Winter Storm Warning 12, NWS Missoula, MT

787 
WWUS45 KMSO 151213
WSWMSO

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
613 AM MDT Fri Sep 15 2017

IDZ010-MTZ006-007-043-161200-
/O.CON.KMSO.WS.W.0012.000000T0000Z-170916T1200Z/
613 AM MDT Fri Sep 15 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 AM MDT SATURDAY
ABOVE 6000 FEET...

* Impacts/Timing: Light snow will continue down to 5000 feet
  through this morning, with solid accumulations above 6000 feet.
  Snow on the trails and back roads at high elevation will be
  consequential for travel and recreation. Low clouds and low 
  visibility can quickly cause disorientation. Also, beware the 
  risk of hypothermia, particularly for those who are not prepared
  for early winter weather conditions. 

* Snow accumulations: 5000 to 6000 feet: Trace to 2 inches. 
  Above 6000 feet: 3 to 8 inches, except up to 12 inches in 
  southwest Montana higher terrain including hills around 
  Georgetown Lake, Pintlar Mountains east to the Continental 
  Divide. 

* Locations impacted include: Bannock Pass, Highway 28 Tendoy to 
  Lone Pine, Highway 93 Lost Trail Pass to Gibbonsville, Lemhi 
  Pass, Highway 93 Sula to Lost Trail Pass, Georgetown Lake, and 
  MacDonald Pass

$$

180 
WWUS45 KMSO 151850
WSWMSO

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
1250 PM MDT Fri Sep 15 2017

IDZ010-MTZ006-007-043-161200-
/O.CON.KMSO.WS.W.0012.000000T0000Z-170916T1200Z/
1250 PM MDT Fri Sep 15 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 AM MDT SATURDAY
ABOVE 6000 FEET...

* Impacts/Timing: Snow will continue down to 4500 feet throughout
  the day, with solid accumulations above 5500 feet. Snow on the 
  trails and back roads at high elevation will be consequential 
  for travel and recreation. Low clouds and low visibility can 
  quickly cause disorientation. Also, beware the risk of 
  hypothermia, particularly for those who are not prepared for 
  early winter weather conditions. 

* Snow accumulations: 4000 to 5500 feet: Trace to 2 inches. Above
  5500 feet: 3 to 8 inches, except up to 12 inches in southwest 
  Montana higher terrain including hills around Georgetown Lake, 
  Pintlar Mountains east to the Continental Divide. 

* Locations impacted include: Bannock Pass, Highway 28 Tendoy to 
  Lone Pine, Highway 93 Lost Trail Pass to Gibbonsville, Lemhi 
  Pass, Highway 93 Sula to Lost Trail Pass, Georgetown Lake, and 
  MacDonald Pass

$$

479 
WWUS45 KMSO 161145
WSWMSO

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
545 AM MDT Sat Sep 16 2017

IDZ010-MTZ006-007-043-161245-
/O.EXP.KMSO.WS.W.0012.000000T0000Z-170916T1200Z/
545 AM MDT Sat Sep 16 2017

...WINTER STORM WARNING WILL EXPIRE AT 6 AM MDT EARLY THIS
MORNING ABOVE 6000 FEET...


$$

Area Forecast Discussion
National Weather Service Missoula MT
431 AM MDT Thu Sep 14 2017

.DISCUSSION...

Bottom Line Up Front: Wet, cool Fall weather coming; say goodbye
to wildfire season.

A significant Fall weather system remains on-track to impact the
Northern Rockies with widespread rainfall and snow accumulations
above 6000 feet along the Continental Divide through early
Saturday. Areas of light rain have already begun to develop across
the region and will intensify through tonight. Relatively cold,
dense air pushing over from east of the Divide is creating gusty
conditions within area valleys, such as the Flathead and Missoula
valleys. These gusty winds will move a lot wildfire smoke around
today, however the presence of smoke will be limited after today.

Snow tonight down to 6000 feet through early Saturday will impact
travelers over the Continental Divide, personnel on area fires,
and high elevation recreation (e.g., hunters, hikers). Low
visibility in the snow elevations may be disorienting at times.
Valley locations, particularly those near the Continental Divide,
will see an extended period of cold rainfall totaling over one
inch in some spots. Some western Montana valley locations will
experience near-record cold daytime temperatures on Friday. North
central Idaho, particularly the Highway 95 corridor, will remain
relatively dry compared to western Montana.

Cold air left behind from this upcoming weather system over the
Northern Rockies will allow valleys to cool considerably Saturday
night, with a high likelihood of freezing temperatures for many
valleys above 4000 feet.

Following a very brief warm-up, the next significant Fall weather
system is anticipated over the Northern Rockies beginning Monday.
This weather system will remain in the neighborhood for nearly all
of next week, with another shot of mountain snow and widespread
cold rainfall at low elevations. Similar to the present weather
system, western Montana appears more favored for rain and snow
amounts compared to north central Idaho.

&&

.AVIATION...KGPI and KMSO will continue to see northeasterly winds
through much of the day today, occasionally gusting near 35kts for
GPI after 14/1800Z this afternoon. KMSO will see gusts approaching
30kts later this afternoon after 14/2000Z. KBTM will also see
gusty winds near 30kts today, though will generally see
northwesterly winds. Aviation sites KMSO, KBTM, and KSMN will see
occasionally lowered visibility due to light rain showers through
the day today. KSMN will remain on the relatively warm side of
the airmass, where a few thunderstorms will be possible between
14/1800-2100Z

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from this evening through late Friday night
     ABOVE 6000 FEET for the Bitterroot/Sapphire Mountains...
     Butte/Blackfoot Region...Potomac/Seeley Lake Region.

ID...Winter Storm Watch from this evening through late Friday night
     ABOVE 6000 FEET for the Eastern Lemhi County.

&&