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000
FXUS65 KMSO 201746
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1046 AM MST SAT DEC 20 2014

.UPDATE...Winter Storm Watch is now Winter Weather Advisories
beginning this afternoon lasting through early Monday.


&&

.DISCUSSION...12z model runs show similar trends to earlier runs
regarding the atmospheric river event over this weekend. Periods
of light snow (mainly over the mountains) are expected to
continue into this afternoon as moisture overspreads the region.
There is growing confidence that most mountain passes will see an
initial period of heavy wet snow later this evening with snow
levels beginning around 3000ft. Snow levels will then gradually
rise overnight with some lower elevation passes seeing a rain/snow
mix or all rain by Sunday morning but passes such as Lost Trail
will likely continue as all snow on Sunday. Overall, hazardous
driving conditions due to snow packed and slick roads are expected
tonight into Sunday over area passes thus Winter Weather
Advisories have been issued.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.




&&

.PREV DISCUSSION... /ISSUED 320 AM MST SAT DEC 20 2014/

..DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
..POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.

AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY from 3 PM this afternoon to 5 AM MST
     Monday ABOVE 4000 FEET for the Lower Clark Fork Region.

     WINTER WEATHER ADVISORY from 7 PM this evening to 5 AM MST
     Monday Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Potomac/Seeley Lake Region...West Glacier Region.

ID...WINTER WEATHER ADVISORY from 3 PM MST /2 PM PST/ this afternoon
     to 5 AM MST /4 AM PST/ Monday ABOVE 4000 FEET for the
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains...Western Lemhi County.

&&

$$





000
FXUS65 KMSO 201746
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1046 AM MST SAT DEC 20 2014

.UPDATE...Winter Storm Watch is now Winter Weather Advisories
beginning this afternoon lasting through early Monday.


&&

.DISCUSSION...12z model runs show similar trends to earlier runs
regarding the atmospheric river event over this weekend. Periods
of light snow (mainly over the mountains) are expected to
continue into this afternoon as moisture overspreads the region.
There is growing confidence that most mountain passes will see an
initial period of heavy wet snow later this evening with snow
levels beginning around 3000ft. Snow levels will then gradually
rise overnight with some lower elevation passes seeing a rain/snow
mix or all rain by Sunday morning but passes such as Lost Trail
will likely continue as all snow on Sunday. Overall, hazardous
driving conditions due to snow packed and slick roads are expected
tonight into Sunday over area passes thus Winter Weather
Advisories have been issued.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.




&&

.PREV DISCUSSION... /ISSUED 320 AM MST SAT DEC 20 2014/

..DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
..POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.

AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY from 3 PM this afternoon to 5 AM MST
     Monday ABOVE 4000 FEET for the Lower Clark Fork Region.

     WINTER WEATHER ADVISORY from 7 PM this evening to 5 AM MST
     Monday Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Potomac/Seeley Lake Region...West Glacier Region.

ID...WINTER WEATHER ADVISORY from 3 PM MST /2 PM PST/ this afternoon
     to 5 AM MST /4 AM PST/ Monday ABOVE 4000 FEET for the
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains...Western Lemhi County.

&&

$$






000
FXUS65 KMSO 201021
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
320 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$





000
FXUS65 KMSO 201021
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
320 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$






000
FXUS65 KMSO 201020
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
320 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$






000
FXUS65 KMSO 201020
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
320 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-eys of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of DISCREPANCY on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$





000
FXUS65 KMSO 201019
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
319 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-size of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of discrepency on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$






000
FXUS65 KMSO 201019
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
319 AM MST SAT DEC 20 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED TONIGHT AND
SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Widespread dense freezing fog with 1/4 mile
visibility or less in the Missoula and central to northern
Bitterroot valleys will persist through the mid morning hours. The
fog will slowly begin to lift and scour out by mid afternoon.

An anomalous moisture plume is still expected to bring heavy
precipitation to the region by tonight. The first slug of
moderately heavy rain will arrive across central Idaho by this
afternoon. Snow levels will gradually rise this evening into the
overnight.

* Lookout Pass on Interstate 90 will experience heavy and
  relatively wet snow from after midnight tonight changing to
  either a mixture of rain/snow or just plain rain by daybreak
  Sunday. Lolo Pass will see a similar change to a mixture with
  rain but the timing for that may be a little later Sunday
  morning and then change back to snow by the afternoon.

* Another area of concern could be the Glacier Park area, but with
  strong westerlies aloft, downsloping affects could limit the
  intensity of snowfall and total snow amounts. Nonetheless, road
  surfaces will be slick at times with snowfall.

* Models continue to paint a bull-size of over an inch of
  precipitation along MT Highway 83 between Swan Lake and Seeley
  Lake...elevations above 4000 feet could see 4 to 6 inches of
  total snowfall through Sunday evening.

* As the plume of moisture shifts south, Lost Trail Pass will see
  heavy snow for much of the day Sunday and could see a brief
  period of rain/snow.

Monday and early Tuesday a ridge of high pressure will put a
brief rest to precip over the region. Valley fog is a possibility
Mon and Tue morning under this ridge.

Late Tuesday through Christmas...All models continue to show a
rather strong and wet weather disturbance moving through the
Northern Rockies. The common denominator is that this period will
be wet BUT there continues to be a lot of discrepency on the
details on where exactly this system moves through the region.
This is a pattern favorable for significant precipitation or snow
in a band just north of the surface low pressure. The problem is
now each model shows a different placement of this low (band of
precip) anywhere from Northwest Montana to central Idaho.
Models should begin to come into some sort of consistency in the
next 3 days for confidence to increase enough for details of
placement and rain/snow amounts potential over the region.

STAY TUNED TO SUBSEQUENT FORECASTS for this may be a significant
system and confidence will increase for exact placement of
potential snow during the critical peak travel over the Christmas
holiday.


&&

.AVIATION...Dense fog will persist at KMSO through 20/1500z. Fog
will gradually lift and clear out at KMSO by 20/2000z. Otherwise
expect cloudy skies with mountain obscurations at times today. The
next storm system will enter the region this evening and persist
through Sunday morning. Valley rain will occur at all terminals,
limiting visibilities and lowering ceilings at times.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH from this evening through late Sunday night
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Lower Clark Fork Region...Potomac/Seeley Lake Region...West
     Glacier Region.

     DENSE FOG ADVISORY until 9 AM MST this morning
     Missoula/Bitterroot Valleys.

ID...WINTER STORM WATCH from this evening through late Sunday night
     Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains.

&&

$$





000
FXUS65 KMSO 192209
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
309 PM MST FRI DEC 19 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED SATURDAY NIGHT
AND SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Snow and rain have started falling lightly across
the Northern Rockies already today, and will continue
intermittently through the day Saturday.

Saturday evening the precipitation really starts to increase as
an atmospheric river of warm, moist air streams into the region.
Snow levels will start around 3,500 feet and start to rise
Saturday night to around 6,000 feet in some locations by Sunday
afternoon. This is expected to cause very difficult travel
conditions over mountain passes with heavy wet snow followed by
rain at times. The ample moisture from the atmospheric river will
cause high precipitation rates at times, which in turn may cause
heavy snow. There is still considerable uncertainty with the
timing of snow level changes, and this coupled with the high rate
of precipitation could cause very big errors in the snowfall
forecasts near the pass levels. As a result, a winter weather
watch has been issued that includes all the area passes for
Saturday night through Sunday. As the storm approaches and we
become more confident of snow levels, the watches may transition
to warnings for the high impact areas and advisories elsewhere.

Meanwhile, confidence is high that there will be a lot of snow at
the highest elevations. Above 6,000-7000 feet, snow amounts in
the Bitterroot, Clearwater, and portions of the Mission and Swan
Ranges will be measured in feet.

Sunday night into Monday, snow showers will linger behind a weak
cold front associated with the system, with snow levels falling.
Due to the warm nature of the atmospheric river, very little snow
is expected in the valleys.

Looking ahead to the Christmas holiday, forecast models are
showing a potent storm tracking through the Northern Rockies
Christmas Eve and into Christmas Day. This storm will have the
potential to bring accumulating snow impacting travel. There is
still a great deal of uncertainty however as various models are
tracking the surface low pressure center hundreds of miles apart,
and they are also varying from run to run. These different tracks
could result in anything from snow at valley floors to only at the
higher elevations. We will be keeping a close eye on this storm,
and should be able to provide better information as we get closer
and forecast certainty increases. For now, be aware that holiday
travel may be impacted.

Colder air will move into the area behind the Christmas storm,
pulling temperatures across the Northern Rockies below freezing.
Temperatures will be cold, but not exceptionally so (mostly just
colder than what we`ve seen recently).

&&

.AVIATION...Intermittent showers will continue through the evening
and tomorrow. Expect mountain obscurations with variable ceilings
and moderate visibility restrictions. Precipitation will be mixed
this afternoon becoming mostly snow tonight. KGPI will be most
impacted by visibility and low ceilings at times, though all area
terminals will be affected.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$






000
FXUS65 KMSO 192209
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
309 PM MST FRI DEC 19 2014

...DIFFICULT TRAVEL OVER MOUNTAIN PASSES EXPECTED SATURDAY NIGHT
AND SUNDAY...
...POSSIBLE SNOW IMPACTS OVER CHRISTMAS EVE AND CHRISTMAS DAY...

.DISCUSSION...Snow and rain have started falling lightly across
the Northern Rockies already today, and will continue
intermittently through the day Saturday.

Saturday evening the precipitation really starts to increase as
an atmospheric river of warm, moist air streams into the region.
Snow levels will start around 3,500 feet and start to rise
Saturday night to around 6,000 feet in some locations by Sunday
afternoon. This is expected to cause very difficult travel
conditions over mountain passes with heavy wet snow followed by
rain at times. The ample moisture from the atmospheric river will
cause high precipitation rates at times, which in turn may cause
heavy snow. There is still considerable uncertainty with the
timing of snow level changes, and this coupled with the high rate
of precipitation could cause very big errors in the snowfall
forecasts near the pass levels. As a result, a winter weather
watch has been issued that includes all the area passes for
Saturday night through Sunday. As the storm approaches and we
become more confident of snow levels, the watches may transition
to warnings for the high impact areas and advisories elsewhere.

Meanwhile, confidence is high that there will be a lot of snow at
the highest elevations. Above 6,000-7000 feet, snow amounts in
the Bitterroot, Clearwater, and portions of the Mission and Swan
Ranges will be measured in feet.

Sunday night into Monday, snow showers will linger behind a weak
cold front associated with the system, with snow levels falling.
Due to the warm nature of the atmospheric river, very little snow
is expected in the valleys.

Looking ahead to the Christmas holiday, forecast models are
showing a potent storm tracking through the Northern Rockies
Christmas Eve and into Christmas Day. This storm will have the
potential to bring accumulating snow impacting travel. There is
still a great deal of uncertainty however as various models are
tracking the surface low pressure center hundreds of miles apart,
and they are also varying from run to run. These different tracks
could result in anything from snow at valley floors to only at the
higher elevations. We will be keeping a close eye on this storm,
and should be able to provide better information as we get closer
and forecast certainty increases. For now, be aware that holiday
travel may be impacted.

Colder air will move into the area behind the Christmas storm,
pulling temperatures across the Northern Rockies below freezing.
Temperatures will be cold, but not exceptionally so (mostly just
colder than what we`ve seen recently).

&&

.AVIATION...Intermittent showers will continue through the evening
and tomorrow. Expect mountain obscurations with variable ceilings
and moderate visibility restrictions. Precipitation will be mixed
this afternoon becoming mostly snow tonight. KGPI will be most
impacted by visibility and low ceilings at times, though all area
terminals will be affected.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$





000
FXUS65 KMSO 191728
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1027 AM MST FRI DEC 19 2014

.UPDATE...Added winter weather advisory for light freezing rain.


&&

.DISCUSSION...Road crews report freezing rain along Highway 2 from
the Columbia Falls area up past Essex. Area temperatures show warm
air aloft with a few isolated pockets of cold air entrenched in
the valleys along the Highway 2 corridor. Expect temperatures to
rise today in that area as they have elsewhere, though the narrow
valleys will take more time to clear out. So a winter weather
advisory for freezing rain was issued in those valleys until this
afternoon.


&&

.AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.


&&

.PREV DISCUSSION... /ISSUED 345 AM MST FRI DEC 19 2014/

DISCUSSION...

The next in a series of weak storm systems will be impacting the
Northern Rockies today, bringing light snow accumulations mainly
to high terrain. Hazardous travel conditions due to snow-covered
roadways will be present in spots, particularly at mountain pass
elevations. However, daytime heating will limit the coverage and
duration of such slick conditions. Valley locations will also
experience periods of snowfall, however little to no accumulation
is anticipated.

The models have not wavered much on moist subtropical flow
pushing into the Northern Rockies this weekend. This system will
bring substantial amounts of precipitation to the region,
especially Idaho and Clearwater counties. North central Idaho
should anticipate 1 to 2 inches of rain late Saturday through
Sunday. While western Montana is anticipated to receive anywhere
from 0.3" to 1.00" of moisture. Snow levels will be steadily
rising during this event, but during the onset of moisture area
mountain passes could receive heavy wet snow. At this time most
mountain passes should anticipate 4 to 8 inches of snow by Sunday
morning, the exception will be Lost Trail which has the potential
to get up to a foot of new snow by Monday morning. The widespread
heavy rain and mountain pass snow will cause considerable travel
impacts this weekend.

Showers are anticipated to linger across the region Monday on
through mid week. Snow levels will be steadily declining so by
Tuesday valley locations could be receiving snow once again. The
models are still showing a colder trough digging over the Northern
Rockies for Christmas into Friday. The latest model runs are
starting to indicate the surface low moving over the area
Wednesday night into Christmas, which could bring widespread snow.
Confidence for this system is still quite low due to fluctuation
on the trajectory of the surface low.

AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 1 PM MST this afternoon West
     Glacier Region.

ID...None.
&&

$$






000
FXUS65 KMSO 191728
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1027 AM MST FRI DEC 19 2014

.UPDATE...Added winter weather advisory for light freezing rain.


&&

.DISCUSSION...Road crews report freezing rain along Highway 2 from
the Columbia Falls area up past Essex. Area temperatures show warm
air aloft with a few isolated pockets of cold air entrenched in
the valleys along the Highway 2 corridor. Expect temperatures to
rise today in that area as they have elsewhere, though the narrow
valleys will take more time to clear out. So a winter weather
advisory for freezing rain was issued in those valleys until this
afternoon.


&&

.AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.


&&

.PREV DISCUSSION... /ISSUED 345 AM MST FRI DEC 19 2014/

DISCUSSION...

The next in a series of weak storm systems will be impacting the
Northern Rockies today, bringing light snow accumulations mainly
to high terrain. Hazardous travel conditions due to snow-covered
roadways will be present in spots, particularly at mountain pass
elevations. However, daytime heating will limit the coverage and
duration of such slick conditions. Valley locations will also
experience periods of snowfall, however little to no accumulation
is anticipated.

The models have not wavered much on moist subtropical flow
pushing into the Northern Rockies this weekend. This system will
bring substantial amounts of precipitation to the region,
especially Idaho and Clearwater counties. North central Idaho
should anticipate 1 to 2 inches of rain late Saturday through
Sunday. While western Montana is anticipated to receive anywhere
from 0.3" to 1.00" of moisture. Snow levels will be steadily
rising during this event, but during the onset of moisture area
mountain passes could receive heavy wet snow. At this time most
mountain passes should anticipate 4 to 8 inches of snow by Sunday
morning, the exception will be Lost Trail which has the potential
to get up to a foot of new snow by Monday morning. The widespread
heavy rain and mountain pass snow will cause considerable travel
impacts this weekend.

Showers are anticipated to linger across the region Monday on
through mid week. Snow levels will be steadily declining so by
Tuesday valley locations could be receiving snow once again. The
models are still showing a colder trough digging over the Northern
Rockies for Christmas into Friday. The latest model runs are
starting to indicate the surface low moving over the area
Wednesday night into Christmas, which could bring widespread snow.
Confidence for this system is still quite low due to fluctuation
on the trajectory of the surface low.

AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 1 PM MST this afternoon West
     Glacier Region.

ID...None.
&&

$$





000
FXUS65 KMSO 191046
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
345 AM MST FRI DEC 19 2014

.DISCUSSION...

The next in a series of weak storm systems will be impacting the
Northern Rockies today, bringing light snow accumulations mainly
to high terrain. Hazardous travel conditions due to snow-covered
roadways will be present in spots, particularly at mountain pass
elevations. However, daytime heating will limit the coverage and
duration of such slick conditions. Valley locations will also
experience periods of snowfall, however little to no accumulation
is anticipated.

The models have not wavered much on moist subtropical flow
pushing into the Northern Rockies this weekend. This system will
bring substantial amounts of precipitation to the region,
especially Idaho and Clearwater counties. North central Idaho
should anticipate 1 to 2 inches of rain late Saturday through
Sunday. While western Montana is anticipated to receive anywhere
from 0.3" to 1.00" of moisture. Snow levels will be steadily
rising during this event, but during the onset of moisture area
mountain passes could receive heavy wet snow. At this time most
mountain passes should anticipate 4 to 8 inches of snow by Sunday
morning, the exception will be Lost Trail which has the potential
to get up to a foot of new snow by Monday morning. The widespread
heavy rain and mountain pass snow will cause considerable travel
impacts this weekend.

Showers are anticipated to linger across the region Monday on
through mid week. Snow levels will be steadily declining so by
Tuesday valley locations could be receiving snow once again. The
models are still showing a colder trough digging over the Northern
Rockies for Christmas into Friday. The latest model runs are
starting to indicate the surface low moving over the area
Wednesday night into Christmas, which could bring widespread snow.
Confidence for this system is still quite low due to fluctuation
on the trajectory of the surface low.

&&

.AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$





000
FXUS65 KMSO 191046
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
345 AM MST FRI DEC 19 2014

.DISCUSSION...

The next in a series of weak storm systems will be impacting the
Northern Rockies today, bringing light snow accumulations mainly
to high terrain. Hazardous travel conditions due to snow-covered
roadways will be present in spots, particularly at mountain pass
elevations. However, daytime heating will limit the coverage and
duration of such slick conditions. Valley locations will also
experience periods of snowfall, however little to no accumulation
is anticipated.

The models have not wavered much on moist subtropical flow
pushing into the Northern Rockies this weekend. This system will
bring substantial amounts of precipitation to the region,
especially Idaho and Clearwater counties. North central Idaho
should anticipate 1 to 2 inches of rain late Saturday through
Sunday. While western Montana is anticipated to receive anywhere
from 0.3" to 1.00" of moisture. Snow levels will be steadily
rising during this event, but during the onset of moisture area
mountain passes could receive heavy wet snow. At this time most
mountain passes should anticipate 4 to 8 inches of snow by Sunday
morning, the exception will be Lost Trail which has the potential
to get up to a foot of new snow by Monday morning. The widespread
heavy rain and mountain pass snow will cause considerable travel
impacts this weekend.

Showers are anticipated to linger across the region Monday on
through mid week. Snow levels will be steadily declining so by
Tuesday valley locations could be receiving snow once again. The
models are still showing a colder trough digging over the Northern
Rockies for Christmas into Friday. The latest model runs are
starting to indicate the surface low moving over the area
Wednesday night into Christmas, which could bring widespread snow.
Confidence for this system is still quite low due to fluctuation
on the trajectory of the surface low.

&&

.AVIATION...

Freezing fog will be an issue near KGPI through 19/1500Z. Another
storm system will move across the Northern Rockies today through
tonight, lowering ceilings and visibility at times in snow and/or
rain, particularly noteworthy near KGPI. Terrain will be
frequently obscured across the Northern Rockies during the next 24
hours and beyond.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$






000
FXUS65 KMSO 182158
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
258 PM MST THU DEC 18 2014

.DISCUSSION...

SNOW CURRENTLY FALLING IN WESTERN MONTANA WILL BE DECREASING THIS
EVENING AS DRIER AIR MOVES IN. LIGHT ACCUMULATIONS ARE STILL
POSSIBLE FOR COUNTIES ALONG THE DIVIDE.

THE BREAK IN PRECIPITATION WILL BE SHORT-LIVED AS THE NEXT IN A
SERIES OF SYSTEMS MOVES INTO NORTH CENTRAL IDAHO AND WESTERN
MONTANA FRIDAY MORNING. PASSES SUCH AS LOOKOUT, LOLO, LOST TRAIL,
AND MARIAS WILL BE THE MOST AFFECTED, AS THEY ARE EXPECTED TO SEE
2 TO 4 INCHES OF SNOW. TRAVELERS OVER THESE PASSES SHOULD LEAVE
ENOUGH TIME AND PREPARE FOR SLICK/SLUSHY CONDITIONS. THE FLATHEAD,
MISSOULA, AND BITTERROOT VALLEYS SHOULD BE WARM ENOUGH FOR
PRECIPITATION TO MELT AND FALL AS LIGHT RAIN.

A VERY MOIST ATMOSPHERIC RIVER EVENT STILL LOOKS LIKELY BEGINNING
LATE SATURDAY THROUGH EARLY MONDAY ACROSS THE REGION, WITH
HEAVIEST PRECIPITATION AMOUNTS EXPECTED FOR CENTRAL IDAHO, THE BOB
MARSHALL THROUGH THE GLACIER REGION, AND MOUNTAIN PASSES ALONG THE
MONTANA/IDAHO BORDER. THE EVENT WILL BEGIN AS HEAVY WET SNOW WITH
COLDER AIR IN PLACE SATURDAY, BUT WILL LIKELY TRANSITION OVER TO
HEAVY RAIN SUNDAY WITH SNOW LEVELS RISING FROM THE SOUTHWEST TO
THE NORTHEAST TO AROUND 5000-6000 FT. IT IS STILL UNCERTAIN HOW
QUICKLY THE SNOW LEVELS WILL INCREASE, WHICH COULD DRAMATICALLY
CHANGE THE AMOUNT OF SNOW ACCUMULATIONS EXPECTED FOR MOUNTAIN
PASSES. LOLO, LOOKOUT, LOST TRAIL, AND MARIAS PASSES COULD SEE 4
TO 12 INCHES OF WET SNOW. ONCE THE SNOW SWITCHES OVER TO HEAVY
RAIN, THIS COULD RESULT IN VERY SLUSHY AND SLIPPERY TRAVEL FOR
UNCLEARED ROADS, IN ADDITION TO A RISK OF ROCK AND MUD SLIDES
PARTICULARLY FOR HIGHWAY 12 AND 14 IN IDAHO. PONDING OF WATER ON
ROADWAYS COULD ALSO BE POSSIBLE FOR RELATIVELY LOW-LYING AREAS AND
SHOULD BE AVOIDED DURING TRAVEL.

THE FLOW RETURNS TO MORE NORTHWESTERLY TUESDAY INTO WEDNESDAY,
WHICH WILL ALLOW SNOW LEVELS TO LOWER ONCE AGAIN, AT LEAST TO
PASS LEVELS. HOWEVER DURING THIS TIME FRAME THE HEAVIEST
PRECIPITATION SHOULD BE ON THE DOWNWARD TREND. FORECAST MODELS
CONTINUE TO SHOW A MUCH COLDER PATTERN SETTING UP AROUND
CHRISTMAS, PARTICULARLY FOR THE WEEKEND FOLLOWING. HOWEVER,
CONFIDENCE IN POSSIBLE SNOW FOR THE CHRISTMAS HOLIDAY REMAINS LOW.
THERE ARE SIGNIFICANT DIFFERENCES BETWEEN FORECAST MODELS IN TERMS
OF PRECIPITATION, SO STAY TUNED!

&&

.AVIATION...LIGHT SNOW SHOWERS AT KGPI AND THROUGHOUT THE AREA WILL
COME TO AN END THIS EVENING. LOW CLOUD DECKS AND TERRAIN
OBSCURATIONS WILL PERSIST ACROSS THE REGION. WINDS REMAIN LIGHT AS
THE NEXT ROUND OF PRECIPITATION BEGINS TO MOVE IN FROM THE WEST
TOMORROW MORNING. KGPI WILL AGAIN BE THE FIRST TO SEE MEASURABLE
LIGHT RAIN BEGINNING AROUND 19/1500Z, AND LATER IN THE DAY FOR
OTHER TAF SITES.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$




000
FXUS65 KMSO 182158
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
258 PM MST THU DEC 18 2014

.DISCUSSION...

SNOW CURRENTLY FALLING IN WESTERN MONTANA WILL BE DECREASING THIS
EVENING AS DRIER AIR MOVES IN. LIGHT ACCUMULATIONS ARE STILL
POSSIBLE FOR COUNTIES ALONG THE DIVIDE.

THE BREAK IN PRECIPITATION WILL BE SHORT-LIVED AS THE NEXT IN A
SERIES OF SYSTEMS MOVES INTO NORTH CENTRAL IDAHO AND WESTERN
MONTANA FRIDAY MORNING. PASSES SUCH AS LOOKOUT, LOLO, LOST TRAIL,
AND MARIAS WILL BE THE MOST AFFECTED, AS THEY ARE EXPECTED TO SEE
2 TO 4 INCHES OF SNOW. TRAVELERS OVER THESE PASSES SHOULD LEAVE
ENOUGH TIME AND PREPARE FOR SLICK/SLUSHY CONDITIONS. THE FLATHEAD,
MISSOULA, AND BITTERROOT VALLEYS SHOULD BE WARM ENOUGH FOR
PRECIPITATION TO MELT AND FALL AS LIGHT RAIN.

A VERY MOIST ATMOSPHERIC RIVER EVENT STILL LOOKS LIKELY BEGINNING
LATE SATURDAY THROUGH EARLY MONDAY ACROSS THE REGION, WITH
HEAVIEST PRECIPITATION AMOUNTS EXPECTED FOR CENTRAL IDAHO, THE BOB
MARSHALL THROUGH THE GLACIER REGION, AND MOUNTAIN PASSES ALONG THE
MONTANA/IDAHO BORDER. THE EVENT WILL BEGIN AS HEAVY WET SNOW WITH
COLDER AIR IN PLACE SATURDAY, BUT WILL LIKELY TRANSITION OVER TO
HEAVY RAIN SUNDAY WITH SNOW LEVELS RISING FROM THE SOUTHWEST TO
THE NORTHEAST TO AROUND 5000-6000 FT. IT IS STILL UNCERTAIN HOW
QUICKLY THE SNOW LEVELS WILL INCREASE, WHICH COULD DRAMATICALLY
CHANGE THE AMOUNT OF SNOW ACCUMULATIONS EXPECTED FOR MOUNTAIN
PASSES. LOLO, LOOKOUT, LOST TRAIL, AND MARIAS PASSES COULD SEE 4
TO 12 INCHES OF WET SNOW. ONCE THE SNOW SWITCHES OVER TO HEAVY
RAIN, THIS COULD RESULT IN VERY SLUSHY AND SLIPPERY TRAVEL FOR
UNCLEARED ROADS, IN ADDITION TO A RISK OF ROCK AND MUD SLIDES
PARTICULARLY FOR HIGHWAY 12 AND 14 IN IDAHO. PONDING OF WATER ON
ROADWAYS COULD ALSO BE POSSIBLE FOR RELATIVELY LOW-LYING AREAS AND
SHOULD BE AVOIDED DURING TRAVEL.

THE FLOW RETURNS TO MORE NORTHWESTERLY TUESDAY INTO WEDNESDAY,
WHICH WILL ALLOW SNOW LEVELS TO LOWER ONCE AGAIN, AT LEAST TO
PASS LEVELS. HOWEVER DURING THIS TIME FRAME THE HEAVIEST
PRECIPITATION SHOULD BE ON THE DOWNWARD TREND. FORECAST MODELS
CONTINUE TO SHOW A MUCH COLDER PATTERN SETTING UP AROUND
CHRISTMAS, PARTICULARLY FOR THE WEEKEND FOLLOWING. HOWEVER,
CONFIDENCE IN POSSIBLE SNOW FOR THE CHRISTMAS HOLIDAY REMAINS LOW.
THERE ARE SIGNIFICANT DIFFERENCES BETWEEN FORECAST MODELS IN TERMS
OF PRECIPITATION, SO STAY TUNED!

&&

.AVIATION...LIGHT SNOW SHOWERS AT KGPI AND THROUGHOUT THE AREA WILL
COME TO AN END THIS EVENING. LOW CLOUD DECKS AND TERRAIN
OBSCURATIONS WILL PERSIST ACROSS THE REGION. WINDS REMAIN LIGHT AS
THE NEXT ROUND OF PRECIPITATION BEGINS TO MOVE IN FROM THE WEST
TOMORROW MORNING. KGPI WILL AGAIN BE THE FIRST TO SEE MEASURABLE
LIGHT RAIN BEGINNING AROUND 19/1500Z, AND LATER IN THE DAY FOR
OTHER TAF SITES.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$





000
FXUS65 KMSO 182158
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
258 PM MST THU DEC 18 2014

.DISCUSSION...

SNOW CURRENTLY FALLING IN WESTERN MONTANA WILL BE DECREASING THIS
EVENING AS DRIER AIR MOVES IN. LIGHT ACCUMULATIONS ARE STILL
POSSIBLE FOR COUNTIES ALONG THE DIVIDE.

THE BREAK IN PRECIPITATION WILL BE SHORT-LIVED AS THE NEXT IN A
SERIES OF SYSTEMS MOVES INTO NORTH CENTRAL IDAHO AND WESTERN
MONTANA FRIDAY MORNING. PASSES SUCH AS LOOKOUT, LOLO, LOST TRAIL,
AND MARIAS WILL BE THE MOST AFFECTED, AS THEY ARE EXPECTED TO SEE
2 TO 4 INCHES OF SNOW. TRAVELERS OVER THESE PASSES SHOULD LEAVE
ENOUGH TIME AND PREPARE FOR SLICK/SLUSHY CONDITIONS. THE FLATHEAD,
MISSOULA, AND BITTERROOT VALLEYS SHOULD BE WARM ENOUGH FOR
PRECIPITATION TO MELT AND FALL AS LIGHT RAIN.

A VERY MOIST ATMOSPHERIC RIVER EVENT STILL LOOKS LIKELY BEGINNING
LATE SATURDAY THROUGH EARLY MONDAY ACROSS THE REGION, WITH
HEAVIEST PRECIPITATION AMOUNTS EXPECTED FOR CENTRAL IDAHO, THE BOB
MARSHALL THROUGH THE GLACIER REGION, AND MOUNTAIN PASSES ALONG THE
MONTANA/IDAHO BORDER. THE EVENT WILL BEGIN AS HEAVY WET SNOW WITH
COLDER AIR IN PLACE SATURDAY, BUT WILL LIKELY TRANSITION OVER TO
HEAVY RAIN SUNDAY WITH SNOW LEVELS RISING FROM THE SOUTHWEST TO
THE NORTHEAST TO AROUND 5000-6000 FT. IT IS STILL UNCERTAIN HOW
QUICKLY THE SNOW LEVELS WILL INCREASE, WHICH COULD DRAMATICALLY
CHANGE THE AMOUNT OF SNOW ACCUMULATIONS EXPECTED FOR MOUNTAIN
PASSES. LOLO, LOOKOUT, LOST TRAIL, AND MARIAS PASSES COULD SEE 4
TO 12 INCHES OF WET SNOW. ONCE THE SNOW SWITCHES OVER TO HEAVY
RAIN, THIS COULD RESULT IN VERY SLUSHY AND SLIPPERY TRAVEL FOR
UNCLEARED ROADS, IN ADDITION TO A RISK OF ROCK AND MUD SLIDES
PARTICULARLY FOR HIGHWAY 12 AND 14 IN IDAHO. PONDING OF WATER ON
ROADWAYS COULD ALSO BE POSSIBLE FOR RELATIVELY LOW-LYING AREAS AND
SHOULD BE AVOIDED DURING TRAVEL.

THE FLOW RETURNS TO MORE NORTHWESTERLY TUESDAY INTO WEDNESDAY,
WHICH WILL ALLOW SNOW LEVELS TO LOWER ONCE AGAIN, AT LEAST TO
PASS LEVELS. HOWEVER DURING THIS TIME FRAME THE HEAVIEST
PRECIPITATION SHOULD BE ON THE DOWNWARD TREND. FORECAST MODELS
CONTINUE TO SHOW A MUCH COLDER PATTERN SETTING UP AROUND
CHRISTMAS, PARTICULARLY FOR THE WEEKEND FOLLOWING. HOWEVER,
CONFIDENCE IN POSSIBLE SNOW FOR THE CHRISTMAS HOLIDAY REMAINS LOW.
THERE ARE SIGNIFICANT DIFFERENCES BETWEEN FORECAST MODELS IN TERMS
OF PRECIPITATION, SO STAY TUNED!

&&

.AVIATION...LIGHT SNOW SHOWERS AT KGPI AND THROUGHOUT THE AREA WILL
COME TO AN END THIS EVENING. LOW CLOUD DECKS AND TERRAIN
OBSCURATIONS WILL PERSIST ACROSS THE REGION. WINDS REMAIN LIGHT AS
THE NEXT ROUND OF PRECIPITATION BEGINS TO MOVE IN FROM THE WEST
TOMORROW MORNING. KGPI WILL AGAIN BE THE FIRST TO SEE MEASURABLE
LIGHT RAIN BEGINNING AROUND 19/1500Z, AND LATER IN THE DAY FOR
OTHER TAF SITES.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$





000
FXUS65 KMSO 182158
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
258 PM MST THU DEC 18 2014

.DISCUSSION...

SNOW CURRENTLY FALLING IN WESTERN MONTANA WILL BE DECREASING THIS
EVENING AS DRIER AIR MOVES IN. LIGHT ACCUMULATIONS ARE STILL
POSSIBLE FOR COUNTIES ALONG THE DIVIDE.

THE BREAK IN PRECIPITATION WILL BE SHORT-LIVED AS THE NEXT IN A
SERIES OF SYSTEMS MOVES INTO NORTH CENTRAL IDAHO AND WESTERN
MONTANA FRIDAY MORNING. PASSES SUCH AS LOOKOUT, LOLO, LOST TRAIL,
AND MARIAS WILL BE THE MOST AFFECTED, AS THEY ARE EXPECTED TO SEE
2 TO 4 INCHES OF SNOW. TRAVELERS OVER THESE PASSES SHOULD LEAVE
ENOUGH TIME AND PREPARE FOR SLICK/SLUSHY CONDITIONS. THE FLATHEAD,
MISSOULA, AND BITTERROOT VALLEYS SHOULD BE WARM ENOUGH FOR
PRECIPITATION TO MELT AND FALL AS LIGHT RAIN.

A VERY MOIST ATMOSPHERIC RIVER EVENT STILL LOOKS LIKELY BEGINNING
LATE SATURDAY THROUGH EARLY MONDAY ACROSS THE REGION, WITH
HEAVIEST PRECIPITATION AMOUNTS EXPECTED FOR CENTRAL IDAHO, THE BOB
MARSHALL THROUGH THE GLACIER REGION, AND MOUNTAIN PASSES ALONG THE
MONTANA/IDAHO BORDER. THE EVENT WILL BEGIN AS HEAVY WET SNOW WITH
COLDER AIR IN PLACE SATURDAY, BUT WILL LIKELY TRANSITION OVER TO
HEAVY RAIN SUNDAY WITH SNOW LEVELS RISING FROM THE SOUTHWEST TO
THE NORTHEAST TO AROUND 5000-6000 FT. IT IS STILL UNCERTAIN HOW
QUICKLY THE SNOW LEVELS WILL INCREASE, WHICH COULD DRAMATICALLY
CHANGE THE AMOUNT OF SNOW ACCUMULATIONS EXPECTED FOR MOUNTAIN
PASSES. LOLO, LOOKOUT, LOST TRAIL, AND MARIAS PASSES COULD SEE 4
TO 12 INCHES OF WET SNOW. ONCE THE SNOW SWITCHES OVER TO HEAVY
RAIN, THIS COULD RESULT IN VERY SLUSHY AND SLIPPERY TRAVEL FOR
UNCLEARED ROADS, IN ADDITION TO A RISK OF ROCK AND MUD SLIDES
PARTICULARLY FOR HIGHWAY 12 AND 14 IN IDAHO. PONDING OF WATER ON
ROADWAYS COULD ALSO BE POSSIBLE FOR RELATIVELY LOW-LYING AREAS AND
SHOULD BE AVOIDED DURING TRAVEL.

THE FLOW RETURNS TO MORE NORTHWESTERLY TUESDAY INTO WEDNESDAY,
WHICH WILL ALLOW SNOW LEVELS TO LOWER ONCE AGAIN, AT LEAST TO
PASS LEVELS. HOWEVER DURING THIS TIME FRAME THE HEAVIEST
PRECIPITATION SHOULD BE ON THE DOWNWARD TREND. FORECAST MODELS
CONTINUE TO SHOW A MUCH COLDER PATTERN SETTING UP AROUND
CHRISTMAS, PARTICULARLY FOR THE WEEKEND FOLLOWING. HOWEVER,
CONFIDENCE IN POSSIBLE SNOW FOR THE CHRISTMAS HOLIDAY REMAINS LOW.
THERE ARE SIGNIFICANT DIFFERENCES BETWEEN FORECAST MODELS IN TERMS
OF PRECIPITATION, SO STAY TUNED!

&&

.AVIATION...LIGHT SNOW SHOWERS AT KGPI AND THROUGHOUT THE AREA WILL
COME TO AN END THIS EVENING. LOW CLOUD DECKS AND TERRAIN
OBSCURATIONS WILL PERSIST ACROSS THE REGION. WINDS REMAIN LIGHT AS
THE NEXT ROUND OF PRECIPITATION BEGINS TO MOVE IN FROM THE WEST
TOMORROW MORNING. KGPI WILL AGAIN BE THE FIRST TO SEE MEASURABLE
LIGHT RAIN BEGINNING AROUND 19/1500Z, AND LATER IN THE DAY FOR
OTHER TAF SITES.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$




000
FXUS65 KMSO 181101
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
400 AM MST THU DEC 18 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...

A very light snow and rain mixture will be present across the
Northern Rockies, particularly northwest Montana and portions of
north central Idaho through today. Precipitation is not
anticipated to be very long-lasting, arriving in waves and lasting
less than an hour per occurrence, however isolated travel impacts
due to recent thin cover of snowfall are possible across much of
northwest Montana. As temperatures warm a bit during the daytime,
the impact of precipitation to the public will lessen
dramatically, with the exception of mountain passes such as
Lookout Pass.

A slightly more potent weather system will move over the Northern
Rockies from the Pacific Ocean Friday evening through Saturday,
bringing several inches snow to mountain pass elevations and at
least a dusting of snow to middle and high elevation valleys.
Snowfall on area roadways, particularly over mountain passes, may
accumulate and create hazardous driving conditions overnight
Friday through midday Saturday. Otherwise, this first weekend
system appears to go through a similar fate of recent systems over
the Northern Rockies, slowly dissipating on a eastward trajectory.
Precipitation and cloud cover will inhibit much warming on
Saturday, however the airmass of this weather system will not be
strikingly different from the airmass currently in-place.

The models are still consistent with the atmospheric river moving
into the Northern Rockies Saturday night through Monday. The
question still remains on how quickly will snow levels rise during
this event. At the onset of precipitation snow levels will be low
enough to cause significant snow on area mountain passes,
especially Lookout pass and Lolo pass by Sunday morning. Then the
precipitation will change over to rain for even the mountain
passes on Sunday with the exception being Lost Trail. Lost Trail
has the potential to see up to a foot of wet and heavy snow during
through out this system. Idaho and Clearwater counties could
receive widespread amounts 1.5 to 2 inches of rain Saturday night
into Monday. This rain could cause a risk of rock and mud slides
particular for Highway 12 and 14.

The upper level flow will transition to a northwesterly trajectory
which will steadily lower snow levels across the region. A few
weak disturbances will move through the area causing period of
widespread snow showers. Again the models are showing a cold
trough of low pressure digging over the region by Christmas.
Certainty is still fairly low on the extent of the impacts from
this system as models diverge on the strength and timing of this
trough.

&&

.AVIATION...Intermittent light snow and rain mix will be present
across portions of northwest Montana and north central Idaho
throughout today. At KGPI, ceiling and visibility will vary a
great deal between bouts of very light precipitation. Terrain will
be obscured for much of the next 24 hours across northwest
Montana, while occasional obscurations will exist elsewhere.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$






000
FXUS65 KMSO 181101
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
400 AM MST THU DEC 18 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...

A very light snow and rain mixture will be present across the
Northern Rockies, particularly northwest Montana and portions of
north central Idaho through today. Precipitation is not
anticipated to be very long-lasting, arriving in waves and lasting
less than an hour per occurrence, however isolated travel impacts
due to recent thin cover of snowfall are possible across much of
northwest Montana. As temperatures warm a bit during the daytime,
the impact of precipitation to the public will lessen
dramatically, with the exception of mountain passes such as
Lookout Pass.

A slightly more potent weather system will move over the Northern
Rockies from the Pacific Ocean Friday evening through Saturday,
bringing several inches snow to mountain pass elevations and at
least a dusting of snow to middle and high elevation valleys.
Snowfall on area roadways, particularly over mountain passes, may
accumulate and create hazardous driving conditions overnight
Friday through midday Saturday. Otherwise, this first weekend
system appears to go through a similar fate of recent systems over
the Northern Rockies, slowly dissipating on a eastward trajectory.
Precipitation and cloud cover will inhibit much warming on
Saturday, however the airmass of this weather system will not be
strikingly different from the airmass currently in-place.

The models are still consistent with the atmospheric river moving
into the Northern Rockies Saturday night through Monday. The
question still remains on how quickly will snow levels rise during
this event. At the onset of precipitation snow levels will be low
enough to cause significant snow on area mountain passes,
especially Lookout pass and Lolo pass by Sunday morning. Then the
precipitation will change over to rain for even the mountain
passes on Sunday with the exception being Lost Trail. Lost Trail
has the potential to see up to a foot of wet and heavy snow during
through out this system. Idaho and Clearwater counties could
receive widespread amounts 1.5 to 2 inches of rain Saturday night
into Monday. This rain could cause a risk of rock and mud slides
particular for Highway 12 and 14.

The upper level flow will transition to a northwesterly trajectory
which will steadily lower snow levels across the region. A few
weak disturbances will move through the area causing period of
widespread snow showers. Again the models are showing a cold
trough of low pressure digging over the region by Christmas.
Certainty is still fairly low on the extent of the impacts from
this system as models diverge on the strength and timing of this
trough.

&&

.AVIATION...Intermittent light snow and rain mix will be present
across portions of northwest Montana and north central Idaho
throughout today. At KGPI, ceiling and visibility will vary a
great deal between bouts of very light precipitation. Terrain will
be obscured for much of the next 24 hours across northwest
Montana, while occasional obscurations will exist elsewhere.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$





000
FXUS65 KMSO 181101
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
400 AM MST THU DEC 18 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...

A very light snow and rain mixture will be present across the
Northern Rockies, particularly northwest Montana and portions of
north central Idaho through today. Precipitation is not
anticipated to be very long-lasting, arriving in waves and lasting
less than an hour per occurrence, however isolated travel impacts
due to recent thin cover of snowfall are possible across much of
northwest Montana. As temperatures warm a bit during the daytime,
the impact of precipitation to the public will lessen
dramatically, with the exception of mountain passes such as
Lookout Pass.

A slightly more potent weather system will move over the Northern
Rockies from the Pacific Ocean Friday evening through Saturday,
bringing several inches snow to mountain pass elevations and at
least a dusting of snow to middle and high elevation valleys.
Snowfall on area roadways, particularly over mountain passes, may
accumulate and create hazardous driving conditions overnight
Friday through midday Saturday. Otherwise, this first weekend
system appears to go through a similar fate of recent systems over
the Northern Rockies, slowly dissipating on a eastward trajectory.
Precipitation and cloud cover will inhibit much warming on
Saturday, however the airmass of this weather system will not be
strikingly different from the airmass currently in-place.

The models are still consistent with the atmospheric river moving
into the Northern Rockies Saturday night through Monday. The
question still remains on how quickly will snow levels rise during
this event. At the onset of precipitation snow levels will be low
enough to cause significant snow on area mountain passes,
especially Lookout pass and Lolo pass by Sunday morning. Then the
precipitation will change over to rain for even the mountain
passes on Sunday with the exception being Lost Trail. Lost Trail
has the potential to see up to a foot of wet and heavy snow during
through out this system. Idaho and Clearwater counties could
receive widespread amounts 1.5 to 2 inches of rain Saturday night
into Monday. This rain could cause a risk of rock and mud slides
particular for Highway 12 and 14.

The upper level flow will transition to a northwesterly trajectory
which will steadily lower snow levels across the region. A few
weak disturbances will move through the area causing period of
widespread snow showers. Again the models are showing a cold
trough of low pressure digging over the region by Christmas.
Certainty is still fairly low on the extent of the impacts from
this system as models diverge on the strength and timing of this
trough.

&&

.AVIATION...Intermittent light snow and rain mix will be present
across portions of northwest Montana and north central Idaho
throughout today. At KGPI, ceiling and visibility will vary a
great deal between bouts of very light precipitation. Terrain will
be obscured for much of the next 24 hours across northwest
Montana, while occasional obscurations will exist elsewhere.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$






000
FXUS65 KMSO 181101
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
400 AM MST THU DEC 18 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...

A very light snow and rain mixture will be present across the
Northern Rockies, particularly northwest Montana and portions of
north central Idaho through today. Precipitation is not
anticipated to be very long-lasting, arriving in waves and lasting
less than an hour per occurrence, however isolated travel impacts
due to recent thin cover of snowfall are possible across much of
northwest Montana. As temperatures warm a bit during the daytime,
the impact of precipitation to the public will lessen
dramatically, with the exception of mountain passes such as
Lookout Pass.

A slightly more potent weather system will move over the Northern
Rockies from the Pacific Ocean Friday evening through Saturday,
bringing several inches snow to mountain pass elevations and at
least a dusting of snow to middle and high elevation valleys.
Snowfall on area roadways, particularly over mountain passes, may
accumulate and create hazardous driving conditions overnight
Friday through midday Saturday. Otherwise, this first weekend
system appears to go through a similar fate of recent systems over
the Northern Rockies, slowly dissipating on a eastward trajectory.
Precipitation and cloud cover will inhibit much warming on
Saturday, however the airmass of this weather system will not be
strikingly different from the airmass currently in-place.

The models are still consistent with the atmospheric river moving
into the Northern Rockies Saturday night through Monday. The
question still remains on how quickly will snow levels rise during
this event. At the onset of precipitation snow levels will be low
enough to cause significant snow on area mountain passes,
especially Lookout pass and Lolo pass by Sunday morning. Then the
precipitation will change over to rain for even the mountain
passes on Sunday with the exception being Lost Trail. Lost Trail
has the potential to see up to a foot of wet and heavy snow during
through out this system. Idaho and Clearwater counties could
receive widespread amounts 1.5 to 2 inches of rain Saturday night
into Monday. This rain could cause a risk of rock and mud slides
particular for Highway 12 and 14.

The upper level flow will transition to a northwesterly trajectory
which will steadily lower snow levels across the region. A few
weak disturbances will move through the area causing period of
widespread snow showers. Again the models are showing a cold
trough of low pressure digging over the region by Christmas.
Certainty is still fairly low on the extent of the impacts from
this system as models diverge on the strength and timing of this
trough.

&&

.AVIATION...Intermittent light snow and rain mix will be present
across portions of northwest Montana and north central Idaho
throughout today. At KGPI, ceiling and visibility will vary a
great deal between bouts of very light precipitation. Terrain will
be obscured for much of the next 24 hours across northwest
Montana, while occasional obscurations will exist elsewhere.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$





000
FXUS65 KMSO 172131
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
231 PM MST WED DEC 17 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...For the end of the work week, two weakening weather
systems will move through north central Idaho and western
Montana. The first shortwave will impact far northwest Montana
late tonight into Thursday. Due to weak forcing, snowfall totals
are expected to be under an inch for all but the highest terrain.

A more substantial system moves in Friday morning bringing
accumulating snowfall to the passes between Montana and Idaho,
especially Lookout and Lolo passes, each of which could see 2 to
3 inches. As it`s predecessor, this system loses steam as it
crosses western Montana, and valley locations should expect only
light rain.

Saturday night through Monday morning an atmospheric river will
impact central Idaho and western Montana. Snow levels will start
out around 3000 ft Saturday afternoon and rise to around 5000 -
6000 feet by Sunday night. As the forecast stands, this will cause
3 to 7 inches of heavy wet snow by Sunday morning to impact
mountain passes. Lookout and Lolo passes will be most affected,
with snow on the lower end of the range affecting Marias and Lost
Trail passes. While forecast confidence is high with the timing
and high moisture for this system, it is not as good with the snow
levels, and as a result confidence is below average for the snow
amounts at the passes.

During the day Sunday, snow levels will rise causing snow to turn
to rain in many areas, generally causing uncleared roads to be a
wet slushy mess. By Monday, 2 to 3 inches of rain is expected in
the Clearwater Mountains and Bitterroot mountains of central
Idaho. The excessive rain combined with temperatures around
freezing will make falling rocks and debris on roads a risk,
especially along highway 12 in central Idaho.

The rest of the week looks showery with the next significant
disturbance coming in around Christmas. This will be a much cooler
system that will likely cause some snow and travel difficulties.
There is a lot of uncertainty associated with the strength and
timing of this system, but models across the board have been
consistent in bringing something through around Christmas. So the
odds of a white Christmas are improving!

&&

.AVIATION...Satellite imagery shows high and mid-level clouds
moving into the area, and this trend is expected to continue
through the rest of the evening. Currently northwest Montana has
the best chance of seeing precipitation in the next 24 hours.
Models depict intermittent snow starting at KGPI around 18/1200Z,however,
accumulations are below an inch.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$





000
FXUS65 KMSO 172131
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
231 PM MST WED DEC 17 2014

...SNOW TURNING TO HEAVY RAIN THIS WEEKEND IN CENTRAL IDAHO...

.DISCUSSION...For the end of the work week, two weakening weather
systems will move through north central Idaho and western
Montana. The first shortwave will impact far northwest Montana
late tonight into Thursday. Due to weak forcing, snowfall totals
are expected to be under an inch for all but the highest terrain.

A more substantial system moves in Friday morning bringing
accumulating snowfall to the passes between Montana and Idaho,
especially Lookout and Lolo passes, each of which could see 2 to
3 inches. As it`s predecessor, this system loses steam as it
crosses western Montana, and valley locations should expect only
light rain.

Saturday night through Monday morning an atmospheric river will
impact central Idaho and western Montana. Snow levels will start
out around 3000 ft Saturday afternoon and rise to around 5000 -
6000 feet by Sunday night. As the forecast stands, this will cause
3 to 7 inches of heavy wet snow by Sunday morning to impact
mountain passes. Lookout and Lolo passes will be most affected,
with snow on the lower end of the range affecting Marias and Lost
Trail passes. While forecast confidence is high with the timing
and high moisture for this system, it is not as good with the snow
levels, and as a result confidence is below average for the snow
amounts at the passes.

During the day Sunday, snow levels will rise causing snow to turn
to rain in many areas, generally causing uncleared roads to be a
wet slushy mess. By Monday, 2 to 3 inches of rain is expected in
the Clearwater Mountains and Bitterroot mountains of central
Idaho. The excessive rain combined with temperatures around
freezing will make falling rocks and debris on roads a risk,
especially along highway 12 in central Idaho.

The rest of the week looks showery with the next significant
disturbance coming in around Christmas. This will be a much cooler
system that will likely cause some snow and travel difficulties.
There is a lot of uncertainty associated with the strength and
timing of this system, but models across the board have been
consistent in bringing something through around Christmas. So the
odds of a white Christmas are improving!

&&

.AVIATION...Satellite imagery shows high and mid-level clouds
moving into the area, and this trend is expected to continue
through the rest of the evening. Currently northwest Montana has
the best chance of seeing precipitation in the next 24 hours.
Models depict intermittent snow starting at KGPI around 18/1200Z,however,
accumulations are below an inch.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$






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