KIRO 7 Meteorologist Sam Argier said with 4 to 8 inches of rain forecast over the Cascades and a high snow level of 7,000 to 9,000 feet, some rivers are expected to spill over their banks.

SLIDESHOW: Heavy Rain Soaks Western Washington WATCH IT: Forecast From Rebecca Stevenson WATCH IT: Major Flooding Possible This Week

A flood watch is in effect for Clallam, Jefferson, Skagit, Whatcom, King, Lewis, Mason, Pierce, Snohomish and Thurston counties Wednesday afternoon through Friday afternoon. Argier said rivers flowing off the Central Cascades such as the Snohomish, Snoqualmie, Tolt, and Stillaguamish are most susceptible and could reach flood stage Wednesday afternoon and into Thursday morning.

Argier said most of the heavy rain is falling in the Cascades and Whatcom and Skagit counties. There will be rain at times through the rest of the Puget Sound region. Some of the driest weather will be around the central Sound, in the rain shadow of the Olympic Mountains, he said.

Major Flooding Forecast On Snoqualmie River

The heavy rain caused the King County Flood Warning System to be activated, and the National Weather Service issued a flood warning for the Snoqualmie River near the falls and Carnation through Friday morning. Major flooding is forecast, with the river expected to reach the 54-foot flood stage at about 7 p.m. Wednesday and crest near 58 feet around 5 p.m. on Thursday.

Flood water on road near fall city Near Fall City

The river is currently at a phase 2 level. The NWS said at a phase 3 level, the Snoqualmie would cause widespread flooding of pasture lands and roads along the river from the town of Snoqualmie downstream through Fall City.

People who live or camp at the Snoqulamie River RV Park and Campground are watching closely, as they do for several months of the year.

UNCUT: Force Of Water At Snoqualmie Falls WATCH IT: If Floods Come, Residents Near Snoqualmie Know The Drill

"If the snow level goes up to 6,000 or more feet, we might as well put our waders on and move on out," said campground caretaker Tony Unruh.

Many Other Rivers Expecting Floods

The Tolt River near Carnation is also under a flood warning and reached a phase 3 level on Wednesday afternoon. The NWS said road closures could be expected along the river in and around Carnation, including the Tolt River Road, while homes in the San Souci neighborhood could see flooded driveways.

WATCH IT: Waters Rise On Tolt River

Other rivers under a flood warning are the Puyallup, Skykomish and Stillaguamish rivers. The Snohomish River is under a flood watch.

People on the Green River, below the Howard Hanson Dam, could also be affected, KIRO 7 Chief Meteorologist Rebecca Stevenson said.

"Rainfall over the Green River basin will be heavy at times, perhaps exceeding three inches over 48 hours," Stevenson said. "Local inflow below the Howard Hanson Dam could be significant."

Mountain Avalanche Danger Elevated, High Winds In Eastern Washington

The Northwest Weather and Avalanche Center has issued several warnings of avalanche danger, ranging from moderate to extreme, for nearly all of the Cascades (more information and area-specific warnings are available at the link).

WATCH IT: Avalanche Danger Increases In Cascades SLIDESHOW: Spectacular Photos Of Snowy Hwy 20

The heavy mountain rain caused the Mt. Baker ski area to close.

Elsewhere, in Eastern Washington, heavy winds were forecast for Wednesday night. The eastern slopes and northern Cascades are under a wind advisory until 8 p.m. Thursday. Winds between 25 and 35 mph with gusts from 40 to 50 mph are expected.

Rain Causes Mudslides In Everett, Seattle

The spring storm is an unwelcome sight for residents in Everett's Valley View neighborhood, where a sliding hillside is tearing homes apart. Some people are predicting that more rain will be its undoing.

“I would guess that hillside is just going to go. I mean, it’s not just that house. Trees over there all are leaning,” said a homeowner’s son, Steve Bigbee.

WATCH IT: Rains Cause Mudslide Danger In Seattle, Everett

The continuing rain could also cause trees to fall over in saturated soil.

Power was cut to a Seattle home at South Lane Street and 29th Avenue South when a tree fell and hit power lines.

March 2011 Is Among Wettest On Record

Argier said this month is the seventh wettest March on record at SeaTac, with 5.85 inches of rain so far. If March rainfall surpasses 6.26 inches, this month will be the sixth wettest March on record.

This month was the 10th wettest on record on Tuesday morning and has steadily notched up the list since.

Temperatures on Wednesday are highs in the upper 50s and low 60s. Winds will be gusty at times, blowing 15-25 mph around Puget Sound. Areas east of the Cascades such as Ellensburg and Wenatchee will be seeing gusts 50 to 60 mph, Argier said.