Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

938 am PST Sun Dec 9 2018


High pressure aloft will continue mild and dry weather through Sunday. A weak upper-level trough will move across Southern California Monday night through Tuesday with cooler weather, increased onshore flow, and a chance for a few light showers. High pressure returns through Friday with warming and gusty Santa Ana conditions in wind-prone areas. Another weather system may arrive next weekend with a renewed chance for some light precipitation.


For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,

No significant updates were needed this morning. Thin high clouds moving into SoCal this morning from the East Pac, but with offshore flow (gradients are running about 7 mb from the deserts) today temperatures will actually warmup a few more degrees compared to yesterday. All in all, another stellar day for the region weather wise. So get out there and try to enjoy the rest of your weekend! The remainder of the previous forecaster discussion is below and remains valid.

Water vapor imagery shows an upper level trough with axis some 700 miles west of San Fransisco, while an upper level ridge lies over the SoCal. High level cloudiness is streaming into SoCal on southwest wind flow ahead of the trough. So filtered sunshine is forecast today as well as on Monday as this high level moisture streams into the area.

The aforementioned upper trough will move inland across NorCal on Monday with the tail end passing across SoCal by Tuesday (GFS keeps it open/inside, while the ECMWF closes it off to just off our coast on Tuesday before pushing south). The low level flow will be offshore with a brief onshore push on Tuesday morning before going offshore. Both of these model solutions have limited moisture. Wrf does show isolated showers west of the mountains on Tuesday. Have kept a slight chance of light showers Monday night- Tuesday. Rainfall amounts will be track to a few hundredths of an inch with most locales dry.

An upper level ridge will build behind the trough. This will result in dry weather along with a Santa Ana wind regime with the peak likely occurring Thursday morning of moderate strength. The recent soaking rainfall alleviates a fire weather risk. Warmth will peak on Thursday when highs could soar well into the 70s west of the mountains.

Next weekend could bring about another potential of precipitation to SoCal, but right now it is not looking significant. Both GFS and ECMWF take an upper low over the Pacific into Baja California next weekend while a longwave trough moves into the U.S. West coast. The result is the brunt of the moisture remaining both north and south of our area. Gfs keeps things dry while the ECMWF does bring some light precipitation into our area next Sunday- Monday. Either way, this is not looking like a significant storm for the area. Included low POPS with precip mention starting next Sunday, along with a late week cooling trend.


091555Z, SCT-BKN clouds AOA 20000 ft MSL with unrestricted vis through Monday morning.


No hazardous marine weather is expected through Thursday.


A long-period west northwest swell from 290 degrees will arrive on Monday, bringing elevated surf of 3-6 ft and strong rip currents late Monday into Tuesday.

Watches, Warnings, Advisories


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