Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 230253
AFDGGW

Area Forecast Discussion
National Weather Service GLASGOW MT
853 PM MDT Sat Apr 22 2017

.SHORT TERM...for northeast Montana...tonight through Mon...
9 PM UPDATE:
Have increased the chance of rain for tonight through Sunday
across the region. The boundary currently over the area will act
as a focus for precipitation to move along during the period.
Otherwise only minor adjustments made to the other elements to
bring them in line with the current conditions.    Proton

Previous Discussion:

morning update: Updated to keep a few sprinkles in the Glasgow
area and eastward this morning and to remove the fog as there is
very little left this morning. Low pressure is centered over Lake
Sakakawea with a stationary boundary extending westward through
our CWA. Stratus deck evident on satellite below another deck of
clouds. Things are pretty slow moving this morning. as for the
forecast concerns...the big thing is the impacts on aviation with
the ceilings and the system coming in tomorrow evening bringing
some substantial moisture to the area.  fransen

A shortwave ridge will be over Eastern Montana with mainly dry
weather. A weak frontal boundary will be along the Canadian
border this afternoon which could bring some isolated showers.
That frontal boundary strengthens somewhat tonight as it drifts
south into the forecast area as a back door cold front and gains
some overrunning moisture which will bring a chance of rain along
the Canadian Border. East winds will also develop tonight which
will likely be strong enough late tonight and Sunday to require a
Lake Wind Advisory over Fort Peck Lake.

Upper trough moves inland from the Pacific on Sunday which will
bring deep moisture inland. A shortwave will break away from this
trough and move across Eastern Montana Sunday afternoon and
night. Moisture will overrun a stalled frontal boundary over
Central Montana and bring widespread precipitation that could
start as early as Sunday afternoon and continue Sunday Night
especially north of the Missouri River and move to the east
Monday morning. Temperatures will be below freezing between
Opheim, Scobey, and Plentywood which will allow rain to change to
snow with a mix of freezing rain possible. At this point, it looks
like there will be an inch or two of snow in this area.

Additional shortwaves are expected on Monday with slow moving
frontal boundary either over the forecast area or just southwest
of it. Will maintain a chance of light rain or snow in areas where
temperatures will be near freezing. Forrester



.LONG TERM...Mon night through Sat...
The extended period remains largely on track from previous
thinking. The new forecast trended toward latest consensus model
blends which continue to capture a broad upper trough over the
western CONUS Sunday night right on through next week. If anything
the trough becomes more amplified toward the end of next week.
This will leave in place broad forcing for ascent and frequent
chances for rain showers. The steadiest rain showers with the
first shortwave look to occur north of the Missouri River where
between 0.10" and 0.25" of total moisture may occur. Most should
fall as rain though a change to snow is possible nearest the
Canadian border where an inch of slushy accumulation cannot be
ruled out.

Additional convective showers will approach the CWA from the west
with a little thunder possible Monday afternoon and evening.
Slight chance to chance pops were maintained for much of the rest
of the extended period given the broad overall pattern in place.
Specific timing and amount are details that will be worked out in
time as model consensus improves and individual shortwave impulses
are better resolved. Maliawco

Previous Long Term Discussion...

Synoptic Setup: Long range begins with an Arctic trough over the
Hudson and Nunavut. Meanwhile the dominant ridge that should
begin forming over the western third of the CONUS is no where in
site. In its place a much weaker high amplitude runs up the front
range from Wyoming to Yukon territory letting shortwave of pacific
air and moisture through as they please.

Monday onward: Long range is really a story of moderated seasonal
temperatures with above average precipitation throughout the
periods. A persistent east wind appears almost every period with
multiple weak shortwaves increasing the chances for moisture
above average to above average and giving almost ever period a
small chance. Rain will be very much play it by ear throughout the
periods with confidence being high in the large scale temperatures
but only average to below average in timing of showers as there
are no definite fronts are to be sussed out of the data yet. GAH



&&

.AVIATION...

FLIGHT CAT: VFR to borderline MVFR.

SYNOPSIS: A stationary boundary remains draped over the region
with a more persistent cloud deck covering all NE Montana TAF
sites. Some clearing is evident south and west of the front, but
it is not yet clear if that clearing will be strong enough to
allow for fog development tonight through Sunday morning for those
sites. Will keep a close eye on this and amend as necessary.
Vicinity rain showers are expected toward the end of this TAF
cycle.

CIGS: Generally 4000 to 7000 feet.

WIND: From the east at about 20 kts.

Fransen/Mickelson


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 6 AM to 6 PM MDT Sunday For Fort Peck
Lake for Central and Southeast Phillips...Central and Southern
Valley...Garfield...McCone...Petroleum.

&&

$$

weather.gov/glasgow


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