Wetand News

This is going to be a week of superlatives over the region, as heavy precipitation will produce both river flooding and a huge snowfall over regional terrain.   Enough snow so that skiers and ski areas  will be jubilant, and enough water that fears of lack of drought this summer will be far less. First, the big picture.  Below is the forecast precipitation over the next 7 days. Precipitation totals are amazing, teaching 10 inches near the crests of the Cascades and Olympics. The snowfall  total over Washington high terrain is amazing (bel0w), reaching about 4 feet near the crest by next Saturday afternoon. Snow descends down to lower elevations in eastern WA and over Whatcom County. Now, the details.  Here are the ensemble forecasts (forecast model run many times) from the National Weather Service GEFS system for precipitation at Stampede Pass at 4000 ft on the eastern side of the Cascade crest.  The gray lines are from the many forecasts, with the black line being the aver

Weather prediction technology has come a huge way over the past decades and yesterday's localized snow event is a great example of how far we have come. The most difficult Northwest forecasting problem is snow prediction. And there is no harder snow problem than a situation marginal for snow and where there are very localized weather effects. Yesterday (Tuesday) was such a difficult snow situation and the high-resolution models did very well. The Forecast As I described in this blog, cold air was in place and an approaching frontal system brought general very light snow, with heavier snow over North Seattle and Snohomish counties.  The models also predicted heavy snow in the Cascades, including its lower western slopes. Below is the high-resolution WRF model forecast of snowfall through 4 AM today (Wednesday) made 4 PM Monday. Light snow from downtown through Tacoma (about 3/4 inch), with heavier snowfall (peaking at 5-7 inches) from Lynwood to Everett.  Heavy snow in the mountains

 The answer is no.    A single major snow event or even a major snow season does NOT mean that global warming is no longer a concern. Similarly, a single weather event (e.g, the summer heatwave in June or the heavy rains in December) does not mean much about global warming. This is a lesson that the media and some activists need to learn--on both sides of the issue. Stevens Pass Let's be honest- -if we were experiencing an extremely low snowpack this year in the western U.S., the media and activists would be crowing about global warming.   The familiar Seattle Times folks (e.g, John Talton, David Horsey, and others), the Guardian,  and the Washington Post, among others, would be putting out the "existential" warnings about it (see David Horsey's cartoon). Grist magazine would do a feature article on snowpack decline and Seattle350 would schedule another protest in front of Chase Bank. But this year they have been quiet. Cartoon by David Horsey and provided by the Seat

 Our region will experience wildly gyrating weather extremes over the next week.    Yes...there is still cold and snow in the forecast.  But before we enjoy the snowflakes, we will experience a strong atmospheric river that will bring very heavy precipitation to the mountains. And to spice it up, strong winds and an extraordinary rainshadow will occur over Puget Sound country. First, the atmospheric river.  As shown below, a plume of wind-driven moisture, thousands of miles long, will push into our region on Friday.  The figure shows integrated water vapor transport--essentially how much water vapor is being transported by the wind.    Let me assure you, these are large values. The huge influx of water vapor will be pushed upwards by our region's mountains, producing intense precipitation.   Below are the predicted totals for 24 hr ending 5 PM Friday.   Wow.  A substantial area over 5 inches in both the Olympics and Cascades. Look closely and you will notice that Seattle and its v

After a relatively dry summer, the Northwest is experiencing one of the wettest autumns in a long time. September and October brought above-normal precipitation around the region.  November is going to smash typical monthly precipitation amounts at most stations. Over the next few days, a powerful atmospheric river of moisture surging out of the subtropics will inundate our region, with the western slopes of some of our terrain barriers experiencing as much as 10 inches of rain.   Falling on saturated soils, westside rivers will surge to flood stage...some to major flood stage. Water vapor satellite imagery (which measures the amount of infrared radiation emitted by atmospheric water vapor), shows an impressive plume of water vapor extending from north of Hawaii into our region.  Perhaps a part of the "aloha spirit" that is not as welcome as others. Model simulations of total atmospheric moisture in a vertical column (in this case for 10 PM tonight) show the potent moisture p

We enjoyed an unusually dry, temperate mid-November, and Thanksgiving Day was a pleasure, but now the brass knuckles of a La Nina winter are about to be revealed. Cold air and a hard freeze will hit the entire state next week, with massive mountain snowfalls that will delight the ski community.   All of us should take steps to deal with the upcoming cold, from unscrewing outdoor hoses, and protecting pets, to ensuring that the region's large homeless population is brought inside or protected. The upcoming situation is a classic for a La Nina winter, in which the central and eastern tropical Pacific is colder than normal.   During such winters, we typically observed a large ridge of high pressure developing over the northeast Pacific, with cool, northerly (from the north) flow on its eastern side (see the forecast upper-level map for Saturday at 10 PM as an illustration). If there are disturbances in that northerly flow, moving south out of Alaska, we can get bouts of mountain snow,