October 27, 2017 – Dry and very warm weather continues through the weekend but with a slight cooling. Temperatures cool slowly to near normal by mid week. A chance of precipitation and cooler than normal temperatures by the end of next week.
Strong high pressure ridging over the west coast will bring another day of fair skies and well above normal daytime highs. Daytime highs today will reach from 10 to almost 20 degrees above normal and generally near yesterdays highs. Winds under the ridge should remain relatively light. Upper ridge weakens just a bit on Saturday allowing for a slight cool off but highs will still be well above normal.
On Sunday forecast models bring a small closed low onto the southern California coast. Main impact for the forecast area will be some high cloud cover and a little more cooling especially the the southern most zones.
A shortwave trough digging down the west coast will displace the west coast ridge farther offshore on Monday bringing still more cooling and variable high cloud cover. Even with this cool off, daytime highs Monday will still run a few to several degrees above normal but this cooling trend will continue going into next week.
Extended discussion (Tuesday through Friday)
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Longer-range models are trending toward a solution that brings an upper trough south over the Great Basin, then retrogrades over southern California on Tuesday. This would be a breezy, dry north wind pattern, with the GFS solution considerably stronger than the ECMWF.
A more substantial pattern change will occur next week as the next upper trough drops south toward the Pacific Northwest. This system has the potential to tap into a fair amount of subtropical moisture and could bring moderate precipitation region-wide. Timing and details are still uncertain at this point, but chances for a changing pattern are on the rise.