Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

338 am PST Sat Nov 18 2017

Synopsis

High pressure aloft near the West Coast and surface high pressure over the Great Basin will bring dry and warmer weather this weekend. Low temperatures in portions of the upper deserts will fall into the lower to mid 30s early this morning and again early Sunday morning with patchy frost possible. For Monday through Wednesday and Thanksgiving, high pressure aloft will strengthen along the West Coast bringing greater warming with high temperatures for Wednesday and Thanksgiving 15 to 20 degrees above average. For late next week, high pressure aloft will begin to weaken and onshore lower level flow will return with cooling spreading inland.

Discussion

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

High pressure near the West Coast this weekend will bring daytime warming with high temperatures around 5 degrees above average. Surface high pressure over the Great Basin will bring locally gusty northeast winds near the coastal foothills and below passes and canyons this morning with most gusts 35 mph or less. With a dry air mass in place and radiational cooling, temperatures in portions of the upper deserts will fall into the lower to mid 30s early this morning and again early Sunday morning with patchy frost possible. There will also be patchy dense radiational fog in some valley locations early this morning, especially in southern portions of the Inland Empire.

For Monday through mid week, high pressure aloft will strengthen near the West Coast with surface high pressure over the Great Basin maintaining very weak offshore lower level flow across Southern California. High temperatures will warm to 15 to 20 degrees above average for Wednesday and Thanksgiving with the warmest valley and inland coastal areas having high temperatures in the 90s, and with high temperatures in the 80s extending to near the beaches.

For late next week, high pressure aloft will begin to weaken and onshore lower level flow will return with cooling spreading inland.

Aviation

181020z, Coast and Valleys, Broken clouds between 1500 and 3500 FT MSL over the Inland Empire and portions of Orange county early this morning are expected to thin/dissipate through 12Z. Areas of lower clouds are expected to develop toward sunup, mainly within 25SM of the coast, with bases 500 to 1000 FT MSL and tops AOB 1500 FT MSL. Areas of BR/FG may reduce VIS AOB 3SM from 11Z-16Z, obscuring higher terrain. Most areas will clear by 17Z leaving clear skies and unrestricted VIS through Sat afternoon/evening. Local NE surface winds 15-20 KT with gusts 30KT in/below Cajon and San Gorgonio Passes through 20Z Sat.

Mountains and Deserts, Local NE winds 15-25 KT with gusts to 30 KT in the San Bernardino, San Jacinto, and Santa Ana mountains, and north of KPSP through 20Z. Otherwise, P6SM SKC.

Marine

No hazardous marine conditions are expected through Thursday.

Watches, Warnings, Advisories

Ca, NONE. PZ, NONE.

Share this forecast!