Summer to wrap-up more like fall as large scale upper Trof desends upon the west….Much cooler temperatures expected by Thursday and Friday with light snow showers a possibility…

Wednesday AM UPDATE:

Latest guidance on the timing of the precipitation has moved up a bit. Light rain is likely in town after midnight tonight with rain turning to snow after about 5:00AM. However, the bulk of the precipitation will be over before the rain turns to snow in town. Amounts of 5 inches still look reasonable over the top of Mammoth Mt at 10,000 to 11,000 feet. However, at the village, amounts look to be about an inch by late morning Thursday. There will be a continuing chance of snow showers Thursday into the evening and again a slight chance of snow showers Friday and Friday night. The weekend looks fair but cooler than normal. Highs in the 50s with lows in the 20s. Great Oktoberfest weather….
Prost!

Dr Howard and the Dweebs……………….:-)

Tuesday Afternoon Update:

This is my first snowfall forecast for the Mammoth area this season. Although I would not put too much creditability to it. Especially since WSFO Reno this afternoon, did not forecast any snow other than a slight chance of snow showers Thursday. In looking at the both the European and American models, it seems to me that there is a good possibility of at least 1 to 3 inches of snow at the 8000 foot level by the evening Thursday. I am going with 3 to 5 inches over the crest by the same time.

CRFC forecasts the freezing level to drop from 9,900 feet at 5:00AM to 8500 feet by 11:00AM. It stays about there throughout the afternoon. In this type of pattern, the snow level will range between 1500 to 2000 feet below the freezing level. I do expect some light accumulations in the Towns of Mammoth and June Thursday. Amounts could be as high as 5 inches over Mammoth MT by Thursday night.

Points worth noting:

1. This second short wave will have good over-water trajectory over the eastern pacific for a short period of time. There is a lot of cold unstable air and there are good vertical motion fields indicated. The upper jet is pointed at the central sierra, mid-morning Thursday. It appears that mid to late Thursday morning will be the best time for accumulations. PWAT of over an inch pushes into the Central Valley Wednesday night into Thursday morning. So for a short time, moisture, the upper jet and good UVM “upward vertical motion” are all there. Snow showers will likely continue during the afternoon. There is another Vort max or two that will slide over the area kicking up a few showers through Friday…

Highs will cool to the mid to upper 40s on Thursday, Lows well down into the 20s. Thus a taste of winter as we say goodbye to the summer. The Equinox is at 1:02PM Friday PDT. So if you looking for a reason to party Friday night, it’s the Equinox!

The Dweeber……………

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Dry weather with seasonal temperatures are expected this last weekend of Summer. Mammoth had its first frost this morning with a low of 32 at the village. It will be a few degrees warmer Saturday and Sunday with lows continuing in the 30s by early morning. Highs at 8000 feet will range in the mid 60s.

Large scale pattern is Highlighted by a weak ridge that will move through our area Sunday and Monday. At the same time, a vigorous upper Trof moves into the pacific NW. The first part of the large scale change is coming in as a NW slider with mainly wind and cooling Monday night into Tuesday. It will be quite breezy in town Monday and Monday night with winds 20 to 30MPH and windy over the upper elevations with gusts to 60MPH+.
Several more waves with in this pattern will drive south next week bringing periods of wind and cooling. The last and strongest wave will arrive Thursday into Friday, There appears to be enough over water with the upper jet to warrant mentioning a chace of either snow showers or light snowfall over the upper elevations. I will fine tune this next week. The Dweebs expect stronger winds developing Wednesday night into Thursday followed by falling high temperatures of 50s during the Day in Mammoth and lows well down into the 20s by sunrise Friday AM, The following weekend looks cooler than normal as well. Best chance of the dusting will be Thursday and Friday next week.

Inter-Seasonal Outlook:

The Climate Forecast systems inter-seasonal outlook this morning shows a return of summer like weather with warmer than normal temperatures the 1st half of October.

Dr Howard and the Dweebs…………………:-)

Fall Pattern shaping up as we say goodbye to the Summer Ridge….Upper Low ejects out Wednesday as the arrivel of the first Fall trof comes through Thursday into Friday……Next stronger Trof may give first dusting over Sierra next week….

Yesterdays thunderstorms brought some nice rains during the afternoon. The two reporting stations in Mammoth indicated between .14 and .19 of an inch. There was small hail as well. The upper level low is getting the boot inland today as the first Fall Trof makes its way through Central CA at 18Z Thursday. Through the process, we’ll have another day of convection today and the chance of some thunderstorms, but today does not look as active as yesterday for Southern Mono County. In fact the Rapid Refresh Model keeps the bulk of the precip from about Mono Lake northward, for today Wednesday.

Longer Range:

Again…the transition from Summer weather to Fall will occur Thursday. Winds over the higher elevation may gust to 50mph at 10,000-11,000 feet over the passes. Much cooler temperatures are expected Friday with highs in the low 60s in Mammoth and low 50s at elevations above 10,000 feet. Overnight lows will trop to the 20s in the back country Friday AM, then the chilly air settles into the lower elevations over the weekend. Weekend Lows will be in the upper 20s and low 30s at elevations between 6500 and 8000 ft with highs in Mammoth in the low 60s.

By Monday some moderation in temps is expected of about 3 to 4 degrees. The warming will be short lived though, as an anomalous cold Trof for late Summer is forecasted to dig into CA Tuesday and Wednesday. Some of the quick details suggest 500MB temps of -19C and 1000-500MB thicknesses in the low 550s by Wednesday. No doubt it will be rather chilly as Summer makes its exit. These parameters suggest highs in the 40s on Wednesday with lows well down into the 20s. Say goodbye to your tomatos?

With this trof, will come the possibility of the first significant dusting of a few inches over the higher elevations. Climo looks good for this with the equinox storm. However, no matter what we expect, weather is always what you will get, so more time is needed to fine tune the details about the weather for the middle of next week.

Dr Howard and the Dweebs…………………..:-)

Old Closed low is drifting north now and will shift east Tuesday through Wednesday Night….Expect an increase of showers and thunderstorms Tuesday afternoon into Wednesday night….Current pattern to transition toward Fall….

A closed low that has been off shore now for over a week is currently making its way northward toward the Central CA coast. A pattern shift with a fall like trof dropping out of BC, Canada is drawing it northward. This closed low will have plenty of upper divergence and surface deformation for showers and Thunderstorm’s anytime between Tuesday and Wednesday night. The showers that developed this afternoon was the first wave coming through. It has pretty much come and gone. However, there is some convection reforming to our south and so can not rule out some showers later this evening.

The closed low off to our south will be moving north the next 24 to 36 hours. Mono county will becoming under the influence of the NE quad with upper divergence and deformation at the surface. No doubt that there will be thunderstorms over the sierra and that some areas will get some pretty heavy rains within the deformation zone, but at the moment, it is unknown where that will set up for Tuesday afternoon and especially Wednesday.

This weather pattern appears to be part of a significant pattern change. A shift from Summer to Fall like weather. What the Dweebs are looking at on a larger scale is a pattern change that will switch the mean upper ridge currently over the Great Basin to Long Wave Troughing over the northern portion of that region. The Transition will not happen over night through but soon enough.

The first trough coming in this Thursday is part the process that is ejecting the cut off through California Wednesday. That trof will spread breezy conditions and cooler air over our region Friday into Saturday. That trof will be followed by an even stronger Trof the following week if the Euro model is correct. So far any showers directly associated with both systems will remain well to our north. However, the nights will really be cooling down this weekend with low 30s in some areas. Further cooling may occur by the middle of next week. Daytime highs in the low to mid 60s Friday.

Tuesday12:00 PM update shows GFS is coming in deeper and so confidence is increasing for the first dusting of snow next week with the “Equinox Storm”

The first blast of Fall Weather is always exciting here in Mammoth. However, it usually is followed by warmer weather into October.

Dr Howard and the Dweebs………………….:-)