Major Storm Cycle Ahead as -EPO Rex Block Forces Strong Southerly Stream into Central West Coast….Copious AR Precipatation Event Probable for the Northern and Central Sierra….

UPDATE 10:45 AM Monday:

The QPF updates keep coming and the resounding questions becomes… will there be a break as several waves of energy are expected to pound Central CA this week.

The series QPF 24 hour bull’s-eyes moves slightly north and south of a pivot point from about Mammoth Pass this week as follows..

  1. Day 1   24 hour amounts  4:00PM Monday to 4:00PM Tuesday      =              .35 to .50
  2. Day 2   24 hour amounts  4.00PM Tuesday to 4:00PM Wednesday =                 4.11
  3. Day 3   24 hour amounts  4:00PM Wednesday to 4:pm Thursday    =                 2.50
  4. Day 4   24 hour amounts  4:00PM Thursday     to  4PM Saturday     =                 2.50
  5. Total day 5 MAX   About 9.5  inches at Mammoth Pass Before Snow levels rise to 9000 ft  This means that the town may get 3 to 4+ feet before AR event.
  6. Total 7 day Max 18 inches over Mammoth Pass

Note:  This has the potential to be one of the historically significant precip events for Central CA.  Considering all the fires the past 5 years, leaving burn scars in the forest.  Rock slides, mud flows, and road damage on the west side of the sierra are being considered….

On the bright side, most if not all reservoirs will be topped out by the end of this storm cycle.  Some Dams may be forced to spill….

PS  I looked at both todays 12Z Monday GFS and ECMWF total 10 day QPF. added them together and averaged them out. They paint about 30 inches of water over a 10 day period at MAX over the Sierra.

 

 

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Monday the 2nd 8:40am update shows that the 1st storm moving in Tuesday afternoon will continue through Thursday morning with snow showers Thursday afternoon into Friday. The storm will drop between 18 and 24 inches of snow in town and about 3 feet on Mammoth Mt.

The big AR event for the upcoming weekend will begin Saturday in town. However, preliminary guidance indicates that the freezing level goes up to 9300 feet Saturday night the 7th.   At this time….Odds are higher that the weekend storm will begin as snow, turn to rain in town Saturday night and into Sunday….then turn back to snow late Sunday night…..  The snow level may rise as high as 9500 by Sunday 12:00PM. This of course is all subject to change…..but confidence is pretty high that a major Atmospheric River Event will hit next weekend……7 day QPF is between 16 and 17 inches over the Sierra Crest near Mammoth Lakes by next Monday AM. The Dweebs expect this forecast may even be under done….  Stay tuned for updates….here and in my weather letter….

 

The Dweeber……………………:-)

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The Dweebs have been watching the global models and their handling of a weather pattern that has already happened before in early December and has been destined to repeat itself again now for January. It appears that the current Arctic front will stall itself out, mostly north of 40N and give way to a strong under cutting, subtropical jet which will eventually couple with the polar jet later this week.  The trend of ensembles are nothing less exciting than the event itself which may deliver some 5 to 8 feet of snow to the Town of Mammoth, (If it is all snow) and some 12 to 16 feet over the upper elevations of Mammoth MT over the next 7 days. We will have two Atmospheric River events, one light to moderate one mid week and the other AR event will hit Saturday into the following Monday. Folks…that one will really get your attention! So pineapple up and ever,

This is a developing pattern with the forecast ability of the details likely only within a 24 to 48 hour period before each surge….The Crescendo is likely over the upcoming weekend into the following week….

Get the shovels ready and the snow blowers fired up and working….We should have a wild 7 days ahead,  beginning soon….

 

More later……………..

 

Dr Howard and the Dweebs…………………………..:-)

Forecast Models Throwing inside slider…..Strike 3 for the Weatherman….Big changes ahead…

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!

Changes Ahead!

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…..

 

The Dweeber…………………..:-)

 

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….

Thursday AM Update:

  1. 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.
  2. 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.
  3. 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.
  4. 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. 
  5. 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…

 

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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.

  1. 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.
  2. 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.

 

Longer Range:

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………………..:-)