Above normal temperatures have Spring run off in full swing….Upper high over the far west continues to build through mid-week then weakens and redevelops further west allowing a cool down to near normal temperatures in the high country over the holiday weekend and beyond…..

The High Country run off from our record-breaking winter is in full swing this week. Main stem rivers to the north will flood pasture land over areas of Western Nevada.

Upper ridge now building north will begin to weaken this Thursday in response to retrogression of the long wave pattern prior to the holiday weekend. This will pull the Eastern long wave Trof further west and allow cooling of some 8 to 10 degrees over the holiday weekend. But don’t worry about high temps bring too cool. I still expect them to range in the mid to upper 60s for the upcoming holiday weekend…..Or slightly above normal.  As the transition begins, our air mass will become a bit unstable Wednesday and Thursday for some late thunderstorm’s possible of the convective style. These will be diurnal only.

According to the ECMWF 5 day means, a closed upper high once again develops over Alaska very similar to the winter of 2017. (-EPO) This is once again is a blocking pattern and the westerlies will be forced underneath, making for a suppressed storm track. The big thing to remember is that this will be June by then and the effects are just usually cooler weather with more wind and a return to freezing temperatures in the high country at night. This looks to occur during the first week of June.

Normal high temperatures in Mammoth now are low 60s with mid 60s by early June.  Low temps are usually in the mid 30s now.

 

More Later….

 

Dr Howard and the Dweebs………………………:-)

Last of the Eastern Pacific Upper Trofs has kicked out to the Desert Southwest with one more inland slider headed southeast today……Warmer weather on the way with beautiful weekened expected.

It was a chilly day in Mammoth Monday with an inch or two of snowfall into town and a few inches over the upper elevations. The Split Trof that spun up a closed low took its time moving through Southern CA Monday. It brought between 6 to 10 inches of snow to the Southern Sierra and a few inches to Mammoth Mountain. This morning dawned with high cirrus and the pines all white again. High temps remained in the upper 30s Monday while early morning lows were well down into the 20s this morning. A hard freeze occurred once again for much of Mono County.

 

On a larger scale, the pattern at 500MB is transiting to a ridge in the west with a Trof in the Midwest. The Long wave Trof over the far Eastern Pacific is progressing east today with one last short wave that will affect the far west and Great Basin with snow showers today through tonight. This short wave is not coming in from the west at this latitude. It is more of a NW slider. Its 130 Knot NW upper jet will enter the NW corner of California by late this afternoon and drive southeast over the Northern Sierra tonight. This is typically a windy pattern for the Central Sierra as the front Rt exit region usually brings down sloping winds to our region. So expect quite the breezy night tonight. By Wednesday the jet axis progresses east, as at the sometime the Eastern Pacific Ridge builds inland into California. Thus the headlined warm up begins in earnest Thursday, then through the weekend.  The Dweebs are expecting high temps well into the 60s by Saturday with summer like convection early next week.

 

Longer Range:

The long-range guidance shows the Spring thaw resuming this weekend through the end of next week…. Highs will remain mostly in the 60s this weekend through the following weekend.   The interseasonal outlook does hint at another but weaker Trof setting up over CA during the first week of June.

 

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

 

 

 

Active Weather Pattern returns as Cut Off Low Season Begins…..Approaching Upper Trough cuts off this weekend to our south, bringing upper divergence and storminess into early next week…..

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……………….:-)