Friday August 26
Cooler weather is on the way, with an interesting start to September now showing up on the long-range charts.
A weak low pressure trough will develop over central NV by Sunday, this pattern, combined with high pressure pointing into the Valley from Baja, can pull monsoonal moisture from AZ / NM over the eastern slopes of the Sierra and bump up the HEAT in the lower elevations and San Joaquin.  The air flow will also keep SMOKE in play, so don’t expect a super blue sky for a few more days.
Models indicate a cool system will push south into the PNW over the weekend, with a secondary and deeper low pressure trough setting up in the Gulf of Alaska by Monday.  This large ‘bowl’ in the atmosphere of cooler air will drop down from the Gulf to a position just west of CA.  This opens the marine air conditioning door with increased onshore breezes and cooler temps.  Temps will drop notably in the Delta on Tue, then spread south into the San Joaquin by Wed.  Right now, we expect the trough to deepen off the coast which, in turn, increases the onshore flow & surface winds to cool down the entire northern 2/3rd of CA even more.  In fact, you can anticipate temperatures to get tapped down to below seasonal norms in the Thu through the early part of the Labor Day Weekend.
One of the longer-range model solutions calls for rain/showers to clip the northern portion of the Sacramento Valley late next Fri into Sat of the holiday weekend; another solution is to keep everyone dry, but cooler, as noted above.  Either way, a change is coming.
Warmer temperatures are expected to return by Tue Sep 6 over the San Joaquin, as a standard ridge of high pressure builds in over southern CA & AZ.  The current outlook holds temps below 100 during the Sep 6-9 period.  We’ll see.  That ridge may magnify and bump up the afternoon highs to 100-102 in Kern Co region by Sep 9 or 10.
Bottom Line:  no threat for precipitation over the San Joaquin over the next 14-16 days, cooler NW breezes will increase as Labor Day weekend approaches.  Cool nights starting Wed Aug 31 through the holiday weekend.
If you like follow Tropical Storm action, please click through the OVS home page to The WxCafe™ Tropical Topical discussion.  There are interesting developments that will ping the news media into a near-frenzy mode.
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