Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

133 pm PST Mon Nov 28 2022

Synopsis

A low pressure system will continue to push into the Great Basin through Tuesday, bringing cooler temperatures, windier conditions, and light showers to SoCal. West winds will continue to strengthen today in the mountains and deserts, with peak gusts 50 to 60 mph. Cooler than normal conditions will persist all of this week. There is the potential for a series of storm systems to bring rain and mountain snow to SoCal late this week and this weekend.

Discussion

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

Marine layer clouds are still holding strong in the valleys and the mountain foothills. Some peeks of Sun will be possible over the next few hours, but overall expect partly to mostly cloudy skies inland this afternoon. Marine layer clouds will again become widespread this evening and tonight, with showers possible at times. The highest accumulations will be along the coastal mountain slopes, though amounts will generally be less than 0.10".

A low pressure system currently situated to our north will push east today into the Great Basin, bringing increased west winds and cooler temperatures, and light showers tonight into Tuesday. West winds will continue to strengthen this afternoon over the mountains and desert slopes, peaking in strength this evening and overnight. Peak gusts will range from 50 to 60 mph, though some higher gusts in excess of 60 mph are possible in the windy I-8 corridor and through and below the San Gorgonio Pass. Wind Advisories have been posted for all mountain and desert areas through early Tuesday morning.

Daytime highs today will be several degrees cooler than yesterday, with many lower elevations only reaching the low 60s, and higher mountain elevations staying in the 40s. Similar temperatures will be observed on Tuesday.

Westerly winds will gradually diminish Tuesday morning. A brief shot of offshore flow is expected Tuesday night into Wednesday as the low pressure system pushes east, which will warm temperatures a couple of degrees on Wednesday in the mountains and foothills. Cooler than normal temperatures are expected for the remainder of this week as broad upper level troughing persists.

There remains considerable timing and placement differences in models and ensembles with a series of low pressure systems moving into the West Coast later this week. Guidance has consistently been showing these low pressure systems setting up late this week and this weekend over the West, so confidence is growing in an unsettled pattern developing. However, the potential impact to SoCal remains highly uncertain at this time.

The first low pressure system looks to push into the Pacific Northwest Wednesday into Thursday, then elongating and pushing southeast late Thursday into Friday. Ec ensembles have been depicting this system dropping south enough to bring us some precipitation Thursday night into Friday, however the GFS ensembles keep this system well to our north, bringing little, if any, precipitation to SoCal.

Another low pressure system appears to push into the Pacific Northwest right on the tail of the first system. Models depict this system pushing into the Pacific Northwest on Friday night and Saturday, dropping south into California on Sunday, potentially pulling in more moisture from the southwest. Models and ensembles seem to be more in line on the timing and placement of this second system.

Quite a messy and uncertain forecast for the end of the week! Due to the uncertainty in the timing of these system impacting SoCal, chances for rain remain in the forecast starting late Thursday and continuing through Sunday. Highest chances of rain currently are Thursday night into Friday, but this could potentially change as we get closer to the event. We hope to be able to nail down some more exact timing details here in the coming days. Stay tuned!

Aviation

282130z, Areas of low clouds with variable bases 2000-4000 feet MSL and tops to 6000 feet will continue through Tue morning from the mountains west to the coast with only partial afternoon clearing this afternoon. Areas of vis 2-4 miles in BR will occur over higher terrain and the inland valleys, and higher terrain will be locally obscured. Patchy -DZ/-SHRA will occur from the west mountain slopes west to coast 01Z-15Z Tue. Generally SCT conditions will prevail Tue afternoon.

W-NW winds 20-30 kt with gusts 45-55 kt and locally higher gusts to 60 kt in prone passes and over ridges will occur this afternoon and evening. Strong up/downdrafts will occur east of ridges as well as pockets of rotors such as in vcnty KPSP. Winds will gradually decrease after 08Z Tue.

Marine

Strong northwest winds to 25 knots and choppy seas of 7 to 10 feet will develop late this afternoon in the outer coastal waters, creating hazardous boating conditions through early Tuesday morning. No additional marine weather conditions are expected through Saturday.

Watches, Warnings, Advisories

Ca, Wind Advisory until midnight PST tonight for Apple and Lucerne Valleys-San Bernardino County Mountains.

Wind Advisory until 8 AM PST Tuesday for Coachella Valley- Riverside County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning.

PZ, Small Craft Advisory from 7 PM this evening to 8 AM PST Tuesday for Waters from San Mateo Point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island.

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