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……………….:-)

As the Fishing Opener has come to a close……Warm Sunny Days are here to stay…At least through the middle of this week….A change in the pattern highlighted by a developing “Cut-Off” low will bring the chance of showers and thunderstorms, with the chance of showers beginning as early as this Thursday through the weekend and beyond.

Its been a beautiful fishing opener, with light breezes over the lower elevations and bright sunny days.  Temps on Sunday topped out in the low 60s while at Crowley Lake, it hit 70 degrees on Sunday. The upper ridge off shore will actually build into California late Tuesday into Wednesday, then shifts east into Nevada Thursday. Because along the western periphery of the upper ridge, we have southerly flow, we get one more day of warming Thursday.  Highs will be close to 70 in the Town of Mammoth.  However, like during the summer, once the upper ridge shifts east, our air mass becomes more unstable with the beginnings of cooling aloft. Towering cumulus just like during the Summer in the afternoon will develop with the possibility of diurnal afternoon and evening showers.  Remember, the first week of May is like early to mid August with the high angle of the Sun.

Following the upper ridges passage, is an upper trough. This trof is progressive and will move to the west coast by this Friday morning. Strong gusty southerly winds will increase over the upper elevations as the rear right entry region of the upper jet approaches. This will destabilize the atmosphere even more continuing the chance of showers. It will be cooler Friday through the weekend with the chance of showers each day and evening. Note: The showers look mostly convective and thus diurnal in nature.

More on next weekends storm:

The upper ridge is forecasted to sharpen up as it slowly progresses east to Eastern Colorado this Saturday, then stalls out. This forces the upper stream trof over California to become Cut-Off from the westerlies. So this is our first cut off low of the Spring the weekend of the 6th.  Cut off lows are very unpredictable and at this time, it is not uncertain where the cut off will develop. For what it is worth, all the forecast models today Sunday afternoon, are trending more toward a stall out along the coast of California as the cut off tracks very slowly SSE. This low may be with us between the upcoming Saturday through the following Wednesday and possibly beyond. This will prolong the possibility of showers and thunderstorms each and every afternoon and evening until it exits.

More later this week…..

 

Dr Howard and the Dweebs………………………:-)