Offshore winds develop Wednesday night into Thursday

Posted at 10:39 AM, Sep 19, 2018
and last updated 2018-09-19 13:39:04-04

We saw plenty of coastal cloud cover this morning but high pressure is developing over the area and that will drive stronger afternoon winds which clears those clouds out.  After sunset tonight the NW winds which will be up to 25mph over the afternoon will slow and ultimately shift NE for many coastal areas.  This will limit the amount of coastal cloud cover tonight into Thursday morning.  

Interior valleys will reach the mid-90s and San Luis Obispo the mid-80s Thursday. The beaches will be mostly in the 70s.  Friday is interesting because the early portion of the day should have some offshore flow and temps will still be warm but not quite as warm.  There is a low pressure dropping into the region which will bring temps Friday down 3-8 degrees for most locations.  The larger impact of this trough will be felt for the weekend when coastal valleys return to the low to mid-70s with interior valleys dropping to about 90 and the beaches returning to mostly 60s with more night and morning clouds returning.

Next week looks to stay dry as well with seasonal temperatures. There has been some model guidance showing optimism about early October showers but I am not buying it yet. There appears to be a deep trough which swings through to begin the month but not sure it gets real rain (outside sprinkles) this far south.  Today the American GFS is actually leaning dry.  This is the notorious end-of-the-run frames and mathematically the most speculative.  I’ll keep an eye on the extended as we get to a higher confidence point in the modeling.

Fall begins at 6:54 pm on Saturday with the equinox.  During the equinox, the Sun crosses the “celestial equator.” Imagine a line that marks the equator on Earth extending up into the sky above the equator from north to south. Earth’s two hemispheres receive the Sun’s rays about equally. The Sun is overhead at noon as seen from the equator, so at this point, the amount of nighttime and daytime (sunlight) are roughly equal to each other.