Beautiful warm weekend to be followed by clouds and cooler weather next week…..Atmospheric River to take aim on Northern CA beginning Thursday with heavy precipitation as anomalous upper jet sags south to the CA/OR Border…..
Saturday October 8, 2016
Posted at 12:37 pm by Howard
Some tweaks to the forecast for the up coming week. AR event is still on track for the Pacific NW and Northern CA with the southerly boundary of the AR now forecasted for Central CA. The are four points worth mentioning in the upcoming event.
- It is going to get quite windy in the central and especially northern sierra. Winds at 700MB will be up in the 50 to 65 knot range with the latter for the Tahoe region. With these warm event storms, it is not uncommon to have significant down sloping drawing strong winds to the surface as well. So the word is batten down the hatches prior to the weekend…..
- There will be at least two to possibly 3 branches of AR for California. The first reaching the Central Sierra Friday around noon through Friday night. That has the potential to bring about .30 to .60 inches of rain to the west side near Yosemite. Less on the east side. Precip amounts taper off radically between Yosemite and Huntington Lake.
- The freezing level will be around 11K to 12K so snowfall will only be over the very highest elevations. There after….it will take the final push or final short wave Sunday into Monday morning, that will bring the possibility of over an inch of precipitation to Mammoth Mt. There is colder air in that system…..Especially by early Monday morning when the freezing level drops to near 8000 feet. That should be good for a snow level of about 6500 to 7000 feet during to coldest period Monday afternoon. However….Most of the precip should be over by then….Most will fall Sunday night with a higher snow level. More fine tuning of amounts and snow levels later this week…
Very anomalous wet pattern setting up for Mid October…. And more importantly, the Dweebs really like the SSTA pattern setting up across the north pacific west to east. It is what I have been waiting for. Hope it holds for the winter! Watch the +PDO to see if it flips and stays for the winter! Next update for September will be coming out in a few weeks….
Forecast on track with unseasonably warm temperatures this weekend with highs in the low 70s and lows in the 20s and 30s. Little in the way of any breeze expected. Great weekend to get lots of fall foliage photos!
Another part of the forecast is on track to bring an atmospheric river event to the pacific northwest, south to Northern CA. With the upper jet axis over the Northern California/OR border during the wettest part of the storm, Northern CA is on track to pick up a bonanza of water for CA in its storage facilities of the various Dams north of Highway 80. The pattern that will be developing is part of the strong blocking that will develop over the state of AK along with the remains of Typhoon Chaba. The Pacific Jet will be forced underneath that block with short wave energy “piling up” the cold air in the Gulf of AK next week. As the Trof loads up, strong upper divergence focuses its moisture upon the pacific northwest with the enhanced pacific jet stream. Eventually the block retrogrades west, which unleashes a deep upper low pressure systems energy into the west coast. Subsequent short wave energy drives its remains into Central Ca, most likely just after the weekend of the 15th. With the block over Eastern Asia by the third week of October, very strong ridging will build south to north over the far west, ending the wet pattern, with a possible heat wave over California during the 3rd week of October.
Note: The wet pattern for Northern California that begins Thursday, will most likely be associated with rain not snowfall at Northern CA ski resort elevations. QPF amounts that the computer models are cranking out are pretty astounding with the Atmospheric River. Some areas may get between 10 and 15 inches of rain in the mountains around Shasta in the very wettest areas. Sure, there will be cooler air following the warm moist rain leaded air mass, that will be followed by lowering snow levels. And….it is possible that the mountains of Southern Mono County could pick up 6 inches to a foot between Monday and Monday Night above 7500 to 8000 feet with the final short wave. However, most of the precipitation will be rain throughout the event over Northern CA, not snow at elevations under 10,000 to 11,000 feet during the wettest part of the storm. Again….The best chance of some snowfall for Mammoth Mt will be Monday and Monday night the 17th….However…some showers are possible before that time frame.
According to the latest 12Z Saturday run of the ECMWF, the bulls-eye for snowfall for the sierra is near Sonora Pass where between 12 and 18 inches is possible at elevations above 8000 feet on the west side of the pass, Monday through Monday night.
More later from the Dweeber!
PS, I will begin my emailing’s of Platinum Powder reports about November 1st. In it will be speculation of the type of Winter I expect and future stormy periods and possible storm cycles. Be sure to sign up this month. If you signed up last year, you need not sign up again…
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Dr Howard and the Dweebs………………………:-)