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Area Forecast Discussion
Issued by NWS Missoula, MT
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FXUS65 KMSO 010338
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
838 PM MST Tue Jan 31 2017

.UPDATE...Downgraded some warnings in Idaho and Montana to
advisories for the remainder of the event. Some warnings still
remain in western Montana.

&&

.DISCUSSION...Snow is tapering off in Grangeville, Idaho and on
the Camas Prairie. The same is happening in portions of west
central Montana. Some light snow will continue tonight with icy
conditions, so advisories remain, but the period of highest
impact is over and the warning has been downgraded.

In the southern Bitterroot Valley, moderate to heavy snow is
still being reported with reports of black ice forming in the
Missoula Valley causing dangerous travel conditions at times, so
the warning there remains.

Likewise in southwest Montana from MacDonald Pass to Homestake
Pass and Butte, moderate snow continues so the warning there
remains out.

&&

.AVIATION...Light to moderate snow continues to fall along the
I-90 corridor from the ID/MT border east to the Continental
Divide, south through west-central Montana and north-central
Idaho. We do expect further enhancement with the snow showers for
KMSO this afternoon and evening between 31/2200Z-01/0400. These
showers could greatly reduce the visibility for a period of time
in this time range. KBTM can expect similar conditions as KMSO
through 01/0600Z. Gusty easterly winds of around 15-22kts will be
possible after 01/0900Z KMSO. KGPI will remain mostly clear with
northeast winds sustained around 15kts with gusts up to 25kts
this evening through midnight.

&&

.PREV DISCUSSION... /ISSUED 543 PM MST Tue Jan 31 2017/

UPDATE...Canceled winter weather advisory for Flathead and
Mission Valleys. Downgraded Lower Clark Fork region warning
to an advisory.

DISCUSSION...Much of the steady snow has ended across the
southern Mission Valley and there hasn`t been any precipitation
falling towards Kalispell at all today. Satellite and radar trends
do show some weak enhancement going on over the southern Mission
Valley and a phone call to a weather spotter northwest of St.
Ignatius confirmed very light snow. This light snow could
continue for the next several hours. Light to moderate snow is
possible for areas between Frenchtown and St. Regis for the next
several hours. Since we are not expecting any heavier snowfall
rates in this portion of the Lower Clark Fork region, we
downgraded the warning.

PREV DISCUSSION... /ISSUED 248 PM MST Tue Jan 31 2017/

DISCUSSION...The winter storm has produced a wide range of
snowfall amounts all across the region today. We have only
received about an inch of snow here at the Missoula airport but
have received reports of 4 inches in the south hills and even up
to 10 inches in Hamilton. Other reports we have received so far
are 6 inches in Greenough, 4.5 inches in Alberton, up to 8 inches
in Georgetown, and 5.5 inches in Greer, Idaho.

For rest of this afternoon and evening, an increase in snow
intensity is expected as the Canadian cold front interacts with
the pacific moisture over west-central/southwest Montana and over
central Idaho. Periods of moderate to locally heavy snow will be
possible especially between Superior to Frenchtown on I-90, near
the Continental Divide in southwest Montana such as MacDonald and
Homestake pass, and in the Camas Prairie of Idaho. Snow is
expected to begin tapering off late this evening across west-
central Montana and central Idaho, but periods of moderate snow
could continue through tonight over southwest Montana.
Additionally, increased east and north east winds are expected
late this evening and tonight, that along with colder
temperatures, will bring concern for refreeze of wet pavement as
the Canadian cold front moves through. Slick conditions may last
through the Wednesday morning commute.

Light snow will linger in portions of north central Idaho and
west central Montana on Wednesday but overall accumulations will
be light with a decreasing trend during the morning.

There is another wave a moisture expected to move into Lemhi
County Idaho late Wednesday. This wave will move northward
overnight and through Thursday and will also interact with a
shortwave from the north. There is still some question on how far
north area of snow will move, but it has been fairly consistent
that snow will fall at least as far north as Grangeville,
Hamilton, and Butte through Thursday.

The shortwave is forecast to pass late Thursday thus ending the
snow and leaving behind cold conditions for Friday morning.

An active southwesterly pattern will bring snow followed by warmer
temperatures and mixed precipitation through the weekend and early
next week. There may be another cold front on Monday that could
enhance snow and cool temperatures.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 5 AM MST Wednesday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 5 AM MST Wednesday Potomac/Seeley
     Lake Region.

     Winter Storm Warning until 5 AM MST Wednesday Butte/Blackfoot
     Region.

     Winter Weather Advisory until 5 AM MST Wednesday Lower Clark
     Fork Region.

     Winter Storm Warning until 5 AM MST Wednesday
     Missoula/Bitterroot Valleys.

ID...Winter Weather Advisory until 4 AM PST Wednesday
     Orofino/Grangeville Region.

     Winter Weather Advisory until 11 AM MST Wednesday Eastern Lemhi
     County...Western Lemhi County.

     Winter Weather Advisory until 4 AM PST Wednesday ABOVE 2000 FEET
     for the Lower Hells Canyon/Salmon River Region.

     Winter Weather Advisory until 4 AM PST Wednesday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

$$
National Weather Service Regional Headquarters
