Archive for November, 2012

Mammoth Mountain Picked Up 6 to 12 Inches of Powder!!! More on the Way…..

According to Cliff Man of Mammoth Mt Ski area…..6 inches of cold dry powder fell at the Main Lodge with up to 12 inches above McCoy Station……More light snowfall is expected today as winds continue to diminish….

WX Discussion:

A Cold Upper Trof is currently over California with numerous showers associated with a Vort Center now climbing the northern portion of the Southern Sierra. It is snow showering again on Mammoth Mountain. The Vort Center and its associated UVM is progged to move mainly south of our area effecting the Southern Sierra the most. Nevertheless, snow showers will occur the remaining part of the morning and possibly into the afternoon as the air aloft is pretty unstable. Latest RAMSIS showing lots of cold open Cellular Cu headed south down the coast on the Cyclonic side of the upper jet. Some of that is swinging inland today into the Southern Sierra. By tomorrow Saturday, the back side of the trof and its associated 115 Knot upper jet will translate (N/S) eastward across California…so expect winds to pick up out of the north over the Sierra Crest and Owens Valley Saturday afternoon. Some Snow shower activity is still possible Saturday morning and into the afternoon as UVM is still indicated….700RH holds in the 70% range until 00z Sunday. So expect both rapid drying and radiational cooling Saturday evening leading to a very cold night!  lows +7F to -5F by Vets AM.

Medium Range:

Short wave ridging builds in Monday for rapidly moderating temps early next week. High temps are expected back up to the low 50s.

The next weather system is being handled differently by the global models as a splitting system that either weakens pretty rapidly as it moves into the Central Sierra (GFS) either Wednesday or Late Thursday. The deterministic run of the ECMWF from last night had more energy into the Southern Sierra Friday.  So at the moment, I am not too excited about this system.  We may get light amounts or we may get nothing. Additionally, the run from last night EC slowed the storm down well off the coast, while building a ridge over western Canada.  I will track both GFS and EC for consistency and see which one seem to have the better handle on it over the weekend.  In the meantime for planning purposes, this does not look like a big deal. What may actually happen is that the storm gets stalled next week and waits for some upstream kicker to boot it in later in the week like Friday. It is the storm that is brewing in back of next weeks splitting system that is of interest! 😉

Longer range:

Both Global Models are touting slow retrogression of the long wave features through Days 10 and 11. This is usually good news if we get good amplification up stream and a consolidation of the upper jet. The 00Z Friday ECMWF had a storm of significance in our future for the 18th/19 of Nov.  And last nights 00z GFS has a good one as well about the same time frame…possibly a day sooner. In fantasyland, yet another one about Thanksgiving.   So for the time being things are looking up for more snowfall before Thanksgiving Day and during holiday weekend…..

 

More Later……….

 

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

Six Feet of Wind Arrives Thursday as Upper Jet Perpendicular to the Sierra combine with warm antecedent conditions at the surface for power gradient across Mono County Thursday PM….Expect close to 40 degrees of cooling by Saturday…

Quick Update Thursday Am:

Not much has changed other then to slow the progress of the system down by 4 or 5 hours.  I did notice again this AM that the westerly flow at 700MB is still shown to continue a bit longer than 24 hours ago allowing the possibly another one to two tenth’s of an inch of QPF to occur. So we may get a couple of more inches now to the earlier forecasted totals. Additionally Snow to Water ratios are going to be a good 20:1 or greater Friday/Ngt. This means that 6 to 10 inches is possible on Mammoth Mtn and 3 to 6  inches in town. The Dweebs would not be surprised if the snow fluffs out with an even higher ratio to H20 as 700mb temps on Mammoth Mt are going down to -12.5C Friday into Saturday AM, according to the latest 12Z Thursday NAM run.  Highs on Saturday will be in the low 20s at the village with night time lows in the low to mid single digits.

No Mono Lake effect is expected along its Western Shores as no ENEasterlies are expected.

 

The Dweeber……………………:-)

 

5:30pm Update:

Just an FYI…18z gfs came in a little bit further west and so now there may be a short period Thursday night into Friday mid morning of Westerly flow at 700mb with RH in the 70% to 90% range. 700mb flow still backs to the NW by about noon through the weekend. So we may get lucky and get a bit more. The 12Z Wed EC did bump up its QPF to about .8 of an inch over the Crest.  The Dweebs are not buying it yet. Will look at the 00z Thur GFS stuff….and if I have time will update late tonight…otherwise will update in the AM.

PS:

NWS has hoisted a High Wind Warning effective at 4:00am Thursday for Mono County. Winds could gust to 70MPH in Mammoth.

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Well….the Mild Fall weather had to end sometime….

So It  might as well end Today!  The weather will be mild with light breezes into the afternoon. Winds will most definitely come up tonight and be full howl Thursday Afternoon.  High Wind Watches have been hoisted for Mono County beginning Thursday at 4:00am.

He is the essence of the storm.

1. All models came into agreement Monday by indicating a much less over water trajectory of the storm. If you remember, the ECMWF had a week ago a good 2+ inches over the crest during the second half of this week. Now the model is showing about .5 to .6 IE, 25% of what it showed at that time.

2. Because of the nature of the storm, most of the moisture will fall post frontal. Meaning that the front will have little in the way of precipitation Thursday Evening. The upper flow will be WNW at 700mb. So Orographics will not come into play with any significance.

3. However, this is a very cold air mass. So whatever we get will be at very high Snow to Water ratios friday and Saturday. As an example, at between 20 degrees and 28 degrees the Snow to H20 can be as high as 15:1. Snowfall at temps 10 degrees to 19 degrees can produce ratios as high as 20:1. Furthermore, at temps between 0F & 9F the ratios can be as high as 30-1. It is still possible to have a foot of snow over the upper elevations out of 1/2 inch of water because of the temperature the flakes will be falling at. 700mb Temps will be between -12 and -14C.  There may also be some lake effect off Mono Lake that may effect the June lake area/Lee Vining area. Historically, there have been cases where that has really boosted snowfall amounts in that region. Will look closer at that tomorrow.

For the most part, the town of Mamoth will receive light amounts of accumulation some 2 to 4 inches, possibly a bit more if we get decent upslope Saturday in the cold air and possibly some slop-over from Mono Lake Effect

 

Dr Howard and the Dweebs…………………:-)

 

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.

One More Warm Day then Cold Blustery Storm to move into the Sierra Thursday PM…..

1:45pm Nov 6th

ECMWF has a total of .8 over the crest through Sunday AM. So we do get up slope and the ratios are probably 13:1 to 15:1 Saturday/NGT.

I guess the best part of all this documenting is that we will all find out at the end of this week, how the models handled the QPF for this pertictualar weather type and trof best.  If we believe the ECMWF qpf, it is getting pretty close to 10 to 12 inches at the higher ratios over the crest considering the up-slope Saturday by Sunday AM. Too bad we don’t have a 5 foot base, or we could call it a nice shot of “Platinum Powder”.

I mentioned the Climate Forecast System earlier today. That it is showing an 500hPa Z,, negitive height anomaly (m) Nov 13th through the 19th Nov (week 2)……centered  20 or 30 miles off the Northern Ca Coast.

SEE:  http://www.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk1.wk2_20121105.z500.gif

The upstream ridge is positive tilt which may cause the upper flow to split as it comes southeast.  Some of the models are trending in that direction. That would favor a system that spins up further south then the graphics show above. This would favor the Southern California mountains in getting hammered with heavy snow with generally lighter amounts for the Eastern Slopes of the Sierra around the middle of next week. (14th) As we all have seen, the Dweeb like to banter a lot when its a week plus away as there are always lots of possibilities…..However when you are 72 hours from showtime, the models are usually in sync.

The storm for the weekend looks like a 5 to 10 inch system between 8,000 and 11,000 feet over a 3 to 4 day period.

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Needless to say, after looking as all the guidance this Am, the QPF ranges from skimpy to light with possibly borderline Moderate over the Mammoth Crest.  CNRFC gives Yosemite about 1/4 inches of QPF while the new 12z GFS and WRF paint somewhere between 1/4 and 1/2 an inch. The EC is the wettest through Saturday with close to .75 (It may be expecting a few inches of (up-slope?)

Keep in mind that temps between 15F and 20F can deliver snow to water ratios as high as 15:1.  So a lot depends upon when the moisture comes in; IE. before the front in the warmer air, with the front or after the front in the colder air.  Looking at the Tuesday 12Z WRF, at 500mb and 700mb, there is good westerly flow aloft between 10,000ft and 18000ft on Thursday/NGT…..However at 700mb, only about 40%-50% RH is indicated. The best 700hr moisture of 50% to 70% comes in behind the front in the NW flow at 10,000ft early Friday.  “Not good for Orographics!”

This appears to be a system that does not get all the players on the line in time for the snap! So as of today Tuesday, light amounts in town would be favored along with strong winds and very cold temps arriving into the weekend. Saturdays highs will be in the mid 20s with night time lows in the single digits!

Note:

The 12z GFS has the Rt Rear entry region effects our area late Thursday afternoon and so decent UVM should occur at that time with the upper jet working its way SE.  again, much of the precip is expected to fall after the front so we will be able to take advantage of the higher ratios.

Dweebs Criteria for light amounts for this area is 1 to 6 inches.  Moderate 6 to 18 inches.

Longer Range:

The CFS is showing a pretty strong negative height anomaly off the California Coast between the 13th and the 19th of November!

 

The Dweebs will take another look at it either tonight or Wednesday AM…………………………..:-)

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Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.