Wind Advisory 11, NWS Missoula, MT

533 
WWUS75 KMSO 110241
NPWMSO

URGENT - WEATHER MESSAGE
National Weather Service Missoula MT
741 PM MST Sun Nov 10 2019

MTZ003-110345-
/O.EXP.KMSO.WI.Y.0011.000000T0000Z-191111T0300Z/
Flathead/Mission Valleys-
741 PM MST Sun Nov 10 2019

...WIND ADVISORY WILL EXPIRE AT 8 PM MST THIS EVENING...

Winds will continue to decrease through the evening.

$$

IDZ005>008-120245-
/O.EXT.KMSO.AS.Y.0001.000000T0000Z-191112T2000Z/
Northern Clearwater Mountains-Southern Clearwater Mountains-
Orofino/Grangeville Region-Lower Hells Canyon/Salmon River Region-
641 PM PST Sun Nov 10 2019

...AIR STAGNATION ADVISORY NOW IN EFFECT UNTIL NOON PST TUESDAY...

* WHAT...Deteriorating air quality due to light winds and 
  reduced vertical mixing.

* WHERE...Clearwater and Idaho Counties.

* WHEN...Until noon PST Tuesday.

* IMPACTS...Periods of air stagnation can lead to the buildup of 
  pollutants near the surface.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

People with respiratory illness should follow their physician's
advice for dealing with high levels of air pollution during
periods of stagnant air.

According to state air quality agencies, prolonged periods of
stagnant air can hold pollutants close to the ground where people
live and breathe. Check with your local burn agency for any
current restrictions in your area.

&&

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Area Forecast Discussion
National Weather Service Missoula MT
343 AM MST Sat Nov 9 2019

.DISCUSSION...Clouds will be on the increase throughout the day
as moisture streams onshore of the Pacific Northwest. Most areas
will remain dry, with mainly clouds. However, a few light
rain showers will be possible this afternoon across northwest
Montana. Temperatures from west-central Montana south into
southwest Montana and north-central Idaho will be relatively warm,
with afternoon highs a few degrees above normal.

The main weather feature will begin to impact the Northern Rockies
late tonight as the arctic front begins to move over the
Continental Divide. Snow levels across the region are expected to
start off relatively high (at or above pass levels) and then
begin to crash as the front moves through during the day Sunday.
Marias Pass will begin to see wintry impacts first, soon after
midnight tonight. Light freezing drizzle is expected just ahead
of the front all along the Continental Divide, before changing to
all snow behind the front. Several inches of snow is still
expected for Marias Pass through the day Sunday. Due to the
combination of snow and strong gusty northeasterly winds, blowing
snow and icy conditions will be a big concern, not only for Marias
Pass, but also MacDonald Pass and potentially Homestake Pass.
Many locations across northwest Montana, will likely see their
high temperatures early in the morning, with temperatures steadily
lowering through the day on Sunday.

The front will slowly makes it's way south, and expected to be
over west-central and southwest Montana by Sunday afternoon. Roads
are expected to be wet before the front arrives and could become
icy fairly quickly as the colder air moves over the area.
Anywhere from 2 to 5 inches of snow is possible, with the valleys
further west of the Continental Divide generally seeing less than
one inch. With all that said, Winter Storm Watches remain in
place for the West Glacier Region and the Butte/Blackfoot Region
for blowing snow and icy conditions through Sunday evening.

In general, pleasant fall weather will become established
throughout the Northern Rockies on Monday and likely persist
throughout much of the week. Unfortunately we're getting to that
time of year where the presence of high pressure results worsening
air quality with time as stagnant, stable conditions develop
within valley cold pool inversions. Fortunately the models do
show a quick moving weather system sliding over the high pressure
ridge which may prove sufficient to mix up the atmosphere a bit
late Tuesday or early Wednesday. High pressure once again tries to
become established for a few more days (Thursday and Friday)
before yet another, perhaps stronger, Pacific weather system
breaks through the ridge just in time to bring valley rain and
mountain snow chances for next weekend.

&&

.AVIATION...Mid to high level clouds will be on the increase
through the day, as moisture streams onshore of the Pacific
Northwest. Most areas will remain dry, though a few light showers
will be possible across northwest Montana, along the MT/ID border.
An arctic front is still expected to begin to impact the region
starting late tonight after midnight across northwest Montana. The
front will slowly move south, and is expected to be over west-
central and southwest Montana by Sunday afternoon. Most of the
wintry impacts are expected to be along the Continental Divide
during this event. Though KGPI, KMSO and KBTM will see periods of
reduced visibility due to snow and blowing snow with the front.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...     Winter Storm Watch from late tonight through Sunday evening West
     Glacier Region.

     Winter Weather Advisory from 8 AM to 8 PM MST Sunday
     Potomac/Seeley Lake Region.

     Winter Storm Watch from Sunday morning through Sunday evening
     Butte/Blackfoot Region.

ID...Air Stagnation Advisory until noon PST Monday Lower Hells
     Canyon/Salmon River Region...Northern Clearwater
     Mountains...Orofino/Grangeville Region...Southern
     Clearwater Mountains.

     Air Stagnation Advisory until 1 PM MST this afternoon Eastern
     Lemhi County...Western Lemhi County.

&&