Can’t Shake the Block…
Thursday Morning Report:
Reports of 2-3 inches at lake level and 5 inches around 6500 and higher. I had 5 inches here in front of the office at 7000 ft. Sugar Bowl is reporting 8 inches up top. That was way more for everyone than expected. The forecast was only for maybe a few inches on the crest but no accumulation at lake level. The cold front was stronger than expected and we picked up all that snow in about 4 hours as it passed through. The temperatures dropped around 20 degrees from the morning when it was near 55 in Truckee and then 32 degree by 3 p.m. when it was snowing.
We have another cold shot with some snow possible Saturday night. Again I’m not expecting much if any accumulation but another suprise is always possible. Looks like we will have to deal with the unsettled weather for another 10 days or so before we have the chance of some quiter and warmer weather moving in. Stay tuned…BA
Wednesday Afternoon Update:
Cold front has a little more moisture and punch than the models showed. Already a few inches along the crest and starting to accumulate in Truckee. Snow levels have dropped as low as 3000 ft. on the West side. Once the snow ends in a couple hours it should melt quickly at lake level.
To use a football term. We have been in a repeat pattern since last November where once a month a blocking pattern sets up and gives us a prolonged period of unsettled weather. The difference right now is that the jetstream is much weaker than in the winter. The ridge is trying to build up from the Southwest but the squeeze is on as blocking to the North is holding the jetstream into the Pacific NW and Northern CA.
The ridge out in the Pacific is in the perfect position for cold storms to dive in if it were winter, and it will try here in May. It looks as if the blocking to the North will start to shift by this weekend but it was successful in keeping some cooler and unsettled weather around when the teleconnections were supporting a ridge. Now as we go into June the teleconnections forecasts point towards a pattern that could support a trough along the West Coast.
There is a quick hitting storm for tomorrow afternoon into tomorrow night and it has a nice little punch of cold air. We should see rain turn to snow even down to lake level tomorrow night but not expecting any accumulations. Nice weather returns going into the weekend but then another storm brings cooler air and a chance of showers on Sunday. Highs at the lake are going to stay in the 50′s at lake level and the 40′s on the mountains after today. There is a chance of some more unsettled weather the middle of next week as we remain stuck between two ridges with a trough along the West coast.
If this was mid-winter I would be saying what a stroke of luck as blocking & the MJO brought us snow instead of sun and now the storm door will stay open, but we are just about at Memorial Day weekend and I’m hoping this isn’t the summer that wasn’t. It’s been pretty amazing the amount of cold air pouring in this Spring, even in the Midwest and South causing all these tornados. The Pacific is cold especially off the coast which has been keeping the summers cool along the CA coast.
I use both the overall Pacific temp (PDO) and the El Nino/La Nina region (ENSO) as a big factor when looking at the winter forecasts. Mod/Strong La Nina in a Negative PDO coming off a strong El Nino is what gave me the forecast of 125% of average snowfall for this past winter. Of course I was way wrong and we picked up over 150% of average. I will be watching the Pacific over the summer to look at next season.
For right now we have a weakening La Nina which tends to support a hot summer, but what about coming off a fairly mod/strong La Nina during a cold PDO with cold water off the coast? Those are the summers of 1956, 1972 & 1974, anyone remember those summers here in Tahoe. I will have to try and find some data. For next winter I like the look of the following winters which are weak La Ninas and a toss up for snow here in Tahoe. Precip was below average for all of them and snowfall for two of them, but 74-75 was so cold the snowfall was above average.
What is interesting is that we are almost directly repeating 1971-75 with a moderate La Nina in 07/08, weak La Nina in 08/09, Strong El Nino in 09/10, and then a borderline strong La Nina this year. Then what looks like a weak La Nina for this next winter. The cold can definitely save you in a below average snow year like we had in 07/08. After that I would expect more La Ninas than El Ninos over the next 10-20 years in the Negative/Cold PDO.
We had the last negative PDO from the mid 1940′s until the mid 1970′s. From 1956-1976 we had 10 La Nina winters and 6 El Nino. From 1976-1996 we only had 3 La Nina winters and 7 El Nino, and that was during the positive/warm PDO. The years during the last cold PDO cycle that did have El Nino winters the above average snowfall winters out numbered the below average 2-1 and the La Nina years almost 2-1. So we should have some good years coming up even if next winter is below average.
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