Nice Break in the Action Today……Cold Forecast continues through Years End….Dweebs Not Buying into Dry Snowless Forecast Next Two Weeks……
Friday December 28, 2012
Posted at 11:25 am by Howard
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.
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!……………..:-)