FXUS65 KGGW 181008
Area Forecast Discussion
National Weather Service Glasgow MT
308 AM MST Fri Jan 18 2019
Synoptic Setup: Forecast begins with a large cold airmass centered
over the Hudson Bay thats spread out over the Canadian Plains, the
Upper Mississippi Valley, and northern US Plains. In response, a
large ridge has begun to develop off the US coastline which
crests around southern British Columbia. Northeast Montana
lies nestled between these two airmasses under northwest flow with
a pacific feed of moisture aloft. Farther west another
trough/ridge couplet lies over the northeast Pacific.
Today through tonight: Pacific moisture feed is expected to cut
off by mid day allowing current snow to diminish into the
afternoon. Cloud coverage should hold into the evening but then
break up during the early morning hours. This will allow lows to
go below freezing in the far northeastern corner of the CWA.
Saturday through Sunday: Ridge to the east will butt into the
cold airmass over northeast Montana and North Dakota which will
form a shortwave in the flow. This shortwave should generate
enough lift to create a fast moving band of snow showers over far
northeastern sections of the CWA. Snow totals with this fast
moving system should be no more than an inch.
Sunday night through Monday night: Next trough will move into
western third of the CONUS while its companion ridge will develop
off the North American Coast. As the trough moves through it will
become the focal point for Arctic air to pour into when it
reaches the Montana High Plains. This cool down at the surface
will be accompanied by a Pacific moisture surge which should
generate another large region wide storm system. Storm totals with
this passage are inexact but all locations look destined for
something. Meanwhile, the ridge off the NA coast will continue to
Tuesday onward: Model breakdown occurs from here onward and
confidence is low with the expectation that the forecast will
change. A developing ridge to the west and intensifying Hudson Bay
Low will leave northeast Montana in northern to northwest flow
aloft with a battle for fluxuating temperatures anticipated from
here onward. This will also generate several fast moving lesser
shortwaves that bring random dustings of snow throughout the
remainder of the forecast but whose timings will obviously change
with each update. GAH
FLIGHT CAT: VFR-IFR
DISCUSSION: Snow will continue across the area until about 18z and
then begin to taper of through the afternoon. IFR conditions
should lift with the snow around the same time and chnage to MVFR
to VFR ceilings through the remainder of the cycle.
WIND: East to northeast at 10 to 15 kts through Friday. Veering to
the southeast and reducing to less than 10 kts Friday night.
Winter Weather Advisory until 11 AM MST this morning for Central
and Southeast Phillips...Central and Southern Valley...Daniels...
Garfield...McCone...Northern Phillips...Northern Valley...
Southwest Phillips...Western Roosevelt.
Winter Weather Advisory until 6 AM MST early this morning for
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