MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES 
AND MT HOOD AREA
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
145 PM PST THU FEB 05 2009

NWAC Program administered by:
USDA-Forest Service
with cooperative funding and support from:
Washington State Department of Transportation
National Weather Service
National Park Service
Washington State Parks and Recreation Commission
Pacific Northwest Ski Area Association
Friends of the Avalanche Center
and other private organizations.

This forecast is prepared primarily for federal, state and 
private snow safety programs in Washington and Northern 
Oregon.

WAZ513-518-519-019-042-501-502-ORZ011-061700-

&&

WEATHER SYNOPSIS FOR THURSDAY AND FRIDAY
Blocking ridge, block no more,
Let westerly flow through the door.
Unfortunately this is wishful thinking,
As troughs to our south are sinking.

Splits and closed California lows,
Are currently the biggest woes.
The Southwest should become quite wet,
With floods and mud slides a reasoned bet. 

Although weak moisture is moving north,
Mainly light snow will issue forth.
But dont give up, its winter still,
And cooling temps will produce a chill.

The south and Hood should be the winners,
Perhaps they are lacking sinners.
But even a little is more than none,
And alot of littles can still be fun.

The primary circulation along the west coast early Thursday 
afternoon continues to center around a moderate closed upper 
low about just off the central California coast. The next 
incoming upper trough in the central Gulf of Alaska is 
expected to drop slowly southward Thursday afternoon, 
gradually merging with and broadening the California upper 
low later Thursday and Friday. This should keep the main 
frontal activity and heaviest associated precipitation well 
to the south of our area for the next several days. However, 
as the previously closed low opens and translates slowly 
eastward, increasing moisture from this low should gradually 
lift northward Thursday afternoon and night. Although 
precipitation amounts should decrease from south to north, 
increasing light rain or snow should reach the Mt Hood area 
early to mid afternoon, the south-central WA Cascades later 
Thursday afternoon and evening, and the northern WA Cascades 
Thursday night, with heaviest amounts expected in the south. 
The generally light precipitation in the north and light to 
briefly moderate precipitation in the south should be 
accompanied by slowly lowering freezing levels and a slight 
increase in winds, primarily in the south.

A greatly weakened northern part of the incoming split 
trough should move over the region Friday morning. Combined 
with relatively weak westerly flow at all levels, again 
slightly stronger in the south, this should maintain light 
to occasionally moderate showers at further lowering 
freezing levels. However, gradually drier northerly flow 
preceding weak and briefly building upper ridging offshore 
mid-late Friday should result in decreasing light showers 
Friday afternoon with a slow clearing trend spreading 
southward Friday night.
&&

WEATHER FORECAST FOR THURSDAY AND FRIDAY

*	OLYMPICS-
Thursday afternoon: cooler and cloudy with light rain or 
snow developing late afternoon or early evening
Thursday night: cool with occasional light rain or snow
Friday morning: cooler with light to occasionally 
moderate snow showers decreasing late
Friday afternoon: light snow showers ending with partial 
clearing
Friday night: slow clearing trend

*	WASHINGTON CASCADES NEAR AND WEST OF THE CREST FROM 
SNOQUALMIE PASS NORTHWARD-
Thursday afternoon: cooler and cloudy with light rain or 
snow spreading northward late afternoon and evening
Thursday night: cool with occasional light rain or snow, 
heaviest south
Friday morning: cooler with light to occasionally 
moderate snow showers
Friday afternoon: light snow showers decreasing with 
partial clearing
Friday night: scattered light showers ending with slow 
clearing trend

*	CASCADE PASSES FROM SNOQUALMIE PASS NORTHWARD, INCLUDING 
SNOQUALMIE AND STEVENS PASSES-
Thursday afternoon: cooler and cloudy with light snow 
spreading northward late afternoon and evening
Thursday night: cool with occasional light snow north and 
light snow or mixed rain and snow south
Friday morning: cooler with light to occasionally 
moderate snow showers
Friday afternoon: light snow showers decreasing with 
partial clearing
Friday night: scattered light showers ending with slow 
clearing trend

*	WASHINGTON CASCADES NEAR AND WEST OF THE CREST SOUTH OF 
SNOQUALMIE PASS-
*	CASCADE PASSES SOUTH OF SNOQUALMIE PASS, INCLUDING WHITE 
PASS-
Thursday afternoon: cooler and cloudy with light snow 
developing mid-late afternoon
Thursday night: cool with light to occasionally moderate 
rain or snow
Friday morning: cooler with light to moderate snow 
showers
Friday afternoon: light snow showers decreasing with 
partial clearing
Friday night: scattered light showers ending with slow 
clearing trend spreading southward

*	EAST SLOPES WASHINGTON CASCADES-
Thursday afternoon: cooler and cloudy with occasional 
light snow or rain developing in the south mid-late 
afternoon, spreading slowly northward Thursday evening
Thursday night: cool with occasional light snow north and 
light to occasionally moderate snow or mixed rain and 
snow south
Friday morning: cooler with light to moderate snow 
showers, mainly higher terrain near the crest
Friday afternoon: light snow showers higher terrain 
decreasing with partial clearing
Friday night: scattered light showers ending with slow 
clearing trend spreading southward

*	MT HOOD AREA-
Thursday afternoon: cooler with light rain or snow 
developing mid-afternoon, slowly increasing late 
afternoon and evening
Thursday night: cool with light to moderate snow
Friday morning: cooler with light to moderate snow 
showers
Friday afternoon: light snow showers decreasing with 
partial clearing
Friday night: scattered light showers ending with slow 
clearing trend late

&&

SNOW LEVELS-CASCADE MTNS
6000 ft N, 7000 ft C and S early Thursday afternoon
5500 ft N and S later Thursday afternoon
4000 ft N, 4500 ft S Thursday night
3000 ft N, 4000 ft S Friday morning
2500 ft N, 3500 ft S mid-day
2500 ft N and S Friday afternoon
2000 ft N and S Friday nightexcept snow levels locally 
near the surface Cascade passes and lower terrain east 
slopes Thursday, rising gradually to free air levels 
Thursday night and early Friday 

SNOW LEVELS-OLYMPIC MTNS
5000 ft Thursday afternoon
4000 ft Thursday night
3000 ft Friday morning
2000 ft Friday afternoon
3000 ft Friday night

Cascade Snow/Freezing Levels refer to the northern Washington Cascades 
(N) through Mt Hood area (S).  Central Washington Cascade snow levels 
(typically near Snoqualmie Pass) are normally midway between indicated N 
and S levels.  Note that surface snow/freezing levels are common near 
the passes during easterly pass flow and may result in multiple 
snow/freezing levels. 

&&

24 HOUR FORECAST OF PRECIPITATION IN INCHES OF WATER 
EQUIVALENT ENDING AT 4AM
                    	FRI 	    SAT

*	HURRICANE RIDGE	.25	     LT .25

*	MT BAKER       	LT .25	     .25
*	WASHINGTON PASS	LT .25	     LT .25
*	STEVENS PASS   	LT .25	     LT .25
*	SNOQUALMIE PASS	.25	     LT .25
*	MISSION RIDGE  	LT .25	     LT .25
*	CRYSTAL MTN    	.25	     .25
*	PARADISE       	.25	     .25
*	WHITE PASS     	.25	     .25
*	MT HOOD        	.5	     .5

&&

WINDS IN MILES PER HOUR (MPH)

*	CASCADE PASS LEVEL WINDS
E 5-15 Thursday afternoon
E 0-10 Thursday night
Variable 0-10 late Thursday night or early Friday
W 0-10 mid-late Friday morning
W 5-15 Friday afternoon and night

*	FREE WINDS AT 5000 FT
S 10-15 Cascades, S-SW 10-20 Olympics Thursday afternoon
SW 10-15 N, 10-20 S and Olympics Thursday night
W 10-15 N, 10-20 C and Olympics, 15-30 S Friday morning
W 5-15 N, 10-20 S and N-NW 15-25 Olympics mid-day and 
early afternoon
N 10-15 N and C, N-NW 15-25 S and Olympics later Friday 
afternoon
N 10-20 N and S Friday night

*	FREE WINDS AT 9000 FT
S-SW 10-20 N, 15-25 S Thursday afternoon
SW 10-20 N and C, 20-40 S Thursday night
W 15-25 N and C, 20-40 S Friday morning
W 10-15 N and C, 15-30 S and N 10-20 Olympics mid-day
N 10-20 N and C, W 10-20 S and N 20-40 Olympics Friday 
afternoon
N 15-30 N and Olympics, N-NE 10-20 C and S Friday night

&&

EXTENDED WEATHER SYNOPSIS FOR SATURDAY THROUGH MONDAY
Following a relatively weak upper ridge and surface high 
that should result in briefly clearing skies Saturday 
morning, increasing high clouds and brief warming should 
spread over the region during the afternoon ahead of a 
moderate though slowly splitting offshore upper low and 
associated frontal system. As the first trough and front 
move over the region later Saturday night and Sunday 
morning, increasing winds and lowering freezing levels 
should accompany increasing light to briefly moderate rain 
or snow. However, the second and stronger trough and 
associated surface disturbance are expected to quickly drop 
southward along the coast Sunday afternoon through Monday 
morning, with a much weaker northern extension of the 
stronger southern trough expected to move over the area mid-
late Monday. This should produce decreasing light showers 
Sunday afternoon, with some light showers or occasional 
light rain or snow slowly spreading northward on Monday at 
continued low freezing levels and generally light winds.

EXTENDED FORECAST FOR SATURDAY THROUGH MONDAY
Saturday morning: mostly sunny and cool
Saturday afternoon: slight warming with increasing high 
clouds
Saturday night: clouds lowering with light rain or snow 
developing in the Olympics and light showers Cascades
Sunday morning: cooler with light to occasionally moderate 
snow
Sunday afternoon: light showers decreasing
Sunday night: light rain or snow Olympics and light showers 
Cascades
Monday morning: light snow developing south slowly spreading 
northward
Monday afternoon and night: light snow showers gradually 
decreasing with some partial clearing

*	SNOW LEVELS
1-3000 ft N and S Saturday morning
2-4000 ft N, 4-6000 ft S Saturday afternoon and evening
1-3000 ft N, 2-4000 ft S later Saturday night and Sunday 
morning
1-3000 ft N and S Sunday afternoon
500 to 1500 ft N, 1-2000 ft S Sunday night and Monday
500-1500 ft N and S late Monday

NWAC weather data and forecasts are also available by calling 
206-526-6677 for Washington, 503-808-2400 for the Mt Hood 
area, or by visiting our Web site at www.nwac.us.

Moore/Northwest Weather and Avalanche Center

$$