Unsettled Weekend Ahead with Showers and Thunderstorms Possible…Upper Cut-Off is now on the move…..
Friday March 29, 2013
Posted at 9:43 am by Howard
Saturday AM Update:
Last weekend update…….
Precipitation to begin by late this afternoon or evening……
Latest AMSU CIRC TPW still shows about an inch of TPW wrapped into a band ahead of the cut-off low. There is a richer pool of PW off the Northern Baja coast which will most likely not be a factor.
Snow levels will begin very high…8500 to 9,000 today then lower late tonight into Sunday. By Sunday, the SL should be at or below 8000 then 7500 by the afternoon., then 6500 ft by Sunday night. On Monday, the SL will rise to 7000 feet.
2 to 4 inches of snow is certainly possible now in town at 8000ft. As mentioned yesterday, the storm is more spring like and accordingly, there could be some thunder. Additionally, snowfalls below the shafts in convective cells would favor even lower snow levels, temporarily.
Updated QPF from CRFC this morning showed about .8 over Yosemite. The EC has about 1.25 of an inch west of the crest by Monday evening. In that the upper jet (shown with the 12z GFS at 300mb), comes in over Santa Barbara., Mammoth is in the favorable front left exit region of the upper jet, tonight into Sunday night. Additionally, a good part of the Precip in the storm will occur during the warm sector…..Snow to water ratios will be low accordingly. Estimates are between 5 to 7 at the main lodge and 7 to 10 inches for the upper mountain by Monday evening.
Next Update Tuesday……
Next storm Thursday and again next weekend……………….:-)
Dr. Howard and the Dweebs………………………….:-)
Latest AMSU CIRC TPW shows about an inch of TPW wrapped into the cut off so far. Further entrainment is possible later today and tonight as a combination of the slow movement of the upper cut off and the Subtropical Jet get closer.
Today’s weather will be partly cloudy with a few isolated showers this afternoon. As the cut off moves towards the coast then onshore, showers will increase Saturday/Ngt. The Snow level will be high….above 8500 until the cool part of the system comes inland Sunday. 500mb-1000mb thickness lowers to near 546DM briefly, so we may have a snow level by Monday AM at 6500ft. Snowfall in town maybe a trace to a inch or two Sunday night into Monday AM. Snow fall amounts over the crest will be 6 to 12 inches by Monday evening. This system will weaken rapidly as it moves inland because it is cut off from the westerlies supply of cold air. It is only coming in because of an upstream kicker ridge. The higher Sun angle of late March and early April will keep a convective component to the system. So Thunder snow is possible Sunday afternoon. Showers will continue Monday and diminish Monday evening. There will be a break mid week before the next storm moves in beginning Thursday.
The ECMWF model’s total Precip for the Sierra Crest near Mammoth Mt, from the 00z Friday Run shows that over the next 10 days between 3 and 4 inches of QPF.
Meanwhile…..the latest DWP Snow Survey data shows the water content of the Snow Pack at Mammoth Pass less then 50% of normal, Similar to where we were last year this time.