Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 300309 AAA

Area Forecast Discussion...UPDATED
National Weather Service GLASGOW MT
909 PM MDT SUN MAY 29 2016

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

Skies are clear over Northeast Montana this evening, but radar and
satellite imagery does show the base of the short-wave trough
sending rain showers and isolated thunder through Central Montana.
The GFS waits until after midnight to bring most showers into our
western zones tonight. The NAM12 comes into agreement with a
chance for limited precipitation before midnight, so will leave
inherited evening pops in.

The radar mosaic shows only showers approaching our west and
southwest. So will leave wx grids thunder-free. Overall, few grid
edits necessary.


Previous discussion:
synoptic setup... A giant area of hot high pressure exists over
the Four Corners and reads out over the Nevada and Wyoming. A
large trough runs from Washington and northern Idaho north into
British Columbia. Between these two large airmasses flow has
become zonal to southwest and is increasingly tightening from
Oregon to Montana.

This afternoon through tonight... an upper level boundary is
anticipated to form along he GGW/BYZ CWA border. The density
discontinuity and associated jet will then sharpen where dry
desert southwest air to the south bumps up against a slightly
moistened pacific airmasses to the north. Just enough instability
may form along this line to generate some isolated showers across
southern zones. NAM and GEM are both still hinting at this while
the GFS and (now the EC) seem to be ignoring it. QPF totals will
be minimal as the surface layer may evaporate a large portion of
any rain that forms and falls. These showers will precede the
synoptic trough to the west latching onto the lee surface mountain
trough and dragging it along with more showers and thunderstorms
Monday morning when the better chances for increased QPF arrive.

Monday through Tuesday... trough arrives Monday and centered
itself over northeast Montana monday night. Cooler temperatures
will move in with it with highs in the 50s and 60s. This will be a
very off and on rain group of periods but only a couple tenths to
three quarters of an inch is anticipated. Majority of the rain
should fall Tuesday morning when a low wraps up with a trowal on
the back side of its. GAH


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

Again only minor updates to the going extended forecast. After the
upper low exits the region Tuesday night, an upper ridge begins
building into the northern Rockies. Warm and dry conditions are
expected through the end of the week. Ebert

Previous long term discussion...As upper low moves to the east
Tuesday Night, northwest flow aloft will bring drier air into
Eastern Montana and end the rain.

Upper ridge will build into Montana on Wednesday with dry weather
and warmer temperatures. A shortwave trough moves across
Saskatchewan on Thursday and brings a dry warm front across the
forecast area.

The upper ridge rebounds on Friday and dominates the weather over
most of the western US through the weekend with dry weather and
warm temperatures. Forrester



SYNOPSIS: Look for increasing mid level clouds tonight as an upper
trough moves into Western Montana. Showers and lowering clouds
are expected Monday morning through Tuesday.

WIND: Light and variable under 15 knots.





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