It’s Cinco de Mayo and Cut-off low season has finally begun.  Current upper ridge that brought low 70s to Mammoth and 90 to Bishop on Thursday has shifted east to the Rockies. This is a full latitude ridge that extend from Northern Mexico to Canada. To our northwest is what appears to be the first is a series of Trofs that will migrate through the west coast.  Some will be progressive and others will become Cut-Off Lows. This will be a challenging pattern for forecaster’s, as mid springtime storms unlike winter storms play by a different set of rules. “CAPE” Convective Available Potential Energy will weigh in heavily with each stormy period now as the Sun’s angle is Summer-like in the western sky.

As our Western Trof approaches today, winds will increase blowing off any convection well into Nevada. By Saturday mid-morning, the Upper Trof is along the west coast with a closed low forming just west of the Bay Area. Southerly flow is increasing over the Sierra as moisture advects in from the south.

During the afternoon on Saturday, the upper center “spins-up” with increasing upper divergence in its NE quadrant. This begins the process of dynamic lift over the Central Sierra along with increasing chances of precipitation over the Mammoth Area. Expect Towering Cu and thunderstorms forming with rain, possible hail, thunder and of course snow over the higher elevations. The snow level will fall over night Saturday night in the Town of Mammoth. Light accumulation’s are expected.

As the upper low moves inland over Ventura County Saturday Night, SE flow will push precipitation up into the Owens Valley.  Up-Slope Flow and precipitation is expected along the Eastern Slopes of the Sierra later Saturday Night into Sunday.  Upslope precipitation may continue through Sunday and possibly Monday at times.  It is uncertain how long the upslope flow along the eastern slopes will continue, as the timing is dependent upon the cut off lows SE exit. This is currently progged the early to the middle of next week. The next upstream system should give Mondays Cut-Off the boot by mid-week.  Forecast models are showing any ware from 6 to 12 inches of snow over the sierra crest by Monday.  The extended outlook shows on and off  unsettled weather with cooler than normal temperatures, as high pressure aloft builds over Alaska in the longer range…

Teleconnections from the ECMWF and GFS show trending -EPO and -WPO the next two weeks.

Thus the Storm track will likely remain suppressed into California.


Dr Howard and the Dweebs……………….:-)