Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 282019
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
219 PM MDT Sun May 28 2017

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

The upper flow pattern consists of a trough that runs through
central Canada and into the Upper Mississippi Valley, and a ridge
that runs northward through the Pacific Northwest and British
Columbia. These two airmasses establish a north-northwest flow
aloft for eastern Montana.

Cool air advection and a strong pressure gradient between low
pressure to the east and high pressure to the west created strong
northwest winds today. Efficient mixing allowed higher gusts from
aloft. These dry winds prompted both a widespread Red Flag
Warning, and a Lake Wind Advisory for Fort Peck Lake. Winds will
decouple this evening, allowing the warning and advisory then to
expire by sunset.

Tonight and Monday the flow aloft will remain strong, but the
pressure gradient will be more relaxed - resulting in lighter
winds compared to Sunday. Models place eastern Montana in a dry
slot between the showers of the trough to our east, and showers
over the stationary frontal boundary to our west. There may be an
increase in cloud cover over the east as a backdoor short-wave
disturbance slides south through North Dakota and clips our
eastern zones. The cooler air behind the cold front will result in
cooler temperatures tonight and Tuesday, very close to normal for
the end of May. Did go slightly below blended guidance for RH,
since conditions have gone drier than suggested by the models.

Templer

.LONG TERM...Tue night through Sun...
No significant updates. Upper ridge slides east through midweek
with warm and dry weather for eastern Montana. As the ridge breaks
down late in the week, the potential for showers and thunderstorms
will increase. Models remain in reasonable agreement with
shortwave for Friday with differences increasing through the
weekend. Ebert

Previous long term discussion: NW flow aloft will linger into
Tuesday as upper low moves to the east and upper ridge builds into
the forecast area from the west. Surface high pressure over
Eastern Montana will allow for dry weather and light winds over
the forecast area.

Upper ridge continues to slide east across Montana Wednesday and
Thursday which will bring warmer temperatures and mainly dry
weather. Models want to bring a shortwave trough/weak frontal
system across Eastern Montana Thursday Night which could bring a
slight chance of showers and thunderstorms.

Models differ Friday and beyond. ECMWF brings a shortwave ridge
Friday and Saturday with mainly dry weather while GFS maintains a
quasi- stationary front on NW flow aloft with chances for showers
and thunderstorms. Will maintain a slight chance of showers and
thunderstorms for now.

Next Sunday, GFS has a ridge while ECMWF bring a shortwave trough
but keeps precip mainly to the north. Will keep forecast mainly
dry for now.

Forrester


&&

.AVIATION...

VFR.

A cold front dropping into northern Montana has initiated some
convection, but mainly to the south of Northeast Montana. Isolated
showers and thunderstorms did pop up during early afternoon near
the Yellowstone River, but have since drifted south.

Wind: Northeast Montana sits between a low pressure trough to the
east and a high pressure ridge to the west. This has created a
strong north to northwest flow aloft that mixed down to the
surface today. Surface winds will slacken tonight after sunset to
around 10kt. Surface winds on Monday will increase again, to
around 15kt, but not be as strong. as the pressure differences
weaken. Monday should be dry.

Templer

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for
MTZ120-122-134-136-137.

Lake Wind Advisory until 9 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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