Archive for November, 2017

Moderate to Strong AR to effect the Central Sierra Wednesday night and Thursday with heavy snowfall expected over the higher elevations…..Weekend looks to be Dry…

WEDNESDAY PM UPDATE:

Wet portion of storm still on its way with high freezing levels well advertised.  Freezing level remain about 9K Thursday Mid Morning through 4:00PM then fall rapidly over night.   In a saturated air mass, the snow level is about 500 ft to 1,000 feet below the freezing level.  Uptown will have the best chance of accumulations tomorrow PM with snowfall likely Thursday night. Downtown Mammoth will most likely see rain or rain snow mix until about 9:00PM -10:00PM Thursday.

Outlook:

 

Improving weather Friday PM with fair weather Saturday.   THe is a smaller system that will bring more snowfall Monday with generally light accumulations.

Long wave hemispheric pattern shift to positive phase of PNA, with Retrogressing of upper high to the Dateline and Eastern pacific Trof north of Hawaii;  Ridge over the west and Trof in the east….:-{

 

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Winter Storm Warning above 8000 feet 400pm Wednesday through 4:00AM Friday. Accumulation’s 1 to 2 feet in the upper elevations of the Town of Mammoth 8000-8500 between Later Thursday Morning and Friday AM.

Between 30 and 50 inches is expected on Mammoth Mt above 9000 feet by Friday.

Snow level lowering to 7000 over night Thursday and 6000 Friday AM

 

From Tuesday:

Here we go again!   What a difference 24 hours makes!  Yesterdays small “AR” has grown in size over the past 24 hours aided by a tropical low along 20N and 130W.  This system’s moisture is being picked up by all global models to add to the fetch from Hawaii. It all adds up to a forecast for a Bonanza of snowfall for the higher elevations. This will certainly kick-start the ski season for Mammoth Mt as up to 4 feet of sierra cement is expected over the Sierra Crest between Wednesday Night and Thursday night.

Here are some of the details:

  1. PWAT up to 1.5 inches is expected in the Bay Area Wednesday night.
  2. 500MB/850MB winds are forecasted up to 50-60 Knots. (Orographics will be maxed out!)
  3. Thus, this is no longer a small AR

 

The snow level will range from 9000 to 9500 feet Wednesday night and come down Thursday morning to between 8000 and 8500. Snowfall amounts in the upper elevations of town may be in the 12 to 18 inch range. The snow level will lower into the lower elevations of town by Late afternoon Thursday.  If by chance the storm slows down Thursday night and continues into Friday AM, the Town could pick up quite a bit more. (I will have more certainty on this Wednesday AM)

Best guess is that Mammoth Mt between the Main Lodge and the crest will be in the 2 to 4 foot range. If by chance the European model is correct, there would be more snow top to bottom.

Outlook:

There is another AR or two looming in our future for Monday of next week and the following Wednesday/Thursday.  Looking at the current GFS set up vs. The ECMWF next week, I noticed that the upper ridge position is currently at 158W. During the next AR, the upper ridge retrogrades about 10 degrees westward to about 168W. The short wave in question begins to split but then consolidates and lifts north as it comes on shore. That would effectively shift the colder portion of the pattern, well to the north of us, leaving us with a Small to Mod AR.

The New12z ECMWF has a different set up and has less emphases on the AR for Monday but instead makes a big deal about what is to follow the day before Thanksgiving. By comparison, the ECMWF shows Mondays system less about major moisture and more about colder air, as the trof in fact does split. Its solution is all about shifting more energy further south so that LA may get rain.

Now I will just mention a bit about the Wednesday before thanksgiving system.  Potentially it is a Major AR! In the subtropical branch, the upper STJ extends back to the dateline this early Tuesday and both the polar and subtropical jets are confluent west of Northern CA Tuesday with Jet O’ genesis to 180 knots!.

The AR comes in underneath the subtropical portion assisted by the Rt rear entry region. Preliminary PWATs are showing up as 1.75 inches near Monterey, CA….close to 300% of normal and STD of +5 Wednesday evening.   This is a long way out but fun to see this Forecast run.  The Freezing level is about 10,000 which is not too bad considering….

 

Stay Cool…Winter is just beginning!

 

Dr Howard and the Dweebs……………………:-)

 

 

 

Small AR expected to impact the Central Sierra Wednesday night pushing south of Mammoth By late afternoon Thursday….Precipitation will begin as early as Wednesday afternoon……Expect a drying trend by Friday Morning then dry through Saturday….

Tuesday AM:

AR has become a moderate to strong AR now with the entrainment of extra moisture from a tropical system…..I will update after 8:30AM this morning the 14th….

 

………………….:-)

 

Monday Pm…Love posting when stuff is happening!

OK…Interesting twist this afternoon!  The new 12z EURO is splitting the trof coming in this Sunday. This is the one that the GFS has going north into Northern CA and the pacific NW with another AR.  But actually there is a fresh twist!  If the EURO is correct, it is going to cause a pretty significant change to our pattern, both upstream and down stream as it kicks the trof over the Eastern US out off the coast.  That would not make snow lovers on the east coast happy!

More importantly, that change if correct and that a big if, will tend to keep our pattern some what progressive and that means more storms hitting the west coast while the GFS wants to cut it all off. The current solution will help LA get some rain as well as the next upstream system actually splits with a lot of energy going south this Sunday into Monday.

I have to say that the ensembles are against the Euro solution, but why the change?   Stay tuned….this is what it’s all about!

 

PS> The snow level this Thursday is going to be critical to the Town of Mammoth, as there is going to be a lot of precipitation falling.  The big question is going to be about how soon the cold air is going to get here.  If it comes in earlier than expected, the town could get over a foot.  It is too early to know at this time. I will update on the potential change that the Euro is showing in the morning, or sooner if the GFS starts to follow later tonight….

 

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

 

Monday AM Update:

CRFC is showing about 3.75 inches of water over the west side of the sierra west of Mammoth Mt, Wednesday through Thursday night. With the snow level rising Wednesday from 8000 feet to 9000 feet, little impact from snowfall is expected in the Town of Mammoth Lakes during the day Wednesday. As the AR shifts south Wednesday night, heavy snowfall is expected above 9000 feet over Mammoth Mt with generally heavy wet snow expected to begin accumulating later Wednesday night/Thursday AM above 8000 feet. The Freezing levels is expected to fall Thursday morning and all day Thursday. Rain-snow mix will become mostly snow during the afternoon Thursday for the Town of Mammoth. I expect over a foot of wet snow at the Village at Mammoth, by Thursday Noon and 4 to 8 inches in town later Thursday afternoon.

At the moment, 18 to 36 inches of snow seems reasonable for Mammoth Mt Between Wednesday and Thursday night.  Precipitation rates will be especially high Wednesday night through Thursday AM.

 

I will fine tune all this in the morning Tuesday and again Wednesday….

 

The Dweeber…………………….:-)

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Forecast models continue to vary on the strength of the 1st wet system of season. The main issues are with the two jet streams, both Polar and Subtropical jets and associated dynamics. The Moisture is a given, but moisture without dynamic lift in an area can play havoc with precip amounts.  I think that we are close enough in time to have a fairly good idea that this will be a wet storm for Thursday from early morning to evening as the meat of the AR according to the 00z Monday European model is between 4:00am Thursday and 4:00PM Thursday.  There will be good orographics,  so precipitation is a given.

The freezing level will be high at about 10,000 feet, however, with subtropical systems, micro-physical processes can mess with snow levels to a big degree, especially during the wettest part of the storm Thursday. However, without much antecedent cold, it is difficult to believe that there will be significant snowfall accumulation below at least 8000 feet Thursday morning.

As cooler air begins to arrive during the afternoon Thursday, the snow level will come down and light accumulations will develop in the lower elevations down to about 7000 by evening. Snow showers are possible Thursday night.   Light accumulations are expected in town, as at the moment, the timing says that most of the precip will be over by late afternoon Thursday. Will update again tomorrow.

 

Potentially, this will be a good base building storm with wet snow from bottom to top on Mammoth Mt.. Amounts could range from “between” 1 to 3 feet. According to the ECMWF, the AR is forecasted to push south of Mammoth by 4:00PM Thursday. The extended looks dry…..

Dr Howard and the Dweebs…………………….:-)

Drier than normal weather pattern for the Southern 2/3 of California likley to continue as upper jet is focused over Northern CA….Expect periods of wind and a chance of snow showers Thursday and again Monday and Monday night as the next upstream’s upper Jet is again focused upon Northern CA……

The Weather over the far west is highlighted by the polar jet located over Northern California. Although there has been plenty of blocking near the Bering Sea the past week, the flow coming off Asia has been split to weakly diffluent at times. West coast weather system’s have been quite progressive with the upper jet bottoming out over Northern CA. This makes for a dry, windy pattern for the Central Sierra with below normal precipitation. This is especially true for the Southern Sierra and southern portions of the Central Sierra including Mammoth Lakes

 

Outlook:

There is some hope in the longer range models this morning as the new 11/8/17 12Z GFS control is showing more consolidated flow coming off Asia after mid month. At the same time, there is plenty of blocking in the -WPO region near the dateline.  The are an increasing number of ensembles in the GFS showing some under cutting of the westerlies with the formation of a Kona Low developing around the 18th of November. It is possible that moisture may get picked up from this area by a deep positive tilt, long wave trof extending SW from British Columbia around the 20th/21st. If this does come together, it would be more of a southern latitude system with a tropical connection or “AR” with fairly high snow levels for Central CA.  This may be followed by a colder system about the 23rd with the upper jet over Central CA as well.

For what ever its worth, the climate model,  the CFSv2  is showing the period  during week 2, which covers the 20th wet for Central CA.

Stay Tuned…the Dweebs got you covered!…….:-)