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000 
FXUS65 KGGW 201453
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
853 AM MDT Wed Sep 20 2017

.SHORT TERM...for northeast Montana...today through Thu...

Going forecast looked good and just refreshed things, such as low
temps this morning, sky and pops through this evening. TFJ

Previous Discussion...
Large upper low spinning over western Canada this morning.
Moderately unstable conditions expected with the cyclonic flow for
the development of a few showers, mainly this afternoon when 
instability is greatest. Temperatures will continue to be below
normal and mixing should be strong enough to push winds into lake
wind criteria. Thus will go with lake wind advisory for mainly the
afternoon. 

Winds should decouple quickly this evening along with showers
ending. Western portion of the trof digs south toward the Great
Basin for upper flow turning to the southwest overnight. Shift in
the upper flow will bring a stream of moisture into southeast
Montana by Thursday and could start to get some showers moving
into the southeast zones by very late in the day. Ebert

.LONG TERM...Thu night through Wed...

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

Thursday night to Saturday: Surface boundary will begin to move 
bringing colder air into the region form the north. This drop in 
temperatures should squeeze out QPF during these periods. With 
overnight lows continuing to drop, Friday night continues to keep 
a chance for a mix of snow and rain north of the high line and 
over high elevation areas such as the Little Rockies. 

Saturday night through Sunday night: 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 the Canadian Rockies and high Plains. 

Monday 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.
Models seem to line up here and confidence appears to be moderate
to slightly above average with a little bit of wiggle room for a
more washed out chinook. GAH


&&

.AVIATION...
VFR conditions are expected through the period. A few showers may
move across the region this afternoon. 

Winds: SW winds will be increasing a bit by noon, then diminish
late today. expect speeds of 20 kts at KGGW, lighter at the other
3 locations (KOLF, KSDY and KGDV). TFJ


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory until 7 PM MDT this evening For Fort Peck 
Lake for Central and Southeast Phillips...Central and Southern 
Valley...Garfield...McCone...Petroleum.

&&

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