Archive for December, 2012

POSITIVE AO DEVELOPING>>>>>> Brief New Years Eve Update: Ridge in the West…. Trof over the Central US. Our weather pattern will highlight drier then normal precipitation and colder then normal temps. The Eastern Pacific high has found a home between the far eastern pacific and the far west. Any storm that happens to make it through the ridge will be weak and likely to bring only light amounts in the way of precipitation. Light amounts are considered between a trace and 6 inches of snow here in Mammoth Lakes. Although this is a dry pattern there are certainly a few weak systems over the next 1 to 2 weeks that has possibilities. One of which may bring a few showers or flurries New Years Day in the late afternoon as we expercience a return of upslope flow.

The best way to forecast these are when both EC and GFS global models are in agreement with the greatest confidence within 72 hours of our region. For the record, the models are all dry with this one…..however if we have some flurries…you’ll know where they came from. Mammoth Mountain is reporting a 10 to 12 foot base. There is probably much more in the upper bowls between Ch-3 and Gondola- 2.

In the meantime, it is cold…..It was -20F at 7:00am at Bryant Field, Bridgeport, Ca this AM. However, under the current inversion, temps are actually about 5 to 8 degrees warmer in the upper elevations today over yesterday. The Dweebs took a look at both the 8 to 14 day outlook and Climate models for a hint when the pattern might turn. In the 8 to 14 day outlook, 500Hpa heights are building over the Northern Pacific, with the upper jet expecting to respond by dipping south into the pacific NW about the middle of January. This would bring a return to wet conditions for Washington and Oregon between the 2nd and 3rd week of January.

The Climate models are indicating the change down into the Central Sierra taking a bit longer. So as “a guesstimate“…figure sometime after the 3rd week of January for some serious weather. The pattern that just developed often times lasts about 3 weeks…… Lets hope for a few small storms in the meantime…..

The Dweeber……………………….:-)

It was cold this morning…Mammoth Airport Hit -17 twice this morning. Once at 5:15am and again about 7:50am. That’s cold!  Short wave ridging was the reason for the very cold temps in the valleys below the resort levels, as the air aloft was forced to the surface by subsidence. Radiational cooling, and especially subsidence has an effect of drying and the lowering of dew points as well down in the colder valleys.

Looking at the short range models…..The upper ridge is expected to amplify again out about 145 to 140west. In fact it builds to latts north of 60N. That will have the effect of pulling down even colder air mixed with continental air over the holiday weekend.  I see 500mb temps at or below -30c in the low and east to the Ca/Nev border and 700mb temps below -12c in the upper low over the Central Sierra Central and especially Eastern Ca. With this coming during the coldest time of the year it is notable!

So….The short wave ridge currently over Mammoth is translating east, while at the same time, the next upper trof to the NW is ripping SE and headed down the west coast. Coastal sections of Ca will get up to an inch of cold rain while further east into the California interior and Eastern Ca much less amounts are expected. 4 to 6 inches possibly at 20:1 ratios over the weekend?  The system over the weekend will come as a one two punch as a “vort center” drops out of Western Canada Sunday bringing a reinforcing shot of continental air and causing daytime highs to remain in the upper teens in Mammoth for Saturday and possibly Sunday. Sunday night temps quite possibly below zero in the Town of Mammoth as the -15C at 700mb flirts with the Eastern Sierra and 1000-500mb thicknesses in the 530DN range

Yes, there will be light snowfall, especially Saturday AM as the coastal slider pumps moisture up from the SW through Mammoth Pass.  Then later in the afternoon the action shift south up through Kern Co and up the Owens Valley with South East Flow, once the upper low is down to about 36 to 35 north lat.  The official forecasts call for little snowfall for the Owens Valley. However, I would not go to the bank on that one, especially if the upper low forms a large enough center and slows….wrapping moisture back up through Kern Co, Ca and further north in a SE flow action. The Dweebs feel that there is a substantial chance for chain controls along parts of the 395/14 highways “Saturday PM into Sunday AM. If your traveling these highways at that time, be sure to carry chains just to be safe….extra blankets and water are always a good idea as well.

Outlook:

Although both the 6 to 10 and 8 to 14 day outlooks are drier then normal…Don’t think that we will not have anymore snowfall. Although we are not likely to have anything like what we have had the past two weeks.  The GFS has a block developing over Western Canada. This implies Ample Short Wave energy that can be forced to break under that block and punch through the mean ridge position, or punch down the W coast.

I will say that the 12z EC has more blocking over the far west with not as much of a block over Western Canada.  This would tend to cut off systems off the Ca coast.   So I think that we can get at least light snowfall or possibly some moderate snowfall with these systems as they weaken and head toward the Great Basin……or possibly some up-slope if they move inland about 35 to 36 north and cut off off the Santa Barbara coast. So the storm track looks to be split with the northern branch the strongest out of Central Canada.  The Dweebs will take a look tomorrow to see how it is all shaping up. The screaming message here is that the GFS has the Hemi pattern progressive without a strong -NAO block to hold a strong 500mb ridge over the far west.  The EC does have more of a block but not that all convincing yet. I think that everything that is going to form over the next week to two weeks will break down and shift east in time.  This may eventually allow for the potential for a wet pattern to return to the Pacific Northwest and likely Northern California by Mid January……

Like your skis………..stay tuned!……………..:-)