Friday, December 31, 2010


Update 7 pm:

Here we go, this weekend we are going to need to make lots of updates with the unpredictability of the cut-off low. Really cold air is locked in place so as the warmer air with the storm rotates in overnight it will create overrunning and lift. Models are coming in a bit faster and wetter this evening which means we could see 2-4 inches by morning. We still have to watch the track of the main low coming onshore Sunday but we could double down on this amount. Stay tuned......BA

Previous Discussion:

Still a complicated forecast for this weekend. You can see the cut-off low nicely on the satellite this morning. The low will work its way down the coast over the weekend and then come inland over Central/Southern CA. The models are still in total disagreement on the exact track and that has a big affect on our snowfall amounts. Basically the question is how far South of us does the storm come inland? NAM says 2-4 inches, GFS says 4-8 inches, and Euro says 15-20 inches. Usually in this case the best thing to do is shoot for the middle. But in my experience with these types of storms we seem to get less and a lot of the snow gets hung up on the crest so I am going with 2-4 inches and we can adjust as it gets closer. We will see clouds and spotty light snow showers Saturday with the best chance for accumulating snow on Sunday.

We will have to watch the storm as it progresses over the weekend. Normal storms ride the jetstream and so wherever the jetstreams points the storms go. Cut-offs are "cut-off" from the jetstream and therefore it is hard to predict where they will go, they can even go backwards. Lots of fun for forecasters.

Next week the ridge builds towards the West coast and we stay quiet all week with normal temps, which is in the 30's for this time of year. Looks like we could see a small storm the second weekend of Jan. as the ridge retrogrades a little West allowing it to slide into Northern CA.

There has been suggestion in a few run of the models including this morning GFS that a blocking high pressure could set up near the Aleutians again between the 10th and mid-month. That could mean we see another repeat of the subtropical feed across the Pacific into CA. This morning's GFS run looked almost exactly like the setup we had with our big storm 2 weeks ago. This is still 10 or more days away, but I have been looking for retrogression of the ridge towards 160w in the long range. If it shifts North as well then we could see a strong jetstream come underneath and we get pounded again.

The trifecta of 3 months in a row getting dumped on mid-month is a possiblity. If we see a 3rd 70+ inch storm Northstar will hit its seasonal average and the rest of winter will be bonus. I know I have nailed it 2-3 weeks out 2 months in a row, but that was part luck so don't take this as fact it's way too early to get our hopes too high. Keep the snow dances going. BA

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