Archive for June, 2011

Tricky Forecast This Weekend As Upper Low Stalls And Wobbles Offshore

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.



The Dweeber……………………….:-)


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Reference Glossary of Weather Terms
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.

Brief update this Morning……It will be cold with highs near 40 at resort levels today…..New guidence showing next WX maker center….coming into California early Monday AM….

Quick update:


New 12z Thursday guidance for both WRF and GFS shows the upper center moving inland Monday Am in a little differently location. The 12z WRF brings the center inland over the Bay Area while the GFS is consistent in taking the center inland through Monterrey Bay. The GFS would be consistently wetter for us, as that aprox 50 mile difference, would keep more of heavier precip to the south longer.  In that the GFS is a better model 4 days out will stick with the current forecast for a light to moderate producing precip maker with some 4 to 8 inches of snow above 9000 feet between Friday night and Monday night. Worth watching is the strong upper high over Mexico and Texas that will try to take the punch out of this system as it ejects inland via California early next week. Weekend temps in Mammoth will be in the low to mid 50s…lows in the 30s before the off-shore system kicks inland Monday with cooler temps to accompany.


Longer Range: (Some current guess work)

An upper level weakness in the mean is forecasted by mid week next week.  So showers are still possible in the upper elevations…although temps will rise with snow levels.

Looking at the Deterministic 12z GFS this morning….Although the eastern pacific high shifts to 140west and high latt blocking appears to weaken off the BC coast by the 10th of June, there is still a lot of blocking over BC…and the northwest Territories, then NW over AK. The westerlies will be suppressed south under this block and then have to split with some energy trickeling to the SSE down the west coast.  So we “may” transit out of our current strong closed low pattern, to one of a late spring thunderstorm pattern. (The Dweebs have been waiting for this) This would be form of winters last winter gasp!

As little vort centers travel SSE, then eject NE through Ca through the weakness, they will destabilize the atmosphere, especially during the PM hours. As we are approach the solstice in about 3 weeks….the Solar Angle will be peaking. This will easily provide the lift necessary as we combine warming temps and periods of cooling aloft for a convective showery pattern for the high country. This happened last June and we ended up with funnel clouds near hot creek in the afternoon. The big question at this time is how much energy will be in the split?  

That will determine how dynamic the impulses will be.


Dr Howard and the Dweebs………………………..:-)


————————————————-
Reference Glossary of Weather Terms
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.

The updated outlook consedes that the train of closed lows will continue at least another week….possibly two

It there an end in sight? It looked that way a week ago….just a head fake!

Coldest May?  Actually for Fresno, both May of 2010 and 2011 were tied at -3.7F degree below normal for the month.

It appears that another in the series of cool upper level low pressure systems will track across the Sierra today and tonight bringing snow showers and gusty winds to our region. Lake wind advisories go into effect at 1:00pm this afternoon and continue through 8:00pm tonight. The strongest winds will occur late afternoon and into the early evening hours with the FROPA. Then an even wetter system arrives for the weekend and may end up bringing a good 4 to 8 inches of snow above 9000 feet Sunday into Monday. Snow showers could begin anytime beginning Friday night. So here we go with another unsettled weekend and the way the WX maps look for next week it may continue for some time. Why? 

OUTLOOK:

WX Discussion….

An expansive warm core ridge is expected to remain anchored from the mid southern states southwest to Northern Mexico. This working teleconnection tied with a persistent positive upper height anomaly off the British Columbian coast will keep a signifacant negative height anomaly in the mean off the Northern Coast for the next week, possibly two. This leads to a series of deep cyclones dropping down into California for the next week to 10 days. The guidance, operational and ensembles are all in agreement concerning the next system to effect California this weekend. After the weekend the ECMWF keeps a trof in the mean over California pretty much all of next week with a series of small features dropping south over our state as either coastal sliders or interior sliders. The next more organized system is poised to drop south in California about Saturday the 12th/Sunday the 13th.  “It ain’t over till its over!” (Yogi Berra)



Dr Howard and the Dweebs…………………………………:-)



————————————————-
Reference Glossary of Weather Terms
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.