Saturday December 31, 2016
Posted at 11:54 am by Howard
Its been interesting to watch the big mass of cold Arctic Air being handled by the forecast models. It is important to realize that it takes a reservoir of cold air to tap from over Canada for the pool to from. Keeping in mind that for the far west coast, which normally does not get this kind of cold air mass, even every 5 to 10 years of this magnitude, the pattern has to be especially out of kilter.
This year up to today, New Years Eve, has experienced a lot of the pattern of the -EPO and -WPO. The negative phase of the Eastern Pacific Oscillation (-EPO) is one where you have a big blocking high pressure system in the Gulf of AK. To get Arctic Air In January to plunge down the west coast, you need the Block to have strong legs as well! This means that it needs to be pretty much a full latitude ridge, just west of 140W and positive tilt as well. However, climo wise, full latitude ridges in January are not that common in this area. They are more common in December. The forecast has been one of tapping the polar vortex and pooling up some amazingly Cold Arctic air and plunging it south through at least Central CA. Temperatures at 10,000 feet (700MB have been forecasted to flirt with -20C for the middle of the new week for Eastern CA and Western Nevada.. That would be highs in the Town of Mammoth in the low teens and nights below zero for a stretch of at least 4 to 5 days! IE A real Pipe Buster! However, this is no longer as likely to happen!
There has been some real back peddling with the southward push of this frigid air mass of late, stalling it out over Northern CA and NW Nevada. To add insult to the weatherman and injury to his ego, the air mass will shift east pre maturely. According to both last nights 00z GFS and ECMWF runs, and now this mornings 12z GFS and European, this happens by Tuesday. An important point to make is that the 12Z deterministic run of the European is similar to the GFS, but is not as dynamically aggressive with the lead undercutting (Storm), that the GFS says will hit the sierra early Wednesday AM, the 4th of Jan. Both models handle short wave energy and the height field differently between Wednesdays storm and the Sunday Storm. This is of concern to any fair weather forecasted between systems. The Sunday (Jan 8th) storm into the following week is associated with a deepening (-WPO). This means that the block over the -EPO region will retrograde to the -WPO region or from the Aleutian chain, into the Bering Sea. The wave length suggests retrogression of the long wave Trof from 120 west to about 130 West, then positive tilt deep into the Subtropics. Thus a major “AR” event is possible about next Sunday into the following week. All Global models show it including the GFS, ECMWF and the Canadian.
So what this all means, is that the odds are, that it will not get as cold, but expect more snow, beginning as early as Tuesday night into at least Wednesday Night…..
Another model run or two with a consistent GFS and or European model run will give the National Weather Service the confidence to either go to a winter storm watch for either Tuesday night or Wednesday or a snow advisory. The Wetter GFS models is suggesting a few feet from the Wednesday Storm. The Sunday through Wednesday storm for the following week is currently showing up as a monster! …… The powder for the Wednesday system looks cold and dry but the platinum powder criteria is becoming less likely….
Dr Howard and the Dweebs…
I’ll have an update written tonight for your New Years Day Weather Letter…..
Mild Weather to give way to unsetteled weather for the weekend….Best chance of snowfall….Sunday night into Monday…Turning much colder as Arctic Front approaching Sunday Night…..”Platinium Power Watch” for Monday through Tuesday Night….
Wednesday December 28, 2016
Posted at 9:33 pm by Howard
Thursday AM Update:
- Cut off low is turning east before any significant effect upon the Central Sierra. Updates show that clouds and a few snow showers possible, but accumulations are very unlikely for the Friday/Night system.
- Saturday’s small coastal hugger from the north may bring 1 to 3 inches of snow Saturday/Evening. This is going to be mainly a storm for the coast and Southern CA. SC Local mountains will do well with moderate amounts of snowfall.
- The most interesting storm will be the storm developing New Years Day Eve. This type of storm has CP; “Continental Polar Air”. It is our coldest pattern for the Eastern Sierra. The Arctic front will move into the High Country Sunday Night with wind and cooling along with the chance of snowfall. Snowfall for the Period Monday through Tuesday night may drop a foot or more of snow, at snow to water ratios of 15:1 to 20:1. Hence, I am issuing a Platinum Powder Watch for that time period.
- Another point to make is for Property managers throughout Mono county including Mammoth Lakes. The Arctic Air will arrive throughout the day Monday and remain over Eastern CA through Thursday night. There will be 3 surges of Arctic Air next week. Be sure to take precaution’s to prevent frozen pipes by turning up the heat in all residence’s and condos Sunday night. This protracted event No doubt will be a Pipe Buster for many in the area.
- For the skiers and boarders coming to Mammoth next week…..Be sure to plan on using face protection during much of next week. The pattern of cold will give way by the end of the week to a milder wetter pattern by the following Sunday or Monday…
From Wednesday PM:
Short term Forecast: The forecast over the weekend is one of which is unsettled. There are small several weather systems that will be effecting the Mammoth Area.
- A cut off low to the Southwest of LA. This system will bring mainly light amounts of precipitation in the form of snow to elevations above 7500 feet Friday. Initial estimates are 1 to 3 inches from the Friday/Night system, over the upper elevations. Highs on Friday will in the low 40s. Lows in the upper teens. The next system will drop down near the CA Coast Saturday or just inland. It is a bit colder and so it will have a bit lower snow levels. Again this system is not expected to be a significant snowfall producer. 1 to 4 inches depending upon exact track, IE; If it remains along the coast, lighter amounts. Winds will not be a big issue through Saturday evening. Highs on Saturday will be in the upper 30s in town with lows in the teens.
- The Sunday/Monday system is a different animal in that is an Arctic front. It will have a lot more wind with it, especially for the upper elevations and it will bring a lot of cold air. Winds will pick up late Saturday night into early New Year’s Day. Snowfall rates will pick up especially Sunday night with 6 to 12+ inches of cold dry powder by Monday, depending upon how fast it moves through and how far west it swings. Note, temps are for the Town of Mammoth.
At the moment, modified Arctic Air will dominate the weather the early to middle of next week. Expect Cold, Breezy weather with periods of snow showers the middle into end of next week with highs in the teens and lows in the single digits and below zero at times.
By weeks end or the beginning of the 2nd week of January, Heavy Snowfall is a possibility.
Today’s hemispheric pattern and future WX progg’s are nothing less than fascinating this Wednesday morning! In early December, I made reference to that fact that the blocking patterns of the Fall would likely redevelop in January and todays ensembles are forecasting just that. The most interesting point about this –WPO or –EPO blocking, is that it is not being forced by the MJO!. It’s forcing is somewhere else and I have not a clue from where! (SSTA’s in the Bering Sea?)
The Difference between the –EPO (Eastern Pacific Oscillation and the –WPO Oscillation) is mostly about the location of the mean upper height anomaly. Whether it is in the Gulf of AK or well over the Aleutians and amped over the Bering Sea. This difference is so profound for California weather that is has to be notable. It is all about the wave length! As an example, with the upper ridge in the –EPO sector, the upper jet usually pulls down cold arctic air from sources via the NW Territories to west central Canada depending on how positive tilt the Gulf of AK, upper ridge is. So next week’s weather will be totally influenced by the –EPO and the trajectory of Arctic air. This is not usually a heavy snow pattern, but one that is exceptionally cold. Cold weather will likely be the weather highlight the first week of January. Then the –WPO pattern will follow, the following weekend as retrogression develops. Once the Upper height anomaly, gets back “toward” the Bering Sea, a new adjustment wave trof will develop well west of the west coast. In that a rich source of Arctic Air has been established, the over water trajectory around this upper air cold pool will be explosive with “Jet o Genesis”. Now here comes the interesting part…. “IF” during the morph from –EPO to –WPO is very successful, the newly positioned long wave Trof will deepen SW and down the west coast and pick up the remains of a Kona Low or subtropical low near Hawaii. That could be the big “AR” event since 1969, “if” the Valleys like the Owens Valley remain trapped in Modified Arctic Air. When? Timing like early the 2nd week of January. It’s a long shot anytime you are thinking about snowfall in feet on the Owens Valley, but this pattern the 2nd week of January is a possibility.
In the meantime, we have a couple of nice mild days ahead with highs in the 40s, lows in the 20s. Winds will remain light through Saturday afternoon. Stronger winds will develop ahead of the Arctic Front “about Sunday, New year’s day. Snowfall will increase Sunday night into Monday.
Maybe a Platinum Powder Watch issued early this weekend. We’ll see how it develops….
That’s all from Dr Howard and the Dweebs………………..:-)
Milder weather ahead as a flat ridge builds in over head….Strong Valley inversions expected…..Next weather system is a California Slider Friday night into New Years Eve…..Bitter Arctic Break out possible just after New Years Day….
Monday December 26, 2016
Posted at 9:50 am by Howard
Todays brief update calls for milder weather into Thursday with highs in the 20s Monday, 30s Tuesday and 40s Wednesday and Thursday. Winds will be light and lows at night in the single digits then teens Tuesday am. The fair weather trend will continue into Thursday with increasing breezes by Friday. The next storm will bring light amounts of cold dry powder Friday night into Saturday. It will be a cold system with gusty winds Friday and Friday night. Highs will cool to the upper 20s by New Years Eve and nighttime lows will cool back into the single digits and teens…
Longer Range Suggests Bitter cold week after New Years Day….
More in My Weather letter tonight or Tuesday AM. http://data.mammothweather.com/landing/