Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 220948

Area Forecast Discussion
National Weather Service Missoula MT
348 AM MDT Thu Mar 22 2018

.DISCUSSION...Waves of warm frontal precipitation are expected in
north-central Idaho and western Montana today. Rain showers are
likely to become widespread with the main warm front during the
late morning and especially afternoon. A gusty cold front remains
on track to move through north-central Idaho and western Montana
during this evening. The timing of the cold front looks to be
around 1-2 hours slower, which results in an arrival time to
north-central Idaho around 6pm-8pm PDT, and near Continental
Divide between 12am-2am MDT. Bursts of heavy rain, snow and
graupel, isolated thunderstorms, and gusty westerly winds around
40 mph can still be expected with the frontal passage. Snow levels
are expected to drop to at least 3,000 feet behind the cold front
with accumulations on mountain passes and mainly grassy surfaces
of lower elevations. Rain and snow showers linger into Friday with
cooler temperatures.

Saturday morning is the next time period we will need to watch
closely as another, even colder, cold front passage is possible.
This second cold front has the potential to bring snow
accumulations for both mountain passes and lower elevations.

Conditions will slowly improve Sunday into Monday as the main
precipitation exits the area. Temperatures will remain a bit below
normal in the wake of the colder air mass, and Monday morning
temperatures could reach down to the teens and 20s for many valley
locations. Weak ridging will extend into the area Monday through
Wednesday, which will allow mostly dry conditions and a gradual
warming trend for the daytime high temperatures.


.AVIATION...Warm frontal showers will increase during today and
will become more widespread after 22/1800Z. East to southeast
winds are still expected to increase due to a pre-cold front
environment but the strongest winds are expected with the cold
front. This cold front will bring graupel, rain and snow showers,
and gusty winds near 40 knots to central Idaho between 23/0100Z
and 23/0400Z and into western Montana by 23/0500z and 23/0900Z.
There may be enough instability with the cold front for an
isolated thunderstorm, mainly over central Idaho between 22/2300Z
and 22/0500Z. Snow levels are expected to drop to at least 3,000
feet this evening and even a bit lower overnight.



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