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000
FXUS65 KMSO 131012
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
412 AM MDT Sat Apr 13 2024

.DISCUSSION...Another mild spring day is expected today with
scattered showers and perhaps a weak thunderstorm concentrated
more towards the southern Bitterroot Valley and Lemhi County into
southwest Montana. On Sunday, models depict an inverted low
pressure surface trough from Grangeville and points north and
east towards west-central Montana. This boundary of converging air
will be the general focus for showers and thunderstorms in the
afternoon and evening hours. Thanks to the airmass being fairly
dry, gusty outflow winds are possible. This may have to be watched
closely as sudden southerly winds could catch boaters off-guard
on Flathead Lake. Around 50 percent of the high resolution models
depict shower-related wind gusts over 30 mph late Sunday
afternoon in the Mission Valley extending up to Polson Bay.

The ensembles have backed off a bit on an elongated period of
wintry weather in the mountains next Tuesday through Wednesday.
The percentile ranges for snowfall have dropped with the 50th
percentile only showing a couple of inches of snow for the Divide
on Wednesday. Our ensemble cluster tool that helps to sort out
"similar" projections shows around 55% of the ensemble members are
depicting the upper level low having a quicker trajectory further
east into the Northern Plains. Now with that said, there could be
enough moisture with a couple of backdoor cold front pushes from
the east to support periods of snow by Wednesday, enough to coat
the roads with some slush above 2500 feet in northwest Montana.
Another impact that will need to be watched will be possible chop
on area lakes with the north to easterly winds. The deterministic
models runs show quite the easterly gradient lingering into late
week next week.


&&

.AVIATION...The focus for scattered showers and isolated thunder
will mainly be over the southern Clearwater and Bitterroot
mountains including the Hamilton, Salmon and Butte terminals late
this afternoon into the evening hours (13/2100z to 14/0600z). For
the valleys, gusty erratic winds, and brief mountain obscuration
are possible. Gusty winds to 25 knots are expected with the
stronger cells. More widespread showers and gusty winds are
anticipated on Sunday from north-central Idaho into west-central
Montana.


&&

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

$$