Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 261917
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
117 PM MDT Tue Mar 26 2024

.DISCUSSION...Unstable northwest flow aloft will allow for a
further blossoming of showers this afternoon and evening. Mountain
passes will continue to see periods of snow cover on road
surfaces, especially after sunset tonight. Valleys will see a mix
of rain and snow, but accumulations will be limited to grassy
surfaces due to the warm surface temperatures.

A short lived ridge of high pressure will build over western
Montana and north central Idaho for Wednesday. This will largely
bring a break in precipitation, but cloud cover will remain over
the region ahead of the next weather system.

The flow aloft will transition to southwesterly Wednesday night
into Thursday ahead of a trough of low pressure digging along the
west coast. Snow levels will initially rise to around 5000 feet
Wednesday evening, before dropping once again Thursday morning
with the passing of a cold front. Forecast model guidance suggests
snow levels will remain above most valleys on Thursday, however
atmospheric profiles suggest otherwise, with slushy wet snow
possible down as low as 2500-3000 feet. Nevertheless, impacts due
to accumulating snow will primarily occur in the higher terrain
and over mountain passes. Snowfall probabilities have not changed
much, with Lookout, Lolo, and Lost Trail passes having a 60 to
80% likelihood of receiving at least 2 inches of snow by Thursday
afternoon. Lost Trail Pass stands a 50% chance of accumulating at
least 4 inches of snow, whereas other passes have only a 10 to
20% probability of this much.

Ensemble models continue to show the energy with the upper level low
pressure trough digging southeastward into this weekend. This
would place a weak trough of low pressure over the Northern
Rockies, resulting in typical early Spring conditions (ie/cool and
showery). There remains around 50 percent of ensemble models
depicting the development of a mid level circulation across
southwest Montana. If this were to develop, snow at all elevations
would be possible for the Butte/Blackfoot region into Lemhi
County.

&&

.AVIATION...Satellite and radar trends appear to confirm model
depictions of enhancing shower activity this afternoon which is
likely to continue until around sunset this evening (27/0200z).
Timing of these showers and their impacts to airfield conditions
remain challenging in the TAFs and thus a variety of TEMPO groups
were utilized at KGPI, KMSO, KBTM, and KHRF to provide additional
forecast information. Most showers will produce brief, limited
reductions in visibility and ceilings. However, the strongest
showers this afternoon will be capable of visibility down to
around 1SM and broken ceilings as low as 1500 feet for a brief
period of time. These showers will significantly decrease in
coverage and intensity shortly after sunset as instability wanes.
Some brief clearing will be possible late tonight and patchy fog
may form towards sunrise at KGPI and KMSO. Otherwise expect
gradually increasing levels of clouds throughout the day with a
return of showery precipitation late in the afternoon and
overnight.

&&

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

$$


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