Fall Weather Review

Fall 2007 was generally cooler and a little drier than normal across Western Washington. At Sea-Tac Airport, September was 1.2 degrees below normal, October 2.2 degrees cool, and November 0.9 degrees below. Rainfall was a notch below normal early in the Fall, near normal in October, and significantly below normal in November (50-65% of normal across western Washington). A very wet storm arrived on December 2-3 however, and the lowlands of Western Washington received about a months worth of rain with just this storm. In the Puget Sound lowlands, 4 to 6 inches of rain fell.  On the Olympic Peninsula, 5 to 10 inches of rain was recorded.  The Skokomish, the Elwha, and the Chehalis rivers all reached a record river flood stage from  this storm.

Notable windstorms occurred on October 18th, with a peak wind at Sea-Tac of 53mph; on November 12th, with a peak wind of 47 mph; and on December 2nd, Sea-Tac had a peak wind of 48 mph.

The strongest winds this fall, in the interior, were with the November storm, peak winds of 55-75 mph were reported across inland Western Washington.  But the strongest winds and most damage this fall were on the coast during the early December wind and rain storm. Winds near the beaches were sustained about 70 mph with gusts to 84 mph.  The Hoquiam airport had winds of 51 mph with gusts to 81 before the power was knocked out.  This was one of the strongest winds ever reported from the ASOS in Hoquiam.

Despite the cool weather this fall, precipitation has been on the dry side, so mountain snowpack is below normal as of the first week of December. Also, the early December storm first added, but then took away from the snowpack for only a little net gain. A more active weather pattern, a cool wet pattern, looked to shape up by the middle of December, which is consistent with the La-Nina phenomenon in the equatorial Pacific.

Snow Trivia

Our area’s weather is terrain driven and snowfall clearly follows that trend throughout western Washington. Can you correctly match these communities with their average annual snowfall?  The answers can be found elsewhere in Skywarn Spotter News.

Location	Amount
Elma	444
Skykomish	5
Forks	699
Arlington	14
Sequim	6
Paradise	4
Snoqualmie	63
Stampede Pass	40

La Nina Underway

Colder than normal eastern and central Pacific Ocean equatorial waters are now in place, meaning that we are now experiencing a La Nina.  Cooler than normal sea-surface temperatures in these equatorial waters are expected to continue through the winter. Hence, La Nina will be with us this winter season. To see images of this phenomenon, please visit the NWS Climate Prediction Center’s web site at www.cpc.noaa.gov/

La Nina’s tend to bring our area at or below normal temperatures and above normal precipitation on average over a winter season.  The seasonal outlook for this winter is quite close, with a wetter than winter expected particularly early in the season, and temperatures at or a little below normal.  This phenomenon also tends to produce a good mountain snowpack.La Nina’s also tend to bring our area increased odds on wind storms and lowland snow events, as well as flooding events.

How to Measure Snow

When snow falls across the lowlands of western Washington, your spotter reports are our  very best source of snow depth information.                 

The National Weather Service uses lots of sophisticated equipment for observing the weather -- such as radar imagery, satellite pictures, and automated observing systems -- but none of these tells us how much snow has fallen. For that we depend almost entirely on our network of volunteer weather spotters. NWS meteorologists use your snow depth reports for critical forecast and warning decisions and for post-event verification.

And since snowfall varies so much over small areas, we want reports from as many spotters as possible. Ideally, we'd like to get a report from every spotter when they receive an inch of snow, again when three inches have fallen, and finally with a storm-total accumulation. You can get your current snow depth reports to us by calling us on our toll free spotter phone number.  As an option on your final storm total report only, you can email us at psusew@noaa.gov.  This email is only be checked after the event is over and is not considered a live operational email address for security reasons.

What is the best way to measure snow? You  get the most accurate results by using two snow boards and a ruler or snowstick. A snow board is simply a flat board, roughly 2' x 2', and white in color so that the board does not absorb solar energy. Use one board to measure total snow accumulation and the other to measure new snow since the last measurement. Snow boards and snow sticks are available to spotters at our spotter training sessions, or you can improvise using plywood, white paint and a ruler. Snow boards provide much more accurate snow measurements than a deck, driveway, or especially a lawn.

For the best measurements place the snow boards in an open area, away from the influence of buildings, trees, and other tall obstructions. (Close to your rain gauge will probably work nicely.) Be sure to flag both boards so you'll be able to find them after they're covered with snow! You can measure snowfall as often as you wish. It should be measured at least once or twice a day and, if possible, shortly after a period of snowfall has ended.

We realize that measuring snow isn't always fun or comfortable, but please know that your reports are extremely valuable to us. Thanks for your efforts! Now ... let it snow! 

Thanks Go To Skywarn Weather Spotter Clallam-40 - Dan Spomer (Clallam-40, Sekiu) has been working hard to enhance weather reporting from western Clallam county. He recently helped install an automated weather station at Lake Ozette and is recruiting a spotter in Joyce, between Sekiu and Port Angeles.  Thanks go to Dan for all his efforts!  

In addition, you can view CWOP and all other on-line weather stations on our web site by visiting our web site at www.wrh.noaa.gov/seattle. and the ‘Obs Map’ link.

Snow Trivia Answers

Elma	6"
Forks	13"
Snoqualmie	11"
Arlington	7"
Stampede Pass	444"
Paradise (Mt Rainier)	699"
Sequim	5"
Skykomish	63"

Back to National Weather Service Seattle's main page www.wrh.noaa.gov/seattle.