30-Day Weather Outlook for January 8, 2018, to February 8, 2018
Summary- The MJO Cycle will be in its inactive phase until about Jan 19-20. During the inactive phase, there will be support for more upper high pressure near the coast and into central California. Rains that occur will tend to have high snow levels.
Support continues in the mid-latitude sea surface temperature anomaly (SSTA) field W of California for troughing at 140-145W, extending NE into Oregon-Washington coast.
The El Niño Southern Oscillation (ENSO) continues in the cool (La Niña) phase. This leads to decreased energy in the subtropical westerlies, resulting in erratically moving cutoff lows.
There is support for troughing, and cold conditions in the east-central US will be decreasing for a couple weeks, with warmer weather making its way into the southern Great Plains states. There continues support for near normal snowfall in the Great Lakes, and N Rockies.
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. Occasional lows and troughs develop in SOCAL as fronts move through central California.
In the Near Term – Jan. 13-27… In the southern California avocado growing areas, from San Luis Obispo County to San Diego County, we still have a risk of warm and dry offshore flow with locally cold nights after mild or warm days. After the one significant rain on the 9th, it will be difficult to realize additional rain in SOCAL during January. Best chances for rain will remain in Ventura-Santa Barbara-San Luis Obispo counties about the 22nd and 27th.
Summary – Jan 28 – Feb 10… 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 cold showers and low snow levels. Frosts and freezes will tend to be more frequent this period.
Seasonal Outlook / La Niña Update...Feb 11 – April 11… Latest solutions suggest continued cold and showery with low snow levels in the SierraNV during Feb, while coastal and valley areas continue drier than normal.
Rains resume in March with some heavy rains possible in NW California and N SierraNV, with heavy snow in the central SierraNV and near Tahoe during March. Rainy and cold conditions possibly reach into Ventura and Santa Barbara Co’s.
For N and Central California, of greatest concern is the chance for below normal temperatures indicated for Feb through some of N and central California, including the Russian Watershed. March appears to be rainy, after some dry and cold periods in Feb. The showery conditions with troughs in March may be followed by freeze events in the first 10 days of April.
In central California, the SierraNV has a better than even chance for above normal rain and snow, from about Placer Co to Madera Co in Feb, and across the entire region in March. There is a chance for some frosts in the first week or so of April in coastal valleys, (Salinas/Pajaro/San Benito Valleys, Edna Valley.
For S California, there is support for a few cold Santa Anas in Feb, and accompanying wetbulb freezes. 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...