Main Upper Jet continues to be aimed at Northern CA with its Moderate AR….Snow for Mammoth to begin late very tonight into Thursday…..Unsettled weather likely this weekend and next week…

2/27/2019. 5:00am

The AR has weakened and moved south into Mono County this morning and light to moderate snow fall can be expected through Thursday. Amounts above 7500 feet including the town will vary between 4 and 12 inches by Thursday afternoon.  There will be a break Friday with a small storm Saturday.  There appears to be a bigger system in the eastern pacific with a sizable AR will affect Mono County next Tuesday and Wednesday. With the AK block breaking down and a higher amplified upstream ridge taking shape, The pattern begins to favor areas more to the south again as the next week progresses.

At this time, the longer range shows no let up in the series of storms for the month of March….

 

the Dweeber……..

 

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Hello Fellow Dweebs!..   I have been asked several times about the Snow Phone and why it has not been working since the end of last month.   Well, it got lost in my move at the end of January, meaning that the phone company was not been able to get the phone line set up mostly due to the weather. That changed today. Hopefully, the weather phone will be in operation this weekend.

Mammoth sure has had an interesting winter so far.  There are actually two full days left of Meteorological winter as March first is the first day of meteorological Spring. This is different than the astronomical seasons by the calendar. The differences in this case, lie more in the behavior of climate in March than the three month previous.

The Past Week;

The forecast has worked out well.  It was indicated that a pattern change would be initiated by the Madden Julian Oscillation some 10 days ago as it was forecasted to move from phase 7 to 8 then cross into Phase 1, (East of the Date line). The tropical convection of the MJO continues strong. In my opinion, it initiated the (-EPO) and that was the cause of the change.  This change happened last weekend and here we are with a Closed Blocking high over Alaska, a strong trof over Eastern Russia and the EAJ forcing itself upon the block, splitting short wave energy under the block in the form of a negative height anomaly between the GOA and NE of Hawaii. The persistent upper low off the coast of the pacific northwest is phased with the flow coming northeast north of Hawaii. This is your moderate AR into Northern CA. Although the bulk of the energy as far as precip is focused from the Bay Area NE to Tahoe as expected, the winds have been horrendous. The cold air left in place from last weeks cold wave initially added to the gradient, then combined with over running warm air advection creating a downslope signature along the Lee of the Sierra Front. Most of the serious winds have been between June Lake along Highway 395 north to Reno. Gusts to about 100 miles per hours toppled several 18 wheelers along the highway Monday afternoon. The Down Slope signature is still there so be careful when traveling. Not only do to the Winds create problems for high profile travelers, but due to ground blizzard conditions, visibility can be reduced to zero at times as well.

Looking Forward:

The AR is shifting south and weakening. Best snowfall for the high country will be Wednesday morning into Thursday with amounts in the Town of Mammoth at the 8000 foot level between 10 and 20 inches and over the upper elevations about 20 to 30 inches between midnight Tuesday night and Thursday evening.  There will be a break Friday with the next system coming in Saturday into Sunday.  The models have been steadily weakening this storm and on the 18Z GFS dampening it out. There is not a lot of confidence in how much snowfall we will get but as time goes by it is looking less and less. Best guess get 4 to 6 inches in town and some 6 to 12 inches on the mountain.  I will update on amounts again on the weekend storm Thursday. I am sure amounts will change.

 

Longer Range:

The MJO is on the move, quickly going from Phases 1 to 3.  According to the MJO composites for March, these are still wet phases for Mammoth.  The pattern seems to become more progressive later next week with the break down of the block. It still looks like we will have the chance for another strong storm about mid week.  For what it is worth, both the 6 to 10 day and 8 to 14 day outlooks from the CPC are wet for Central CA.   In that the pattern goes into transition again next week, I will hold off on any serious outlook until later this week.

 

Dr Howard and the Dweebs……………………:-)

 

 

 

 

Cold weather to remain this week with light snowfall Wednesday night and Thursday……Pattern Transition likely next week….

Thursday AM the 21st…

looking at the 00z ecmwf and gfs…they come to agreement at this time of bringing the bulk of the precipitation with the initial AR to Northern California with the biggest push of precipitation for Mammoth beginning about March 1st through that 1st weekend of March. There after, there will be a series of storms affecting the central sierra as the upper jet favors our area again. Theses systems are likely to have subtropical connections as well.

In that the upper jet will be up in Oregon early next week, the best forcing will be closer to the jet.  Copious amounts of rain and snow seems destined for the northern part of our state beginning early next week with lighter amounts for the Central Sierra. The central and the northern part of the Southern Sierra is likely to benefit better about the 1st or 2nd of March with another possibly stronger forcing period early the following week.  So….The first good opportunity for Dynamic forcing will be about week away  A second storm after the March 2nd storm at this time looked even stronger as it is further south. There are another two systems possible afterwords…..  More later…..

 

will check on the longer range QPF after the weekend….

 

The dweeber……..

 

 

Wednesday night;

The second storm dropping south on Sunday will stall out some where north of highway 80 to the Oregon border with polar jet being confined to OR/CA border early next week. The polar jet is also parallel to the upper flow so this looks to be a stationary boundary. This area of bounty sets up with mild moist pacific air mass flowing in, under the polar jet. It appears that there is some confluence of the flow at 500mb between the mid pacific air and the polar jet just a few hundred miles off the Northern CA coast Monday. It also appears that either the right rear entrance region of the polar jet and or possibly a weak extension of the subtropical jet will become active next week as well.

So initially, the best forcing looks to be over Northern CA early next week. However, this mid pacific moisture can produce light over running snowfall here, as there is plenty of cold air around the central sierra.

The GFS also has a modest AR moisture tap that begins over Northern Ca Monday and slides south to the Central  Sierra Tuesday into Wednesday. So the likelihood of precipitation is increasing with snowfall a possibility as early as Sunday or Monday, however better chances toward mid-week. At the moment, although the first AR has a moderate Moisture tap, it does not look like a major storm as there is little vertical motion.

It should be noted that AR moisture usually needs strong vertical motion for it to become a heavy precipitation producer. At this time those features may come later in the week like the following weekend with the possibility of a stronger looking AR in tonight’s 00z GFS.

By this Monday, there should be plenty of ensemble members for a much better idea what kind of animal we are looking at next week.

The tempo is picking up…….⛷🏂

 

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Wednesday the 20th

The prospects for another AR as touted in several posts prior to this one are increasing now as last nights 12z Euro has come in step with the GFS idea of a strong eastern pacific oscillation in the negative phase. (-EPO)

The global models have followed the MJOs movement from phase 8 which it is into now, to phase 1, which moves it to the east of the dateline. This transition often, but not always creates, 1. Fast meridional flow (n/s) with the results of building a big blocking high over Alaska, followed by the undercutting of the westerlies. The trick for the forecasters in this case is to determine which global solution is the correct one at distance, between the euro model which is deeper with the newly formed eastern trof or the shallower gfs solution. The shallower trof is more progressive and moves quicker to the east and thus opens the AR door quicker to the west coast.

Timing between the models is at the soonest….about a week away, to as late in the ecmwfs case the end of that weekend.

This pattern has the potential to be a major event for CA…..

As always…..patterns can change….So the Dweebs will keep you all in the loop…..

 

Dr Howard and the Dweebs…….

 

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The month of March often has two faces for the forecaster as the first half of the month is more like winter while the second half is more like spring. The second half of that month is much less reliable for longer range forecasting so the Dweebs will take note accordingly….

After an exceptionally cold February, there appears to be relief on the way for next week. However, This week will still be exceptionally cold as the persistent western trof dominates through this work week. The latest GFS 12z run along with its ensembles still shows a -EPO set up by the next Wednesday. This is highlighted by strong positive height anomaly over the state of Alaska. The westerlies naturally under cut this block this time of the year.

The differences between the EURO and the GFS are seen week two as both models move the western trof east.  However, the euro has a much deeper eastern trof and further south. This models solution would cause stronger height rises along the west coast while the GFS is more shallow and east west with its eastern trof and more progressive. Both models have a belt of westerlies under cutting the AK high, however, the GFS is faster moving it into the west coast while the EC solution is slower because of the deeper eastern trof solution.

Additionally, the GFS has the MJO in phase 8 Longer than the  EC.  The storms off the west coast early next month are likely to have an AR connected to them and so they will be good Percip producers when they come in, sometime during the first week of March.

In the meantime expect the cold weather to continue this week with temperatures becoming much milder as we get into and progress through the following week.

snowfall tally’s from the Wed/Thur storm will be 1 to 3 inches in town and 3 to 6 on the Mt.

Mammoth Mt 5 Day Summit Storm Total 102 inches with base at top closing in on 20 Feet….The remainder of week will be cold with periods of light snow…..Week 2 still in question…..

It appears that we have come to an end of the big storm for the month of February. The weather will be cold through the end of this week with temperatures running some 15 to 20 degrees below normal. A California slider will bring a reinforcing shot of cold air into California Wednesday night and Thursday bringing additional cooling and continuing the trend of highs in the teens and 20s this week. There will be light snow that will bring some 3 to 6 inches of platinum powder during Wednesday night and Thursday. The will be some warming by next Sunday but highs may still remain below freezing.  On an interesting note, both Lake Crowley and Bridgeport residents may be greeted by low temperatures > -20F Tuesday morning so throw another log or two in the wood burner tonight. I call it a three dog night.

Longer Range:

looking at both the RMM2, the gfs phase diagram, MJO phase space, the MJO is still forecasted to stay in phase 8/1. Historically this is associated with the under cutting of the westerlies in February and early March. Beyond Mid March, the relationship breaks down. The European models ensembles show a strong -EPO and closed upper high over Alaska. This block should force the westerlies to the south, back into California. However, not until the first week of March, so we have a nice break coming up through the end of February…….Enjoy!