60F at one's head and 32F at one's toes

Yesterday, I skied up to Stampede Pass with a group of weather-oriented folks to visit the repaired National Weather Service observing site.   It was amazingly warm, with yesterdays air temperature at that location reaching 61F between 3 and 4 PM (see plot).  At the same time, the snow was melting at the surface, so we know the temperature of the snow surface:  32F.     So roughly a 30F difference between my head and toes!

But the contrasts don't end there.  The temperature dropped to the mid-30s by 3 AM today--12 hours later.  And that was accompanied by snow!   So sunny and hot to cold/windy/snow a few hours later....you got to love our weather here.

Here is the National Weather Service ASOS observing site, high on a platform above the snow.

On the left is a rain gauge, a freezing rain sensor, and a laser ceilometer.

 On the right, a precipitation type identifier, a temperature/humidity sensor, and a visibility sensor.

Stampede Pass is the home of many power line swaths, which afford some wonderful views, although the snap, crackle, and pops of the power lines can be disconcerting.

The sky yesterday was full of high cirrus/cirrostratus associated with an approaching front.   But there were also many lenticular (lens-shaped) mountain wave clouds.  Here is a sample.

Lenticular clouds often form downstream of our mountains when a weather system approaches.  First, the approaching system is associated with increasing relative humidity, so that the additional lift forced by the mountains produces clouds.  Second, wind perpendicular to the mountains increasse, which is good for business of the waves produced by the mountains.

We were very fortunate to be accompanied by Randy Cryer, a long-term observer (and resident) at Stampede Pass, who told us about the history, geology, and meteorology of the pass, and particularly the large impact of the early trains.  I told him that he should write a book about Stampede Pass.

Virgil G. Bogue discovered the pass on March 19, 1881.   The northern Pacific railroad would go through the pass, and as work on the project proceeded, Mr. Bogue sent out a new foreman to speed-up the work.  The men had enough and quit. The response: "No work, no eat," and the men stampeded for the valley and therein came the name.

While we were at the pass we noticed a number of general aviation aircraft flying across the area.  Randy told us that the weather station was established in 1943, when several aircraft crashed as they crossed the Cascades.   Some of you may remember that when the weather station was closed for a year in 1990, several planes crashed with some fatalities.  It is good that the weather station, with its excellent observing equipment, is back online.

Taste of Summer in Early Spring

The last few days have been the warmest since October, with Seattle Tacoma Airport reaching 70F twice (see image below).  We are talking about being 15F above normal!

Let's compare this to the same 4 week period last year.   Generally similar, although last year had more days above normal.

And during the last few days we have been seeing the classic summertime low clouds on the coast, with a minor marine push this morning.  Enough to bring some light drizzle to the early visitors to the new 520 bridge.  Friday morning was the first try for the marine air, as shown by the image at 9:30 AM, with tendrils through the Strait and the Chehalis Gap south of the Olympics.

 By 2 PM, the shallow low clouds had retreated to the the coast.  Still plenty of snow in the mountains.

Last night and this morning, an upper level trough moved towards the coast (see 500 hPa, roughly 18,000 ft at 11 PM Friday).

This weak trough, and its associate upward motion, deepened the low level marine layer and enhanced the onshore pressure gradient.  The result:  more persistent clouds and some very light drizzle.  Here is the visible satellite picture at 9:15 AM Saturday--Puget Sound was covered.

 At 2:30 PM most of the low clouds had burned off, with a remnant left to the NE of the Olympics.  No wonder folks on the 520 bridge got a sunburn.

The dry conditions will end tomorrow night as a modest front moves to the coast during the late afternoon and into the interior around midnight (see forecast precipitation for the three hours ending 8 PM).

But don't be too depressed.  ANOTHER strong ridge will develop midweek with more temperatures near 70F.