Cooler Breezy Weekend to be followed by Clouds….Showers and Possible Thunderstorms Tuesday and Wednesday, with some Upper Elevation Light to Possibly Moderate Snow as well……The Memorial Day Holiday Weekend Looks Fair and Warmer with highs well into the 60s……
Saturday May 17, 2014
Posted at 9:28 am by Howard
No Real Changes from yesterdays discussion except to tweak the QPF and snow levels and raise temperatures over the Holiday Weekend.
This AM’s Snow level is verifying a bit lower at 6500ft. The freezing level was 7500 at 5:00AM. The SL will rise a bit this afternoon but remain as low as 7000-7500. Tonight, the snow level rises to 8000 and by Wednesday PM 9000 FT.
Amounts still look possible in the 6 to 8 inches range over-all over the next 3 days, depending on where exactly the upper low sets up over the Great Basin Wednesday.
The Dweebs do not expect any issues with local roads from this weather system… With that said…..Tioga and Sonora passes may close for a day or two. However, with as warm as it is going to get….. I would Imagine that they will be open for the Holiday weekend.
See the following link for up to date Tioga Road info: http://www.dot.ca.gov/hq/roadinfo/sr120
See the following link for Sonora Road info: http://www.dot.ca.gov/hq/roadinfo/display.php?page=sr108
Monday AM Update:
Everything looks good for a late spring storm that will bring snowfall amounts of about 6 to 7 inches at the 9000 foot level and possibly as much as 7 to 9 inches over the Mammoth Crest between Tuesday AM and Wednesday night. The storms total QPF according to the new 12z GFS is about an inch over Extreme Southern Mono County. This is associated with the track of the upper low and its deformation axis, as it swings southeast Tuesday and then lifts NE toward NE Nevada early Wednesday morning.
According to the new 12Z GFS, the upper low comes inland over the Bay Area about midnight tonight and shifts SE to about Death Valley by 5:00pm Tuesday. It then lifts North East into Nevada Tuesday night into Wednesday morning. The Cold Pool Follows the track of the upper low to the south of it through Wednesday night. It then appears that the cold pool will sheer south Thursday as the upper low redevelops and becomes cut off over Southern CA.
According to the new 12Z Monday GFS, the snow level will be the lowest at 12Z Tuesday with its freezing level at 7700 feet at 5:00AM. So the Town of Mammoth will have its best chances of accumulating snow of some 2 to 4 inches at 8000ft Tuesday morning. Even though there will be light accumulating snow Tuesday AM, the local roads are pretty warm and so there may not be much effect on travel locally, except over the highest elevations of town. With that said, the high elevation passes like Tioga may close for a few days but I would imagine reopen by Thursday or Friday at the latest. The storm will be out of the high country by Thursday at the latest…… It will be a warm weekend with highs in the mid to upper 60s, both Saturday and Sunday.
This mornings Monday 12z GFS has about an inch total of liquid EQ for Mammoth. With the snow level rising during part of the storm, the Snow to Water ratio will be less than it could be. Its Bulls-Eye is between Bishop and Big pine and paints about 1.3 inches.
Based upon the 12z GFS, 6 inches plus is reasonable at the main lodge with a bit more over the crest. Last nights GEM (Canadian) had the Bulls-eye in the same place as this AM’s GFS with similar amounts of QPF….. however a bit more snowfall was indicated.
However, last nights 00z Monday ECMWF had the Bulls-Eye more over Central Mono County further to the north. It also suggested that there could be up to 9 or 10 inches within that Bull’s-eye. I’ll take another look at the ECMWF’s QPF as soon as the new 12z run is finished running later this morning. Sometimes a compromise is in order…..
New ECMWF is in, with up to .9 over the crest. However it gives only light amounts Tuesday. Most of the amounts are evidently associated with heavy convective snow showers.
HPC gives the crest about 3/4 of an inch of precip. So best guess is 6 to 8 inches over the upper elevations…. 9K to 11K
Don’t forget to look toward the North Star late Friday night into early Saturday AM for a chance of viewing a new meteor shower. Earth will pass through a stream of debris from Comet 209P/LINEAR. The encounter could spark a new meteor shower. Forecasters aren’t sure how many meteors will appear; anything is possible from a complete dud to a magnificent meteor storm. Best estimates fall between 30 and 200 meteors per hour between 11:00PM May 23rd and 2:00AM, May 24th local time. Skies will be moonless after 8:15PM
Sunday AM Update:
All of last night model runs have the track of the upper low about the same as the Canadian GEM had earlier in the week. Its been great to see the Canadian model do so well. I would imagine that the Canadian Gov. has been spending more $$ in their computer programing and so meteorologists may have a better tool to use next winter out over the west. At least from my perspective, I will follow the Canadian Model (GEM) more closely in the future, to see how its verification does over all.
The storm is a very significant one from a precipitation perspective, for so late in the season. Although I want to see some more model runs today and tonight, the thinking with most models is that there up to a good solid inch of QPF in it over a 48 hours period for the South Central Sierra. . The storm will become very convective and so there will be some areas over the sierra, between Mammoth and Mt Whitney that may get up to a foot of snow, over the ridges. Once again this will depend upon the exact track and how it swings inland across Central and South Central CA.
HPC 5 day QPF puts the Bull’s-eye of 1.2 inches, “storm total” by mid-week…Very Close to Mammoth Mt. That’s up to a foot of snow at 10:1. Does this mean that Mammoth Mt will get a foot? It is possible…..but my take is that as of this AM, the Bulls-Eye is a little south of our area from this mornings guidance. The Exact track of the small upper level feature will be the directive.
Here is a transcript from HPC as it pertains to the dynamics of the system and our area:
THE HIGHEST QPF ON DAY 2 SHOULD BE ASSOCIATED WITH THE BEST LIFT AND MOISTURE OVER NORTHERN CA. MID LEVEL COOLING COULD RESULT IN SOME CONVECTIVE ELEMENTS IN THE PRECIPITATION FIELD…AND THE WESTERLY LOW LEVEL FLOW WILL AID THE UPSLOPE PROCESS. A LARGE AREA OF 0.25 TO 0.50 INCHES OF QPF WAS PLACED ACROSS SOUTHERN CENTRAL OR AND NORTHERN CA. THE SLOW MOVING MID LEVEL SYSTEM REACHES SOUTHERN NV BY THE END OF DAY 3. THERE IS SOME EVIDENCE IN THE GLOBAL MODEL SOLUTIONS (MOST PROMINENT IN THE 00Z GFS) THAT A DEFORMATION ZONE COULD FORM “NORTH OF THE MID LEVEL CENTER” OVER CENTRAL NV. THE COMBINATION OF BANDED PRECIPITATION AND UPSLOPE FLOW SHOULD RESULT IN A LARGE AREA OF 0.25 TO 0.50 INCHES OF QPF ACROSS MUCH OF WESTERN AND CENTRAL NV…”AS WELL AS THE SIERRA NEVADA RANGE IN CA“.
I will UPDATE again later this afternoon…..
Dr Howard and the Dweebs………………………………..:-)
Saturday mornings weather was mostly clear with calm winds. High temperatures will be about the same as yesterday with highs in the upper 60s. Todays big change will be a moderate zephyr (west wind) that will develop mostly due to the upper ridge collapsing and its axis shifting eastward. Some gradient is indicated later today but the winds will be mostly Zephyr related. Today Saturday’s breezes will be in the 15 to 25 MPH range by afternoon but will mostly diminish over night then pick up again Sunday.
A 1000-500MB thickness guidance shows Surface Gradient’s with 4 bars between SFO and the Owens Valley at 00z Monday (5:00pm Sunday). So winds with Gusts of 40MPH in Mammoth is possible by late afternoon Sunday. It will be windier over the crest as well. Sundays afternoons winds are likely to continue well into the night…then diminish somewhat after midnight toward Sunrise.
A 1000-500mb thickness pool of 546DM is located just NW of the Bay area at 5:00PM Monday. A small jet let of 90knotts is onshore over Monterey Bay at this same time. Moderate divergence aloft is over the Northern Sierra Monday evening while Convergence Aloft is located NW of the Owens Valley. This cold pool and upper divergence will move inland SE over the Bay Area Monday night. Finally reaching the Mammoth area by midnight at the latest. The tighter isobars are over the Owens Valley by that afternoon and into that evening, So Wind Advisories are possible for the Bishop area Monday PM.
This thickness pool over Central CA will provide a lot of the instability for showers and thunderstorms over the Central Sierra and the Eastern Sierra Tuesday through Wednesday. Most of the precip in the Sierra is expected Tuesday and Tuesday evening. Again as mentioned earlier, the exact track of this feature is critical to where the most precip will fall. At the moment, the models are the most bullish over Central NV. This includes the GEM. However, with the high elevated heat source of the sierra, there will likely be quite a bit of convective enhanced precip going on Tuesday PM associated with the cold pool.
Latest Model guidance from last nights 00z Runs were not as bullish on moderate amounts of snowfall Tuesday and Wednesday. With between .25 and .75. So we are back with between 3 and 6 inches of Snow over the crest by Thursday PM, instead of late yesterdays 6 to 9 inches. Will update Sunday AM for snowfall totals Tuesday into Wednesday over the upper elevations based upon on tonight’s guidance …. Dr Howard and the Dweebs……………………….:-)