Moderate Winds over the upper elevations with very light snow falling at the 8200 foot level Sunday Evening…..Slower Evolution to storm system underway….Net result the same……
Sunday November 30, 2014
Posted at 9:53 pm by Howard
Comment: Nice Fetch developing out of the ITZ this afternoon. This fetch is getting juicer by the hour……Quite the rainfall event coming for LA Tomorrow/Night. Great news! But problems for the Foothill Burn Communities….for potential mud flows….
Monday PM Update: Some clarification due to phone calls today….
The biggest problem by far this morning is with snow levels with this storm. Not as much an issue after midnight Tuesday, but more so Tuesday afternoon and night. The temperatures are pretty much isothermal through the layer, which could mean that there is the possibility of microphysical processes going on….which would create quite the problem for forecasting amounts, “In town”…not on the mountain!
Snow levels could vary between 8500 and 7000 for this storm. The thinking this morning is that during the heaviest portion of the storm, the snow level will be around 8K. So for a period of time, it will be pretty sloppy in town, Tuesday afternoon into the night.
In simple terms….if you have 2 inches of water possible and the snow level is at 8000 feet, you could get 2 to 4 inches of sloppy wet snow on the ground at 7500 to 8K. However, the snow level will fluctuate between 7K and 8500…..So it will be problematic for forecasting for the Snow Pushers.
If by chance the iso layer goes down all the way down to 7K, will end up with 2 feet in town. That is not impossible, but unlikely. So 6 to 12 inches still seems reasonable. If we get more…great! As far as the upper elevations go…..2 to 3 feet will set us up for the Christmas holidays……Remember, this is dense heavy base building snow. It is absolutely the best type of snow that we could want. It becomes more difficult to ski it out! So…. Go ahead and book it for the holiday…you will not be disappointed…. And……The Dweebs see another series of storms about mid month. That will be the icing on the cake!
A moist SW flow pattern will continue throughout much of this week until the eastern pacific ridge strengthens next week. There is some strengthening and better organization to the next short wave Friday night and Saturday that now track into the Sierra south to Southern CA. This now appears to be a better storm for the Sierra then earlier thought. So….more rain could fall for CA as well as snowfall for the high country. Thereafter we ridge up for a while next week with the next series of storms likely colder based upon the position of the MJO and its composites for December. This appears to begin as we approach mid month……
Upper long wave cold core closed was spinning at 140 west and will end up ejecting a few short waves before coming through mid week. Today, showers and moderate rain fell over the LA basin and into the mountains of the Southern CA. In Mammoth only a dusting has fallen so far with very light snowfall occurring this evening with mild temperatures at the 8200 foot level. 30s…
The latest guidance shows the passing of the first short wave today, and short wave ridging following on its heals for Monday and Monday night. Although there are height rises ahead of the main upper low, the upper flow is very moist and so plenty of over running moisture will occur with little precipitation if any Monday/Night. The Freezing level Monday will be about 10,500 to 11,000 feet. Again little or no precipitation is expected Monday and Monday Night.
Height Falls begin Tuesday AM as the main upper low approaches the coast. By later Tuesday morning or afternoon, Precipitation rates will pick-up with about a 12 to 36 hour period of potentially moderate to heavy precipitation expected into Wednesday. The Snow Level looks like 7500 to 8500 feet Tuesday until it begins to come down later in the afternoon. It should be all snow Tuesday Night in town and well into Wednesday. The snow that falls will still be wet. We still could get “between” 2 and 3 feet of heavy snow over the upper elevations. (9K and above) and 6 to 12 inches at 8000 ft. The cold core or should I say cool core is only about -18C at 500MB as it comes in. So this is going to be a wet storm for the high country with good sierra cement. This is actually just what we need for the upper mountain for base building. I will add again that there is a coupling of the Subtropical Jet and a Weak Southern branch of the westerlies Tuesday and Wednesday. Coastal sections of Southern CA potentially could get a lot of rain this coming week. IE (several inches)…in the foothill communities….
Beyond this particular storm for the upcoming week are additional short waves in this moist SW flow that may effect Southern CA more then the Central Sierra. It will be showery the second half of this week here in Mammoth. There is a tremendous amount of moisture up at 700 MB associated with the subtropical jet that is progged to flow over the state this week. More dynamics will be focused further south later in the week for Southern CA as the upper flow splits and become difluent. So there may be another period of significant rainfall to watch out for after mid week.
Looking down the road the MJO is moving through the pacific and will reemerge back out over the Indian Ocean toward Mid month or about there after. After this week we may have to wait awhile for another opportunity for significant snowfall. This is not to say we will not get more storms, but stronger west coast ridging will return eventually between now and mid month. Watch the MJO as it approaches phases 8/1. Sometimes AR events are associate with that phase for CA. Getting caught up with the WX this week….The Dweebs will update mid week or sooner if necessary.
By for Now…..