Biggest Storm in Two Years bears down on Southern Ca….Sierra Braces for Major Dump……
Tuesday February 25, 2014
Posted at 1:12 pm by Howard
Thursday AM Update:
Not much to add this morning…. I picked up 8.5 inches at the 8200 foot level and I understand that Mammoth Mountain picked up about a foot at the main lodge with up to 15 inches over the upper elevations. I personally estimate that with the water content and the colder temps, more like 17 inches is up there.
Storm #2 looks better for us then it did yesterday as the upper cyclonically curved jet and UVM between 17Z to 22Z will really pound the Mammoth Sierra. Additionally, looking at the 700mb heights and RH from the new 12Z Thursday WRF, there is now a fairly sustained period of quasi SW flow which will add orographic’s to the mix. The WRF has the upper flow over the Mammoth Sierra more southerly late tonight then becomes more Southwesterly about 15Z Friday. The 700 flow continues between Southerly and southwesterly on and off through the afternoon. So Mammoth is on the boarder of the 700MB flow that is between these two directions. This is much better then the last few days guidance with southerly flow. So the models may not have a complete handle on the QPF because of the potential now for orographic’s. IE We may get more snowfall from the Friday/Saturday storm than is predicted.
So we may get another 25 to 35 inches at 10:1 over the Mammoth Crest by Saturday night.
The longer range still shows the upper ridge building over the west coast with time……Next week will be unsettled with periods of snow showers but nothing strong at this time…..
Dr Howard and the Dweebs……………….
WHY SO MUCH QPF IN THE MODELS FOR THIS AREA?
I have been researching the reasons why the HPC QPF has been going so hog wild on the QPF for this particular area of the Sierra. I can understand why for LA and for parts of the Southern Sierra. However, why so far north with southerly flow and with little orographic’s in play for storm #2.
When you think about it, the reasons are not all that complicated. The answer I believe lies in the Upper Jet dynamics associated with Storm #1 and especially the 2nd storm.
In storm #1 the upper jet “was” expected to be pretty zonal across Southern California. Now it is coming in from the SW across Pt Conception. The Left Front Exit region is very close to Mammoth now with strong divergence aloft and a VT max just to the south of Mammoth. This in itself will give the QPF a boost later tonight, especially after midnight.
Storm #2 the upper jet is not zonal either. It is cyclonically curved, coming into Pt Conception early Friday AM and rotating up through the Owens Valley during the day. This creates strong UVM over the entire Southern Sierra chain up to Mammoth.. Thereafter, we become under the Cold Pool Saturday and Saturday Night with a lot of unstable air. Expect additional accumulations.
The upshot is about 4+ inches of water over the Pass…..
So there it is……………………!!
PS…. Trying to get the Mammoth WX data logger online later tonight…
I have not seen this much open cellular CU between 30N and 40N since the winter of 2011! It’s nice to see it happen again! All systems are go for one heck of a storm for Southern California Ca. The recent burn areas of my hometown in Glendora should take extra precautions now by sandbagging areas around homes below canyons.
The latest QPF is up to 8.5 inches from the latest HPC output in some of the coastal ranges of Pt Conception and the foothills of both valleys. There may be more rain in “some areas” that has fallen in two years down there.
So again the big story will be the enhanced Asian Jet that is making its way through the far eastern pacific. Both the EC and GFS is painting about 3 to 4 inches of water up on the Mammoth Pass. And if it were not for the best forcing to the south of us, this would be one of the EPIC and memorable 4 to 6 foot dump. Well instead have to settle for 3 to 4 feet over the crest and a couple of feet in town by weeks end. There is the chance that snow showers may continue for sometime after the storm is through Saturday, so that several more inches could accumulate over the upper elevations throughout the weekend and even a few into the following week.
There are two separate storms. A smaller storm Wednesday night in which the town will get 5 to 8 inches and the biggie Friday AM through Saturday 12 to 15 inches will fall. Approximately double that for the Crest…..
I see a small system about the middle of next week, mainly effecting Tahoe, then we ridge up for the following weekend of the 8th…..
After that well see…….
Dr Howard and the Dweebs…………………………:-)