Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 282147

Area Forecast Discussion
National Weather Service Missoula MT
247 PM MST WED JAN 28 2015

.DISCUSSION...The Northern Rockies is under the influence of a
northwest flow with some scattered cumulus clouds thanks to some
lingering moisture and instability. The ridge of high pressure
will quickly redevelop overnight through early Friday. This will
bring strengthening inversions, cold pools, and a return of
valley fog. The ridge begins to break down late Friday as a
weather disturbance enters the region.

A weak arctic front will give a glancing blow to locations along
the Continental Divide Saturday afternoon and evening. Little
moisture will be associated with the front, however some light
snow accumulations are possible in the mountains, more
particularly over Marias Pass and the Glacier National Park
region. Just enough cool air will make to the valleys of western
Montana for a return of more seasonable temperatures.

A more moist system is anticipated to impact the Northern Rockies
Sunday and Sunday night. There is still some uncertainty on the
timing, as the GFS is 6 to 8 hours faster than ECMWF, as well as
wetter. Another forecast problem will be precipitation type for
the valleys of western Montana and central Idaho. Cold air is
expected to be in place across northwestern Montana which would
lead to all snow; however, for locations along and south of I-90,
as well as the valleys in central Idaho, a mix of rain and snow
is more likely. Snow levels will begin to rise late Sunday, which
should turn all valleys to rain, with the mountains continuing to
see light snow.

Occasional weather disturbances will move through the continued
northwest flow late Monday through early Wednesday. Late Wednesday
and beyond, climatology will be used as model solutions diverge
from one another significantly.


Overnight fog leading to low visibilities and low cloud decks will
be the biggest concern for area terminals. Clear skies will allow
for quick cooling of the lower atmosphere this evening. Model
soundings show fog and/or log cloud decks forming at KGPI, KMSO,
and KSMN by early morning. Additionally, recent precipitation will
further enhance fog chances near KSMN. This afternoon`s light
winds reduce chances for fog at KBTM. No precipitation is
expected across the area.



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