Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 300139

Area Forecast Discussion
National Weather Service Glasgow MT
739 PM MDT Mon May 29 2017

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

Nice clear evening, wind is becoming light and variable for the
overnight hours. No adjustments made this forecast period. Proton

Previous Discussion:

Upper ridge extending from the Canadian Rockies into the Great
Basin will slowly move east over the next few days. Canadian high
pressure dropping across the northern plains will bring a dry and
more stable airmass into the region tonight and Tuesday.

With clear skies and light winds, along with dry airmass, could
see temperatures drop to near freezing in some locations tonight,
particularly the northeast corner of the state. Sunny weather
expected on Tuesday with winds beginning to turn toward the east
as the high moves into the Dakotas. Ebert

.LONG TERM...Wed night through Mon...

An amplified ridge, extending north through the Northwest
Territories into the Arctic Ocean, will control conditions for the
next several days. Hot desert air from the Southwest creeps north
towards Montana during this period. The increased heights and
sunshine will drive temperatures higher Wednesday and Thursday,
10F to 15F degrees above normal.

Conditions change Thursday evening when a broad trough stretching
out into the Gulf of Alaska sends a wave and a cold front into
the Pacific Northwest. This trough picks up ocean moisture,
sending it into the Northern Rockies and Northern High Plains.
Timing-wise, the cold front will be positioned at the western
doorstep of our CWA at 00Z Friday. Both the EC and the GFS suggest
precipitation to begin Thursday evening. Convection is expected,
but CAPE and LI will be weak to moderate, with efficient mixing.
The moisture feed will keep precipitation going all Thursday night
and Friday. Models show increasing amounts of QPF for Friday as
the moisture feed is almost due north into our region. Timing
between GFS and the EC drift apart around Friday. GFS is slower,
keeping the precipitation going longer before it drifts into North
Dakota. The EC exits Friday evening, whereas the GFS lingers
until Saturday evening, based on the strength of a short-wave
kicking through southern Saskatchewan. In any case, Sunday looks

The next wave to affect the region once again has timing and
location issues. But it does suggest more precipitation beginning
late Monday. Due to uncertainty increasing with time, updated
grids with blended guidance.

Previous discussion -
Upper ridge will move east across Montana Wednesday and Thursday
which will bring warmer temperatures and mainly dry weather.

Shortwave trough and weak frontal system is expected across
Eastern Montana Thursday Night and Friday which could bring a
chance of showers and thunderstorms.

GFS is slower than the ECMWF in moving the trough to the east
Friday Night. Will linger a chance of showers and thunderstorms
into Friday Night mainly in the east. Saturday looks mainly dry
with an upper ridge.

Sunday looks dry although models differ on flow aloft. GFS has a
ridge while ECMWF has SW flow aloft. Both models are pointing
towards an upper trough early next week with a good chance of



VFR. High pressure will keep mostly clear skies over the region
overnight and Tuesday.




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