Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
251 AM MDT Sat Mar 20 2021

.DISCUSSION...Model guidance agrees that the low pressure system
to the west will weaken and open into a trough today. Cloud cover
and showers will increase in coverage today as the trough
approaches. Cooler air in association with today's trough will
also cause breezy west and northwest winds for this afternoon.
Cold air aloft will again create enough instability that a
lightning strike or two is possible. Snow levels will be lower
today than we've had recently, but impacts from daytime snow look
minimal and mainly at mountain pass levels. During this evening,
the trough is expected to pass to the east and convective allowing
models show showers lingering, especially over Lookout Pass and
Lolo Pass, so impacts from snow showers cannot be ruled out after
sunset.

Sunday's forecast holds cloud cover and showers chances. There
may be enough drying during the late morning and early afternoon
on Sunday for showers to mainly be in the terrain, but moisture is
forecast to arrive during the late afternoon and evening,
bringing increasing shower coverage.

Another trough is progged to pass through north-central Idaho and
western Montana on Monday. Mountain and mountain pass snow
accumulations have a high probability of occurrence, and many
inches of snow are possible on mountain passes along the ID/MT
border.

A drying trend from Tuesday night through Wednesday morning
remains. There are still timing differences for the trough, that
will impact the region during the second half of the week, but
cool and showery conditions can be planned for on Thursday and
Friday.

&&

.AVIATION...Cloud cover is increasing from the south, which is
forecast to lower through the morning. The low pressure system to
the west is forecast to open into a trough and pass through the
Northern Rockies today. Radar projections show increasing shower
coverage, that will obscure terrain. A tightening pressure
gradient is forecast to develop today as cooler air advects into
the region, so breezy westerly and northwesterly winds are
expected by this afternoon. Snow showers look to linger through
the evening, bringing light mountain snow accumulations,
especially along the ID/MT border.

&&

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

Special Weather Statement
National Weather Service Missoula MT
1022 AM MDT Sat Mar 20 2021

MTZ004-201745-
Lower Clark Fork Region MT-
1022 AM MDT Sat Mar 20 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN MINERAL AND WEST
CENTRAL SANDERS COUNTIES UNTIL 1145 AM MDT...

At 1021 AM MDT, Doppler radar was tracking an area of intense snow
showers along Interstate 90 between Lookout Pass and Haugan.

Visibility one-half mile or less will be possible, along with slick
surfaces and quickly changing conditions.

Locations impacted include...
Haugan, Saltese, Taft and East Portal.

LAT...LON 4745 11572 4746 11565 4748 11563 4749 11569
      4752 11571 4754 11571 4754 11568 4750 11532
      4734 11538 4738 11561 4738 11565 4742 11569
      4743 11576
TIME...MOT...LOC 1621Z 259DEG 18KT 4748 11548