Public Information Statement
Issued by NWS Missoula, MT

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Public Information Statement
National Weather Service Missoula MT
200 PM MST Mon Jan 8 2018

...December 2017 Summary for Central Idaho and Western Montana...

The first week of December started off mild with only light amounts
of snowfall including 4 to 6 inches in Glacier National Park and
the Seeley Lake region. A strong area of high pressure locked in
over the region during the second week causing colder than normal
temperatures in the valleys with low stratus and fog in places. It
was also during this time that several places reported snow crystals
falling from the low clouds, sometimes causing a light dusting.
During the second half of the month the pattern became more active
with several storm systems bringing wintry impacts that affected the
holiday season, two of which were considered major winter storms:
18 through the 20 and 27 to the 30. Both of these storm
events involved the juxtaposition of subtropical moisture and cold
air locked in the valleys. Arctic air seeping out of Canada also
contributed to blowing and drifting snow from the Flathead Valley to
along the Continental Divide in both events.

During the 18-20 storm event, between 8 to 12 inches of snow fell
across northwest Montana including the Flathead Valley and Seeley
Lake region and more than 2 feet was measured at our West Glacier
COOP in Glacier National Park. Anywhere from 4 to 8 inches of snow
fell across portions of central Idaho including Orofino in
Clearwater County. Freezing rain slickened up roadways across west-
central Montana causing severe driving conditions in places. Heavy
wet snow caused high to extreme avalanche conditions, power outages,
tree falls, school cancellations and a plethora of automobile
accidents.

During the last several days of the month, the second major winter
storm produced heavy snow with most northwest Montana locations
receiving close to a foot of snow and the heaviest amounts ranging
from 2 feet north of Thompson Falls to 3 feet at Bull Lake, between
2 and 3 feet fell across Glacier National Park and in the Seeley and
Swan lake areas, close to 2 feet fell between Bonner and Ovando and
also between Clinton and Bearmouth. In central Idaho the Powell and
Elk River areas saw over 3 feet of snow while 4 to 8 inches fell in
low elevations north and east of the Camas Prairie. This storm also
produced freezing rain from Polson south to the Bitterroot Valley
where ice accretions amounted to a tenth of an inch. Freezing rain
was also reported along Interstate 90 and Highway 200.  Severe
driving conditions were reported by the Montana Department of
Transportation for multiple locations and even the Idaho
Transportation Department labeled several roadways in central Idaho
as "Difficult" during the storm. Besides heavy snow, freezing rain,
blowing and drifting snow, bitterly cold wind chills down to 35
below zero were experienced between West Glacier and Marias Pass.
Heavy wet snow over west-central Montana also contributed to more
tree falls and power outages.

Official Climate Station stats:

Glacier Park International Airport:
 - Average temperature = 21.5 degrees, -2.8 degrees colder than normal
 - Total Snowfall = 32.8 inches, +16.5 inches above normal. 6th
    snowiest December since 1899.
 - Precipitation = 2.37 inches, +0.81 inches above normal.
 - Sep-Dec 2017 snowfall = 42.0 inches, 15.3 inches above normal.
 - The total seasonal average is 55.7 inches.

Missoula International Airport:
 - Average temperature = 23.4 degrees, 2 degrees below normal.
 - Snowfall =  21.2 inches, 10.2 inches above normal. 6th snowiest
   December since 1893.
 - Precipitation = 1.62 inches, 0.58 inches above normal.
 - Sep-Dec 2017 snowfall= 27.3 inches, 10.3 inches above normal.
 - The total seasonal average is 37.9 inches.

Other interesting and unofficial climate information:

The NWS cooperative observer located 2 miles northwest of Heron,
Montana reported: 51.7 inches of snow (4.3 feet) in December.  This
makes it the 6th snowiest December on record since 1912. The average
snowfall for December is 24.8 inches.  They also have reported 73.1
inches (6.1 feet) for the Sep-Dec 2017 period which is 39.5 inches
(3.3 feet) above normal!

The NWS cooperative observer station at West Glacier, Montana in
Glacier National Park recorded a whopping 59 inches of snow during
December which is 24.7 inches (2 feet) above normal.  Since
September they have received 75.1 inches (6.3 feet) which is 21.2
inches above normal through December. On average, December is the
snowiest month with January coming in at 2nd for West Glacier.

The NWS cooperative observer station at the Hungry Horse Dam
recorded 53 inches(4.4 feet). Since September it has recorded 80.4
(6.7 feet) of snowfall.

The NWS cooperative observer station at the Seeley Lake Ranger
Station recorded 38.5 inches (3.2 feet) which is 9 inches above
normal.  A CoCoRaHS spotter 1.2 miles east of Seeley Lake reported
73.4 inches (6.1 feet) for the month of December.

A CoCoRaHS spotter located 2.9 miles southwest of Ovando reported
43.1 inches (3.6 feet) of snow for December.  In Powell, Idaho the
Idaho Transportation Department measured 90 inches(7.5 feet) of snow
with 7.80 inches of precipitation for the month of December.  There
isn?t an official climate station in Powell anymore, but the highest
snowfall reported by the older Powell COOP station between 1962 and
2013 was 115 inches set in December 1996, 108 inches in 1964 and
93.6 inches in 1971.  So this month was definitely an above normal
event for Powell.

The NWS cooperative observer station in Fenn, Idaho recorded
33.0inches(2.8 feet) of snowfall which is 16.1 inches above normal
making it the 8th snowiest December since 1940. Dec. 2016 had 44
inches which ranks 2nd highest.  It also reported 8.14 inches of
precipitation which is 4.13 inches above normal and ranks the 5th
wettest December on record since 1940.  What?s also astonishing is
the fact that it reported 14.94 inches of preciptitation during the
Nov-Dec 2017 months which is 5.77 inches above normal and ranks the
2nd wettest Nov-Dec period with 16.82 inches falling in Nov-Dec
1995.

-Noble


$$



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