Upper Ridge Building in Now for a Couple of Days…Warmer Days in the Upper Elevations expected through Tuesday with cloudiness increasing Wednesday for a slight chance (20%) of some very Light Snowfall Thanksgiving…….
Sunday November 24, 2013
Posted at 11:54 am by Howard
Monday AM Update:
As indicated a few weeks ago, the Dweebs indicated that a major pattern change would begin to occur about the end of November. However, it was also indicated that it was not known if the pattern would be a wet one. Here is what we know.
1. Here is the main teleconnection we are dealing with. The -WPO, which is similar to the -EPO, but displaced much farther west. This link shows the teleconnection pattern for the positive phase…… just flip the anomaly then see the negative phase pattern: http://www.esrl.noaa.gov/psd/forecasts/reforecast2/teleconn/images/wpo.composite.gif
This is what is known:
1. Both GFS and the ECMWF are going to both amplify and consolidate the eastern pacific ridge early next week a little west of 140W. There are several short waves that will be able to tap cold arctic air from very high latitude’s, and pull it down near the coast line of BC. While an upper level Arctic low develops over the Pacific Northwest bringing some of the coldest air in quite awhile to that region, there is the possibility that subsequent short waves will continue to push the Arctic ribbon further south into the Great Basin as the week progresses. This would put Western Nevada and Eastern CA into the deep freeze for a while with below 0 temps possible at night. There is also the possibility that in time the upper flow may buckle out over the ocean where that would be beneficial in bringing a wet pattern into the Sierra later next week. So now, the ball in motion for a major pattern change next week…there are lots of possibilities.
The most likely one’s to begin with in the longer range are for:
1. Potential for high winds
2. Potential for Major Cold beginning 1st week of December….
3. The potential for a major “Cold Snowstorm” as the upper flow buckles off shore and moves south later next week…. (PS the deterministic 12z Monday ECMWF is all over that idea)
So hang in there………its going to get nasty!
Dr Howard and the Dweebs……………………………….:-)
The pattern in general continues to involve to the redevelopment of the -WPO but displaced “More to the West”. The WPO in the negative phase is highlighted by a high latitude block in the Gulf of AK with lower pressure aloft underneath. The trend of the -WPO will again be displaced much further west with time which is not good for the central west coast. With it ‘s current extension into Western Canada, short waves split with the stronger branch into Southern CA.
In the meantime, we have a transitory short wave upper ridge which is building in for some fair weather. It will allow inversions to set up with some 15 degree of daytime warming expected in the upper levels by Monday/Tuesday. Very Light winds are expected early this new week.
The next short wave will again be forced under the extension of the block well west of AK that extends to Western Canada. What appears to happen is that the short wave trof comes through the upstream ridge as it heads SE toward the South Central Coast…However at the same time the upstream ridge retrogrades and amps northward essentially cutting off the life of the system and leaving it offshore to die. Thus the short wave is being effected by a chronically chaotic pacific transitory pattern. It is possibly an eastern pacific wavelength problem that needs the time scale of climate as the only cure. Where is the MJO when we need it???
At this time, additional snowfall in general is really not in the cards for the Central Sierra over the Thanksgiving holiday. There is only a slight chance at best.
The Dweebs see a very cold Arctic Air mass that will slide SSE out of the BC the first week of December. There are some Ensemble Members that take it into the Great Basin and many that take it to the Rockies. This will have to be watched as although it does not mean a lot of snow, it means the potential of major wind if the upper jet is right and very cold temps for our area. Should this system track further west into the Great basin. It would be (a pipe buster) sometime during the 1st week of December. At this time, the Dweebs are not confident in knowing the track of the short wave associated with this cold so stay tuned…….
Dr Howard and the Dweebs………………….:-)