Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 212036 CCA

Area Forecast Discussion
National Weather Service Missoula MT
233 PM MDT Wed Mar 21 2018

Satellite imagery this afternoon reveals a large-scale trough
digging southwards into the northeastern Pacific, while clouds
and showers are tracking along the southwest flow over Pacific
Northwest and Northern Rockies. Sunny breaks in the clouds have
been hard to come by, which has resulted in a few places staying
a little cooler than forecast today. Webcam images also show that
some of the clouds have been able to produce very light shower
activity in the mountains, but little to none in the valleys.

There will be an increasing chance for showers by Thursday area-
wide as a cold front begins to move out of Washington and Oregon.
Ahead of this front there will be the potential for some locations
in western Montana to warm into the middle 50s, but that will be
dependent upon showers and clouds. The cold front will move across
the Camas Prairie, Idaho between 5 and 7 pm PDT and then into
western Montana between 11 pm and 1 am MDT Friday. Expect bursts of
heavy rain, snow and graupel showers, and gusty westerly winds near
40 mph with the frontal passage, especially over central Idaho where
there could also be an isolated chance for an embedded thunderstorm.
Rain will change to snow showers above 3,000 feet over central Idaho
Thursday evening, but it may only accumulate on grassy surfaces.
Mountain passes along the Idaho/Montana border and Marias Pass will
experience a dusting or minor slush accumulation of snow Thursday

Conditions remain showery Friday and Saturday under an unstable,
moist atmosphere. Mountain and valley snow will impact most of
western Montana and north central Idaho, although snow
accumulations will be minor. By Sunday, the weather will start to
slowly improve, giving way to a potentially clear and cold night.
Monday`s low temperatures could dip into the single digit and
teens around southwest Montana and along the Continental Divide,
particularly if skies really do clear out.

Beyond Monday, the extended range forecast models show increasing
agreement on much less active weather with more sun and mild
temperatures mid-week into late next week.


.AVIATION...Expect fluctuations with the cloud ceilings due to
shower activity through Thursday. Showers activity will become
more widespread after 22/1800Z, while east to southeast winds
will increase due to a pre-cold front environment. A cold front
will bring graupel, rain and snow showers, and gusty winds near 40
knots to central Idaho between 23/0000Z and 23/0300Z and into
western Montana by 23/0500z and 23/0900Z. There is some
instability that the cold front may tap into to trigger an
isolated thunderstorm, mainly over central Idaho between 22/2300Z
and 22/0500Z.



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