Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 281515 AAA
AFDGGW

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
915 AM MDT Sun May 28 2017

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

Visual GOES this morning reveals northwest flow aloft with
few-to-scattered mid-level clouds flowing over Northeast Montana.
There is some convection off to the west that is not drifting in
our direction. A look upwind shows fewer clouds for now, which
goes along with the stable conditions, and drier & sunnier
prediction for today.

The main story is the winds. Due to the low RHs expected with the
strong, dry northwest winds expected, a red flag warning has been
issued. This elevated concern for critical fire wx conditions has
also been highlighted by SPC. Conditions over Fort Peck Lake also
justify an NPW. Update was to include the latest guidance and
observations into the forecast.

Templer


Previous discussion -
Synoptic Setup: A trough runs from the Northwest territories down
through the Canadian Prairies and into the eastern Dakotas and
Upper Mississippi Valley. A ridge runs upward through the
Intermountain west into the Pacific Northwest and British
Columbia. These two airmasses establish a northern to northwest
flow aloft for eastern Montana.

Today: Cold air will drop south in the flow to the east and
intensify the pressure gradient across the region. This will
lead to an increase in winds speeds with nearly 20 to 25 kts
sustained and gusting to nearly 35 kts by the afternoon. In
addition, model data is pushing for min RH around 20 to 25 percent
through the afternoon. However the last 2 days have been almost 5
percent drier than predicted, and this trend is not expected to
change. So, have shrink-stretched the lowest points down further
to below 20 percent. This has lead to both Red Flag and Lake Wind
Advisory criteria for the afternoon. Winds were also switched from
the typical Super/ConsShort to ConsMOS in order to capture the
higher winds in a well mixed atmosphere.

Tonight through Monday: as the atmosphere decouples winds will die
off rapidly with sunset with a light northern wind by midnight.
While flow aloft will be strong high pressure forming up north
should cut down some of the gradient mixing down Tuesday with
relatively lighter winds compared Sunday. GAH


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

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...

FLIGHT CAT: VFR.

SYNOPSIS: Low pressure exiting to the east and high pressure
building to the west will lead to strong winds today which may
generate crosswind concerns for small aircraft.

WIND: Northwest at 5 to 15 kts early this morning, increasing to
20 to 25 kts sustained, gusting 35 kts in the afternoon, veering
to the north and calming to less than 10 kts near midnight.

GAH/st


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 1 PM this afternoon to 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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