30-Day Weather Outlook for February 13, 2017, to March 13, 2017
Summary- Troughing continues to focus to the west of California between 130W and 145W. Troughing also increases into the southern deserts and SOCAL as the southern storm track becomes more active.Troughing occurs during Feb 16-23 with wet conditions.Troughing migrates slightly east, putting us in a cold pattern with snow showers in the Sierras and return of cold conditions through all of California, with some offshore flow mixed in during February 24 – March 1.For March, the dry, cold pattern with troughs and showers in the southern deserts dominates during the first week of March. Although northern California turns dry for a while in March, SOCAL and the southern deserts have a tendency for recurrent cold showery conditions.There is support for the next series of storms into all of California during March 19-23, after a long, drier than normal pattern.The La Niña period ends quickly, and the current trend for an El Niño anomaly to develop will continue thru March, to induce more troughing into SOCAL and central California with a continued trend of colder and wetter than normal.As El Niño becomes more active during the next two months (March and April), and the southern storm track continues, the incidence of severe thunderstorms (TSTMS) and tornadoes may shift to above normal, along with above normal rainfall for Oklahoma, Kansas, and north Texas.
In the Near Term – February 16 – March 2… The NOAA/CPC outlook for February 21-27 shows wetter and colder than normal for all of California with a trough over California. Precipitation is well above normal for the Sierras, Central Calif south to Ventura County and cold. We agree with this. This argues for temperatures averaging below normal, plenty of snow for the Sierras above 4500 ft, and frosts/freezes in SOCAL in the dry air following frontal passages and any Santa Anas that may occur, especially aboutthe last week of February and first few days of March.
In the southern California avocado growing areas, from Santa Barbara Co to San Diego Co, Rains occur from February 16-18, 20-23 and 25-27. Freezes are most likely February 24 and 28, and March 2.
Summary – March 3 – 17… In the southern California avocado growing areas, from San Luis Obispo south, our guidance from CFSDaily suggests that after a dry period, the rains restart about the March 17 with the southern storm track in place, and El Niño forcing starting up, it is reasonable to suggest some rains into SOCAL beginning again about mid-month or March 17. However, until the rains restart, there continues a risk of frosts in early to mid-March with CFS supporting colder than normal conditions overall for the San Joaquin Valley south thru SOCAL.
Seasonal Outlook/La Niña Update...March 18 – April 30, 2017… La Niña becomes weak or nonexistent beforethe first part of March, and El Niño conditions will continue to increase, inducing troughs in S and SE California – Arizona. The combined effect of large scale mid-latitude and equatorial (El Niño) influences will be to maintain a colder and wetter than normal pattern for SOCAL in the latter part of March thru April.
For SOCAL, late March is wetter than normal, with snow in the mountains. Arizona also is wetter than normal due to persistent troughing and an active southern storm track. April continues the trend for cooler and wetter than normal for SOCAL and showers in Arizona.
...Alan Fox, Fox Weather LLC...