Weak Spliting off shore trof will allow a small upper low to drift through Southern Ca Wednesday/Thursday…..Expect a brief period of Airmass Modifacation to develop Wednesday for some Showers and Thunder…..Rest of the week looks dry with slightly above normal temperatures……Then Southerly Flow may move back into the Southern Sierra about Mid-Week………
Tuesday August 21, 2012
Posted at 6:59 am by Howard
Quick Thursday AM update:
Looking at the short, medium and longer range Guidance…..Monsoon season for the Central Sierra may be winding down. The guidance is showing more troughing in the extended for the west coast which will tend to keep more of a SW flow aloft over the Sierra. This is a dry pattern for the most part. That is unless another of those little buggers closes off and comes in like yesterday. Even so, PWAT will likely be less.Expect fair weather for the next 7 days with afternoon breezes into the evening hours. Highs in the mid to upper 70 and lows in the 40s.
Longer range shows below normal temps beginning just after mid Sept associated with stronger trofing off the Pacific North West coast..
Wednesday Am Update:
It was a pretty sleepless night last night as numerous thunderstorms developed over the southern sierra then moved over the south central sierra at about 1:30Am. This occurred as the weak upper level low that was supposed to come in over Paseo Robles came across Monterrey Bay last night…..Dynamic forcing, strong UVM and upper divergence occurred over the southern and south central sierra. Mammoth picked up .29 hundreds of an inch of rain and there were over 310 lightening strikes recorded over both the west side and east side of the Sierra. Certainly not good news for fire agencies…..
At this time, the upper low at 700mb is centered over the south central San joaquin valley. However dynamic forcing associated with the cyclonically curved upper jet has now pretty much moved into Nevada. So isolated storms will be generated by heat today VS dynamically driven last night.
It will begin to dry out tomorrow Thursday and be fair through the weekend with highs in the upper 70s…..lows in the 40s.
Latest guidance is showing a split developing in the off shore upper trof. Latest 06z GFS has the upper center crossing near Paso Robles, Ca Wednesday AM, between 12z and 18z. At 500mb the upper center is 584dm. The track should take it SE through Kern County and the Mojave desert, throughout the day Wed and into Thursday…..exiting about noon Thursday through the Ca/NV/AZ borders.
As the low approaches the coast late tonight and Wednesday morning………a rapid increase of southerly flow is expected into the southern Sierra and extreme south Central Sierra. Moisture and dynamics will briefly increase chances of isolated showers and thunderstorms. The deepest moisture should remain to our south over Southern Inyo County….then SE over San Bernardino counties. This looks to be a one day event for the high country of Southern Mono County as drier air works back into the high county Thursday. Temperatures will cool slightly to the mid 70s. Lows in the upper 40s.
Outlook through the rest of the week looks pretty nice with highs back near 80 with lows in the mid to upper 40s. Expect the usual afternoon zephyr breezes. Next change in the pattern begins to develop the very end of this week or the following Monday as the upper high over the four corners redevelops and the toasty 594Dm at 500mb height line pushes west into SE California again this summer. Monsoon moisture may surge one last time into the Southern Sierra for isolated TSRWs about the middle of next week with high temps back into the low 80s as we finish off the rest of August on a warm note……
Dr Howard and the Dweebs………………………………….:-)
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