Wetand News

The atmospheric river has reached the Pacific Northwest and moderate rain has spread across much of the region. The water vapor satellite imagery is impressive, showing a potent plume of water vapor moving northeastward from off the Pacific (see below).  Looks scary, doesn't it?    Some folks rate atmospheric rivers like hurricanes and tornadoes, and they rank this event as an AR4 (atmospheric river, category 4), out of a possible 5. This atmospheric river not only has moisture, but strong winds from the south-southwest, producing a very impressive rainshadow to the northeast of the Olympics (see radar image at 7:30 PM below).  Yellow and orange indicated the heaviest precipitation, with the southeast side of the Olympics getting the worst of it now.   In contrast, it is TOTALLY dry from Sequim to northern Whidbey Island in the rain shadow.   So if you want to go on an evening stroll...you know where to go. The precipitation total so far (through 7 PM) is shown below.  Over an inch

 For those thinking that a lamb-like spring was coming early, think again. Very heavy rain and flooding will be arriving on Monday, the result of a potent atmospheric river.  Some locations in the lowlands will receive 2-4 inches on Monday, with twice that in "favored" mountain locations. The origin of our wet future is a strong atmospheric river, a narrow region of large amounts of moisture, originating in the subtropics.  To illustrate, below is a plot of total moisture from the surface to the top of the atmosphere at 4 AM Monday.  As you might guess, the reddish colors are the largest amounts. This atmospheric river starts north of Hawaii and heads northeastward right into our region. But it is not only moisture that counts, but the rate at which moisture is approaching our region.   That is why meteorologists prefer to view integrated water vapor flux (IVT) , an impressive-sounding term that actually means wind speed times water vapor.  Just drop the term "IVT"

 My new podcast is out (see details below), and I cover two important topics:  the radical change in our weather that will occur this weekend, and the substantial variations in local temperatures on cold nights. Take a look at the upper-level (500 hPa, about 18,000 ft ASL) flow this morning and on Monday night.  This morning, the ridge is right on the coast--a situation associated with sinking air and sunny skies. But on Monday evening, the ridge has moved inland and the Northwest is in strong southwesterly flow off the Pacific.  A large trough is offshore.  This is a warm/wet pattern. Total precipitation through 4 PM Monday is impressive (see below), with locations in the mountains getting more than 5 inches! My podcast gives more details on the forecast.  And my podcast also describes and explains the large local variations of low temperatures on cold mornings, such as on Wednesday. It all makes sense if you know what is going on, and you will after you listen to the podcast. To list

 More snow is coming tonight for the lowlands of Northwest Washington and the Columbia Basin.   But before I get into that, check out this morning's visible satellite image showing a nearly cloud-free Washington State and northern Oregon.   Just spectacular.   You can see the snow over the mountains as well as regions of non-mountain snow over the eastern Washington and Oregon lowlands.  As predicted, this morning was very cold across the region, with several observing stations with temperatures dropping to daily records (see below). Over the lowlands of western Washington and Oregon, many locations dropped into the teens, particularly away from the water.   East of the Cascades, single digits were prevalent, with some locations dropping below 0F.   One location in eastern Oregon declined to -10F! As noted, daily low-temperature records were broken at several locations, such as Seattle 23° (old record 24° in 2018),  and Olympia 14° (old record 16° in 2018).  A weak upper-leve

The forecast models did quite well during the past day, with the cold air and light snow moving in yesterday and this morning. Yesterday light snow fell over the northeast Olympic Peninsula, with a band extending over northern Kitsap and Camano Island.   And this morning, very light snow fell over Puget Sound (see picture below).  A few flurries are now occurring, but those should end soon. Bellevue, Courtesy of Dr. Peter Benda The lows last night in the west ranged from the mid-20s around Bellingham to roughly 30F in western WA and Oregon away from the water.  Teens were prevalent in eastern WA, with some single digits into terrain.  But the coldest temperatures were in valleys of the uplands of eastern Oregon, where one station got to 1C. The air is now cold enough to snow throughout the region, but precipitation is essentially over as the upper-level trough that provided uplift moves away.   Winds coming out of the Fraser River valley were extraordinary last night, with gusts getti

 Record cold, heavy mountains snows, extreme winds, and lowland snowflakes. Winter conditions have returned to the Northwest. Heavy snow fell across the Cascades last night, with nearly two feet at Stevens Pass and about a foot at Snoqualmie.  Chains are now required for both passes. T he snow was particularly heavy in the central Cascades.  Why? Because a convergence zone, forced by the Olympics, created a band of enhanced precipitation, stretching across Puget Sound and into the Cascades, something illustrated by the radar image around 4 AM this morning (the red arrow shows the band)  Cold Air in Two Stages A Pacific cold front, associated with an upper-level trough of low pressure, moved through yesterday, with cooler air and northwesterly flow (from the northwest) aloft.   Thus, the bountiful snow in the Cascades.  This was stage one. In stage two, cold air pours into central British Columbia and pushes southeast of the Rockies, as the upper-level trough of low pressure over the No

 A late February cold snap with snow is coming to the region, and my new podcast provides the details. The instigator of the cold fun is an upper-level trough (area of low pressure) that will move southward along the eastern side of a huge northeast Pacific ridge of high pressure. Upper-level flow (500hPa) Late Saturday Initially, western Washington will be too warm for snow, but the mountains will enjoy bountiful flakes (see snowfall total through 10 PM Sunday) But as I describe in the podcast, on Monday, western Washington has a snowy chance, as a Puget Sound convergence zone forms south of Everett (see snow total through 4 PM Monday).  Some snow may also occur on the northeast side of the Olympics (e.g, around Sequim) as northeasterly flow moving out of the Fraser River valley is forced to ascend by the terrain. Snowfall total through 4 PM Monday To listen to my podcast,  use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the

During the past week, many major media websites have headlined a study by some UCLA researchers suggesting that the Southwest U.S. is in a megadrought--the worst in 1200 years-- and that global warming is the prime cause.     To illustrate, below is the front page of the LA Times.  And the Seattle Times highlighted the megadrought claims as well.   Unfortunately, there are some major problems with this study and many of the hyperbolic claims--as I will explain below.     The US Southwest has clearly experienced a dry spell recently, but global warming (a.k.a. climate change) is only a minor contributor compared to natural variability.  Decadal dry periods are not unusual or unknown for the U.S. Southwest.  They have happened many times before during periods when human-caused climate change could not be the origin. Why 22 years? A key aspect of this paper is its claim that the last 22 years were the driest over the southwest U.S. for the past 1200 years.   Their measure of dryness was

 Winter has not finished with us.  Another shot of snow is heading for the mountains.  And some lucky folks in the lowlands may see some snowflakes! Another cold Arctic Blast is coming our way on Sunday. As discussed in earlier blogs, there has been a major ridge of high pressure over the eastern Pacific (see upper-level 500 hPa pressure/height map for about 18,000 ft ASL at 1 PM today, below).   Such ridges are quite frequent during La Nina years like this one.   Troughs of lower pressure can move southward down the eastern flanks of such ridges....and you can see one over southern California right now.  It is raining now around LA. But on Sunday morning, another trough will move around the high...a strong trough...and one that will be in the right position to draw cold air into the region....with the most frigid stuff east of the Cascade crest (see image below) Cold air will move in later on Sunday and Monday.   To prepare you for the chill, here is the sea level pressure map (solid