Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 190832

Area Forecast Discussion
National Weather Service Glasgow MT
232 AM MDT Tue Sep 19 2017

.SHORT TERM...for northeast through Wed...

A cold front will move to the east this morning. SW flow aloft
will prevail today ahead of an upper low in British Columbia and
Alberta. Shortwaves within the SW flow aloft may allow for some
isolated to scattered showers at times. West winds will develop
behind the cold front this morning. Wind speeds should stay below
Lake Wind Advisory criteria today.

While the upper low remains over Alberta and British Columbia
tonight, surface high will build into the forecast area tonight
which will allow for dry weather.

The surface high moves to the east on Wednesday. A strong
shortwave trough on the Pacific off the BC coast will take the
western end of the upper low and move it southeast into the
Pacific NW. This will turn the flow aloft to the SW over Montana.
At this point, Wednesday looks dry over Northeast Montana as the
moisture stays to the west of the forecast area. Forrester

.LONG TERM...Wed night through Tue...

Synoptic Setup: Long range begins with a long strong of southwest
flow running from central California through Wyoming the Dakotas
and southern Manitoba. Directly behind it a large trough stretches
from northern California through the Pacific Northwest, Alberta,
and northern Saskatchewan. Behind that a large ridge resides south
of the Aleutians and moving into the Gulf of Alaska. The coldest
air of the northern hemisphere sets over the Arctic Ocean just
north of the Alaskan North Slope.

Wednesday night through Thursday: Frontal boundary across the
region will not move much as the trough behind it gains strength.
This should keep temperatures up in the 60s for highs. Skies
should also be mostly cloudy to overcast due to the pacific
moisture stream by aloft with only a slight chance for rain

Thursday night to Friday night: Surface boundary will begin to
move bringing colder air into the region form the north. This drop
in temperatures should squeeze out more QPF during these periods.
With overnight low continuing to drop would not be surprised if
by Friday night a mix of snow and rain is possible for any

Saturday through Sunday: Bulk of the trough will move through
during this time bringing the coldest temperatures. but with the
temps stabilized out showers should become progressively less.
Meanwhile, the Gulf of Alaska Ridge will move inland over British

Sunday night onward: RIdge will nose out over alberta spilling
over into a slight warming chinook that will press up against the
slow exiting trough. This should stabilize the atmosphere and
trend temperatures upwards during this time with current models
estimating the chinook to reach central Montana by Monday night.



VFR conditions will prevail today and tonight. A cold front will
move to the east this morning with west winds 10 to 15 knots
developing behind it. Isolated to scattered showers are possible
today across the region with mid level clouds. Skies will clear
this evening as high pressure builds into the area. West winds
will diminish to 5 to 10 knots this evening.




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