293
FXUS65 KMSO 241906
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
106 PM MDT Mon Jun 24 2024

.DISCUSSION...Westerly flow aloft with the upper level jet
positioned just north of the border and some low level instability
will keep the forecast for this afternoon dry and windy for much
of the Northern Rockies. Westerly flow gives way to a ridge of
high pressure on Tuesday. While dry (low relative humidity)
conditions continue, winds will relax under the ridge. Daytime
high temperatures on Tuesday through Wednesday will rebound back
up from today, reaching the upper 80s to low 90s in the valleys of
western Montana, and the mid to upper 90s in western Idaho and
Clearwater Counties.

As the ridge moves east on Wednesday, a trough of low pressure
will approach the Pacific Northwest. Flow aloft will transition
to the southwest, bringing Pacific moisture with it. There will be
enough instability, wind shear, and moisture available on
Wednesday afternoon to fuel thunderstorms across Lemhi County and
southwest Montana (20 to 30 percent chance), as well as Idaho
County and northwest Montana (about 15 percent chance). Model
forecast soundings indicate potential for strong winds (30 to 40
mph gusts) associated with any thunderstorms that are able to
form. A cold front associated with this system will pass on
Wednesday afternoon or evening, resulting in temperatures dropping
to slightly below normal for the balance of the work week. The
low will arrive in the Northern Rockies by Thursday afternoon.
Expect widespread rain and enhanced westerly winds. The northerly
track of the low and the southerly position of the upper level jet
will favor northwest Montana and Clearwater County for
precipitation and southwest Montana and Lemhi County for wind.
Salmon will have about a 60% chance of exceeding 30 mph gusts, and
Butte will have about a 30% chance. The wettest area will be
along the Canadian border and the Continental Divide north of
about Highway 200, where there will be about a 40 to 50 percent
chance of exceeding 0.25 inches by Friday morning.

Friday will be a transition, as high pressure begins to build back
for Saturday morning. Model consensus is favoring high pressure
for Saturday. Agreement breaks down on Sunday, with about 40% of
ensemble solutions showing more unsettled weather.


&&

.AVIATION...A ridge building over the region today and tomorrow
will keep aviation impacts to a minimum with VFR conditions today
and tomorrow. Expect gusty west winds of 20 to 25 knots at KSMN
and KBTM through this evening.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$