Snow Now Falling In Mammoth

Snowfall began at 3:00am this morning and is now expected to continue for several days. No surprises this morning with QPF on track. Updated HPC 5 day amounts for the south central sierra is up to 14 inches over the period along the west side and 9 to 10 inches over the crest. This means that Mammoth MT is likely to receive a good 10 to 12 feet in the coming 5 days. (10:1 ratio)

The Town of Mammoth 4 to 6 feet. It still appears that for the most part, it will all be snow for the town. There are several waves within the subtropical fetch now currently connected to the central coast. Periods of strong vertical motion will coincide with heavier snowfall rates. Moisture Flux Divergence within the flow is expected to be extreme.

As far as the models go over the next 3 or 4 days…..the large upper low in the gulf of Alaska will remain pretty much stationary with a swift zonal flow underneath that system. The upper jet at 160knots stretches from 160w to the west coast just south of 40 north. The little eddies or impulses that streak across the zonal flow are enhanced areas of vertical motion and represent potential heavier areas of precip when they move on shore.

Looking at the CIRA TPW loop from AMSU  http://amsu.cira.colostate.edu/TPW/global.htm You can see the juice up to 35 to 40 mm within the stream . A subtropical upper low near 30 north- 175 west is keeping the pump juiced.

Analogs:

There has been some talk around town of this being a pineapple connection. A pattern similar to February 1986.  This is not true. The February 16 through 19th event was a true pineapple connection.

The analog shows that a blocking high became cut off over Alaska while the typical upper jet diverged to the right and dug back an upper trof that became confluent with the subtropical jet which road over a subtropical ridge into California. The 500mb heights over Mammoth went as high as 570dm and we had 6 to 7 inches of rain over a heavy snow pack. That was the winter that the Sherwin’s slid.

This system is totally different. Instead of high pressure in the northern Gulf of AK, there is a  deep vortex.  The blocking high is out near the dateline in a quasi REX configuration. Check out the analog at http://vortex.plymouth.edu/reanal-u.html then compare to current 3 day means.

Better analogs are 1968 11/28; 1971 11-28; 1961 12/22 and 1966 11/29



The Dweeber………………………:-)

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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.

Mammoth Readies Itself For A “Mammoth” series of Storms!

Just had discussion with Alex…..Leed forecaster with NWS RNO:

One more day “today” to make sure everything is in order.

Check list:

1. If you have a gas powered electric generator, make sure you have gas and it is working properly.

2. Snow blower working, extra sheer pins available and of course shovels handy.

3.   It look like more snow now as the models are coming in cooler. Nevertheless, those that are in low lying areas of town should clear out their culverts to make sure they are free of debris.

5. We are expecting a good 3  to 4 inches of water EQ in the Town of Mammoth between Friday night through mid day Sunday. (2 to 3 feet+)   High winds of 60 MPH in town, coupled with the heavy snow fall will create a loading problem for trees and power lines. Be prepared for possible power outages.

It will be a mess in town Saturday so CHAIN UP for 4WD may become a necessity.

Again the  models have been trending a bit cooler the past 24 hours and so it may be, that the period of rain will be shorter lived for the town, which will impact the town with more snow.  Avalanches may becomes a problem in non controlled areas. You folks in the June Lake loop should be prepared as well as you will get buried…..

Folks…this will be the kind of snow that you get stuck in. Even for 4WD’s. Very heavy, dense, moisture leaden cement. So get your chains ready for your FWD’s Saturday and be extra safe!

Better yet, probably a good idea to stay home!

UPDATE:

A deep Eastern Pacific closed low is forecast to drift toward the Pacific Northwest with the center remaining off shore into Sunday. This cold upper low and associated polar jet will combine with a fetch of tropical and subtropical moisture emanating out of another tropical low located along the date line at 23 north latitude. This tropical low which has been part of an ongoing REX block has been tapping moisture out of the ITZ. The under cutting subtropical jet and associated moisture will combine with the polar jet, north and east of the Hawaiian islands creating a copious precipitation event for both Northern and Central California.  Then into next week……although the models retrograde the tropical low…..the remaining moisture train continues a few more days and continues to be entrained, into the  long wave trof parked off shore.

A steady stream of moisture along with strong upward vertical motion will impact the northern 2/3s of the state. The upper jet aligns from Oregon to Central Ca through the weekend gradually sliding southward.  This mornings the latest guidance still shows that the heaviest precip will be through Northern and Central Ca….with QPF totals, according to HPC, up to 6 inches by Sunday morning. Another 5 to 6 inches is expected between Sunday morning and Tuesday morning.


Outlook:  More storms on the way over the holiday with breaks……

One more thing……although the REX block breaks down the middle of this week…it redevelops the following week…..


Update Friday:


On the realm of Global warming and Global cooling……

Did you folks know that the sun is unusually quiet?

In fact it is spotless again this morning.

Geoff Sharp is a solar scientist.

Below are his comments this morning…..

2010/12/16 8:00 1133  is still just visible but is under the threshold at 240 pixels. There is a small speck region measuring 83 pixels in the early northern region that shows some potential on the magnetogram. There is also another region on Stereo Behind about to rotate on that may be worth watching. Its cold in the NH right now, the predicted massive northern winter is beginning to happen.

Yesterday’s adjusted F10.7 flux figures measured at 20:00 UTC recorded 84.2 (87.5), on the way down again. The DSN value for today is 110 with the previous measurement at 214.


SEE:  http://www.landscheidt.info/?q=node/189


——————————————————————————–
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.

Very wet system headed into the sierra Friday night and should continue through early Sunday am

Lots of good ingredients coming together for quite a bit of precip this weekend. The well touted subtropical jet will play quite the part the next 7 days in putting a good dent in the annual snow and water totals for the high country.


This mornings 12z GFS still showed the REX block at the dateline and the long wave trof at 143w,  smack dab in the middle of the Gulf of AK. The polar jet extends from 160W through Northern California along 35 to 40 N. So what we have is one big pacific ocean “Lake Effect” with the subtropical and polar jets pretty much coupled off shore. A nice mix for Sierra Cement!

QPF: HPC has a walloping 9+ inches for the period Wednesday Am through Monday AM with the main emphasis Saturday through Monday.  Lead forecasters at WSFO-RNO are a bit more conservative at 6 Inches.

The big question revolves around the snow levels.  The consensus at the moment with the forecasters up in Reno is that the precip will be in the form of snow Friday night changing to rain below 8500 ft in the Town of Mammoth Saturday Afternoon then changing back to Snow Saturday night with the snow level back down to 7ooo or 7500 feet.

All forecasters will be very interested in seeing the 12z Saturday Oakland sounding to get a more exact idea on whether this will be snow or rain in town.

2:15 pm Update

Here is an excerpt from the latest EFD from the NWS Camp Springs MD

ONSHORE STRONG ZONAL MID LEVEL PACIFIC FLOW WILL SHEAR IN ENERGY IN
PIECES WITH ONE BETTER DEFINED FRONT COMING IN AROUND MONDAY.
EXPECT HEAVY PRECIPITATION INTO NORTHERN AND CENTRAL CALIFORNIA AND ESPECIALLY THE CENTRAL
SIERRA REACHING SOUTHERN CA SUNDAY AND MONDAY. TOTALS OVER THE WEEK MAY EXCEED 10-12 INCHES LIQUID EQUIVALENT WITH HIGH AMOUNTS FALLING AS SNOW IN THE SIERRA.

 

 

THE CENTRAL SIERRA QPF GUIDANCE EXCEEDS 16 INCHES LIQUID OVER A 4 DAY
PERIOD
. THIS MOISTURE WILL EXTEND EASTWARD INTO THE GREAT BASIN AND ROCKIES OVER THE WEEK END WITH LOCALIZED HEAVY ROCKY MOUNTAIN SNOW IN UT/WY AND CO. AS A DEEPER EASTERN PACIFIC TROF EVOLVES LATE PERIOD AND RIDGING BUILDS OVER CENTRAL CONUS EXPECT STRONGER PACIFIC INFLOW
TO SHIFT BACK NORTHWARDS TARGETING NORTHERN CA AND OR.

Comment:

Is this hype?

See Wednesday’s Complete discussion

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html



Here is some criteria for snowfall in the sounding; 

 


 

I. Micro-physical processes

A.  Oakland sounding

      1. There must be a temperature in the column at or below

           -15C between 650mb and 500mb    (dendritic growth zone)

      2. Critical temps at 700mb at or below -2c

      3. The Air Mass saturated 650mb down to 500mb and lower.

      4. There must be UVM!  (upward vertical motion)


Stay Tuned…………..The Dweeber…………………..:-)


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Reference Glossary of Weather Terms


http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html