Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 301333

Area Forecast Discussion
National Weather Service Missoula MT
633 AM MST MON NOV 30 2015

.DISCUSSION...The ridge of high pressure that has sat over the
Northern Rockies the past few days, will remain overhead for at
least another couple days. Strong valley inversions will persist
during this time. Valleys north of I-90 will have another day of
low stratus today and possibly tomorrow. The Missoula Valley and
the Seeley/Swan region will likely see low stratus develop early
this morning around sunrise. The occasional light snow
flurries/showers will be possible for those with the stratus deck
again today. Valleys along I-90 in southwest Montana will see
pockets of freezing fog this morning through early afternoon. This
could produce a few slick spots on local roadways, especially
bridges and overpasses, so drive carefully.

A weak shortwave trough will still try to move through the high
pressure Wednesday through Thursday, though recent models continue
to weaken and slow the progression of the wave. However, due to
the persistent cold pools, any light snow/freezing rain that does
fall could create problems for area roadways. Locations most
likely to be impacted will be northwestern Montana and central
Idaho valleys.

Toward the end of the week, models try to suggest further
"disruptions" of the ridge pattern by streaming several
disturbances into the region. This will support additional
modifications of valley cold pools, allowing valley max
temperatures to warm above freezing in most places and also
promote the return of better air quality. However, each day the models
continue to trend weaker and slower with these incoming
disturbances, leading to less confidence of widespread rain and
snow. The best chance for widespread precipitation with mountain
pass snow looks to be Friday at this time, but the drying ridge is
quick to reclaim its place Friday night into at least early


.AVIATION...Strong cold pools will persist over the region today,
and likely through tomorrow. As a result, the stratus deck over
northwestern Montana will stick around for at least another day.
Aviation sites, such as KGPI, will continue to see low ceilings
of around 1000 feet. Site KBTM will see vicinity fog, which could
briefly drift over the terminal at times this morning, greatly
reducing the visibility. KMSO will see a brief reduction of
visibility this morning around sunrise due to freezing fog, that
will lift into a low stratus deck late morning. All aviation sites
that see the low stratus deck will also have periods of
occasional light snow flurries/showers today.



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