoor enthusiast should be
prepared for cold and very wind conditions in the high country.
Along with the wind, temperatures will be dropping quit rapidly
after the frontal passage Friday. Friday's highs will barely make
it into the 70s for the valleys of western Montana, with areas in
Glacier Park topping out in the low to mid 40s. Lows Friday night
and Saturday morning will be approaching freezing and below in
some areas along the divide, the valleys dropping into the low
40s. Temperatures will begin to rebound on Saturday with another
high pressure ridge moving back into the region. Valleys will be
back in the upper 70s, however the higher terrain will remain
chilly with highs in the upper 50s.

Sunday through Tuesday the models are coming into better agreement
that a ridge of high pressure will build over the region and
return north central Idaho and western Montana to warming and drying
conditions. Temperatures have been trended up and chances of
precipitation decreased to account for this. Models now show a
break down of the ridge Wednesday of next week with a cold frontal
passage. They vary a bit on frontal passage timing, but Wednesday should
be cooler and more showers with this feature.

AVIATION...Scattered showers and thunderstorms remain across
northwestern Montana this morning which will continue to affect
areas around KGPI. Showers will quickly dissipate and move out of
western Montana as sunrise approaches. Today will be a nicer day
with mostly sunny skies as high pressure builds back into the
region. Breezy afternoon west winds will begin to pick up for all
aviation sites after 22/2000Z and begin to diminish around sunset
tonight.

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.MSO WATCHES/WARNINGS/ADVISORIES...
MT...FIRE WEATHER WATCH from Thursday afternoon through Thursday
     evening Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Missoula/Bitterroot Valleys.

ID...FIRE WEATHER WATCH from Thursday morning through Thursday
     evening Southern Clearwater Mountains.

     FIRE WEATHER WATCH from Thursday afternoon through Thursday
     evening Eastern Lemhi County...Western Lemhi County.

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