Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 261008

Area Forecast Discussion
National Weather Service Missoula MT
408 AM MDT Wed Oct 26 2016

.DISCUSSION...A moist weather disturbance is currently producing
widespread rain across central Idaho and west-central Montana this
morning. This feature will continue to shift northward through the
day, with the focus of precipitation moving into the Idaho
panhandle and northwest Montana. The warm origins of this airmass
will keep snow levels above mountain passes, thus few impacts are

Despite cloud cover, abundant moisture at the surface has led to
the development of fog, which has become locally dense through the
Missoula valley and valleys of the Lower Clark Fork Region. Fog
will likely fluctuate through the morning hours and may be slow to
burn off due to stable atmospheric conditions.

Precipitation will remain across far northwest Montana tonight,
while the rest of western Montana and central Idaho will see some
drying. Forecast models are indicating some breaks in the clouds
by Thursday morning, generally along and south of Interstate 90.
Clear skies and abundant moisture at the surface will set up
conditions favorable for the formation of fog. Fog could become
dense, affecting travel Thursday morning.

A weak cold front will shift through the region on Thursday,
bringing widespread showers to all of western Montana and central
Idaho. Northwest Montana and north central Idaho will continue to
see the heaviest precipitation as the front passes.

Forecast models continue to struggle with the evolution of the
next weather disturbance for Friday/Friday night. The timing of
this system has slowed and seems to be trending on a more southern
track. Due to poor model consistency over the last few days with
this system, confidence is not overly high during this period.
However, current solutions show central Idaho and southwest
Montana receiving the most precipitation, while far northwest
Montana may actually see a bit of a dry period.

Saturday and Sunday: A transitory upper level ridge will move off
to the east and allow for the area to be once again under southwest
flow. Showers and morning fog will yet again be possible throughout
the weekend.

Later Sunday through Monday: A pattern change is expected across
the northeastern Pacific with a deepening trough over the Gulf of
Alaska. This will allow for the offshore closed upper level low
complex located just west of northern California to move onshore
and track east and north across the Northern Rockies bringing
another round of precipitation. It would seem fitting to end this
record wet month with more rain. As this system exits the area by
Monday night, residual showers will remain in the mountains while
passes and valleys could see more fog development into Tuesday

Tuesday onwards: Weather models differ on how they want to handle
the next trough that moves onshore, but there could be an
increasing chance for precipitation by later Tuesday or Tuesday
night. Both the GFS and ECMWF show some type of system on
Wednesday or on Thursday that could bring pass level snow. A
general westerly flow pattern with periodic disturbances will keep
our weather unsettled while temperatures will generally be near
normal for early November.


.AVIATION...A disturbance continues to move through central Idaho
and west-central Montana this morning, producing widespread
showers. Widespread obscurations of the terrain can be expected
across all of central Idaho and western Montana this morning due
to low ceilings and precipitation. The weather system will
gradually shift northward through the morning, moving the focus of
precipitation and terrain obscurations into northwest Montana by
late this morning. Despite cloud cover, areas of valley fog have
developed this morning due to abundant low level moisture. KMSO,
KGPI and KBTM may all be impacted due to fog through the morning
hours. Ceilings and visibility will likely fluctuate quite a bit, and
could be locally dense at times. Fog may be somewhat slow to lift
this morning due to stable atmospheric conditions.


.CLIMATE...October 2016 is well on its way to being one of the
wettest Octobers on record. This is especially true across
northwest Montana and north central Idaho, where many locations
have already broken the record, with 6 days remaining in the
month. The Hungry Horse climate station located at the dam broke
its record earlier this month and will likely get over 10 inches
for the month, which would be 3 inches above the previous record
of 7.34" set back in 1995. Kalispell and Olney, Montana and the
Dworshak, Idaho climate stations will likely receive enough rain
to break their all time records by the end of this week. Missoula
and Heron, Montana and Pierce, Idaho may get within reach of the
top 10 wettest Octobers.



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