From a drizzle to a deluge just 41 miles apart: Olympic Rain Shadow works its magic

Western Washington is pretty well known for its microclimates, but it's rarely so obvious as it was during our Wednesday rain storm.

Seattle netted just over 2 inches for the storm, but some places got a whole lot more, and other places got a whole lot less.

A rain gauge at Jefferson Creek in Mason County, along the eastern slopes of the Olympic Mountains, received 6.86 inches of rain over 24 hours, according to the National Weather Service office in Seattle. But just 41 miles away in Port Townsend? All they received was 0.08 inches. That's a gradient of 0.165 inches of rain -- per mile! Or roughly an inch more every 6 miles.

It's all thanks to the Olympic Mountains, which brought both the feast to Jefferson Creek and the famine to Port Townsend. We had a very strong and moist southwesterly flow coming off the Pacific Ocean and slamming into the Olympics. As the air rises up the mountainsides, it cools and condenses and essentially undergoes a process like a sponge being wrung out. Jefferson Creek was right in the heart of that area.

MORE | How Does The Olympic Rain Shadow Work?

But once the air climbs the mountains and sinks down the northeastern side, a reverse drying process gets under way, "eating" up the moisture and leaving areas like Sequim and Port Townsend dry.

Outside the Olympic Mountain's sphere of influence, rainfall totals were in the 1.5-3.0" range.

Seattle nearing some gaudy rain records for February

In Seattle -- one of those places not affected by the Olympics -- the storm total sat at 2.37 inches as of 11 a.m. Thursday. It's enough to put Seattle at 7.84 inches for the month, making it the 5th wettest February on record at Sea-Tac Airport, and 6th wettest if you count the Downtown Federal Building records which go back to 1892.

Some other interesting rainfall tidbits, courtesy of the National Weather Service office in Seattle:

  • 1.63" fell on Wednesday alone, which not only set the daily rainfall record for Feb. 15, but was tied for the 9th-wettest February day on record.
  • Believe it or not, one of those dates we tied with? Last Thursday, which also had exactly 1.63" of rain. Feb. 18, 1968 also had 1.63" of rain.
  • It's the third day this year with 1.50" of rain or more in Seattle. Only three years have had 4 days with 1.50"+ -- 1996, 1968 ad 1933.

Seattle's wettest February on record was 9.11" set in 1961. With more showers in the forecast and still roughly half the month to go, it's certainly reachable!

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