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!

 

Mammoth Mt Boasts biggest February on Record with up to 23 feet of New Snow…..Current storm total up to 7 feet with another 12 to 18 inches on the way…..

Sunday…the 17th,

The GFSX just finished running and not surprisingly it too has picked up on the retrogression of the eastern pacific ridge next weekend and the eventuality of the -EPO blocking pattern over Alaska. The resulting westerly flow undercuts the block and sets up a milder mid pacific storm track, compared to the more northerly track we have experienced the past several weeks. Modified Arctic air has been the theme with the dominate polar jet  the past weeks….  That looks likely to change with more Maritime pacific air masses moving more zonally across the pacific. This too is potentially a wet pattern for the Sierra. Although we do not know, as it is too early, where the East Asian jet will set up over California, it potentially will bring a period of wet storms to California with a series of AR filaments brushing the golden state.

In the mean time for the upcoming week, it will be cold in the high country with inside slider systems bringing periods of snow showers with light amounts of snowfall through Thursday or Friday. Highs will remain below freezing low 20s, with lows single digits at 8000 feet.

 

The Dweeber……….:-)

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Sunday 6:00am. 5 day storm total on Mammoth Mt.  5 to 8  feet…. More to fall today… 3 to 6 inches

 

11:30pm

Just a quick look at the new 00z feb 17 euro this evening, shows a large positive upper height anomaly developing over Alaska in the EPO region days 8  9  10.  A strong belt of lower to mid latitude westerlies is working its way east toward the central west coast. This would initiate a series of ARs with a mid latitude storm tract during the week 2 period. In that the EC is better at distance…The Dweebs will keep a wary eye on this trend. This has the support of the MJO.

BTW..it looks unlikely that the current typhoon over the west central pacific will have any affect on the westerlies…the tropical storm does get absorbed by the westerlies, however little if any amplification occurs…

 

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From Saturday AM;

Platinum Powder now falling over Mammoth Mt with about another 12 to 18 inches expected by Sunday evening…most of which will fall today as the last of the storms including Wednesday night and Thursdays AR, moves south and east. This month of February has been exceptional!

The hemispheric pattern has been exceptional as well with parts of the pattern acting more like La Niña with the negative PNA over the west while the equatorial pacific mimics El Niño…..quite the combination.

For the most part..the MJO has wagged the winter dog since December. I think that we are dealing with a Nino basin that is in a weak El Niño state while at the same time the atmospheric coupling has been greatly suppressed by some large-scale upper convergence…

Looking at the dynamic models…the MJO is progressing slowly east..so there is going to be a pattern change week 2. The  MJO or ERW has already spawned a typhoon in the west-central pacific which depending upon its phasing with the westerlies, may throw a monkey wrench into the longer-range models for the last week of this month. I will also add, as In the previous discussion; where the MJO is located, it favors AR’s. If this MJO does not get off the dime soon, it is just a matter of time before the west coast gets hit with another AR. It is not being shown in the GFS week 2, but is gaining ensemble members in the European week 2 period with an awesome extension of the EAJ on this mornings 12Z run. On the contrary, the climate models as well as the GFS are not as yet picking it up. So confidence is low at this time.

 

In the meantime…it will  be cold this week with periods of snow showers and below normal temps…great for carving turns  on California’s premier ski mountain….the following weekend storm is in question again.

 

 

High temperatures will remain below freezing for the next 5 to 7 days.

 

Dr Howard and the Dweebs…………..:-)