Monday AM update:


Of note, dew points are on the increase from south to north over Inyo County this morning, as at the same time, temps are rising. PWAT’s ranges from, .75 to 1,00 over the Owens Valley. Additionally, mid level moisture is increasing and being fed by two areas, one over the Channel Islands to the south and more importantly an area from possibly an old Mesoscale convective cluster NW of Vegas/Pahrump. This area is advecting rapidly toward the Owens Valley.  Surface pressure charts keeping the thermal trof back more toward the sierra crest today for good surface convergence. as well. All in all, it looks pretty active this afternoon and again tomorrow with TSRWs and possible some localized areas of heavy rain. If you our in the open and hear thunder, take cover!


It’s mid month July and time to look for thunderstorms and pattern’s associated with the Monsoon/Southeasterly flow.  As many know, late July and early August is climatically the peak of the Monsoon season here in Mono County.  Thunderstorms over the Sierra? There have been very few so far. However, you don’t have to go far to find them. They have been near the extreme southern portions of Mono County, near and west of Sherwin grade and especially over the Benton area, and along the White Mountains and especially Eastern Bishop, CA.

Why?   Why not Mammoth?

The position and strength of the continental high, east and south of us and its strength, in relation to any Trofing in the Eastern GOA and pacific NW, governs where the thermal trof sets up over the far west.  This is the plain vanilla pattern that is so common throughout the Summer here.   This Summer so far has been highlighted by weaker high pressure over the Great Basin and the Desert Southwest and stronger Trofing NW, and thus the thermal trof has been mostly over Nevada during the late afternoon when the best chances of rain occurs.  Don’t get me wrong, the Monsoon has been quite active over AZ, and as of late, Southern NV.  However, the Mono Zephier, has been quite strong too, developing strongly along the eastern slopes of the sierra, whereby the Mono County Convergence Zone is further east than normal so far. This zone shifts even further east to near the CA/NV border by Mid to Late afternoon.  As a result, the Mono County Sierra has been spared both rainfall and “Lightning” from TSRWs. So the upshot from no storms in the Sierra is no lightning caused fires too!

In looking at the GFS model Surface pressure/500 MB flow, the pattern is to remain static for the next 2 to 3 days. Thereafter, the trof strengthens off the pacific NW later next week for a drying trend along with a strengthening Zephier.  This diminishes the thunderstorm threat even further for the Mammoth area. As you may remember, the ECMWF from the month of May forecasted a wet July for the high country; its been wrong!

The Thermal Trof axis, or the axis of lower surface pressure and surface convergence is likely to remain east of Mammoth Lakes through that period. Bishop, Ca is much closer to that axis and so Bishop is likely to have better chances of rain and thunder the next few days.

For Thunderstorm lovers, there is still plenty of time calendar wise, for pressures aloft to build in from the ESE, and the Thermal trof to retrograde to the Central Valley, before moving over the Eastern Sierra for afternoon thunderstorms.


Stay Tuned!!


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