Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 180923

Area Forecast Discussion
National Weather Service GLASGOW MT
223 AM MST Wed Jan 18 2017

.SHORT TERM...for northeast through Fri...

Upper ridge currently over Montana will move to the east today.
This will allow warm and dry weather to continue. Chinook pattern
remains in place today with some high clouds. Although shallow
inversion remains, warm air advection has allow temperatures to
stay warmer overnight than previous nights which will allow for
warmer temperatures today.

Upper flow begins to turn southwest this afternoon as upper trough
begins to dig in towards the California coast. Winds and warm air
advection aloft ease but with the inversion weakening warm
conditions will continue. Moisture generally remains west of the
divide until Thursday Night. So forecast will remain dry through

The trough moves inland Thursday and Thursday Night turn the flow
aloft more southerly. A cold front moves through the area
Thursday Night with limited moisture. A shortwave on southerly
flow aloft could bring a chance of rain or snow to the western
half of the forecast area on Friday. Forrester

.LONG TERM...Fri night through Wed...

Synoptic Setup: long range begins with a large trough over the
western half of the United States and Canada. A Pacific airmass
in habits this airmass from the Four Corners to central Alberta.
At that point arctic air takes over and runs north into Alaska. To
the west a large trough sets over the northeast Pacific with a
slightly cooler airmass than whats over northeast Montana.

Friday night onward: as the heat embedded in the previous ridge
exits to the east pacific air across the region will continue to
modify colder and colder over the snow pack each nigh period
through the long range. There are no major cold fronts within the
long range but there are more subtle features which bring ever so
slight cooler temperatures from one period to the next and long
with slight chance for very limited new snow fall in nearly every

The biggest frontal change and drop in temperatures appears to
happen when the second cooler trough from the pacific moves
across the area Sunday and get a slight modified arctic air
infusion. However models hold on just beyond the long range
around Thursday bringing in a warm pacific ridge into the region
again. So, no arctic plunge or big snowfall event is anticipated
at this time. GAH




SYNOPSIS: A weak chinook will bring mid to high clouds across the
region as well as a low level inversion through the early to mid
morning hours.

LLWS: Surface inversion could lead to Low Level Wind Shear before
it mixies out around 12-15Z. But at this time chances are low as
speeds are not quite fast enough above the inversion according to
VAD profiler.

WIND: Southwest at around 5-10kt, except at KGGW winds may be
more southeasterly at times.





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