637 
FXUS65 KMSO 052143
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
243 PM MST Tue Nov 5 2019

.DISCUSSION...A Canadian cold front has begun to slide across the
Continental Divide this afternoon, with temperature drops and 
northeasterly winds already evident along Highway 2 down to about 
Essex. As it continues to slide south and westward this evening 
and overnight, breezy northeast to east winds are expected to 
develop. The strongest winds will be through exposed 
canyons/valleys of northwest Montana, where gusts to near 40 mph 
will be possible. The main impacts will be to area lakes, where 
choppy conditions will develop as a result. 

Light snow is expected to develop this evening and overnight as 
cold air continues to spill into western Montana. Mountain Passes 
along the Continental Divide (Marias, MacDonald and Homestake) 
will be briefly affected by light snow accumulations and breezy 
winds. Most valleys will remain dry, though some light snow is
possible around Flathead Lake and the Seeley/Swan valleys.  

Winds and precipitation will generally taper off through the day
Wednesday. Temperatures will generally run 10 to 15 degrees cooler
than what was observed on Tuesday.  

High pressure rebounds over the area beginning Thursday and
lasting into Saturday. More stable conditions will lead to morning
fog/low stratus and possibly degraded air quality. Temperatures 
are expected to gradually warm and return to near seasonal normals
by Friday. 

Another Canadian cold front is expected to move into western 
Montana Saturday night into Sunday. In addition to breezy
northeast winds, forecast models continue to show the potential
for more moisture to accompany this system. Snow impacts are
possible, particularly across northwest Montana.  

&&

.AVIATION...A Canadian cold front has begun to push across the
Continental Divide into northwest Montana this afternoon.
Northeast to east winds will continue to strengthen through gaps
and canyons through the evening as the airmass slips south and
west. KGPI will see northeast winds increasing around 06/0200z 
and will likely peak around 06/0900z with gusts up to 35 kts 
possible. KMSO will see winds shift to more of an easterly
direction around 06/0600z and will see gusts up to 25 kt around
06/0900z. As this cold air moves in, mid to low level cloud cover
will increase from northeast to southwest. Lower ceilings and
snow showers will likely cause the terrain to become obscured,
especially along the Continental Divide. KBTM may see a period of
low ceilings and visibility due to light snow between 06/0900z 
and 06/1500z. Winds and snow will decrease through mid day
Wednesday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...Air Stagnation Advisory until noon PST Friday Lower Hells 
     Canyon/Salmon River Region...Northern Clearwater 
     Mountains...Orofino/Grangeville Region...Southern 
     Clearwater Mountains.

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

&&

$$