Here is the official starting point for data retrieval from the USGS site

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Here are my links to National Weather Service (NWS) river forecasts for:

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Pick your own river basin to forecast

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Here are my links to gages in the Chehalis River Basin - as of 11/13/2006. 
Chehalis River Basin
Link to USGS DataGage Name
12020000 CHEHALIS RIVER NEAR DOTY, WA
12020800 SOUTH FORK CHEHALIS RIVER NEAR WILDWOOD, WA
12021800 CHEHALIS RIVER NEAR ADNA, WA
12024000 SOUTH FORK NEWAUKUM RIVER NEAR ONALASKA, WA
12024400 NF NEWAUKUM RIVER ABOVE BEAR CREEK NEAR FOREST, WA
12025000 NEWAUKUM RIVER NEAR CHEHALIS, WA
12025100 CHEHALIS RIVER AT WWTP AT CHEHALIS, WA
12025500 CHEHALIS RIVER AT CENTRALIA, WA
12025700 SKOOKUMCHUCK RIVER NEAR VAIL, WA
12026150 SKOOKUMCHUCK RIVER BL BLDY RUN CR NR CENTRALIA, WA
12026400 SKOOKUMCHUCK RIVER NEAR BUCODA, WA
12026600 SKOOKUMCHUCK RIVER AT CENTRALIA, WA
12027500 CHEHALIS RIVER NEAR GRAND MOUND, WA
12031000 CHEHALIS RIVER AT PORTER, WA
12035000 SATSOP RIVER NEAR SATSOP, WA
12035002 CHEHALIS RIVER NEAR SATSOP, WA
12035100 CHEHALIS RIVER NEAR MONTESANO, WA
Wynoochee River Basin
12035400 WYNOOCHEE RIVER NEAR GRISDALE, WA
12036000 WYNOOCHEE RIVER ABOVE SAVE CREEK NEAR ABERDEEN, WA
12037400 WYNOOCHEE RIVER ABOVE BLACK CREEK NR MONTESANO, WA