Another Cold System will move through Thursday and Friday with warm advection pattern developing over the weekend…..Thus freezing levels on the rise over the weekend….
Tuesday February 4, 2014
Posted at 9:54 am by Howard
Just took a look at the; NCEP Rapid Refresh (RAP) initial 2-06-2014 1900Z
Between that rapid update model and the valley radar it is evident that everything behind the front this morning has gone south and is now lighting up over the southern sierra. The upper jet probably remained too far off shore for any meaning full spill over. With the upper jet moving south, off shore, were out of the effects of this system for the most part except for a few showers now.
Warm air advection will begin to make its way into the Central Sierra later in the day Friday with snow levels low enough for light snow in Mammoth. Thereafter, the main hose moves into the northern sierra, spreading precipitation south by means of orographic and isentropic lift ahead of the warm front. QPF amounts in the models are usually under done and indicate only about 1.5 inches for Mammoth, which probably needs to be doubled for our area. So 3.00 of liquid is the state of the art at the moment with a lot of heavy snow still expected for elevations above 9,000 feet Saturday through Sunday night. Unfortunately for those in the snow removal business, with the snow level expect to rise to 8000 feet Saturday and 8500 Saturday night, there is not going to be much to push around. Snow levels will range between 8000 and 8500 hundred feet into Sunday afternoon. In fact the timing of the warmest air is Saturday night and so there may not be enough diurnal cooling for the rain to change back to snow that night. You will have to wait until the last piece of energy comes through Sunday night for the rain or rain snow mix to return to snow. That may begin to occur as early as Sunday mid to late afternoon and should be all snow in town Sunday night for a good plow!
The weather begins to turn showery very early Monday AM….then we clear out during the day Monday and probably earlier than later.
Mammoth Mountain should still see “at least” two feet of base building snow this weekend and hopefully more…..
PS: Here are some tabulations from my good friend Bob Sollima who is a hobbyist hydrographier here for Mammoth Pass. I really appreciate him sending me records from time to time. As you can see from his data, we are doing than some of the driest years already. The precip that is coming this weekend will help as well.
Feb. survey: 2014 = 8.5 in. H2O (currently at 22% of full winter precip ave.)
1977 = 4.3 in. H2O ….end of winter result = 20.5% of average
1991 = 4.7 in. H2O ….end of winter result = 67.4% of average
1987 = 7.3 in. H2O ….end of winter result = 51.0% of average
2012 = 8.7 in. H2O ….end of winter result = 48.3% of average
2007 = 8.8 in. H2O ….end of winter result = 41.9% of average
1976 =10.1in. H2O ….end of winter result = 44.8% of average
1948 =10.2in. H2O ….end of winter result = 60.2% of average
1994 =10.3in. H2O ….end of winter result = 57.2% of average
Thursday 11:40AM update…
Brief update to indicate that snowfall from the front has already moved through leaving 4 to 5 inches up on Mammoth Mt. earlier this AM. Any snowfalls that occurs for the rest of the day should be isolated with further accumulations less than an inch… The action is currently both to the south of us and to the north of us up in the Northern Sierra. More later as to the reason….
Jus took a look at the “RUC” Rapid Update
Thursday AM Update:
Although it does not look quite as wet as it did yesterday, the QPF and moisture plume for the 5 day period is in the 2.00 to 3.50 inch range for the Mammoth Area between the town and the Sierra Crest. The Dweebs are expecting that over the upper elevations, there could be initially some dry powder then some heavy wet snow, with totals in the 2 to 3 foot range above 9000 feet by Monday AM.
Remember, that the snow to water rations are expected to be reduced significantly as we go in time from Saturday into Sunday. Then afterword’s…..The 12z Thursday GFS guidance for Sunday during the late afternoon and night look pretty interesting this morning as the main forcing (+PVA) with the upper jet is progged to come though at about (06Z Monday )10:00pm Sunday night. Thus some heavy snowfall is very possible for the Town of Mammoth and over the crest Sunday evening if that is correct. Precipitation should be ending during the late morning hours Monday with the upper jet redeveloping back to the north Monday night into Tuesday. There is another system that we will have to keep our eye on for Wednesday.
Snow levels will be problematic in town with the precipitation all snow in town through Friday, then afterwards the snow level going up above 8000 feet later Saturday and remaining above 8000 through mid Sunday afternoon.
So all in all, this is not what I would consider to be a drought buster storm for Mammoth. However, snowfall wise we could certainly see a few feet of snow over the highest elevations and the fact that the moisture content will be overall high is great news for those concerned about water,
QPF in this kind of pattern will change daily until we are within 24 hours of the event. This is true as well for the snow level forecast……So stay tuned and the Dweebs will do their best to keep an accurate WX picture without the hype.
Dr Howard and the Dweebs……………………………..:-)
Lots of chatter now around town about the upcoming series of storms. I want to put it all into perspective…
Storm number one is still a cold storm. It is getting a little moisture from the Hawaiian tap well to the WSW but the air mass that it is mixing with is cold, so expect Snowfall to water rations of possibly 15:1. The QPF from California Rivers Forecast center is showing about 7 tenths so a foot still looks go over the upper elevations and hopefully a little more. The town could see 4 to 6 inches and a bit more above the village.
Storm #2 as per the last discussion below is still looking wetter. But for those that are seeing all the red-painted upon the graphics, be advised that we really do not know where the freezing level is going to be. CRFC is taking the level up to about 10,000 by Sunday. In a saturated air mass, there is little difference between the snow level and the freezing level, so you can not count on the usual 1,000 to 1500 foot under the freezing level rule. However, there are microphysical processes that will allow snow to fall from the dendritic crystal growth zone to the surface at 8000 with the Freezing level at 10K so it might be snow or it might be rain. Well have to wait another day or two find out. Either way this is not what I would consider a major precipitation event for Mammoth but it may be the biggest storm of the winter so far.
The new 12z ECMWF paints about 4 inches over Mammoth Lakes, for the 5 day period including storm #1. So at this time we will benefit from the AR connection but not like Tahoe north where amounts of up to 9 inches are indicated mover the Sierra adjacent to Susanville.
The PWAT is impressive at 1.25 to 1.5, and with 5 day amounts approaching 10 inches of water, qualifies as a strong AR event. As a comparison, the upcoming event is nothing like some of the past excessive events that painted over 25 inches for a 5 day period, in years past.
Wednesday AM Update:
The guidance has changed over the past 24 hours and has trended wetter for our area for both systems. One result of the change is that it will not get nearly as cold. Additionally, with less amplification upstream, pacific air will become more dominant over time Friday and into the weekend as the pattern actually becomes more Zonal. This is really a change over the short to medium term.
1. Model guidance has shown a significant change over the past few days in less amplification of the off shore eastern pacific ridge, and thus much less deepening with the modified arctic air over the northwest into the far west. Much of this cold air mass in the pacific north-west will now become more stretched out east-west with the bulk of it heading east. The western portion will assist cyclogeneses as the upper flow becomes confluent with the upper jets off shore. As the upper flow becomes rapidly west to east Thursday, the first system takes a more southerly track as heights are pretty low at that point in time. That main target is the southern and central sierra including Mammoth Lakes. I would not be surprised if the town got 6+ inches by Friday AM and the upper elevation well over a foot as snow to water ration’s will be pretty high.
2. The second system is also trending wetter. In fact this is an atmospheric river related system that now has impressive precipitable water amounts forecasted to 2 inches. The trajectory is from the Hawaiian islands and although the main focus is still Northern California, is has trended a bit south of late.
Any further shift south by Saturday could result in heavier precip amounts for our local sierra over the upper elevations in the 1 to 2 inches (or more) range. At a 10:1 ratio, that could be an additional 10 to 20+ inches above 10K. The freezing level will rise close to 10,000 feet by Sunday. So what ever snow falls in town Saturday, will become pretty mushy by Sunday.
Stay tuned……..I will update either later today or again in the AM…….
Dr Howard and the Dweebs…………………:-)
I have looked at the all the guidance this morning and the west coast ridge is still doing the same thing. That is, moving back and forth between 140West and 120west. So either its going to be colder than normal and drier than normal or, warmer than normal and drier then normal. In either situation and in between we can get light or occasionally a moderate shots of precipitation. However, you’re not going to get to the pattern that we want along the west coast without a shift in the high latitude block in the -WPO position eastward to the -EPO.
The MJO has been locked in 6/7 and it keeps circulating the same like a skipping record. If this were a moderately strong Enso year the subtropical jet would have swept the legs out from under the current west coast pattern.
Now a new Climatologist claims that “it is” the negative phase of the PDO with the addition of the neutral ENSO conditions for the excessive west coast dryness. The claim is that during the negative phase of the PDO and with its protracted cycle in time, drought over the west are more common because of the effect of weaker and far fewer warm phase El Nino Events. Possibly……there is certainly more logic in that statement as compared to others lately. One comment about the weather in the east this winter, is that this years winter has proven that the AO and NAO in the positive phase can certainly produce very cold winters without those oscillations being in their deep negative phase for long periods of time. Which is more of a concern to long-range forecasters I think.
OK….here we go again….
With the eastern pacific ridge out about 135 to 140west, another system will makes its way into the pacific NW over the next few days allowing another shot of very cold air to advect into the Great Basin. There will be an increase of wind over the crest Wednesday into Thursday as the heights fall north to south instead of the preferable west to east. The upper Jet is going to spin up to the south of us, pulling in a little pacific air and moisture for some light snowfall Thursday and into the night. (2 to 5 inches). Then as the system shifts east Friday, the upper jet will lift north through us into the Pacific Northwest over the weekend and become anti cyclonically curved. Thereafter, the upper ridge axis sets up over or just off the CA coast for an extended period. Meanwhile over the weekend, the hose appears to be pointed at Northern CA and eventually the pacific northwest. So again we get the southern remains of the moisture fetch with higher snow levels over the weekend and early next week.
Looking at the climate models, they still insist upon a significant wet period, for the northern and central sierra in their 45 day outlooks. However, either they are totally wrong, or they are too fast, as I see nothing in the ensemble’s suggesting that this far south.
Yes….with an anti cyclonically curved jet as by buddy Tom C points out, you can get significant precipitation with heights between 576DM and 570DM. However, I have not seen any sign of any sustained robust upper subtropical jet anywhere near this latitude/longitude to suggest that is going to happen yet, except possibly this Sunday for a time. We might get a moderate shot of precipitation from the Hose to the north of us. Otherwise, we wait and wait for later in February and March, while hoping our water storage will be blessed with more water….
Dr Howard and the Dweebs……………………………:-)