Friday Update:

Currently, a weak upper low is west of Northern Baja reacting with the Continental High and Mammoth is in-between the two. This has spun up a weak 50 knot jet and is producing high clouds that is streaming through our area. This little feature will lift NE over Northern CA later today and tonight and RH will diminish at 300MB later today and tonight as this feature moves away.   Tomorrow Saturday, the upper flow backs to the South later in the day and eventually SE by Sunday. This opens the door to increasing RH at 700MB (Monsoonal Flow) and so expect mid-level clouds to increase from the South later in the day Saturday with a lot more mid level moisture pushing into our area Saturday night and Sunday. It should remain dry Saturday with warmer temps because of the lack of high clouds.   By Sunday, we may become over developed (Mostly Cloudy Early) and so any thunderstorms would be isolated. Further moistening will occur Sunday night into Monday and into Tuesday for a better chance of afternoon and evening TSRWS. There are a couple of VT centers that will lift through the sierra between Monday and Wednesday as well.  By Friday the 1st…The upper flow begins to back to the SW and drier air begins to move back into our region. The Blues Fest will be Hot ! 😉

Quick Look at the new 12Z GFS 700 Temps….shows 15C isotherm over Mammoth during the late afternoon and Saturday afternoon.  This is quite warm and will promote highs in the Mid 80s today and Saturday.  700MB moisture begins to increase later Saturday and into Sunday. 700 temps begin the fall off toward 10C by Sunday into the middle of next week.  Temperatures do begin increasing again back up to 15C the following weekend. As far as the possibility of any remaining thunderstorms from mid week….it all depends upon the strength of the upper flow and its ability to flush the moisture out.

The Dweebs will take a good look at that next Wednesday……

Note: +15C at 700MB with drier conditions in July and no significant cloudiness, usually gives Mammoth highs in the mid 80s……+10C = mid to upper 70s

Dr Howard and the Dweebs…………………………………………………………………:-)


From Thursdays Discussion:


Upper trofing off shore has been weaker than most Summers and the Subtropical high has been more persistent in directing both moisture and dynamics into the Eastern Sierra. Currently…we are now being influenced by an Eastern Pacific Trof associated with a Closed Upper low over the pacific NW. This storm will actually bring snowfall to the upper elevations of Mt Rainier today. With the current dry fetch of SW flow over the Sierra, the usual process of getting rid of the Monsoon moisture and stabilizing the local Air Mass over Mammoth Lakes has taken place.

Stabilization will only last about 5 days though. This is what has been unusual this Summer. Usually it is the other way around with more of a persistent trof to the west of us, keeping our air mass drier and more stable. This Summer it is different, with more episodes of SE Flow and Dynamics. Why? Because of the stronger than normal long wave trof over the Great Lakes emanating from the PV east of Hudson Bay.

Seasonal Discussion:

This is not the first episode of a system diving south out of Canada creating one of the coolest Summers in the Great Lakes region, south and SE. It is only this time that it’s origin is out of the North Pacific. Nevertheless, this is why it continues to be so hot in many areas of the Great Basin and the Monsoon more persistent further west. Long wave trofing in the east and a ridge in the west….. A familiar teleconnection? So this time, an upper low over Washington will lift NE to Alberta Canada tonight…then push east to Saskatchewan Canada Friday night, as it squashes the big 600DM upper ridge over Colorado. As the short wave shifts SE over North Dakota Saturday night, The short wave pushes on the eastern flank of the upper subtropical continental high, squeezing it westward after tilting it negative. This action forces the upper high to build negative tilt into Eastern Nevada by the end of the week and into Monday. This sets up the SSE flow of dynamics and monsoonal moisture from AZ, Sunday into Monday. At the moment the ECMWF is a bit more aggressive in its westward push of increasing heights than the GFS. A bias that seems a bit more accurate this Summer. As far as sensible weather…after a fair and warmer then normal weekend….expect an increasing threat of Thunderstorms over Eastern CA early next week. Whether this pattern is a major player in Mammoth’s weather is not known at this time. As usual, it depends upon where the direction of the little spokes of vorticity set up in relation to the sierra.

Inter seasonal tropical update:

The majority of dynamical model forecasts of the RMM index continue to indicate weak or incoherent MJO activity during the next two weeks. These include the GFS, Canadian, JMA and Taiwan Central Weather Bureau models. The ECMWF and CFS forecasts, however, indicate a more amplified, eastward propagating signal over the next few weeks. The propagation speed is somewhat fast and of generally only weak to moderate amplitude. This may be primarily in response to the somewhat slowly evolving Kelvin Wave. The MJO is unlikely to play a major role in anomalous tropical convection and highlighted impacts are principally based on the KW and ERW evolution, the tilt toward a warm ENSO base state and model guidance.