A Series of Moderate Snow producing weather systems will move through mainly Central and Southern California…..Cooler Weather with lower freezing levels expected….
Monday December 10, 2012
Posted at 9:27 am by Howard
Monday Am Update….Wednesday’s storm is a Moderate Class Storm: <6 to 18 inches…..
The Eastern pacific ridge continues its retrogression this week allowing several short waves to effect the central and southern west coast. Although these are not heavy precipitation producers, they will bring moderate amounts of snowfall to our region.
Highlights of System’s Nature:
The models still do not have a good amount of agreement in the fine details of this 1st system.
I Just saw the new 12z Monday GFS.
I like the position of the exit region better now for the Mammoth area. Although it moves through pretty quickly over a 12 hour period, their is quite a bit of UVM “now” crossing our area Wednesday night into Thursday AM. This should make for heavy snowfall for several hours now. There will be plenty of wrap around snow showers Thursday and it will be chilly…..With highs in the 20s Thursday now. Additionally, the GFS really slows the upper low down and lingers it over the SJ valley pretty much for 24 hours between Thursday 4 AM though Friday 4AM, then accelerates it east Friday AM. The next upstream system for the end of the week, is being handled a lot different now. It remains off shore and does not come into Ca at all. I am not buying into the actions of the end of the week system yet as according to the new GFS…it is a no show….
The 12Z Monday NAM:
1. Long wave axis is over the top of California which will tend to slow the systems down as they come into the state..
2. The upper Jet is moderate in strength and initially, does not come inland across the Sierra. As the system digs southeast…it slows and forms a closed low just west of the Bay Area about Wed Noon. There after….the upper jet rounds the base of the newly formed upper low with the front exit region providing most of the UVM over the Northern portions of the Southern Sierra, while Mono County remains in the deformation zone/axis.
The bulk fo the upward vertical motion remains just to the south of Mono County while at the same time the bulk of the 700mb RH moisture is over Mono County. The closed upper low tracks ESE from the Bay Area with a period of up-slope possible later Wednesday night/Thursday AM. The upper jet rounds the base of a forming closed center effecting South Central Ca. and favoring the central and southern SJ valley and the especially the west side of the Sierra….
2. The system slows as it approaches the coast and closes off. Good for wrap around for Mono County. This Model suggests a storm in the 6 to 12 inches range.
I need to see the ECMWF this afternoon….
Note; these snow compact weather systems tend to concentrate the heaviest precip over a smaller area. Nevertheless…the bulk of the precipitation will be with the southern and central sierra this time with quality snowfall…
Comment……the storm total for the Wed/Thursday system may reach the upper limits of moderate……12 to 18 inches if the GFS is correct…..will fine tune in the morning or sooner if the opportunity presents its self….
Dr Howard and the Dweebs…………………..:-)