Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 191102
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
402 AM MST Mon Feb 19 2018

.DISCUSSION...Wind chills continue to be an issue across western
Montana this morning as a fairly tight pressure gradient produces
gusty easterly winds. Western Montana has or will see wind chill
readings from -5 to -25 this morning with the coldest occurring
near the Continental Divide from Helmville down to Anaconda. The
pressure gradient appears to relax this afternoon allowing the
easterly winds to subside and along with gradual warming
temperatures today, the threat of dangerous wind chills should
diminish be late morning/early afternoon.

A subtle disturbance is currently causing light snow around the
Pullman area of Washington this morning. This weak feature should
drift to the southeast throughout the morning and produce
additional accumulating snow over the Orofino/Pierce area down to
Grangeville and Whitebird grade. Thus Winter Weather Advisories
remain in affect through this morning with the snow gradually
dissipating throughout the afternoon hours.

The Northern Rockies remain under a cold northwesterly flow
tonight into Tuesday. Some clearing is anticipated for tonight
which should allow temperatures to drop dramatically, potentially
to the coldest readings this season for a few location.
Temperatures are expected to be below zero for most of western
Montana and in the single digits for north central Idaho. Another
subtle disturbance will drift through the northwesterly flow on
Tuesday and Tuesday night which could cause some light snow
showers throughout the region.

From midweek onward the forecast can be summarized with the
following: Continued cold with ever so gradual warming &
occasional light snow. Overall weather models all agree that the
upper level flow pattern will remain very stable over the next 7
to 10 days. The resultant continental wide (spanning coast to
coast) long wave trough of low pressure will place the Northern
Rockies under northerly to northwesterly flow most of the time.

Periodic weak weather features are likely to glide south from
Canada and produce occasional light snow or snow flurries. But
there will also be periods of clearing in between these
disturbances and if these happen to occur over night then
temperatures could quickly fall. Both the ECMWF and GFS briefly
develop westerly flow across the area next weekend which could
interject some additional Pacific moisture into an already very
cold air mass. This appears to be our next best chance for
snowfall and perhaps a weak reinforcing shot of cold air. But
confidence is rather low regarding how much snow we could possibly
see or if that reinforcing shot of cold air could happen.

&&

.AVIATION...Breezy easterly winds remain over the Northern Rockies
through this morning causing localized blowing snow and very cold
wind chills. Also a subtle disturbance will drift into north
central Idaho causing light snow near KGIC this morning. Both the
wind and shower activity is anticipated to diminish this
afternoon.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Wind Chill Advisory until 1 PM MST this afternoon
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Potomac/Seeley Lake Region.

     Wind Chill Advisory until 1 PM MST this afternoon
     Missoula/Bitterroot Valleys.

     Wind Chill Advisory until 1 PM MST this afternoon Lower Clark
     Fork Region.

     Wind Chill Advisory until 1 PM MST this afternoon
     Flathead/Mission Valleys.

     Wind Chill Advisory until 1 PM MST this afternoon West Glacier
     Region.

     Wind Chill Advisory until 1 PM MST this afternoon
     Kootenai/Cabinet Region.

ID...Winter Weather Advisory until 1 PM MST this afternoon Eastern
     Lemhi County...Western Lemhi County.

     Winter Weather Advisory until noon PST today Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

     Winter Weather Advisory until noon PST today Northern Clearwater
     Mountains...Southern Clearwater Mountains.

&&

$$



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