753
FXUS65 KMSO 082027
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
227 PM MDT Sat Jun 8 2024

.DISCUSSION...Northeast winds will increase in strength across
northwest Montana this evening, first in the Glacier region as
early as 6 pm, then points west. There continues to be an 80
percent chance for sustained winds of 20 mph or greater in the
gaps and lakes of the region. Because of this, we have issued wind
advisories for the Glacier Region, Swan Lake and the Flathead
Valley and Flathead lake starting mid-evening through early Sunday
morning. Those who will be recreating on these lakes should be
aware that these northeast winds can be quite hazardous for small
craft. On April 14 of 2022, kayakers on Swan lake were overcome by
the sudden onset of strong northeast winds. The winds are
expected to decrease after midnight. With up to a 7 millibar
northeast pressure gradient Sunday morning between dawn and 10 am
MDT, there may be some gap locations that experience an uptick in
gusty easterly winds over 20 mph before subsiding.

Showers and thunderstorms are still on track on Sunday afternoon
and evening. The highest probability for storms remain south of
Interstate-90 to Lemhi County and southwest Montana. Initially the
showers will contain gusty winds, but will be followed by heavy
rain. Gusts to 35 mph will be common, but around 20 to 30 percent
of the ensemble members depict greater than 35 mph across southern
Idaho County, Lemhi County and Silver Bow including the Butte
area. Only one member depicted a gust to 53 mph across southern
Lemhi County. There is a 50 percent chance that these
thunderstorms could produce rainfall rates of greater than 0.30 of
an inch. There is a 15 percent chance that the one hour rate
could exceed 0.50 of an inch south of Salmon and also near Butte.

An upper wave will keep showers and thunderstorms in the forecast
on Monday, with breezy 15 to 25 mph afternoon westerly winds. The
flow becomes more zonal on Tuesday and westerly winds will be a
little stronger. There is a 50 percent chance that wind gusts
could exceed 30 mph across western Montana valleys on Tuesday
afternoon. Residual moisture could trigger a few mountain showers
across northwest Montana. By Wednesday, a drier air mass will move
into the region, but it will remain breezy. This drier air will
allow for temperatures to fall into the 40s by Thursday morning.
There is a 60 percent chance that temperatures could fall into the
30s including Yaak, Polebridge, Seeley Lake, Dixie, and higher
valleys of southwest Montana. High temperatures through the end of
the week will continue to be 8 to 10 degrees above average for
this time of year.

For the long range...most of the ensemble clusters depict
southwest flow with possible thunderstorm activity from Lemhi
County into southwest Montana on Friday. Saturday seems to be the
transition day as 85 percent of the clusters depict a large trough
to our west with a possible cold front passage. Thereafter, there
doesnt seem to be any consistency in how this trough evolves
over us: 42 percent of the ensemble clusters depict a warmer
pattern, 32 percent depict an open wave, while the other 26
percent show a deepening trough which would bring cooler
temperatures and a wetter solution.

This is the time of year that we get multiple inquiries on when we
will get an extended dry period so that farmers can cut their hay.
For many locations, little to no precipitation is expected after
Monday through Saturday, but there is a 30 to 40 percent
probability that greater than 0.10 of rain is possible next Sunday
and Monday (June 16 and 17).


&&

.AVIATION...VFR conditions are expected all day. A backdoor cold
front is expected to push westward starting in the Glacier region
by 09/0100Z (7 pm MDT), then into western Montana by 09/1200Z (6
am MDT) Sunday morning. Easterly winds between 20 and 45 knots are
expected at ridgetop along and west of the Divide during this
timeframe. Low-level channeled terrain and downslope winds up to
35 knots are expected, especially along the western foothills of
the Whitefish Range, Livingston/Lewis Ranges, Swan Range and
Mission Range. With a tight easterly gradient Sunday morning,
there could be a brief period where east winds to 20 knots could
mix down to the surface between 6 am and 10 am MDT Sunday.
Afternoon thunderstorms are expected to develop from southern
Idaho County to points east into southwest Montana and Lemhi
County. Heavy rain, gusty winds to 35 knots, graupel, and
lightning are the main threats.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory from 6 PM this evening to 5 AM MDT Sunday for West
     Glacier Region.

     Wind Advisory from 8 PM this evening to 5 AM MDT Sunday for
     Flathead/Mission Valleys.

ID...None.
&&

$$