12-25-2020

Models have come in drier with system tonight and Saturday..   1 to 6 inches over the Sierra at elevations above 6500 feet.

next system is colder for  Sunday night and Monday..  However, it too will be a light precip producer for the east side. Two to 6 inches……

it will be colder than normal the next week….

 

Outlook shows a series of fast moving storms affecting mammoth through mid January.  All in the light to moderate range for snowfall….

Dr Howard and the Dweebs….

 

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I. As we approach the end of the year….There appears to be 3 more weather systems that will bring snowfall to the high country;

  1. The Christmas Day Eve system
  2. The Sunday/Monday system
  3. The New Years Eve system

II. Currently off shore we have a mid latitude upper high that will make its way onshore today. So a beautiful day it will be with highs in the 40s.  Winds over the crest will diminish as well. To the south of this ridge is a weak subtropical low that is getting the boot from an upstream upper jet.

Currently our airmass is very dry, This weak subtropical low will serve to juice up our airmass for the next two systems arriving over the weekend.

The Friday Night system into Saturday will bring mainly light to moderate amounts of snowfall.   The Freezing level; in town will begin at about 8K, but will lower over night.  So early in the system it will be very wet snow.  The Structure of the the upper jet shows two branches. One the polar and other subtropical. The southern branch favors Mammoth with most of the dynamics remaining to our north, La Nina style.  CRFC QPF is showing .79 inches for Yosemite and about the same for Huntington Lake. That suggests 4 to 8 inches on the mountain with some 2 to 4 in town by Saturday afternoon.

There will be a break between short waves, with the next system splitting and diving south during the day Sunday. This 2nd system is problematic due to the nature of the split. It will favor the Southern Sierra. So more time is needed to provide better accuracy in the QPF. I will update for the Sunday night/Monday system on Christmas Day….

The last system for 2020 is expected “about” New Years Eve. Potentially it could be a major storm as a pattern change involving retrogression of the eastern pacific (long wave) ridge to the dateline is being suggested in the longer range guidance.

 

Tropical Forcing:

Although the MJO has not been a positive force because of La Nina’s destructive interference of the tropical mode, there is evidence that other modes of tropical variability are in play, These may be  affecting the extra tropics. There has been atmospheric wave breaking (Equatorial Rossby Wave Breaking) over the Indian ocean as touted by the CPC. These Tiny Dancers may be influencing the mid latitude circulation to some extent.