Winter Storm Warning 13, NWS Missoula, MT

427 
WWUS45 KMSO 080236
WSWMSO

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
736 PM MST Sat Dec 7 2024

MTZ005-080345-
/O.CAN.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Missoula/Bitterroot Valleys-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY IS CANCELLED...

Temperatures have warmed, ending the threat for freezing rain. 

$$

MTZ001-080600-
/O.CON.KMSO.WS.W.0013.000000T0000Z-241208T0600Z/
Kootenai/Cabinet Region-
736 PM MST Sat Dec 7 2024

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 11 PM MST THIS 
EVENING...

* WHAT...Heavy mixed precipitation. Likelihood of major impacts from 
  snow and ice is greater than 60 percent. Total snow accumulations 
  of a trace to 2 inches and ice accumulations around one to two 
  tenths of an inch.

* WHERE...Highway 93 Eureka to Whitefish, Highway 2 Kalispell to 
  Libby, Highway 56 Bull Lake Road, and Highway 37 Eureka to Libby.

* WHEN...Until 11 PM MST this evening.

* IMPACTS...Roads, and especially bridges and overpasses, will 
  likely become slick and hazardous. Significant ice accumulation on 
  power lines and tree limbs may cause widespread and long-lasting 
  power outages. Plan on slippery road conditions.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in 
your vehicle in case of an emergency. The latest road conditions for 
the state you are calling from can be obtained by calling 5 1 1.

&&

$$

IDZ005-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Northern Clearwater Mountains-
636 PM PST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 7 AM PST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent, and 3 to 6 inches of snow is 50 percent. Ice 
  accumulations around one to two tenths of an inch. Winds gusting 
  as high as 35 mph.

* WHERE...Highway 11 Pierce to Headquarters, Elk River, and Pierce.

* WHEN...Until 7 AM PST Sunday.

* IMPACTS...Travel could be very difficult. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

IDZ006-MTZ006-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Southern Clearwater Mountains-Bitterroot/Sapphire Mountains-
736 PM MST Sat Dec 7 2024 /636 PM PST Sat Dec 7 2024/

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST /7 AM 
PST/ SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent, and 3 to 6 inches of snow is 50 percent. Ice 
  accumulations around one tenth of an inch. Winds gusting as high 
  as 40 mph in the mountains.

* WHERE...Lolo Pass, Highway 93 Sula to Lost Trail Pass, Dixie, 
  Highway 12 Lowell to Lolo Pass, and Elk City.

* WHEN...Until 8 AM MST /7 AM PST/ Sunday.

* IMPACTS...Travel could be very difficult. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

IDZ007-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Orofino/Grangeville Region-
636 PM PST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 7 AM PST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 2 inches of snow is 60 
  percent. Ice accumulations up to one tenth of an inch.

* WHERE...Greer Grade, Camas Prairie, and Grangeville and vicinity.

* WHEN...Until 7 AM PST Sunday.

* IMPACTS...Plan on slippery road conditions. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

IDZ008-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Lower Hells Canyon/Salmon River Region-
636 PM PST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 7 AM PST SUNDAY 
ABOVE 3000 FEET...

* WHAT...Snow above 3000 feet. Likelihood of minor to moderate 
  impacts from around 1 to 2 inches of snow is 60 percent.

* WHERE...White Bird Grade.

* WHEN...Until 7 AM PST Sunday.

* IMPACTS...For MODERATE impacts from snow, expect disruptions to 
  normal activities. Hazardous traveling conditions. Use extra 
  caution while driving. Closures and disruptions to infrastructure 
  may occur.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

MTZ002-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
West Glacier Region-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent, and 3 to 6 inches of snow is 50 percent. Ice 
  accumulations around one tenth of an inch. Winds gusting as high 
  as 45 mph near mountain passes, such as Marias Pass.

* WHERE...Bad Rock Canyon, Highway 83 Bigfork to Swan Lake, Marias 
  Pass, Polebridge, and Essex.

* WHEN...Until 8 AM MST Sunday.

* IMPACTS...Travel could be very difficult. Gusty winds could bring 
  down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

MTZ003-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Flathead/Mission Valleys-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent. Ice accumulations up to one tenth of an inch.

* WHERE...Flathead Lake, Mission Valley, Polson, and Flathead Valley.

* WHEN...Until 8 AM MST Sunday.

* IMPACTS...Plan on slippery road conditions. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

MTZ004-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Lower Clark Fork Region-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent, and 3 to 6 inches of snow is 40 percent. Ice 
  accumulations around one tenth of an inch. Winds gusting as high 
  as 45 mph in the mountains.

* WHERE...Highway 200 Trout Creek to Heron, I-90 Lookout Pass to 
  Haugan, Evaro Hill, and Highway 200 Thompson Falls to Plains.

* WHEN...Until 8 AM MST Sunday.

* IMPACTS...Travel could be very difficult. Gusty winds could bring 
  down tree branches.

* ADDITIONAL DETAILS...Little if any snow accumulation is expected 
  in the valleys, with the main snow impacts at higher elevations 
  including Lookout Pass.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

MTZ007-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Butte/Blackfoot Region-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 80 
  percent, and 3 to 6 inches of snow is less than 10 percent. Ice 
  accumulations around a light glaze. Winds gusting as high as 45 
  mph.  A period of intense snow showers Saturday evening could lead 
  to rapidly changing visibility.

* WHERE...Homestake Pass, Butte, Highway 12 Garrison to Elliston, 
  Georgetown Lake, and MacDonald Pass.

* WHEN...Until 8 AM MST Sunday.

* IMPACTS...Plan on slippery road conditions. Gusty winds could 
  bring down tree branches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

MTZ043-081500-
/O.CON.KMSO.WW.Y.0055.000000T0000Z-241208T1500Z/
Potomac/Seeley Lake Region-
736 PM MST Sat Dec 7 2024

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM MST SUNDAY...

* WHAT...Mixed precipitation. Likelihood of minor to moderate 
  impacts from ice accumulations and 1 to 3 inches of snow is 90 
  percent, and 3 to 6 inches of snow is 10 percent. Ice 
  accumulations around one tenth of an inch.

* WHERE...I-90 East Missoula to Bearmouth, Highway 200 Bonner to 
  Greenough, and Highway 83 Seeley Lake to Condon.

* WHEN...Until 8 AM MST Sunday.

* IMPACTS...Travel could be very difficult. Strong winds could cause 
  damage to trees and power lines.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling. The latest road 
conditions for the state you are calling from can be obtained by 
calling 5 1 1.

&&

$$

Area Forecast Discussion
National Weather Service Missoula MT
717 AM MST Fri Dec 6 2024

.UPDATE...Issued a freezing fog advisory for the Camas Prairie in
Idaho due to low visibility and ice formation possible on
roadways. Fog will likely continue into this afternoon.

&&

.DISCUSSION...

KEY MESSAGES:

-  Wintry mix late tonight through Saturday, then a Pacific cold
   front will bring breezy and moderate snow showers Saturday
   evening through Monday.

Fog and stratus will once again impact area valleys across the
Northern Rockies today. Freezing fog has become quite dense in the
Missoula and Bitterroot valleys overnight, which has prompted an
advisory. Expect low visibility and scattered slick spots on your
morning commute. Very light snowfall is possible today as well in
areas that have experienced stratus the past couple days.

The ridge of high pressure will begin to flatten this evening, as
moisture from the Pacific begins to stream overhead. This
moisture will introduce above freezing temperatures in the mid-
levels, that will allow for a wintry mix to fall through the
stratus layer across north-central Idaho and northwest Montana
through Saturday morning. There is a 40-50 percent probability for
this to occur in north-central Idaho and up to a 65 percent
probability in northwest Montana, north of I-90. While the
probabilities are low, at 10 percent, there is a chance that the
precipitation will be in the form of freezing rain, leading to a
higher impact across the area.

A Pacific cold front is still expected to arrive late Saturday,
bringing moderate snow and gusty winds to the mountains and
mountain passes through Sunday evening. Snow levels will
initially rise to around 6000 feet ahead of the front, then
crash to most valley floors by Sunday morning. Convective showers
behind the front could bring snow showers to area valleys, though
only a trace to one half inch of snow is expected. The mountains
and mountain passes in western Montana and north-central Idaho can
expect as much as 4 inches, and 9 inches on the high end to fall
from Saturday evening through the day Sunday. Expect wintry
conditions if you plan to travel in the higher elevations this
weekend.

A secondary system is on track to bring snow showers across the
region Monday. This pattern is good for snow in the mountains,
but also across north-central Idaho. The probability for
Grangeville receiving around 2 inches of snow is 20 percent, but
closer to 100 percent in the Clearwater, Bitterroot, Mission, and
Swan Range.

Ensemble models depict an upper ridge developing thereafter, but
it may only last a couple of days before another system could
bring wintry precipitation to the region. The latest Climate
Prediction Center forecast has a 40 to 50 percent chance leaning
above average precipitation for December 11 through 15.

&&

.AVIATION...Dense freezing fog and low stratus is expected to
remain in place across many valley locations across the Northern
Rockies throughout the day today. KMSO in particular could see the
dense fog lowering visibility between 1/4SM-1/2SM through
06/1600Z this morning. Ceilings across the region will hover
between 200-400ft for KGPI, KMSO and KHRF into the afternoon hours.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Freezing Fog Advisory until 2 PM MST this afternoon for
     Missoula/Bitterroot Valleys.

ID...Freezing Fog Advisory until 1 PM PST this afternoon for
     Orofino/Grangeville Region.

&&