High Wind in Montana, February 1, 2020

Area Forecast Discussion
National Weather Service Glasgow MT
922 PM MST Fri Jan 31 2020

.DISCUSSION...

EVENING UPDATE:
Changes to the forecast focused on the rain/snow showers moving
across the western side of the CWA on radar. These appear to be
about 20 to 30 miles west of the position they anticipated at
during this hour. The next 4 hours worth of PoPs were also updated
to account for this timing delay. Sky fields were also updated
with the latest data. Wind speeds look to be on track if only a
little over forecast, so have left them alone. As of 915 PM Most
of the echos are beginning to fall apart. This is a good thing
too, as temperature profiles suggested freezing rain if they had
stayed together. GAH

AFTERNOON UPDATE:
Main forecast concerns continue for the upcoming High Wind event
and Fire Weather event for tomorrow, Saturday, Feb 1. See the fire
weather discussion for more information.

A mid level jet streak of at least 90 knots is expected to spread
through the state of Montana, east of the continental divide from
early Saturday morning through late Saturday night. An upper level
ridge of high pressure and much warmer than normal temperatures
remains in control over the region - especially the southwestern
parts. Even though the associated lapse rates are weaker than
would usually support high winds reaching the surface, there seems
to be enough model data consensus to support it for the higher
elevation areas, like our southwestern Phillips County.

It should be noted that any precipitation or shower activity in
the area during this time would easily pull those stronger winds
down to the surface. Currently, all shower activity is expected to
end just after midnight tonight. But, next shifts should keep a
close eye out for surprise or unexpected showers during the day on
Saturday, which would require us to consider expanding the High
Wind Warning beyond its current scope.

By early Sunday morning, widespread winds will diminish as the jet
streak exits the area.

Sunday through Monday, the flow regime becomes more zonal as a
cold Canadian air mass begins to shunt the warm air toward the
south. A trough of low pressure and much colder air will move
through the area through the beginning of next work week. The
associated precipitation will be confined to southern Montana, and
will likely only clip our souther Petroleum County with around 1
inch of new snow.

Wednesday and beyond, NW flow aloft will return to the region as
temperatures slowly moderate with warm high pressure trying to
push in from the west. Expect multiple periods of scattered rain
and snow showers in this extended period.

---BMickelson

&&

.AVIATION...

FLIGHT CAT: VFR

DISCUSSION: Above normal temperatures and partly cloudy skies
expected through the cycle.

LLWS: Low level wind shear will start at KGGW 06z and spread to
the other terminals early in the morning. About 2000 ft off the
surface, expect winds of 40 to 50 kts with gusts in excess of 60
kts. This will last until about 09Z Sunday. Watch out for wind
shear and crosswinds. North-South oriented runways will be
impacted the most.

WIND: Light and variable tonight. West and increasing to 35 kts
sustained with gusts to 40 kts on Saturday. Decreasing to 10 to
20 kts mid-Sunday Morning.

---BMickelson/GAH

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 8 AM to 11 PM MST Saturday for MTZ135>137.

High Wind Warning until 8 PM MST Saturday for Southwest
Phillips.

&&

weather.gov/glasgow