Wrapping up the Month of September and being retrospective..it has been a real warm one……Our first either inside or outside slider will make its way through Northern and Central CA Sunday…..Showers and possible snowfall is expected….
Tuesday September 29, 2015
Posted at 11:07 am by Howard
- The 06z GFS has a better organized but small system ejecting through Central and Northern CA. There is plenty of moisture for it to interact with. The models generate between .25 and .35 over Southern Mono County Thursday with a freezing level of 11,000 feet. In that it is convective, a snow level down to 9500 would not be unreasonable. So a few inches of snow is possible over the higher elevations Thursday. Expect clearing weather by Friday AM. High Temps will cool to the low 50s Thursday with 30s possible by morning…
2. Continuing with regards to the new model runs from last night. As indicated yesterday, the ECMWF has been pretty bullish in dropping a small compact deep closed low over California’s interior with its primary effects to be light snowfall Sunday. The system has small but chilly cold pool as indicated below in yesterdays discussion. The model’s run was pretty consistent on this.
3. It is the 06z GFS that is struggling to get a handle on the same system. Last night’s run drops the same system south over the pacific NW then as far south as Northern CA where it stalls it while it’s upper jet energy phases with an upstream upper low directly to the west. The 250UA jet prog develops an upper jet across Central CA with has implication’s for better QPF but a higher snow level, Sunday into Monday. The fact that the ECMWF drops the low south from Northern CA to about Fresno may mean that we may see a hybrid that combines the west to east upper jet of the GFS with a deepening upper low like the EC thus eventually creating a more cyclonically curved upper jet over CA with time. The snow level would end up higher but the QPF higher as well between Sunday and Monday. The screaming message here is that if you are in the back country between late Saturday night and Monday, you should prepare for the possibility of a winter storm capable of producing 6 inches to a foot above 8500 to 9K feet. This is not a forecast just some possibilities…..
Dr Howard and the Dweebs………………………………..:-)
Current Analysis and days 1 and 2 progs show a continuation of the moist mid and upper level flow over the Central Sierra. Even my wife Donna mentioned to me that she observed Virga over the weekend. Several spotters from the NWS Hanford reported some sprinkles Monday as well. The flow is out of the Tropics in the super heated Nino 3.4 region. Upper divergence is no doubt playing a role associated with the Positive tilt trof centered west of Northern CA that will make its way inland Thursday with a slight chance of showers. This is not a big deal, but this pattern occurring about 2 months from now would be. Current mid latitude pattern is NOT being driven by ENSO…Just mid latitude forcing…Heights are pretty high with this mid latitude upper low and so it remains pretty mild with the high temperature over Mammoth Lakes Monday at 70. By the way…Fall colors are in full spectrum at elevations above 9000 to 10,000. They are coming on over the lower elevations between 7200 and 9000k as well. However, we are still a good week or two before they really are going strong over Mammoth.
The Euro has been toying the idea of an outside slider for CA the past several days and is holding on to the idea today. The GFS which does not have quite the resolution has been toying with the idea the past several day on and off. This mornings 12Z GFS run showed an inside slider type system making is way down from the Eastern Gulf of AK
Here are some note worthy’s:
- 12z Tuesday GFS 500MB temps over Mammoth Sunday Evening -15C
- 12Z GFS 700MB temps over Mammoth Sunday evening +2.5C
- ECMWF 500MB temps over Mammoth Sunday Evening -19C and -2C at 700mb.
- This is a big difference and a big deal for the North Central Sierra Sunday morning! The current track of the ECMWF is more west! The QPF has gone Hog Wild with over 2 inches of precip for areas like Amador County as they are in the NE quad of the upper low. If this system takes a track further south and west, it will be a big deal for Mammoth Lakes and Tioga Pass as well. As it is now, we could get a few inches of snow above 8,000 feet “IF” this model verifies! It is too soon to be sure through…stay tuned….
The positive SSTA’s along the west coast continue to be impressive. No doubt they will affect the over lying atmosphere Diabatically. Once the Deserts cool off later in October, it will be interesting to see how the west coast ridge sets up again and how the blocking will be with the RRR. This may delay the rainy season. Well See….