Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 112144

Area Forecast Discussion
National Weather Service Missoula MT
244 PM MST Mon Dec 11 2017

.DISCUSSION...The forecast of low clouds (stratus), freezing fog
(producing rime ice or hoarfrost), and below normal temperatures
will remain common this week throughout many valleys across
Central Idaho and Western Montana. Some snow flurries or ice
crystal deposition may occasionally precipitate from the stratus,
but only amount to at most a light dusting of white. An Alberta
Clipper will skip across Eastern Montana and North Dakota, leaving
some mid level moisture strewn across the Idaho Panhandle and
Western Montana Tuesday night into Wednesday. This could help
improve conditions where freezing fog exists, lifting the fog into
a stratus deck. The additional mid level/mountain top moisture
could produce more widespread light snow flurries. But still only
a skiff of snow seems most likely.

High pressure rebuilds over the area on Thursday with inversions
strengthening yet again. However models still indicate a pattern
change is on the way starting sometime Friday when a cold front
quickly sweeps through the Northern Rockies. There could be some
potential for freezing drizzle at the onset of precipitation. But
light snow seems most likely given the lack of warming aloft ahead
of the cold front. But we`ll keep evaluating this part of the
forecast as model confidence builds in the coming days. The rest
of the weekend continuing into next week still appears to be
fairly active as a series of weak weather features are forecast to
pass through the flow. But models are still not very consistent
with their placement of the upper level jet stream and larger
scale upper level pattern over the Pacific Ocean. And thus, while
a pattern change is certainly welcome, no big storm systems seem
likely at this time through the middle of next week.


.AVIATION...Strong valley inversions will remain the next several
days with abundant stratus and areas of freezing fog. KGPI, KMSO
and KSMN will experience low ceilings from stratus with the lowest
ceilings during the morning hours. Freezing fog is possible
mainly at KMSO during the overnight and morning periods.
Occasional snow flurries will also be possible, especially around
KMSO with only trace amounts expected.



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