Black and White TV

A turkey vulture flew over Yosemite Village, about 100 meters up, at 7:30 this morning. Especially on this cold, snowy sun-up, I take this to mean that the vulture roosted in Yosemite Valley rather than soaring upcanyon on thermals from lower elevation - something new for our neighborhood. Will condors be next?
More frazil ice formed up in Yosemite Creek this morning, covering all the channels and scouring more forest terrain of its natural duff. A good volume of slurry flowed into the Merced River. Frazil flowed in Ribbon Creek, too, and it went downstream of Northside Drive for the first time this season.
The handful of planted redbuds in Yosemite Valley are blooming; they endured a taste of snow overnight. Dogwoods are making progress, with some 'blossoms' up to 10 cm across and just starting to turn white.

Tioga Road is Open

Tioga Road is not open to vehicles, but people have been traveling it all winter on skis, snowshoes and splitboards. More snow is accumulating this week, but we know it won't last long. NPS road crews have plowed from Crane Flat up to the White Wolf intersection, through an average of 7 feet of snow. Cyclists should soon be permitted to ride from Crane Flat up the highway a few miles - but be wary of administrative and maintenance traffic that may not be expecting you, and don't go beyond the marked closure points, even if you see bare pavement. Besides heavy equipment, there are avalanche dangers up here, too.
I stopped near the park's high-tech Wastewater Treatment Plant in El Portal this morning and noted four species of swallows in flight there: barn, rough-winged, cliff and violet-green. It's good to be an aerial insectivore at this time of year.

All Hydrologies

In the sun, our tremendous snowpack is moving downhill in more and bigger creeks flowing into Yosemite Valley. The heavy wet snowstorm that damaged a lot of trees 22 January is continuing to have its effects now, with fallen branches and tree trunks blocking some stream channels. There's a small ephemeral stream that drains the gully east of Sentinel Rock and the lower part of the Four Mile Trail; you've hopped over it if you've hiked this trail between May-August. On the Valley floor it usually runs through a culvert under Southside Drive and down toward the Merced River. A fallen black oak is sending it down a small overflow channel, where there is no culvert beneath the road. It's exciting to see it creating a new pond in Chapel Meadow at the moment.
Eagle Creek is flowing nicely, but it's not in its main channel at Northside Drive; I'll hike up there soon to see what's diverting it to the west. Sentinel Creek, Ribbon Creek, Bridalveil Creek are all flowing quite strongly now and the river has gone above average volume, to almost 2000 cfs at Pohono Bridge last night. Table Rock is all but covered. Great times to be a mallard or a merganser.

Muir Day and Earth Day

Yesterday was Muir's birthday, today is the Earth's. Saturday is National Junior Ranger Day. There's a lot to celebrate during National Parks Week. In honor of all this I just had a chance to talk about Yosemite, the Half Dome day use permit system, our new California quarter, the merger of Yosemite Association and Yosemite Fund, etc. with Jeffrey Callison on Sacramento's NPR station (www.capradio.org/insight). He's another Scotsman (like Muir) who has made good in the Golden State. I hope we'll have an mp3 of our chat posted on the Association website soon.
Steve Bumgarder's excellent frazil ice film is getting lots of notice, as it should. If you haven't seen it yet, it's worth a look. It's not been posted on the park's website yet, but you can find it here. It's still possible for a few more weeks that we'll have frazil form up in any of the Valley's growing side streams. If you're in the park and the Valley is below freezing at night, it's worth it to go out early to scope Yosemite Creek for fresh slurry.

Spring progress

More new snow in Yosemite Valley (see the Ahwahnee Meadow webcam at www.yosemite.org) and the high country. Road crews plowed 4 miles up from Crane Flat through modest snow cover.
Turkey vulture and Pacific slope flycatcher in El Portal. Cassin's vireo and Northern oriole on Monday's birdwalk. Tanager has been heard and seen in El Portal, but I haven't encountered them yet in the Valley.
Bears are increasing their activity throughout the Valley. Mariposa Grove Road will still be closed to cars for a while, though it's open for pedestrians. Shuttles from Wawona to that trailhead will start up in a couple weeks.

National Parks Week

Free park entry has made for a busy weekend of lots of visitors in Yosemite Valley. I see cars parked in places I've not seen them before. Turkey vulture seen again yesterday, canyon wren singing at Swan Slab. Raven drinking sideways from a puddle atop a granite boulder.
Yosemite Creek has increased in volume, with more mist blasting off of Lower Yosemite Falls; nice rainbow at 8 a.m. All Valley side streams are gradually rising into more channels now, and they'll continue to grow for some weeks yet. Another foot or two of high country snow expected Tuesday will slow this week's runoff to a bit later.
Tioga Road plowing usually gets going from the Crane Flat side now, but the coming weather will stall that some. There's still 53 inches at Tuolumne Meadows, with more depth between there and Crane Flat, not to mention an extra ration of downed trees from our one damaging February storm. Glacier Point Road plowing operations are chewing into a depth of 7 feet of snow there. Winter still rules the uplands.

Tanager and Waterfalls

Tom Steinstra had a nice article on Yosemite's waterfalls in the San Francisco Chronicle yesterday. It's very true that things are picking up, though recent cool weather has held the river volume to below average. Peak flow may be later and higher than average, though many variables over the next 6-8 weeks will affect what we actually get. The river has a long way to come up yet.
Heard then saw my first 2010 western tanager at the Yosemite Association office in El Portal this afternoon. The neotropicals are arriving in the live oak canopy. Nice birdwalk yesterday in the Valley, with many highlights including four kinds of woodpeckers. Shortly after we finished, ranger Karen Amstutz added two more woodpecker species. Join me every Monday and Thursday at 8 a.m. through May.

New Arrivals

Michael Ross reports a western kingbird and an ash-throated flycatcher in El Portal, in the Merced Canyon. Black-throated gray warblers are working their way up from El Portal, through the extensive live oak canopy toward the Valley, singing their buzzy song for the past couple of weeks. It's still chilly and leafless in the Valley, so the caterpillars on which the arriving warblers feast haven't really emerged yet. Aside from the versatile yellow-rumps, other insectivores are holding off their arrivals here. It won't be long, though.
Steve Bumgardner reports that yesterday was our 8th day of good frazil ice flow in Yosemite Creek. Watch for his terrific footage of frazil in action to be posted in the 'Photos and Multimedia' section of www.nps.gov/yose early next week. His "Yosemite Nature Notes" videos are an excellent resource.

Yosemite's Water Flow

The Merced River has more than doubled in volume (to more than 800 cfs at the Pohono gauge) over the past 4 days due to the warming that has followed Monday's snowstorm.
In addition to good flow from Tenaya, Yosemite and Bridalveil Creeks, we also see water now reaching the river from Sentinel, Eagle, Ribbon and Royal Arch Creeks. Horsetail Creek is flowing on the surface into Wosky Pond, though the pond isn't full enough to connect to the river on the surface.
Table Rock is still high and dry and the Merced has a long way to go to reach full snowmelt volume. Depending on how the next 4-6 weeks continue to warm, it should at least double or maybe triple its current flow. Splish-splash!

Migrants Arrive in Yosemite

I saw my first Northern Oriole in El Portal last night, starting to sing in a (non-native) deciduous treetop. It hadn't been there for the previous 20 minutes, so I feel like I literally saw it arrive from the tropics to its breeding ground. Yellow-rumped Warblers just started singing in Yosemite Valley today. Flickers and red-wings are singing in the Valley, though Monday's snow temporarily displaced the male blackbirds from their prominent territorial perches in Cook's Meadow. Three turkey vultures soared together a few hundred feet above Cook's Meadow at noon. We very seldom saw vultures in the Valley before five years ago; now they're seen each summer.

Yosemite's Curious Frazil Ice

2 April 2010

This is the month when locals look for frazil ice flows in Yosemite Valley. They can occur below any of our waterfalls, but are most often seen on large scale below Lower Yosemite Falls, when deposits can cover acres with what looks like snow, and can persist for months. We've had frazil forming on several recent mornings in Bridalveil and Yosemite Creeks.

It's hard to describe this material and its origin if you haven't seen it for yourself. Look at http://www.nps.gov/yose/photosmultimedia/ynn.htm in May for an NPS video that'll give you an idea. Imagine a creek turned into a slurry of suspended ice particles, or a lava flow made of ice, or spilling a million-gallon slushie drink into the forest.

It forms mostly in the spring when warm temperatures melt snow into high run-off and lots of mist in the waterfalls, then overnight freezing temperatures turn a portion of the spray into ice droplets, which flow along in the full creek. Because we get these conditions regularly, Yosemite is one of the best places to observe this 'waterfall spray ice' being created and then slowly melted away. There's a persistent myth that these deposits represent the sudden collapse of the Upper Yosemite Falls snow cone (a huge mound of ice that accumulates below the falls), but this is emphatically not the case. Frazil flows happen when it's quite cold, beneath falls with no snow cones, and they can happen repeatedly for weeks.

If you're lucky enough to be in the park this month, stroll by the base of the falls for a look.