Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 292020
Area Forecast Discussion
National Weather Service GLASGOW MT
220 PM MDT SUN MAY 29 2016
.SHORT TERM...for northeast Montana...tonight through Tue...
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
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
FLIGHT CATEGORY: VFR should last through the current TAF cycle
with MVFR not anticipated until after the cycle Monday night into
SYNOPSIS: High pressure will bring mostly clear skies this
afternoon with a few high clouds. Look for increasing mid level
clouds tonight as an upper trough moves into Western Montana.
Showers and low clouds are expected Monday morning through Tuesday.
WIND: West to southwest around 10 to 15 knots this afternoon,
becoming light and variable overnight.