Large Scale Summary
- Support for troughing focuses near 140-155W. The main governing agent is the MJO with a maximum along about 165-175W.
- Precipitation Amounts and Fire Risk: There has been a momentary decrease in fire risk for the Sierras of northcentral to N California due to increased
moisture from rains and mountain snows. Below average precipitation is suggested for SOCAL in the remainder of Oct. Below average precipitation for NORCAL appears most likely from the Bay Area northward, and above average precipitation for the North Coast: Mendocino Co to far SW Oregon. - N to NW flow events occur in NORCAL and the Northcentral California coast. These dry windy events, typical of Fall, produce cold upwelling of the near
coastal waters. This combination is not as robust for above normal rainfall into Central California, so we should see more prolonged dry spells develop at times in Nov despite few good rain events in mid to late Nov.
Near Term Forecast
NORCAL
- PRECIPITATION DATES: NOV 12,16,18, 25-27.
- COLD/FREEZES/WINDS: Nov 13-14, 19-21, 25-27windy, 28-29 freezes
- WARM/DRY PERIODS: NOV 4-6, 13-14
- MOUNTAIN SNOWS: NOV 22-23,25-29
CENTRAL CALIFORNIA:
- PRECIPITATION DATES: NOV 12,16,18,25-27
- COLD/FREEZES/WINDS: Nov 13-14, 19-21, 25-27windy, 28-29freezes
- WARM/DRY PERIODS: NOV 4-6, 21-23.
- MOUNTAIN SNOWS: NOV 12,16-18, 25-29
SOUTHERN CALIFORNIA
- PRECIPITATION DATES: NOV 16,18,25
- COLD/SANTA ANA WINDS: 13-14, 19-21, 26-28windy, 28-30 freezes
- WARM/DRY PERIODS: Nov 4-6,22-24
- MOUNTAIN SNOWS: Nov 16,18,25
SOUTHERN CALIFORNIA DESERTS
- PRECIPITATION DATES: NOV 16,18,26-27
- COLD/N-NE WINDS: 13-14, 19-21, 26-28windy, 28-30 freezes
- WARM/DRY PERIODS: Nov 16,18,25
- MOUNTAIN SNOWS: Nov 16,18,26
Medium Term Outlook: Dec 1 – Dec 31
NORCAL:
- PRECIPITATION DATES: Dec 1-3,16,18, 25-27.
- COLD/FREEZES/WINDS: Dec 4-6,20-22,28-31.
- WARM/DRY PERIODS: Dec 7-14, 23-24
- MOUNTAIN SNOWS: Dec 1-3, Dec16-18,25-28
CENTRAL CALIFORNIA:
- PRECIPITATION DATES: Dec 12,16,18,25-27
- COLD/FREEZES/WINDS: Dec 12-14.16-18, 27-30,
- WARM/DRY PERIODS: Dec 21-23, 24-25,31.
- MOUNTAIN SNOWS: Dec 1-3,16,18, 25-27
SOUTHERN CALIFORNIA
- PRECIPITATION DATES: Dec2-3, 16,18,25
- COLD/SANTA ANA WINDS: Dec 15, 19-20, 27-30
- WARM/DRY PERIODS: Dec 21-23, 24-25,31
- MOUNTAIN SNOWS: Dec 1-3, 16, 18, 25-27
SOUTHERN CALIFORNIA DESERTS
- PRECIPITATION DATES: Dec 16, 18, 26
- COLD/N-NE WINDS: Dec 15, 19-20, 27-30
- WARM/DRY PERIODS: Dec 21-23, 24-25,31
- MOUNTAIN SNOWS: Dec 1-3, 16, 18, 25-27
Outlook for Dec 1 – 31:
- The Madden Julian Oscillation (MJO) shows a tendency for troughing in the subtropical mid N Pacific west of the Central California and NORCAL. How close these troughs extend to the California coast is problematic at this time, and forecast solutions for Dec are inconsistent! There is better support for troughing near the ORWA (Oregon-Washington) coast.
- Northern California Dec 1-31: Rain dates estimate: Dec 8-10, 16-18, 20-23,27-30.
- South half of California: Dec 1-30: Rain dates estimate: Dec 8-10,11-18,20-24,27-30.
DISCUSSION OF NOAA/NCEP/CPC MAPS DEC 2025, JAN-FEB 2026
- The latest guidance from NOAA/NCEP/NWS/CPC suggests that Dec 2025 remains mostly dry through mid Dec, as in Nov. Sometime near the 20 Dec or between 12/23/25-01/01/26, it turns wet, as we often see around the holidays. The main wet month is January 2026, with focus of significant rains from about Sacramento Delta south to SOCAL. Above average snow levels are currently indicated for the NORCAL mountains and Sierras, and for SOCAL mountains. That scenario is consistent with potential for Atmospheric River (AR) systems in Jan for most areas of California, except the North Coast.
- Eventually, the belt of westerlies in the mid to eastern N Pacific has support to meander far enough south to tap more subtropical moisture for storms coming into California, beginning in late December 2025 and January. The latest CFSv2 information for Feb 2026 shows a possible pause in the rains, with well below average rain amounts for California, but with above average amounts for Washington and Oregon. This signal is also consistent with recurrent Atmospheric River conditions in Feb 2026, as the storm track migrates back northward for Feb.
A Few Comments on the Larger Picture and La Nina
- As of Oct 25-27, there was some indication of a weak La Nina pattern focused in the central and west portions from 120W out to the Dateline. However, La Nina has been increasing, i.e. ìgetting strongerî. However, this is not a classic La Nina pattern, and there are large areas of anomalously warm water near the equator from the Ecuador coast to about 125W. There is also anomalously warm sea surface (positive SSTA pattern) from Hawaii to N Baja California. The SSTA pattern in the midlatitude N Pacific west of California still supports troughing in the areas affecting NORCAL and Washington-Oregon. Bottom line: itís a ëmixed bagí regarding La Nina. Even though La Nina is present, there is support for plenty of variation in the pattern. Despite La Nina, central and southern California do not appear persistently dry through the normal rainy months of Nov - Mar. There is certainly support for some dry months during that period. A wet January is also reasonable, and forecasted by NOAA/NWS/NCEP/CPC CFSv2 outlook maps. Even considering the possibility of a wet January, this forecaster would not hold out much confidence in above average rainfall for March 2026, especially after what appears to be a warm and dry (possibly ìbone dryî) Feb. In general, it would be more likely for us to get one good wet storm in March, even if rainfall for the entire month is near or a little below normal.
Figures and Text: Alan Fox, Fox Weather, LLC
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