Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

325 am PDT Fri Jun 22 2018

Synopsis

High pressure aloft will bring a few degrees of additional warming today with the heat peaking today. Weakening high pressure aloft and stronger onshore flow will bring about 5 degrees of cooling for inland areas on Saturday and another 5 degrees on Sunday. This will be followed by slow warming for the early part of next week, then gradual cooling the for the latter half of next week. The marine layer will keep coastal areas cooler with areas of night and morning coastal low clouds and fog extending inland into the western valleys, except farther into the inland valleys for late Saturday night into Sunday morning.

Discussion

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

Short Term

(today through Sunday), High pressure aloft centered over northern Baja will bring a few degrees of additional warming with the heat peaking today.

The marine layer is near 1500 to 2000 feet deep with satellite imagery showing widespread stratus over the coastal waters extending inland across about the western half to two-thirds of the San Diego County valleys, and into the western and southern portions of the Inland Empire. Similar coverage is expected for tonight into Saturday morning.

For the weekend, high pressure aloft will weaken and shift southward as a low pressure system moves inland through the Great Basin. This will strengthen the onshore flow which will spread cooling inland. Inland areas will cool around 5 degrees on Saturday and another 5 degrees on Sunday. The marine layer will deepen with coastal low clouds extending farther into the inland valleys for late Saturday night into Sunday morning.

Long Term

(Monday through Thursday), Weak high pressure aloft will move across Southern California early next week. This will bring a slow warming trend from Monday through Tuesday or Wednesday with Tuesday and Wednesday not quite as hot for inland areas as today. A trough of low pressure will develop near the West Coast late in the week with a cooling trend for Thursday into next weekend. Areas of night and morning coastal low clouds and fog will extend inland into the western valleys.

Aviation

220925z, Coast/Valleys, Low clouds with bases 900-1500 ft MSL and tops to 1800 ft MSL continuing up to 25-30 miles inland this morning. Local vis 3-5 SM likely where clouds extend into the inland valleys. Clearing inland 15Z-17Z and partial clearing at the coast 18Z-22Z. Clouds will begin to spread inland again after 23/00Z with bases remaining near 1000-1500 ft MSL.

Mountains/Deserts, Mostly clear with unrestricted VIS through Saturday morning.

Marine

No hazardous marine weather is expected through Tuesday.

Watches, Warnings, Advisories

Ca, Excessive Heat Warning until 8 PM PDT this evening for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning.

PZ, NONE.

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