Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 240255 AAA
AFDGGW

Area Forecast Discussion...UPDATED
National Weather Service GLASGOW MT
855 PM MDT Sun Apr 23 2017

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

Sent an update tonight to expand the coverage of the winter
weather advisory based on the latest model consensus showing the
wrap-around precipitation later tonight becoming a mess of a
wintry mix further south and east than previously thought.
Collaboration with neighboring office area confirms the need for
this expansion. Snow accumulations around 2 inches expected, along
with up to a tenth of an inch of ice from freezing rain.

BMickelson

Previous short term discussion: Today has and will continue to
offer a couple of different challenges across northeast Montana.
First, several reports in northern Valley, Daniels, and Sheridan
Counties have come in this afternoon with 2 inches of snowfall
accumulation with a little bit of ice, and even one report of 4
inches was reported north and west of Outlook.

Another round of freezing rain and snow will occur tonight, with
additional icing and snow covered roads possible. Daytime snow
accumulations can be difficult to attain given the strong April
sun angle, but after dark, any snow that occurs with temperatures
at or around freezing will surely accumulate. Thermal profiles
also support a continued freezing rain risk in these same areas as
the next push of precipitation crosses through. Given the
expected additional snow accumulations of an inch or two combined
with another coating of possible ice, the going Winter Weather
Advisory appears in overall fine shape and so will leave it in
place for now. The evening shift will have to monitor Roosevelt
County with a watchful eye tonight. Some of the model guidance
produces a period of high QPF in this area. Temperatures should be
in the mid 30s, a little above freezing, but with dynamic cooling
in heavy precipitation, should temperatures end up a degree or two
lower than expected, icing could become a problem here and an
advisory expansion necessary. Will hold off on this idea for now
given the uncertainty.

Convective thunderstorms are showing up on radar and approaching
Petroleum County. Will carry a thunderstorm mention this evening
in the southwest zones given the observations and recent trends.

Lastly, with wind speeds remaining elevated in and around the Fort
Peck Lake area, the decision was made to extend the Lake Wind
Advisory through 10 PM this evening to allow the evening shift to
assess trends.

Consensus model blends have precipitation ending Monday
morning, though new showers may enter the picture in the southwest
zones Monday afternoon with perhaps a little thunder given
forecast sounding convective parameters in the area.

Maliawco


.LONG TERM...Tue night through Sun...

Made very few changes to the inherited extended period forecast.
Model consensus continues to show a large area of low pressure
aloft, and a series of disturbances will follow that general track
as they drop down through the Rocky Mountains and into the central
plains.

Models continue to show northeast Montana on the colder side of
the pattern, and as was mentioned in the previous discussion, rain
showers that change to snow overnight when precipitation occurs
looks to be the pattern throughout the week. Wednesday and
Thursday still look to be the most likely period for a few light
showers, but models still diverge some on the placement and timing
of these showers.

Hickford

Previous Long Term Discussion...
The extended forecast period will be dominated by a large low-
pressure trough pattern aloft as repeated large weather
disturbances dive toward the south and southeast from the Rocky
Mountains through the high/central plains regions.

While this will likely result in weather conditions more active
and interesting elsewhere, NE Montana will reside in the colder
air influence of this pattern. Cold enough, in fact, to introduce
a chance for rain changing to snow each night if precipitation is
in the area. This seems most likely from Wednesday morning through
Thursday with what seems like a back-door cold frontal system from
Saskatchewan. Models are generally presenting this precip as
scattered and somewhat disorganized, but tried to adjust the
forecast to line up with the best model consensus I could find.
May result in a few periods of light accumulations of snow across
our northern zones.

Thursday night through the weekend, a large and powerful low
pressure system digs even further south through the central and
southern Rockies and will probably set the stage for some severe
thunderstorms over the central plains region by Friday afternoon.
Again, NE Montana is completely removed from any of these severe
weather dynamics to be of any concern. Just dealing with a
repeated cold and unsettled weather patterns locally.

BMickelson


&&

.AVIATION...

SYNOPSIS: A progressive westerly flow aloft will keep active
weather going over northeast Montana through the early part of the
week. A stronger wave in the flow will pass from west to east
overnight, bringing periods of IFR conditions as well as the
possibility for frozen mixed precipitation through Monday morning
along and NE of a line from Thoeny to Saint Marie to Wolf Point to
Sidney.

Flight Conditions: MVFR to IFR this evening through Monday
morning.

CIGS: Generally 500 to 2000 feet, with CIGS lowering below 1000
feet overnight in places.

Weather: Some FZRA could possibly mixed with -RASN and PL
overnight into early Monday Morning. Affected TAFs primarily KOLF,
KSDY.
WIND: From an easterly direction at about 10-20 kts, decreasing
to 6-8kts and becoming more northerly overnight.

tc


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 AM MDT Monday for Daniels...
Eastern Roosevelt...Northern Valley...Richland...Sheridan...
Western Roosevelt.

Lake Wind Advisory until 10 PM MDT this evening For Fort Peck
Lake for Central and Southeast Phillips...Central and Southern
Valley...Garfield...McCone...Petroleum.

&&

$$

weather.gov/glasgow



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