Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 200412

Area Forecast Discussion
National Weather Service Glasgow MT
912 PM MST Fri Jan 19 2018


Evening Update (9pm MST): Some fog has begun developing in Malta
as the cloud deck has cleared out of the area and radiational
cooling plus the reformation of the low level inversion have
brought the temp to the dew point at Malta airport. This trend is
generally expected to continue eastward as the cloud deck clears
out of further areas. The limiting factors continue to be winds
and the speed of departure of the cloud deck, but the reinforcing
factors are the reformation of the low level inversion, and the
ability of the surface to freely radiate out to space and rapidly
cool the surface temperature to the dewpoint. Thus the fog
potential remains through the morning hours tomorrow, and will
need monitoring through the day tomorrow for the potential for fog
tomorrow night as well. Bigelbach

Afternoon Update (4pm MST): With added atmospheric
moisture due to melting snow resulting from warm conditions
across northeast Montana today, and the potential for clear skies
overnight as the weak cold front continues to pull out of the
region, some patchy to areas of freezing fog have been introduced
through tomorrow afternoon, mainly confined to lower elevation and
river valley areas. The extent of the potential for fog will be
dependent on when and if clearing occurs across the region. Winds
of 5-10 mph may also be a slight inhibitor for fog, but this may
be overcome by the strength of the radiational cooling, as well as
the affects from the return of subsidence to the region as
another inversion layer may develop across many parts of the
region. Otherwise, the rest of the forecast is fairly benign and
thus in good shape.


PREVIOUS DISCUSSION: An upper trough swings through the West
Coast tonight, then undercuts Montana. This will leave a ridge to
our north in Canada, allowing for clearing skies from the north.
Cooler air will drift in, enhanced by these clearing skies. Thus
lows are expected to fall into the teens and lower 20s.

The weekend ahead will feature a splitting trough moving over the
region with the colder air from the northern stream affecting
Northeast Montana. With a much colder start to the day, highs will
struggle to reach above freezing. With remaining snow cover,
overnight lows Saturday night are expected to fall into single
digits across the north and teens in the south. This cooling
trend will continue Sunday.

A narrow ridge Sunday night will help warm Monday highs a bit.
An clipper system of limited strength will approach from the
northwest late Monday, with some increasing cloud cover. Though,
with not much in the way of moisture, do not expect much
precipitation. This clipper may enhance the mixing for the
slightly warming highs. A long-wave ridge follows Tuesday with
close to normal temperatures through Thursday.

Later in the second half of next week, models shows a broad,
long-wave trough working through the West and middle states.
Expect temperatures to trend lower than average with a few periods
of snow.




Expected Flight Category: VFR

Synopsis: The cloud deck associated with the cold front that
passed through last night is still drifting out of the region. In
its wake, some fog has begun to develop west of the sites in the
clearing skies. Winds, and the speed at which the cloud deck
drifts out of the region, will be the potential limiting factors
for the formation of any dense fog over the sites through morning,
though chances for formation will remain during the overnight
especially where the cloud cover clears out. Otherwise, generally
pleasant flying conditions are expected through the weekend.

Winds: Expect mostly west to southwest winds at 5-10 kts
throughout the period.





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