Friday August 19
Key issue in this week’s update is the SMOKE from the Cedar Fire.  The lower level air flow has been from the east, hence a smoky southern San Joaquin.  The southeasterly component of the upper level air flow will continue to trigger the occasional thunderstorm over the southern Sierra until Mon or Tue next week.  The whole pattern will shift next week.
Temps have remained above normal, yet a tad cooler than a week ago.  Expect the trend to continue – high 90s through the weekend.  Likely return of 100+ heat by next Wed Aug 24.  Air flow aloft and at the surface will have a westerly component, so the SMOKE issue will drift east, away from the Valley.  Temps will continue to be above 100 F all the way until at least Sunday Aug 28.  Humidity will be seasonal through the period, as will the wind (or lack of it!).  Great drying weather, for sure.
Models toy with showing the formation of a weak upper level low cell just west of San Francisco come early September.  This type of pattern draws mid-level moisture from the southwest over the San Joaquin, raising humidity to above normal.  We’ll keep an eye on this potential pattern, as thunderstorms do become probable along the western slopes of the Sierra, and even a chance for a pop-up storm over the Valley itself.
“What this country needs is fewer experts on what this country needs.”

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