Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

930 am PDT Mon Mar 27 2017

Synopsis

Low pressure aloft will bring gusty west winds to the mountains and deserts through early this evening. Otherwise, partly to mostly cloudy skies will prevail west of the mountains with temperatures a little below normal. High pressure building into the Great Basin will bring locally gusty northeast winds below passes and canyons tonight and Tuesday. Mostly clear skies will prevail Tuesday and Wednesday with warmer weather. Another low pressure system will move by to the northeast Thursday and Friday and will bring strong westerly winds to the mountains and deserts and cooler weather. Fair and warmer weather will prevail next weekend under high pressure.

Discussion

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

Mostly cloudy skies prevailed west of the mountains with patchy fog along the coastal mountain slopes. The morning NKX sounding had the inversion base of 3500 feet, but webcams and humidity profiles show the moist layer as high as 6000 feet in San Diego County. With the deep marine layer, clouds will be slow to clear especially in the valleys and mountain foothills. West winds were already strong in the mountains and deserts with a 59 MPH gust at White Water West just east of San Gorgonio Pass, though most windy areas had peak gusts between 35 and 45 MPH this morning. Local WRF model and Cansac- WRF show these winds continuing through around 7 PM tonight, then weakening somewhat as offshore flow develops.

The low pressure trough axis was over So-Cal with two main waves but not enough moisture for precipitation in our forecast area. The trough will shift to the Four Corners tonight with rather tight height gradients under NW flow behind the trough. A surface high will build over northern Nevada late tonight and Tuesday and contribute to moderate offshore flow, with surface MSLP gradients around 10 MB from west-central Nevada to San Diego, though very much northerly in orientation versus northeasterly. That will result in winds below E-W ridges, mainly San Bernardino County, with some winds in the Santa Ana Mountains. Mountain waves will not be particularly strong, with most of the winds below the crests but not as much in the valleys, except briefly late Tuesday morning after surface heating results in some mixing. Overall, peak gusts will be 45-60 MPH. San Diego County will see very little of this wind due to the northerly gradients. Winds will mostly decrease by Tuesday mid- afternoon. By Tuesday morning, most areas will be clear, so that combined with the cold low having exited to the east, will result in 5-10 deg F warming in most areas to slightly above normal. Wednesday should be quite warm with temps around 10 deg F above seasonal normals, which means a lot of 80s in the Inland Empire and far inland valleys of San Diego County.

Models continue to have a deep low tracking from far northern California to far northern Arizona from Thursday to Friday. This inland track will most likely keep our area dry, but the mountains and deserts could have strong winds. Temperatures will decrease, though just to near or very slightly below normal by Friday. The low will track east over the weekend with fair weather to follow. Offshore flow will be rather weak though. Temps will increase again to 5-10 deg F above normal by Sunday. Another inland closed low could drop down from the north early next week.

Aviation

271615z, BKN-OVC015-035 with tops to 5500 ft through 19Z with mountains obscured in clouds and fog. After 19Z the clouds will scatter out from north to south with clearing expected at KSNA, KONT and KSBD. SCT-BKN020-030 lingering through 23Z at KCRQ and KSAN before clearing. Mostly clear skies Tuesday.

Strong westerly winds 20-40 kt over the mountains and into some of the deserts today with areas of strong up/downdrafts and LLWS over and east of the mountains. The winds shift northeasterly after 04Z and surface in the Inland Empire through 23Z impacting KONT, KSBD and possible KSNA with strong up/downdrafts and LLWS.

Marine

A Small Craft Advisory is in effect for strong northwest winds and rough seas through Tuesday. Northwest winds will increase again Thursday and continue through Friday leading to more choppy seas and hazardous boating conditions.

Beaches

West to northwest swells will bring elevated surf of 3 to 6 feet most of the week with occasional sets to 7 feet.

Watches, Warnings, Advisories

Ca, Wind Advisory until 10 PM PDT this evening for Apple and Lucerne Valleys-San Diego County Deserts-San Diego County Mountains.

Wind Advisory from 10 PM this evening to 2 PM PDT Tuesday for San Bernardino and Riverside County Valleys-The Inland Empire-Santa Ana Mountains and Foothills.

Wind Advisory until 2 PM PDT Tuesday for Riverside County Mountains-San Bernardino County Mountains-San Gorgonio Pass Near Banning.

PZ, Small Craft Advisory until 8 PM PDT Tuesday for Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island.

Small Craft Advisory from 1 PM this afternoon to 8 PM PDT Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm.

Share this forecast!