MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES
AND MT HOOD AREA
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
130 PM PDT SUN MAR 22 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-ORZ011-231600-
&&
WEATHER SYNOPSIS FOR SUNDAY AND MONDAY
A narrow but elongated upper level trough of low pressure
extends from along the Pacific Northwest coast southward to
the southern California coast Sunday afternoon. The trough
is drawing up a band of showers from the south Sunday
afternoon. The heaviest showers within the forecast area
have been in the Mt Hood area with gradually less shower
activity to the north. Showers should continue to move
across the area through Sunday evening as the trough
gradually shifts inland.
The upper trough should move inland later this evening and
east of the area overnight and early Monday. Cool and
unstable air under the trough should maintain showers
overnight Sunday and early Monday morning at lowering
freezing levels. A brief increase in northwest crest level
flow late Sunday afternoon and evening may cause a
convergence band to form over the central Cascades to
enhance showers there through the evening.
A brief upper ridge should transit the area early Monday to
cause a brief dry period ahead of the next approaching
system from the west.
The next system currently out near 145 W in the eastern
north Pacific is expected to move to the Washington coast
Monday morning and to the Cascades by midday Monday. This
frontal system should produce light to moderate
precipitation through Monday night at slightly rising
freezing levels.
&&
WEATHER FORECAST FOR SUNDAY AND MONDAY
* OLYMPICS-
Sunday afternoon and evening: Increasing light snow
showers.
Sunday night: Showers and clouds decreasing becoming
partly cloudy.
Monday morning: Increasing clouds with light snow
developing.
Monday afternoon and night: Light to occasionally
moderate rain or snow.
* WASHINGTON CASCADES NEAR AND WEST OF THE CREST-
* CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE
PASSES-
Sunday afternoon and evening: Increasing light snow
showers, possibly moderate central area in convergence.
Sunday night: Showers and clouds decreasing becoming
partly cloudy.
Monday morning: Increasing clouds.
Monday midday: Light rain or snow developing.
Monday afternoon and night: Light to occasionally
moderate rain or snow.
* EAST SLOPES WASHINGTON CASCADES-
Sunday afternoon and evening: Increasing light snow
showers.
Sunday night: Showers and clouds decreasing becoming
partly cloudy.
Monday morning: Increasing clouds.
Monday afternoon and night: Light snow.
* MT HOOD AREA-
Sunday afternoon and evening: Gradually decreasing light
to occasionally moderate snow showers.
Sunday night: Showers and clouds decreasing becoming
partly cloudy.
Monday morning: Increasing clouds.
Monday midday: Light snow developing.
Monday afternoon and night: Light to occasionally
moderate snow.
&&
SNOW LEVELS-CASCADE MTNS
2000 ft N, 2500 ft S Sunday afternoon
1500 ft N and S Sunday night
1000 ft N and S early Monday
1000 ft N, 1500 ft C, 2000 ft S Monday afternoon and
night
SNOW LEVELS-OLYMPIC MTNS
1500 ft Sunday afternoon and night
1000 ft early Monday
1500 ft Monday afternoon
3000 ft Monday 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
MON TUE
* HURRICANE RIDGE LT .25 .25
* MT BAKER LT .25 .25-.5
* WASHINGTON PASS LT .25 .25
* STEVENS PASS LT .25 .25-.5
* SNOQUALMIE PASS LT .25 .25-.5
* MISSION RIDGE LT .10 LT .25
* CRYSTAL MTN LT .25 .25
* PARADISE .25 .25-.5
* WHITE PASS .25 .25
* MT HOOD .25-.5 .25
&&
WINDS IN MILES PER HOUR (MPH)
* CASCADE PASS LEVEL WINDS
W 10-20 with occasional higher gusts Sunday afternoon and
evening
W 5-10 Sunday night and Monday morning
Variable 0-10 Monday afternoon
W 5-15 Monday night
* FREE WINDS AT 5000 FT
SW 10-20 N, W 15-25 S and Olympics mid-day Sunday
W 10-20 N, 15-25 C and Olympics, W-NW 20-30 S Sunday
afternoon and evening
W-NW 10-20 N, C, and Olympics, W-NW 20-30 S Sunday night
SW 5-15 N, W 5-15 C, NW 5-15 S early Monday morning
S-SW 15-30 N and C, SW 20-30 S midday and Monday
afternoon
W 15-25 N and C, W 20-30 S Monday night
* FREE WINDS AT 9000 FT
W-NW 15-25 N and C, NW 20-30 S Sunday afternoon
W-NW 10-20 N and C, NW 15-25 S Sunday night and early
Monday
W-SW 15-30 N and Olympics, W-SW 25-35 C and S Monday
afternoon
W-NW 15-25 Monday night
&&
EXTENDED WEATHER SYNOPSIS FOR TUESDAY THROUGH THURSDAY
A strengthening northwest flow is expected behind the front
Monday night. This should cause increasing orographic
precipitation as a short wave disturbance is carried across
the region later Tuesday. The strong northwest flow aloft
should also allow for cooling with the increasing
precipitation through Wednesday morning.
A rebuilding flat upper ridge should allow for decreasing
showers later Wednesday. The ridge should gain strength late
Wednesday And Thursday to allow for partial clearing and
little chance of precipitation with decreasing winds.
EXTENDED FORECAST FOR TUESDAY THROUGH THURSDAY
Tuesday morning: Light snow showers.
Tuesday afternoon and night: Increasing moderate to heavy
snow showers, heaviest central part in convergence.
Wednesday morning: Cool with moderate snow showers.
Wednesday afternoon: Decreasing light snow showers.
Wednesday night: Light showers ending with slow clearing
trend.
Thursday and Thursday night: Partly cloudy.
* SNOW LEVELS
1-3000 ft N and S early Tuesday
1-2000 ft N and S late Tuesday through Wednesday morning
1-2000 ft N, 1500-2500 ft C, 2-3000 ft S late Wednesday
2-3000 ft N, 3-4000 ft S Thursday
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.
Kramer/Northwest Weather and Avalanche Center
$$
