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Mountain Weather Forecast

Issued: 2:09 PM Wednesday, December 17, 2014
by Garth Ferber

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 Wednesday & Thursday

A weak splitting upper trough will move to the US west coast on Wednesday and Wednesday night. Winds will be light with light showers and a bit of a drop in the snow levels by Thursday morning.

A short break between systems should be seen Thursday.

A moderate front will start to reach the Olympics Thursday afternoon and cross the Northwest on Thursday night. This will cause moderately increasing winds and mostly moderate precipitation Thursday night. A slight rise in snow levels in advance of the system should be seen Thursday afternoon and evening.

 

Weather forecast for Wednesday & Thursday

Olympics, Washington Cascades near and west of the crest, Mt Hood
Date Weather
Wednesday Morning - Wednesday Night

Light rain or snow showers.

Thursday

Mostly cloudy. Light rain or snow reaching the Olympics in the afternoon.

East slopes of the Washington Cascades
Date Weather
Wednesday Morning - Wednesday Night

Light rain or snow showers at higher elevations.

Thursday

Partly or mostly cloudy.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Wednesday Morning - Wednesday Night Snow Level 4000' 4000' 2000' 4000' 4000' *
Thursday Morning Snow Level 3000' 3000' 1500' 3000' 3500' *
Olympics
Date Elevation
Wednesday Morning - Wednesday Night Snow Level
4000'
Easterly Flow*
Thursday Morning Snow Level
3000'
Easterly Flow*
Thursday Afternoon - Thursday Night Snow Level
5000'
Easterly Flow*
Northwest Cascades
Date Elevation
Wednesday Morning - Wednesday Night Snow Level
4000'
Easterly Flow*
Thursday Morning Snow Level
3000'
Easterly Flow*
Thursday Afternoon - Thursday Night Snow Level
4000'
Easterly Flow*
Northeast Cascades
Date Elevation
Wednesday Morning - Wednesday Night Snow Level
2000'
Easterly Flow*
Thursday Morning Snow Level
1500'
Easterly Flow*
Thursday Afternoon - Thursday Night Snow Level
2000'
Easterly Flow*
Central Cascades
Date Elevation
Wednesday Morning - Wednesday Night Snow Level
4000'
Easterly Flow*
Thursday Morning Snow Level
3000'
Easterly Flow*
Thursday Afternoon - Thursday Night Snow Level
4500'
Easterly Flow*
South Cascades
Date Elevation
Wednesday Morning - Wednesday Night Snow Level
4000'
Easterly Flow*
Thursday Morning Snow Level
3500'
Easterly Flow*
Thursday Afternoon - Thursday Night Snow Level
5000'
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 Thu Fri
Hurricane Ridge .25 .50
Mt Baker Ski Area .25 .75
Washington Pass lt .25 .25 - .50
Stevens Pass .25 .25 - .50
Snoqualmie Pass .25 .50
Mission Ridge lt .10 .25
Crystal Mt lt .25 .25 - .50
Paradise .25 .75
White Pass .25 .50
Mt Hood Meadows .25 .75

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

Date Direction - Speed
Wednesday Morning - Wednesday Night E 10 - 20
Thursday Morning E 0 - 10

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
Wednesday Morning SE 5 - 15 SE 5 - 15 SE 5 - 15 SE 10 - 20
Wednesday Afternoon SW 10 - 20 SE 5 - 15 SE 5 - 15 SE 5 - 15
Thursday Morning SW 10 - 20 SW 5 - 15 SW 5 - 15 SW 5 - 15
Thursday Afternoon SSE 25 - 35 SSE 15 - 25 SSE 15 - 25 SSE 10 - 20
Olympics
Date Elevation
Wednesday Morning SE 5 - 15
Wednesday Afternoon SW 10 - 20
Thursday Morning SW 10 - 20
Thursday Afternoon SSE 25 - 35
Thursday Evening SW 25 - 35
Northwest Cascades
Date Elevation
Wednesday Morning SE 5 - 15
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 15 - 25
Thursday Evening SSE 15 - 25
Central Cascades
Date Elevation
Wednesday Morning SE 5 - 15
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 15 - 25
Thursday Evening SSE 20 - 30
South Cascades
Date Elevation
Wednesday Morning SE 10 - 20
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 10 - 20
Thursday Evening SSE 15 - 25
Olympics
Date Direction - Speed
Wednesday Morning SE 5 - 15
Wednesday Afternoon SW 10 - 20
Thursday Morning SW 10 - 20
Thursday Afternoon SSE 25 - 35
Thursday Evening SW 25 - 35
Northwest Cascades
Date Direction - Speed
Wednesday Morning SE 5 - 15
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 15 - 25
Thursday Evening SSE 15 - 25
Central Cascades
Date Direction - Speed
Wednesday Morning SE 5 - 15
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 15 - 25
Thursday Evening SSE 20 - 30
South Cascades
Date Direction - Speed
Wednesday Morning SE 10 - 20
Wednesday Afternoon SE 5 - 15
Thursday Morning SW 5 - 15
Thursday Afternoon SSE 10 - 20
Thursday Evening SSE 15 - 25

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
Wednesday Morning S 10 - 20 S 20 - 30 S 10 - 20 S 15 - 25
Wednesday Afternoon SW 10 - 20 SW 20 - 30 SW 10 - 20 SW 10 - 20
Thursday Morning SW 10 - 20 SW 15 - 25 SW 10 - 20 SW 10 - 20
Thursday Afternoon SW 20 - 30 SW 25 - 35 SW 15 - 25 SW 25 - 35
Northwest Cascades
Date Direction - Speed
Wednesday Morning S 10 - 20
Wednesday Afternoon SW 10 - 20
Thursday Morning SW 10 - 20
Thursday Afternoon SW 20 - 30
Thursday Evening SW 40 - 50
Northeast Cascades
Date Direction - Speed
Wednesday Morning S 20 - 30
Wednesday Afternoon SW 20 - 30
Thursday Morning SW 15 - 25
Thursday Afternoon SW 25 - 35
Thursday Evening SW 50 - 60
Central Cascades
Date Direction - Speed
Wednesday Morning S 10 - 20
Wednesday Afternoon SW 10 - 20
Thursday Morning SW 10 - 20
Thursday Afternoon SW 15 - 25
Thursday Evening SW 30 - 40
South Cascades
Date Direction - Speed
Wednesday Morning S 15 - 25
Wednesday Afternoon SW 10 - 20
Thursday Morning SW 10 - 20
Thursday Afternoon SW 25 - 35
Thursday Evening SW 45 - 55

Extended Weather Synopsis for Friday through Sunday

An upper trough should follow the front on Friday morning. A very weak ridge (blink and you might miss it) should pass over the Northwest Friday afternoon. This should all lead to generally decreasing showers on Friday at slightly lower snow levels.

It should be quite a weekend in the Olympics and Cascades. A 160 knot jet over the northeast Pacific Ocean will become pointed at the Northwest Saturday and Sunday. Strong flow and heavy moisture will move over a broad flat ridge and across the Northwest Saturday and Sunday. Snow levels will rise quite a bit though maybe not quite as high as earlier indicated. Overall it looks like a lot of wet snow at higher elevations and a lot of rain at the lower elevations over the weekend.

Extended Weather Forecast for Friday through Sunday

Olympics, Washington Cascades, Mt Hood
Date Weather
Friday

Decreasing light to moderate rain or snow showers heaviest near and west of the crest.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Friday Snow Level 3000' - 4000' 3000' - 4000' 1500' - 2500' 3000' - 4000' 3500' - 4500'
Saturday Snow Level 4500' - 6500' 4000' - 6000' 1500' - 2500' 4500' - 6500' 5500' - 7500'
Olympics
Date Elevation
Friday Snow Level
3000' - 4000'
Saturday Snow Level
4500' - 6500'
Sunday Snow Level
3500' - 4500'
Northwest Cascades
Date Elevation
Friday Snow Level
3000' - 4000'
Saturday Snow Level
4000' - 6000'
Sunday Snow Level
3500' - 4500'
Northeast Cascades
Date Elevation
Friday Snow Level
1500' - 2500'
Saturday Snow Level
1500' - 2500'
Sunday Snow Level
4000' - 5000'
Central Cascades
Date Elevation
Friday Snow Level
3000' - 4000'
Saturday Snow Level
4500' - 6500'
Sunday Snow Level
3500' - 4500'
South Cascades
Date Elevation
Friday Snow Level
3500' - 4500'
Saturday Snow Level
5500' - 7500'
Sunday Snow Level
5000' - 7000'

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.