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Mountain Weather Forecast

Issued: 2:04 PM PST Saturday, January 21, 2017
by Kenny Kramer

The NWAC program is administered by the USDA-Forest Service and operates from the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a wide variety of federal, state and private cooperators.

Weather synopsis for Saturday & Sunday

An upper level and deepening surface low pressure center is well off the Oregon coast Saturday afternoon. Over the next 36 hours this feature will move slowly north to be off the Washington coast by Sunday midday before gradually retreating to the southeast. The majority of the associated precipitation will move inland well south of our forecast region over the next few days. In the Pacific Northwest, two distinct short wave disturbances should rotate from south to north through Sunday, causing periods of generally light snow showers.

The first band of showers was slower to move into the forecast region, but arrived over the Mt Hood area late Saturday morning and is nearing Mt Rainier early Saturday afternoon. This band will continue to spread light to briefly moderate showers across the region through the afternoon reaching the north areas Saturday night. A brief decrease in showers is expected later Saturday night between the two short wave disturbances.  

A deepening surface low pressure system is expected to develop well offshore of Washington by early Sunday. The main effect will be to strengthen the ESE winds over the forecast area, especially through the Cascade Passes and near the central WA Cascade crest during the early morning hours Sunday, before diminishing by Sunday afternoon.

The next band of showers should follow a similar path with increasing showers over the Mt Hood area early Sunday, spreading northward through the day Sunday. The SE low level flow should help the east slopes of the Cascades with enhanced precipitation. 

The upper and surface low circulations begin to walk and drift south offshore Sunday night as high pressure begins building offshore. This should usher in an extended dry period in the PNW.

Weather forecast for Saturday & Sunday

Olympics
Date Weather
Saturday

Increasing light snow showers late afternoon and evening.

Saturday Night

Light snow showers ending.

Sunday Morning - Sunday Evening

Increasing light snow showers.

Washington Cascades near and west of the crest including Stevens, Snoqualmie, and White Passes
Date Weather
Saturday Afternoon - Evening

Increasing light to moderate snow showers, mainly on the volcanoes in the south Cascades Saturday afternoon, spreading northward through the evening, Lighter showers in the Cascade Passes.

Saturday Night

Light snow showers decreasing.

Sunday

Increasing light to moderate snow showers, mainly on the volcanoes in the south Cascades Sunday morning spreading northward through the afternoon and evening, Lighter showers in the Cascade Passes

East slopes of the Washington Cascades
Date Weather
Saturday Afternoon - Saturday Evening

Increasing light snow showers heaviest south part.

Saturday Night

Light snow showers ending.

Sunday

Increasing light snow showers heaviest south part.

Mt. Hood Area
Date Weather
Saturday Afternoon

Light to moderate snow showers.

Saturday Night

Light snow showers ending.

Sunday

Increasing light to moderate snow showers Sunday morning, diminishing Sunday afternoon.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Afternoon Snow Level 3000' 3000' 2000' 2500' 3000' *
Saturday Night - Sunday Snow Level 3000' 2500' 1000' 2500' 2500' *
Olympics
Date Elevation
Saturday Afternoon Snow Level
3000'
Easterly Flow*
Saturday Night - Sunday Snow Level
3000'
Easterly Flow*
Sunday Night Snow Level
2500'
Easterly Flow*
Northwest Cascades
Date Elevation
Saturday Afternoon Snow Level
3000'
Easterly Flow*
Saturday Night - Sunday Snow Level
2500'
Easterly Flow*
Sunday Night Snow Level
1500'
Easterly Flow*
Northeast Cascades
Date Elevation
Saturday Afternoon Snow Level
2000'
Easterly Flow*
Saturday Night - Sunday Snow Level
1000'
Easterly Flow*
Sunday Night Snow Level
1000'
Easterly Flow*
Central Cascades
Date Elevation
Saturday Afternoon Snow Level
2500'
Easterly Flow*
Saturday Night - Sunday Snow Level
2500'
Easterly Flow*
Sunday Night Snow Level
1500'
Easterly Flow*
South Cascades
Date Elevation
Saturday Afternoon Snow Level
3000'
Easterly Flow*
Saturday Night - Sunday Snow Level
2500'
Easterly Flow*
Sunday Night Snow Level
2000'
Easterly Flow*

Cascade Snow / Freezing Levels noted above refer to the north (approximately Mt Baker and Washington Pass), central (approximately Stevens to White Pass) and south (near Mt Hood). Freezing Level is when no precipitation is forecast.
* Note that surface snow levels are common near the passes during easterly pass flow and may result in multiple snow / freezing levels.

24 Hour Quantitative Precipitation ending at 4 am

Location Sun Mon
Hurricane Ridge lt .25 lt .25
Mt Baker Ski Area lt .25 lt .25
Washington Pass lt .25 lt .25
Stevens Pass lt .25 lt .25
Snoqualmie Pass .25 lt .25
Mission Ridge .25 .25
Crystal Mt .25 .25
Paradise .50 .25 - .50
White Pass .25 .25
Mt Hood Meadows .50 .25 - .50

Winds in Miles per Hour (MPH) "Cascade Pass Level Winds"

Date Direction - Speed
Saturday Afternoon - Saturday Night E 10 - 15
Sunday Morning - Sunday Mid-day E 20 - 30

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. Winds near the passes tend to be highly channeled by the topography and normally blow either easterly or westerly depending on the surface pressure gradients that drive such winds.

Free Winds at 5000' (in Miles per Hour (MPH))

Date Olympics Northwest Cascades Central Cascades South Cascades
Saturday Afternoon SE 10 - 20 SE 5 - 15 SE 5 - 15 SE 10 - 20
Saturday Night - Sunday Morning SE 20 - 30 SE 15 - 25 SE 20 - 30 SE 20 - 30
Olympics
Date Elevation
Saturday Afternoon SE 10 - 20
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SE 5 - 15
Northwest Cascades
Date Elevation
Saturday Afternoon SE 5 - 15
Saturday Night - Sunday Morning SE 15 - 25
Sunday Afternoon - Sunday Night SE 5 - 15
Central Cascades
Date Elevation
Saturday Afternoon SE 5 - 15
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SE 5 - 15
South Cascades
Date Elevation
Saturday Afternoon SE 10 - 20
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SSW 5 - 15
Olympics
Date Direction - Speed
Saturday Afternoon SE 10 - 20
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SE 5 - 15
Northwest Cascades
Date Direction - Speed
Saturday Afternoon SE 5 - 15
Saturday Night - Sunday Morning SE 15 - 25
Sunday Afternoon - Sunday Night SE 5 - 15
Central Cascades
Date Direction - Speed
Saturday Afternoon SE 5 - 15
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SE 5 - 15
South Cascades
Date Direction - Speed
Saturday Afternoon SE 10 - 20
Saturday Night - Sunday Morning SE 20 - 30
Sunday Afternoon - Sunday Night SSW 5 - 15

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. These winds and the 9000 ft winds below also indicate "free" winds, or those winds in the atmosphere not influenced by terrain. Topographical effects may produce greater or lower wind speeds in certain locations as well as significant variations in direction.

Free Winds at 9000' (in Miles per Hour (MPH))

Date Northwest Cascades Northeast Cascades Central Cascades South Cascades
Saturday Afternoon SSW 20 - 30 SSW 15 - 25 SSW 20 - 30 SSW 35 - 50
Saturday Night - Sunday Morning SSE 20 - 30 SSE 20 - 30 S 25 - 40 S 40 - 55
Northwest Cascades
Date Direction - Speed
Saturday Afternoon SSW 20 - 30
Saturday Night - Sunday Morning SSE 20 - 30
Sunday Afternoon - Sunday Night SSW 5 - 15
Northeast Cascades
Date Direction - Speed
Saturday Afternoon SSW 15 - 25
Saturday Night - Sunday Morning SSE 20 - 30
Sunday Afternoon - Sunday Night SSW 5 - 15
Central Cascades
Date Direction - Speed
Saturday Afternoon SSW 20 - 30
Saturday Night - Sunday Morning S 25 - 40
Sunday Afternoon - Sunday Night SSW 10 - 20
South Cascades
Date Direction - Speed
Saturday Afternoon SSW 35 - 50
Saturday Night - Sunday Morning S 40 - 55
Sunday Afternoon - Sunday Night SSW 10 - 20

Extended Weather Synopsis for Monday through Wednesday

An upper level low should continue to move south off the California coast early Monday. There may be one last weak band of showers rotating northward to about the Mt Hood area early Monday morning before the upper low moves south away from the region.

An upper ridge should build over the northeast Pacific Ocean by late Monday through Wednesday. This should usher in a period of cool and dry northerly flow aloft and mostly fair weather with light winds Monday through Wednesday. Freezing levels should respond gradually at the nearing upper ridge, but remain seasonal. 

Extended Weather Forecast for Monday through Wednesday

Olympics, Washington Cascades, Mt Hood
Date Weather
Monday Morning - Monday Mid-day

Chance of light snow showers Mt Hood area. Otherwise becoming partly cloudy elsewhere.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Monday Morning Snow Level 1000' - 3000' 1000' - 3000' 0' - 2000' 1000' - 3000' 1000' - 3000' *
Olympics
Date Elevation
Monday Morning Snow Level
1000' - 3000'
Easterly Flow*
Monday Afternoon - Wednesday Freezing Level
3500' - 4500'
Northwest Cascades
Date Elevation
Monday Morning Snow Level
1000' - 3000'
Easterly Flow*
Monday Afternoon - Wednesday Freezing Level
3000' - 4000'
Northeast Cascades
Date Elevation
Monday Morning Snow Level
0' - 2000'
Easterly Flow*
Monday Afternoon - Wednesday Freezing Level
2000' - 3000'
Central Cascades
Date Elevation
Monday Morning Snow Level
1000' - 3000'
Easterly Flow*
Monday Afternoon - Wednesday Freezing Level
2500' - 4000'
South Cascades
Date Elevation
Monday Morning Snow Level
1000' - 3000'
Easterly Flow*
Monday Afternoon - Wednesday Freezing Level
3000' - 4000'

Freezing Level is when no precipitation is forecast.
* Note that surface snow levels are common near the passes during easterly pass flow and may result in multiple snow / freezing levels.