December 24, 2009
A ridge of high pressure over the California coast will keep Tahoe clear through Christmas Day before a modest storm tries to nudge its way through the barrier to bring some new snow to the Sierra over the weekend. But the prospects are iffy at best, and if we do get snow, it will be just a few inches.
The low pressure system forming in the Pacific Northwest is forecast to break into pieces as it arrives in California Saturday night. The biggest chunk of that storm's energy looks as if it will spin down the coast all the way to Baja California, where it will hang out for a day before making its way east.
The energy that remains should cross the Sierra in two waves. The first would be Saturday night and would be quite weak, possibly producing a few snow showers. A second wave would arrive on Sunday, and if it stays on track could add up to 6 inches to the snowpack above 7000 feet. The forecast is showing only about one-quarter inch of precipitable water for the Sierra, so the pickings are pretty slim. Snow levels would be below 5000 feet by Sunday morning if that system does make it past the ridge.
The storm door will remain open after that, but it's not clear that anything will step through it. Some of the forecast models are showing another small storm possible Monday and Tuesday. Other models show the region remaining mostly dry. One thing for certain is that there are no megastorms on the near horizon. Anything we get between today and Tuesday is going to be a modest little addition to the coverage.
Check www.tahoeloco.com for updates as these storms approach.
El Nino Watch
The El Nino condition in the Pacific Ocean is holding strong, with sea surface temperatures 1.8 degrees Celsius above average in the week that ended Dec. 21. Anything greater than 1.5 degrees above average is considered a "strong" El Nino if it persists at that level for three consecutive months. The big question is when we will see that condition translate into tangible effects on the Sierra weather. History suggests that a strong El Nino will bring warm wet storms to Southern California, with some of those veering far enough north to bring rain and heavy high-elevation snow to Tahoe. Most of the long-range forecasts are still suggesting that we will see something along those lines after the start of the year. But so far most of the storms we've seen have had a typical northerly orientation.
SHAKE, RATTLE AND ROLL
Did you know that there was an earthquake in Tahoe this week? A magnitude 3.7 temblor struck at about 9 p.m. Tuesday about five miles northwest of Incline Village. It was followed by nine aftershocks. No major damage was reported.
MONTHLY WEATHER ALMANAC FOR DECEMBER TO DATE
High: 50 on Dec. 1, 4
Low: -15 on Dec. 9
Average temp: 23.0
Departure from norm: -6.2
Normal precip for the month: 4.34Percent of normal: 79%
Total snowfall: 46.9 inches.
SOUTH LAKE TAHOEHigh: 51 on Dec. 1Low: -13 on Dec. 8
Average temp: 27/8
Departure from norm: -5.0
Normal precip for the month: 5.40 inchesPercent of normal 38%
Total snowfall 28.0 inches.
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