30-Day Weather Outlook for January 2, 2018, to February 2, 2018
Summary- The MJO Cycle is transitioning to a lower activity level. As this occurs, there will be support for more upper high pressure near the coast and into central California.
Support continues in the mid-latitude sea surface temperature anomaly (SSTA) field west of California for troughing west of California and extending NE into the Oregon-Washington coast.
The El Niño Southern Oscillation (ENSO) continues in the cool (La Niña) phase. This opposes activity in the subtropical storm track and encourages development of erratically moving cutoff lows.
There is support for troughing and cold conditions in the east-central US. There is support for near or above normal snowfall in the Great Lakes, middle Atlantic region, and NE U.S., as well as Montana – the upper Midwest states through late Jan.
Support exists for intermittent rainy episodes, while snow with high snow levels continues in the SierraNV.
For S California, warm sea surface temperatures are present to the west and southwest, but the La Niña pattern tends to discourage development of subtropical westerlies. Lows and troughs develop near SOCAL or in NW Mexico, producing risk of more Santa Anas, or predominant offshore flow.
In the Near Term – Jan. 6-20… In the southern California avocado growing areas, from San Luis Obispo County to San Diego County, we still have risk of warm and dry offshore flow with locally cold nights after mild or warm days. Rains on Jan 4-5th and 9-11th will be light to moderate. During the dry periods, crisp cold nights follow warm days.
Summary – Jan 21 – Feb 3… In the southern California avocado growing areas, from San Luis Obispo south, rains will be mostly occurring in N California and the SierraNV. However, a cutoff low is always possible in such an erratic pattern, with some showers. Mostly above normal temperatures are indicated, but watch for some occasional frost or freeze risk during cold Santa Anas that may develop the last week of Jan or first of Feb.
Seasonal Outlook / La Niña Update...Feb 4 – April 4… Latest solutions show colder with more rain and snow in the SierraNV in Feb, while coastal and valley areas continue drier than normal. There is suggestion of a wet March upcoming for all of central and N California, and possibly into Ventura and Santa Barbara Co’s in SOCAL.
For N and Central California, of greatest concern is the chance for below normal temperatures indicated for Feb through some of NW and central California, along with dry conditions. This type of configuration points to a higher risk of frosts, at least during early to mid Feb. March appears to be a wet month through central and N California and possibly into Ventura Co.
In central California, the SierraNV has a better than even chance for above normal rain and snowfall, from about Placer Co to Madera Co. Most of the rain appears to develop during Feb 10-19th. March is wet in central California.
For S California, there is support for cold Santa Anas, and accompanying wetbulb freeze events. The first part of Feb is cold and mostly drier than normal in S California. The ensemble (NMME) model suggests more showers in the first half of March 2018 for the southern half of California.
...Alan Fox, Fox Weather LLC...