Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

417 am PDT Mon Oct 25 2021

Synopsis

Cooler with widespread rain spreading southeastward across the area this afternoon with showers ending from the northwest in the evening. Stronger and gusty south winds will become westerly in the afternoon, then diminish from north to south tonight. Dry and a little warmer on Tuesday, then greater warming on Wednesday and Thursday with weak offshore flow. Weak onshore flow will return during next weekend spreading cooling inland and bringing a return of night and morning coastal low clouds and fog.

Discussion

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

Short Term

(today through Wednesday), A Pacific low pressure system with a weakening atmospheric river will move across southern California today, moving east of the area tonight and Tuesday. While some lighter rainfall may develop this morning, especially along south facing slopes of the San Bernardino County mountains, the widespread rainfall with the front is expected to spread southeastward across the area this afternoon, reaching northern Orange County around noon and northern San Diego County during the early afternoon. Rainfall will be greater to the north with less to the south. Showers are expected to end from the northwest in the evening.

For Orange County, the Inland Empire, and surrounding mountains, rainfall is expected to range from around one-third inch near the coast to 1 to 2 inches on the coastal slopes of the San Bernardino County mountains with locally greater amounts. Snow levels around 10000 feet will lower to around 8000 feet during the early evening with any snow limited to the highest peaks.

For San Diego County, rainfall is expected to range from around one-quarter inch near the coast to one-half to one inch in the mountains. High desert areas will receive around one-quarter inch with less than one-tenth inch in the lower deserts.

Stronger and gusty south winds will become westerly in the afternoon, then diminish from north to south tonight. The strongest winds are expected along and near the desert slopes of the mountains with stronger gusts to around 55 mph.

Dry with slower warming on Tuesday with weak offshore flow and greater warming on Wednesday. With the warming on Wednesday, high temperatures for the deserts into the mountains will be a few to around 5 degrees below average with high temperatures for the coast into the western valleys a few to around 5 degrees above average.

Long Term

(Thursday through Sunday), Weak offshore flow will continue on Thursday with Thursday high temperatures a few to around 5 degrees above average for the deserts and around 10 degrees above average for the coast into the western valleys. Weak onshore flow will return on Friday which will spread cooling into the coast and valleys. The onshore flow will spread cooling farther inland during next weekend with night and morning low clouds and fog returning to coastal areas.

Aviation

251030z, Coasts/Valleys/Mountains, Low clouds with bases 1500-2500 feet MSL and tops to 4000 feet will continue to develop and spread into the entire coastal basin this morning. Terrain between those elevations will be obscured. RA expected to start in Orange County around 21Z, with isolated SHRA possible ahead of the main front as early as 17Z. RA will move from northwest to southeast, reaching San Diego County around 23Z. Vis will be reduced to 2-4 SM and cigs may become locally under 1000 feet MSL during the heaviest RA. Dry conditions expected for all areas after 06Z tonight with gradually clearing conditions into early Tuesday.

Strong southerly winds with strong up and downdrafts on and in lee of ridges 30-40 knots with gusts 50 knots. Wind shift with frontal passage in coastal airports between 23-02Z.

Deserts, SCT-BKN high clouds AOA 20000 feet MSL lowering to 5000- 7000 feet MSL with -RA between 23-03Z. Gusty north to northwest winds expected after 21Z Mon. Gusts 25-30 kt expected. Strong up and downdrafts near the mountains.

Marine

A cold front will bring strengthening southerly winds today, with a shift to northwest as a front moves through coastal waters this afternoon and early evening. Winds and seas will present hazardous conditions for small craft. Conditions will gradually improve late tonight and Tuesday. Check the Small Craft Advisory and Coastal Waters Forecast for details.

Beaches

A long period west swell and a long period south swell will combine to produce high surf and dangerous swimming conditions today through early Wednesday. Check the High Surf Advisory and the Surf Zone Forecast for details.

Watches, Warnings, Advisories

Ca, Wind Advisory from 10 AM this morning to 2 AM PDT Tuesday for Apple and Lucerne Valleys-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning.

High Surf Advisory from 11 AM this morning to 3 AM PDT Wednesday for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ, Small Craft Advisory from 11 AM this morning to 5 AM PDT Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm-Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island.

Visit this site often? Consider supporting us with a $10 contribution.
Learn more

Share this forecast!