Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 261016

Area Forecast Discussion
National Weather Service Missoula MT
416 AM MDT Fri Apr 26 2019

...Significant snow accumulations from a late season winter storm
expected Saturday evening through Sunday morning...

.DISCUSSION...A change to an active weather pattern over the
Northern Rockies will begin today. First, a fairly strong cold
front will usher in widespread showers over western Montana and
north-central Idaho during the day. Also gusty westerly winds
approaching 40 mph may be possible along and behind the front
later this afternoon and evening. The higher wind gusts are
expected to be across southwest Montana and Lemhi County in Idaho.
Most locations will have a chance for rain, though northwest
Montana will see the bulk of the precipitation, where 0.25" to
0.75" of rain is possible. Snow levels may lower just enough to
where Marias Pass could see light snow this evening.

The more significant weather system is expected to begin to impact
the region Saturday as a low pressure system drops south out of
Canada. The onset of the precipitation could bring light snow to
areas of northwest Montana above 4500 feet. However the high sun
angle this time of the year should limit the length of time any
snow could accumulate on the roads. The higher impacts are
expected later in the afternoon and evening Saturday, as a cold
front pushes through and lowers the snow levels. Glacier National
Park, and Highway 2 from Essex to Marias Pass will see the bulk of
the impacts due to snow Saturday evening and Sunday Morning.
anywhere from 4 to 8 inches of snow is possible above 3500 feet,
with the higher elevations of Glacier National park and Marias
Pass potentially seeing slightly higher amounts. Gusty northerly
winds up to 40 mph, or higher is also possible, further reducing
visibility over Marias Pass. Due to the expected impacts, and
weekend recreational activities, a Winter Storm Watch has been
issued for the areas above, starting late afternoon Saturday
through Sunday morning.

Temperatures come Monday morning will be quite cold across the
Northern Rockies within the drying atmosphere. Readings in the 20s
are expected which could present an inopportune late Spring
frost/freeze that could damage plants. In fact, some places could
even be presented with anomalously cold mornings on Tuesday and
Wednesday as well. Though some light valley rain/mountain snow showers
are also expected to continue early this next week as main upper
level storm system ever so slowly migrates to the east. They will
undoubtedly be a secondary concern this late in spring. A drying
and warming trend is expected to take hold during the second half
of the week. By next weekend we may very well have temperatures
right back near normal under slowly building high pressure.


.AVIATION...Clouds will be steadily moving into the Northern
Rockies over the next 24 hours as an approaching cold front will
impact the region Friday afternoon. The lowest cloud decks and
precipitation appears to move into northwest Montana Friday
morning then push through the remainder of the region throughout
the day. Rain will become possible at KGPI and KMSO, though KGPI
and neighboring air fields across NW Montana should probably
prepare for more widespread precipitation. Meanwhile KSMN and KBTM
will periodically flirt with wind gusts surpassing 40 mph later
this afternoon.


MT...Winter Storm Watch from Saturday afternoon through Sunday
     morning West Glacier Region.


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