Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

913 am PDT Wed Jun 19 2024

Synopsis

Building upper level ridge in the Southwest US will lead to a warming trend late week and into the weekend. High temperatures this weekend will be as much as 8 to 12 degrees average for the inland valleys onto the lower coastal mountain slopes as well as the deserts. Nights will be warmer over the weekend into early next week for the lower deserts and foothills with a shallow increase in lower level moisture. Mid level monsoonal flow will increase from Sunday into early next week. The marine layer will keep coastal areas cooler with areas of night and morning low clouds spreading into portions of the valleys late at night.

Discussion

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

Deep marine layer up to 3000 feet MSL this morning with large coastal eddy in the California Bight. This will burn off at normal rate but low clouds could linger on the beaches. Weak southwest flow aloft continues due to upper level trough in place. This pattern will gradually weaken and retreat with rising upper level heights (warming aloft). The coastal eddy fills and weakens on Thursday so lowering marine layer. This pattern increases this weekend leading to significant warming for inland valleys, higher terrain and deserts to above average daytime highs of 5 to 12 degrees. Mid level monsoonal flow around the upper high to our east draws in higher levels of water vapor. This could bring mid level clouds into our deserts and mountains and possible increase in low level moisture levels. This is the main challenge for determining high temperature values this weekend into early next week. Likely will need heat advisories for Inland Empire and heat watch (leading to warning) for the deserts as heatrisk levels increase with areas of major.

.AVIATION, 191600Z, Coast/Valleys, Widespread coastal low clouds with bases 1000-1900 ft AGL and tops to 2500-3000 ft MSL will burn off 17-19Z with partial clearing at the immediate coast affecting CRQ and SAN. Low clouds begin to spread back inland after 20/01Z and moving 10 15 miles inland by Thursday morning. Bases will be near 1000 ft MSL with tops to 2000 ft MSL and dissipated coastal eddy.

Mountains/Deserts, Mostly clear with unrestricted vis through Thursday morning. Local gusts to 20 knots.

Aviation

191600z, Coast/Valleys, Widespread coastal low clouds with bases 1000-1900 ft AGL and tops to 2500-3000 ft MSL will burn off 17-19Z with partial clearing at the immediate coast affecting CRQ and SAN. Low clouds begin to spread back inland after 20/01Z and moving 10 15 miles inland by Thursday morning. Bases will be near 1000 ft MSL with tops to 2000 ft MSL and dissipated coastal eddy.

Mountains/Deserts, Mostly clear with unrestricted vis through Thursday morning. Local gusts to 20 knots.

Marine

No hazardous marine weather conditions are expected through Sunday.

Watches, Warnings, Advisories

Ca, None. PZ, None.

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