A Few More Systems this Week then a Break…….Eastern Sierra still stuck with the Split Flow Blues……
Sunday December 14, 2014
Posted at 10:47 pm by Howard
Mammoth Mt Snow plot picks up about a foot over night…Here near the village about 6 inches….
Another 5 to 10 inches by Wednesday morning possible
3 to 5 in town…
Latest QPF from HPC again going hog-wild with a 5 day Bull’s-Eye total near the Mammoth Mtn Summit of 2.2 inches of water. CRFC updated with 1..36 for Yosemite through Saturday AM which takes in consideration of the mountain effects. The FOUS data from Fresno shows .97 hundreds. It also show some significant UVM of 25.2 at the 36 hour period based upon the 18Z output. That means that the heavier snowfall would increase toward 10:00PM Tuesday night. In that there is little Jet support for this storm over the Mammoth area, well just have to hope for a good Deformation Zone to set up.
Here are some thoughts. This system is colder than the last system. So the snow to water ratio will be greater than the last storm. Whatever falls will be all snow for the Town of Mammoth.
Updated amounts for the week…..best guess at this time. (Subject to change) Snowfall totals of 5 to 10 inches in town and “between” 12 to 22 inches over the upper elevations. (5 day totals) The upper limit is certainly not the main forecast. Rather it is a best guess based upon the spread. The timing is over a period that includes several short waves and their QPF total.
Dr Howard and the Dweebs……………………….:-)
Monday AM Update:
Very Weak UVM coming through this morning with another slightly stronger Vt Max coming through Tuesday AM at 12Z.
Main Shot of energy splits with best dynamic portion diving south “off shore” toward Southern CA. Only sheds of UVM come into interior Central CA Tuesday Night/Wednesday AM
What a Mess!!!!
Given the latest 12Z Run of the WRF and GFS…there is little confidence in QPF or snowfall amounts the next 3 days… We may only see a few inches in town with of course the crest doing the best. It is interesting to note that CRFC gives Yosemite and Huntington Lake over an inch of QPF the next few days. Normally, that would give us at least a foot over the crest. With orographic’s two feet. With a split flow pattern like this may be only half!
Comment: Medium range models are still not doing as great a job as they could of. The Dweebs will stick with Days 1 thru 3.
Both 6 to 10 and 8 to 14 day outlooks are drier then normal. So other than inside sliders….we’ll keep waiting….
Even though the skiing is great up on the hill…we want more snow! Why?Because…..we always want more snow right?
Latest QPF from Sunday Nights guidance. Best guess for snowfall between Monday night and Wednesday night.
4 to 8 inches in town; 8 to 15 inches between 9K and 11K
Note, this system is still splitting. The main upper jet is still well south of us. However, at this point orographically, the first system is better than the last, even though the last system for Tuesday night is stronger….
There are several reasons for the split flow pattern that weaken storms over the Central Sierra. The more common explanation is usually a persistent long wave upper ridge over the west. However, it’s usually much more than that. The wave length at 500MB across the CONUS may play havoc in forecasting this ski seasons weather. And…..even though the pattern can be progressive, the split can still remain. The good thing these days is that the global models are handling the west coast split better than they did back in the late 1980 and early 1990s. Back then, even the 72 hour AVN model would not show the split. This would drive forecasters crazy when the split did not show up until seemingly the last moment. I remember those days very well and often times the only product that one could see the split show up was the 500mb 5 day means. There…You could see it plain as day. However, that west coast split was often times nowhere to be found in the dailies.
Coincidently, “Weak El Ninos winters” are famously associated for west coast split flow patterns. Yes there is an association, but as usual, not always. Weak warm event conditions are forecasted to be better than 50/50 this winter, and…..we just happened to be currently experiencing a pattern that resembles past weak warm event winters…..Humm….?
Unless you have a subtropical hose pointed at you, it takes dynamics to get the big snows here on the eastside. In order for that to happen, you must have the upper flow at 500mb consolidated and progressive through the Sierra. That has not happened yet this season. Will it happen? Hard to say…..
But there is a good chance that we will be struggling with this split for sometime to come.
The issue with this pattern over East Central CA, is that short waves (Storms) are being forced to slow down as they approach the long wave upper ridge over the west. As the systems slow down, the energy because of the physic’s, diverts to the Right. This causes the storm to actually spin up and intensify while changing course toward Southern CA. So while Northern CA gets hammered with rain, as well as the west coast south to Southern CA, the Eastern Sierra gets left with the east edge of the systems UVM with weakened dynamics at best. The other big issue is, as these system split and head for SC, the upper flow becomes southerly. So not only do you not get the UVM energy (Upward Vertical Motion) through the Sierra, you also lose the orographics as well. We may be forecasting several of these types of systems approaching the west coast this year. This will diminish the accuracy of both the QPF as well as timing. So we will have storms this year that are forecasted to bring a lots of snow that will actually bring little. There will also be times when we get a lot of snow when little is forecasted. This is going to be a tough year for the forecaster here in the central sierra, especially on the east side. The models will be saying trust me…but can we?
The next two short waves approaching CA shown on the models a few days ago were expected to perform with the 1st system progressive through the sierra and the second splitting and heading south. The latest 00z Monday GFS modeling shows the first system holding on better further east, with more lift actually through the Sierra. Is this another head fake? Should one believe it? I’ll take a good look at it Monday. Either way, the system is still splitting. The question remains as how much energy gets through….
On another note, we can get precipitation from other patterns even with the west coast split. For one, storms that come out of the NNW. As long as the upper jet has over water trajectory, we can get some decent snows. Additionally, remember the Tonopah Low? We have not had the effects of a good Tonopah Low for a log time here in the Eastern Sierra. Maybe 2015 will be the year for it. The Tonopah Low can give fabulous upslope snowfall for the Eastern Slopes…..