Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 190216 AAA
AFDGGW

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
816 PM MDT Fri Aug 18 2017

.SHORT TERM...for northeast Montana...tonight through Sun...

GOES imagery of North America shows broad upper-level trough
across Alaska and extending through the Yukon Territory into the
northern reaches of British Columbia and Alberta. A wave/cold
front can be seen out ahead of the trough advancing in our
direction. This dry front will reach our area by morning.

Tonight, there is a narrow and weak upper ridge in place over
Northeast Montana to begin the evening with mostly clear skies.
But broad band of clouds is evident on the satellite view that
will move tonight. So expect increasing clouds. A surface trough
over Central Montana will maintain mostly east winds intially.
That trough shifts east tonight. The result will be wind in the
west counties shifting to the northwest before morning. Only
edits were to include the latest near term guidance.

Templer


Previous discussion -
Synoptic Setup: Hot Desert Southwest air is moving up intoa ridge
running over Wyoming, Montana, and Sasakatchewan. To the northwest
a Trough of cool pacific air is drops down from Alasaka through
British COlumbia. Southwest flow resides over the Pacific
Northwest and Alberta.

This afternoon through tonight: Ridge across the area will exit
into the Dakotas. Smoke and haze across the region today will
likely settle in overnight as conditions stabilize near sundown.
Meanwhile, the trough will exit the front range and firms up a
cold front behind it.

Saturday: The front is anticipated to hit Northeast Montana
between 3 to 9 AM and tomorrow with the strongest winds gusting
behind it around 6 to Noon. The front itself should by dry with no
known moisture source to act on with the low level lift. Smoke
across the area should rapidly evacuate near the surface. As RH
will be very low and downslope may force it lower, when combined
with the winds have decided to add a Red Flag Warning for the
southeast two thirds of the CWA.    GAH


.LONG TERM...Sun night through Fri...

Models showing the peak for High-based thunderstorms to occur
Sunday Night. Increased pops slightly over model blend to account
for this.

Otherwise, rest of forecast looked good. TFJ

Previous Discussion...
The Northeast Montana forecast is picked up Saturday evening with
zonal flow aloft and a dry cold front having passed through the
area during the day. So, wind behind the front will be northerly,
but calmed down from the day. Weak disturbances along the frontal
boundary could generate a few showers and thunderstorms, but a
surface high should keep most of that south of our area Saturday
evening. However after midnight, a short-wave trough moves in from
the west to ride along the frontal boundary. This could initiate
rain showers and thunderstorms into Sunday, tapering off Sunday
evening through Monday morning. Near normal temperatures.

Monday morning a second, more energetic, quick-moving, trough
from the west could initiate another round of showers and thunder
Monday afternoon and evening. Near normal temperatures.

Tuesday and beyond, models show a broad upper ridge moving over
the Divide for warmer, quieter and dry conditions at least
through mid-week.

Beyond that, model differences in location and timing of the next
trough/storm system grow. But both the GFS and the EC bring in a
rather large system from the Gulf for the weekend with a return to
near normal temperatures.

Templer


&&

.AVIATION...
FLIGHT CAT: VFR.

SYNOPSIS: High pressure is in place this evening. A cold front is
anticipated to move through the area overnight but conditions
should remain dry.

WIND: Southeast wind ahead of a front this evening, becoming west
to northwest at 10 to 20 kts behind the front Saturday.

GAH/Proton


&&

.FIRE WEATHER...
An upper-level trough and cold front moving through northern BC &
Alberta can be seen on GOES Satellite imagery. Because of this
front, locally enhanced to critical fire weather conditions are
expected for Saturday.

This dry cold frontal passage out of Canada is initially expected
to reach our area Saturday morning. This will shift wind around
to the northwest. Wind will begin increase by mid-morning to a
gusty 15 to 25 mph. Relative humidity percents will again drop
into the teens and lower 20s.

With continued dry fuels, gusty wind, and low relative
humidities, critical fire weather conditions are expected for most
of Northeast Montana, and a Red Flag Warning is in effect for
those areas. The northwest area, however, will continue to have
enhanced fire weather conditions and will be monitored for
possible inclusion later into the warning.


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 8 AM to 8 PM MDT Saturday for
MTZ120-122-136-137.

&&

$$

weather.gov/glasgow



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