Weather Service Report

FXUS65 KGGW 030941

Area Forecast Discussion
National Weather Service GLASGOW MT
241 AM MST Sat Dec 3 2016

.SHORT TERM...for northeast through Mon...

Weak frontal system with shortwave trough will move through
Eastern Montana today. The system will bring areas of light snow
at times during the day. Winds will become northwest this
afternoon behind the front.

The trough moves to the east this evening. The forecast area will
be between systems late tonight and Sunday Morning with mainly dry

Sunday will be a warm day ahead of the cold front that moves
through the area in the late afternoon and evening. The cold front
will bring a much colder air mass into the region Sunday Night
with an upper trough moving through Montana during the day on
Monday. Models differ on moisture and precipitation with this
system. Will mention a chance of light snow in most areas. Temperatures
will be much colder on Monday and will likely be steady or slowly
falling as cold air advection continues and gusty northwest winds
develop. Forrester

.LONG TERM...Mon night through Sat...

The extended period begins Monday evening with the base of a long-
wave upper trough plunging south into the Northern High Plains,
leading the way for an incursion of frigid Arctic Air. 00Z Tuesday
850mb temperatures are progged by GFS at -18C. By 18Z, progged at
-24C. This will drive most surface lows to single digits below
zero. Tuesday surface highs will only rise into single digits
above zero, about 20F degrees below normal.

The winter storm system will have mostly moved out of the area at
the start of the extended period and will begin stacking up on
Tuesday over northern Minnesota. So expect only tapering off light
snow locally Monday evening. The strongest northwest winds will
also have moved on east, but CAA will reinforce those winds
into the evening. This is not usually picked up well by the
models. Expect widespread low stratus in the wake of the departed
system to stick around through at least Wednesday, and maybe

This will also be the first wind chill event of the season, with
probable headlines. Winds will remain elevated at 10-20 kt which
will lead to wind chills 20-25 below north of the Hi-line Tuesday
morning, and 20-35 below everywhere Wednesday morning. Wind
chills continue for Thursday morning too. But with an upper ridge
beginning to build up in the West, wind chills should remain below
advisory level for Friday morning.

With the ridge comes a warm front where Pacific moisture rides
across the Divide. This overrunning moisture will find cold
conditions, which will possibly lead to accumulating snow through
Friday night.




An upper level disturbance dropping south from Canada has send
limited moisture through Montana this morning.

Radar imagery this morning shows a band of precipitation echoes
moving east reaching GGW around 09Z. This band was ahead of the
models by a couple of hours, which required amends. The low
deepens today to bring in additional moisture. Snow should end by
mid evening.

Expect VFR initially, then periods of possible MVFR/IFR when
light snow showers pass over the terminal areas.

Wind: southwest 5-10kt early this morning. Late morning and
afternoon winds become west to northwest and increase to 15-25kt.






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