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Archive for December, 2021
Cold Western Trof Shifts East This Weekend bringing a beautiful ski weekend……Another potent storm sets up over the eastern pacific next week…..
Tuesday December 28, 2021
12/29/2021
The forecast remain the same through the weekend as the current western trough gets ready to exit. One more system today whose short wave is splitting off shore will bring the lions share of precipitation to Southern CA today and tonight. Here in the high country, some 6 to 10 inches is expected on Mammoth Mt with half of that in town.
Tomorrows progs has the large scale upper trough shifting east a bit. That sends all the short waves down through Nevada. With short wave energy over land, over snow cover all the way to the Canadian border, there is little in the way of air mass modification, meaning modified arctic air will highlight our temps Friday into the Holiday with snow showers Friday. Bridgeport valley may go -20 to -25F Saturday AM. Good news is that if you Bridgeport folks want to warm up, drive up to the resort levels over the weekend as temps will be inverted! Highs in the 30s in Mammoth and June.
The trend in the longer term, IE next week is to keep the Tuesday storm, further north now. So not a lot of confidence on how much if any snowfall we may get. In the past 5 days, the ECMWF had the right idea with west coast height rises VS the GFS that was overly deep with the January 4th storm. It is now questionable if we will have a major storm here in the Southern and Central Sierra Tuesday as the models are trending that system more to the north, as the hemispheric pattern goes into transition. The transition appears to involve a break down in the north-central pacific block. Additionally the Pacific North American pattern that has been negative goes neutral. This all adds up to a milder weather trend, especially later in the week with the possibility of west coast ridging returning. Will an AR affect the west coast later next week before we ridge up? Only the shadow knows! 😉
Dr Howard and the Dweebs……………………:-)
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One Item about weather patterns is that they never remain for long periods in their same form. Watching the week two (fantasy charts) is one way to catch what change there will be in our outlook period. This winter so far and Fall has been very humbling for the vast majority of climate or interseasonal forecasters as this is a La Nina Winter, and as winters go, they have a dry bias in the southern half of the state. As we have seen thus far, not all La Nina winters are dry for the south west coast.
Currently, according to the CA data exchange, the San Joaquin Drainage is 170% of normal for the 27th of December. We are off to an amazing start!!
From the Dweebs Desk this Morning;
Our current frigid Western Trough has a couple more impulses to deliver. One that is bringing some wind to the high country this morning with a chance of light snow. Another that will bring light to moderate snowfall Wednesday and Wednesday evening. Some 5 to 10 inches is expected for Mammoth Mt by early Thursday AM. Daytime highs will continue in the low 20s with lows in the single digits. The cold upper trof exits Thursday, as a couple of inside sliders drop down the eastern slopes. Some light snowfall accumulations are expected Thursday evening and Friday. Beyond Friday is the skiers dream. A massive snowpack for December and fair weather. If you are reading this out of the area, this is the weekend you have been waiting for!!
Longer Range:
There appears to be one more storm associated with this pattern before the current upper high blocking pattern over the North Pacific breaks down. This new large scale trough is being handled differently by the global models in that the GFS is much deeper and has a stronger upper Jet for Central CA at this time. It boasts some 3 to 4 feet of snow on Mammoth Mt at distance, However, the EC brings in about 1/2 of that. The Jury will be in by this weekend. The Big News is that the pattern is going into transition. This begins about the 6th of January. The Classic Closed anticyclone shows up over Alaska. Additionally the European Global has the same Anti Cyclone Signature in the same time frame….So confidence is increasing in the outlook period. Why is this significant? In January, when the upper jet runs Supreme, the westerlies can break under a blocking pattern when the MJO goes from phase 7 to phase space 8. SEE Example above. The MJO progressing from 7 to 8 has the effect of extending the East Asian jet, thus pinching off upper high and cutting it off over Alaska. This can unleash a nasty, mild in temperature and possibly strong to extreme AR along the west coast. Keep in mind that this is not a forecast at this time, but it is definitely something to watch out for the following weekend of the 8th and beyond.
Heavy Snowfall this morning followed by a splitting system Wednesday….A bout of modified arctic air later this week….Chats about blocking pattern….
Monday December 27, 2021
Were off to one of the best starts in a water year since winter 2018/19. The reason? A mid pacific Blocking Pattern that has persisted for several weeks…. It is important to note that blocking patterns are not all alike. A blocking ridge over the far eastern pacific brings cold to the east and dry weather to the far west. However, a block in the northern latitudes well North of Hawaii and at times west to the Bearing Sea can force storm energy to drop south from the Arctic via AK or British Columbia…….Or there is always the possibility of the westerlies undercutting the block which can unleash a lower latitude storm track. We love north Central Pacific Blocking Patterns as more often than not, that is the way California and especially Southern CA gets their rain!!
After today’s 2 to 3 foot dump of platinum powder on Mammoth Mountain, there will be one more system that will split off shore and actually favor Southern CA this time with heavy rainfall developing Wednesday into Thursday. This system may produce only light to moderate snowfall in Mammoth Wednesday. (6 to 12) inches. After Wednesday, we go into an inside slider pattern which is extra cold and snow showery….Thursday night through Friday evening…then cold through New Years day. The north pacific ridge dampens this weekend and so there will tend to be a break in the precipitation for CA Saturday and Sunday.
Next week is uncertain. As while the American models show the North Pacific Block redeveloping and Amplifying northward setting up another protracted stormy period Wednesday through Saturday, the ECMWF does not agree as it is overall less amplified, then pinches off the upper high well to the north. We may get some snowfall out of that pattern but it is a much less potent storm than the GFS. As always, time helps resolve longer range forecast issues!
As mentioned before, I believe that this is the Winter of the AR for California with more coming later this winter. More later……:-)
Dr Howard and the Dweebs…………………:-)
Platinum Powder Alert for Sunday AM…..with 1 to 2 feet of Platinum Powder possible….Additional Storm totals of 2 to 5 feet by Tuesday AM….Turning Colder….
Friday December 24, 2021
Oops!
Not sure what’s happened with the pattern out over the pacific. It looks like the blocking high that would not die….
canceling the big change in the pattern for the time being…..concerned where the pattern is going…..,
Sunday the 26th,
Latest update shows cold Trof to being additional amounts of snowfall through New Years…..However, big change in the pacific pattern will break down the central pacific ridge and thus will bring an end to the current siege of storms, “during the first week of January”….By the weekend of the 8th, the Dweebs expect an upper ridge to dominate the far west for a while. Note…….There may be one more storm early the first week of January.
Dr Howard and the Dweebs……………………:-)
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AR with many areas in the high country receiving 6 inches + of Water past 3 days…. The AR ended up in the Low level 3 range and has been extremely beneficial to California Water Supply. The snow level went as high as 8500 feet Wednesday Afternoon and was down to 5500 at 6:00AM Thursday AM. Our storms will bring all snow to resort levels through the end of the year now. There is a Platinum Powder Alert for Sunday AM for the possibility of some 1 to 2 feet of cold dry powder on Mammoth Mtn. 7 day QPF suggests between 7 and 9 inches of water additional through New Years. 6 to 8 more feet of snowfall by years end from today.
For those that are interested, The upper hemispheric pattern is being forced by the MJO in Phase 7. It been static there and strong. It has strongly contributed to the mean position of the blocking ridge between the GOA and the Bering Sea.
- SEE: https://www.wpc.ncep.noaa.gov/medr/mrfmeans.shtml
- The question remains where does the MJO from here in the weeks to come. The CFS suggests phase 8. That location often highlights a Closed High over or near the Bering Sea.
See: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml
AND and another AR above week 3…….. 
Again….The big question remains….Where do we go from here? There is going to be a major transition in the pattern during the 1st week of January. Pattern recognition suggests Phase 8 by the Climate forecast System which can be very wet for CA. We’ll see…..
Merry Christmas and Happy Holidays to all from Dr Howard and the Dweebs……………………..:-)
