Wind Advisory 7, NWS Missoula, MT

448 
WWUS75 KMSO 211555
NPWMSO

URGENT - WEATHER MESSAGE
National Weather Service Missoula MT
955 AM MDT Thu Sep 21 2023

MTZ003-220600-
/O.CAN.KMSO.WI.Y.0007.000000T0000Z-230922T0000Z/
/O.NEW.KMSO.LW.Y.0007.230921T1555Z-230922T0600Z/
Flathead/Mission Valleys-
955 AM MDT Thu Sep 21 2023

...LAKE WIND ADVISORY IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FLATHEAD 
LAKE...

* WHAT...Northeast winds 25 to 35 mph with gusts up to 45 mph across 
  the southern end of Flathead Lake towards the Narrows and Yellow 
  Bay.

* WHERE...Flathead Lake

* WHEN...Until midnight MDT tonight.

* IMPACTS...Strong winds and rough waves on area lakes will create 
  hazardous conditions for small craft.

* ADDITIONAL DETAILS...The winds will fluctuate this afternoon, but 
  become strong again by this evening.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Boaters on area lakes should use extra caution since strong winds 
and rough waves can overturn small craft.

&&

$$

MTZ002-007-043-211700-
/O.CAN.KMSO.WI.Y.0007.000000T0000Z-230922T0000Z/
West Glacier Region-Butte/Blackfoot Region-Potomac/Seeley Lake
Region-
955 AM MDT Thu Sep 21 2023

...WIND ADVISORY IS CANCELLED...

The strong winds across the area have lessened.

$$

Area Forecast Discussion
National Weather Service Missoula MT
249 AM MDT Wed Sep 20 2023

.DISCUSSION...The pattern change that we have been following the
past several days is still on track to arrive today, as a cut-off
low pressure circulation develops. The center of the low will
slowly migrate out of British Columbia this morning, and move
south through eastern Washington and Oregon this afternoon. A
notable drop in temperatures will occur across all of the
Northern Rockies, with temperatures running 15 to 20 degrees below
normal by Tomorrow.

We are also still expecting (70 to 90 percent chance) widespread
wetting rains (>= 0.10") for the majority of western Montana and
north-central Idaho to fall today through Friday. Areas with the
least chances continues to be the lower elevations of Lincoln
County in northwest Montana. Locations that will likely see the
higher amounts will be southwest Montana, Lemhi County, and along
the Continental Divide, including Glacier National Park. These
areas have a roughly 40 to 60 percent chance of receiving 0.50" or
more of precipitation.

Given the location of the center of the low pressure system being
to our west, this will open the door for cooler Canadian air to
spill over the Continental Divide into western Montana, lowering
snow levels. Snow levels down to 6500 feet are looking likely by
Thursday morning, with the higher terrain along the Continental
Divide and southwest Montana seeing a few inches of wet snow. For
those recreating in the backcountry, raw conditions should be
anticipated tomorrow due to the combination of temperatures in
the upper 30 to low 40s, breezy northeast to east winds, and
rain/slushy snow. Elsewhere, expect to at least see a dusting of
snow on the peaks that are above 6000 feet when you wake up
tomorrow morning.

Speaking of the wind, confidence is increasing that most of
western Montana will begin to experience an increase in easterly
winds late this evening through tomorrow afternoon. The higher
valleys along the divide, and the favored east to west gaps and
canyons (Badrock & Hellgate Canyons) could see periods of gusts
reaching 35-40 mph from sunset through sunrise tomorrow morning.

Forecast models generally agree that the low pressure system will
finally eject out of the region by Saturday afternoon. Southwest
flow is expected over the region, which will allow temperatures to
warm back towards seasonal normals.

&&

.AVIATION...A change in the overall weather pattern will begin
today, as a cut-off low pressure system slides south out of
British Columbia, and across eastern WA/OR. As the low moves to
our south and west, a tight easterly pressure gradient will
develop, creating an increase in east to northeast winds across
western Montana and north-central Idaho. The Strongest winds are
expected in western Montana where KGPI, KMSO, KBTM and KHRF could
have gusts in the 25-30kt range from 21/0000Z-21/1200Z. Widespread
wetting rains are also expected from this evening, and continuing
through the day Thursday.

&&

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