Tricky Forecast This Weekend As Upper Low Stalls And Wobbles Offshore
Friday June 3, 2011
Posted at 9:11 am by Howard
Still Updating…….at 9:30am….
12Z GFS has come in through 324hours.. The model has upper center crossing the coast about Big Sur about 12z Monday AM then east of Mammoth into Central NV 00z Tuesday. (5:00pm Monday) The upper center is stretched north and south through the Sierra Monday about 12:00pm. There is another impulse that will be shower generating that will swing through Tuesday afternoon. So expect some showers Tuesday in the high country.
Outlook shows weak troffing after this storm mid week with gradually rising temps. Once temps get up to normal (65 to 70) late spring TSRW pattern may develop later in the week.
From 8:30am Friday…..
The unseasonably deep upper low is now heading south. At 8:30am the Dweebs located the upper center about 134W-43N heading SSE.
The big problem for our area with this system is one of the forecast for the weekend, here on the east side of the sierra crest. Given the current model guidance, the bulk of the deep moisture and I mean deep….holds west of the Sierra through much of Sunday. This is because the upper center stalls offshore beginning about midnight tonight and just wobbles within a a 50 mile radius through about Sunday afternoon. It is Interesting to note that this system has tapped into some pretty impressive moisture. The TPW on the latest AMSU/SSMI scans show between 1.5-2.0 on the back side of this system wrapping into the southern portion of the storm. The latest CRFC information brings Yosemite close to an inch of QPF by Monday morning. However, given the nature of this storm, most of this will fall over the western slopes up the sierra crest with lighter amounts over the east side.
The NWS is broad brushing the weekend forecast to include showers for the Mammoth area Saturday and Sunday, however the Dweebs want you to know that it is entirely possible that this low could wobble far enough west or southwest to keep us dry through much of Sunday. That is until the upper center begins to eject ENE between Monterrey Bay and the Bay Area Sunday night through Monday. Sunday night and Monday are expected to be very active as far as precipitation with the possibility of a heavy band of precip moving through the eastern sierra later Sunday night into Monday morning. Nocturnal thunder is a possibly. Freezing levels according to CRFC will be about 10,000 on Saturday and 10,500 on Sunday. So expect the snow level to remain above 9000 feet through Sunday afternoon. The snow level will come down into the town early Monday morning along with the cool thickness pool as the upper center ejects NE through our state Monday afternoon, around or just north of Tahoe City. The last vort center should be east of Mammoth by 03z Tuesday using this mornings 12Z WRF.
The Dweebs wanted to mention that unrelated to the Mammoth area, as this upper low moves onshore during Sunday afternoon, the combination of strong solar heating, rapidly increasing lapse rates and dynamics will come into play. There may be a possibility of hail and cold core funnels over the Sac Valley later in the afternoon. I am sure that wind sheer profiles will be scrutinized by the NWS in the Sunday morning package for that area.
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Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.