30-Day Weather Outlook for October 10, 2017, to November 10, 2017
Summary- Troughing will continue in the central Pacific with fronts approaching Washington-Oregon, with rain. There is increasing support for troughing in the southern Plateau area east of Southern California. This should begin to increase the support for dry winds and frosts into S California valleys later in Oct and into November.
Support exists in the sea surface temperature anomaly (SSTA) field for a long wave trough in the east central North Pacific near 140-150W, a storm track extending east into the coast of Washington and Oregon. These subtropical rains will approach N California.
High pressure will extend from the E North Pacific to the N and central California coast. Cold fronts coming south from Washington move into the Great Basin, with most of their moisture bypassing California. This will produce a tendency for some more windy offshore flow events in N and central California and coastal eddies in S California. Some Santa Ana winds are possible also in S California, mostly in the southcentral region (San Luis Obispo Co-Santa Barbara). Rains appear to develop during October 19-23rd into N and northcentral California.
In the Near Term – Oct. 13-27… In the southern California avocado growing areas, from Santa Barbara County to San Diego County, there emerges more support now for clear, cold nights in the valleys, with lows into the mid to upper 30s in the coldest valley spots during the final week of Oct. Watch for possible frosts during Oct. 13-15th, 18-19th and on the 25th. There appears to be a Santa Ana event during Oct. 25-28th.
Summary – Oct. 28 – Nov. 10… In the southern California avocado growing areas, from San Luis Obispo south, we will start to see alternation between Santa Anas and showery events. However, it also means a greater potential for some cold nights with wetbulb temperatures dipping into the 30s more consistently.
Mostly dry and mild days with cool or cold nights are more likely for this period. During about the first week of Nov, there is a chance for a shower, but the second week (Oct. 11-17th) appears to have the best chance for rains into SOCAL.
Seasonal Outlook / La Niña Update...November 11 – December 31, 2017… November continues the drier than normal trend in N and Central California, and drier than normal in S California. The best chances for rains or showers in November are about the 11-17th, then again around the 28-30th.
Dec still looks wetter than normal for N and Central California. A period of heavier rains and storm events often occurs during December 18-23rd and 27-30.
Southern California appears to return to near normal rainfall during Dec, with possibly a little wetter than normal in Santa Barbara and Ventura Counties.
...Alan Fox, Fox Weather LLC...