Yesterday's storm delivered with Alta, Snowbird, and Brighton all apparently colluding to report 15 inches this morning. Poor Solitude reported only 10 inches.
It's a wonder anyone could measure anything yesterday given the wind. I was out during the relatively peaceful mid-morning hours and caught some beaten up snowflakes on my ski pants. Look closely and you can find a few pristine ones, but otherwise it was mostly fragments.
Later in the day, as Gordon Lightfoot once wrote about the storm that wrecked the Edmund Fitzgerald, "the wind in the wires made a tattletale song" as a few gusts of over 100 mph were recorded at one mountain top observing site. Snowfall rates also increased, maximizing in the late afternoon, resulting in the temporary closure of Little Cottonwood Canyon.
The storm persisted, however, for a few hours longer thanks to the so-called "Alta Cloud." If you ever wondered what the Alta Cloud looks like, below is a radar image showing radar returns in the post-frontal northwesterly flow concentrated over the high terrain surrounding Little Cottonwood Canyon. Sorry Park City. No soup for you.
The snow has ended and there's some blue sky out there now, but expect the wind to be a tormentor on the ridges the next couple of days. We are wedged between an upper-level ridge off the coast of California and an upper-level trough over northwest Canada, leading to strong northwesterly flow at upper levels. The NAM 300-mb (roughly jet-stream level) wind vector and wind speed forecast for 5 PM MST this afternoon (0000 UTC 7 Feb) shows very strong flow extending through the Pacific Northwest to Colorado. Maximum winds along the Montana-Idaho border are in excess of 70 meters per second (140 knots).
This morning's sounding at the airport has a peak wind speed of 120 knots at about 250 mb.
That's pretty high (9 km above the airport) and winds at mountaintop level are a more sane and reasonable 25 knots, but overall the pattern is one favoring strong ridge-top flow during the period with some waxing and waning of flow strength as weak disturbances move along the jet. The middle left panel below shows estimates of wind speeds at 11,000 feet for Little Cottonwood Canyon derived from the NAM and you can see values near 70 mph at times through Monday morning.
Conditions down in the canyons are more difficult to predict. Sometimes they are decoupled from the ridge-top winds. Other times the strong winds scour down to low levels. Add your observations from today in the comments below as I'm doing the WFH thing today.
Mid morning gusts were moderate at Sugarloaf with limited snow transport, probably about as strong at Catherine area traverse with the trees moving excitedly. Not noticeably windy once off ridges. Snow was remarkably firm in some areas and really nice and supportive with a soft upper few inches in other more sheltered areas. Groomers at the top of Collins were very crusty by 11:30am where it was gusting pretty solidly.
ReplyDeleteThanks for sharing. I don't really understand how to forecast whether or not winds will be strong in the mid elevations. Waiting for people smarter than me to figure it out.
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ReplyDeleteSaturday noticed two wind directions in close proximity. We saw winds from the SW flagging off of Superior, Baldy, AF Twins... But at the same time out of the NW on Cardiff-Flagstaff among other areas. Lots of swirling?
ReplyDeleteBoth Saturday and Sunday the NW winds were nuking in Big Cottonwood Canyon. Seemed to be blowing straight up the drainages, not crossing over and filtering down from the ridgetops. Skiied USA bowl on Saturday and the entire bowl was hammered- found good skiing in the aspens that were on the lee of the ridge that separates Guardsman Road from USA bowl (on the Guardsman side), but even down in the trees the wind was having its way. Skiied Beartrap on Sunday, and the winds seemed to be even stronger. Even deep in the Beartrap Glades the wind was scouring down from the ridgetops (Beartrap bowl has a pretty strong NW kick meaning the wind was "in its face") and also coming up from the drainage ('splain that one!). Also saw one of the biggest slides I've seen in the Wasatch lately in West Monitor-- essentially the whole bowl fractured out. Be safe out there!!
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