Area Forecast Discussion

SYNOPSIS

Gusty winds over the mountains and deserts and light precipitation in the coastal basin expected this afternoon into early Wednesday morning. Thursday will be a little warmer and dry with weaker winds. Cooler conditions likely this weekend, with periods of increased winds and another round of light precipitation west of the mountains.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

A trough of low pressure is expected to move east across Central California today into Wednesday. Visible satellite at 11 AM was showing clouds moving into Orange County, clouds are expected to spread south and east across the area. Additionally, areas of light rain will spread south and east across the area this afternoon and evening. Accumulations of 0.10" or less are expected in the coast and valleys, with totals up to 0.25" on the coastal slopes of the mountains. The San Bernardino County mountains are the most likely place to see accumulations up to 0.25". Rainfall rates are expected to be 0.10" or less per hour. Dry conditions will return by mid- Wednesday morning.

Southwest to west winds have already started to weaken, with gusts to 45 mph being observed through the San Gorgonio Pass at 11 AM. Winds will peak in strength this evening. Strongest winds will be over the mountains and into the deserts. Peak gusts of 40 to 60 mph expected, with a few isolated gusts to 65 mph on the northern slopes of the San Bernardino mountains. Winds will decrease through the day Wednesday with gusts mainly 35 to 45 mph, locally up to 55 mph through wind prone passes like the San Gorgonio Pass.

Dry and warmer conditions expected on Thursday. Highs along the coast will be a few degrees warmer, with inland locations up to 7 degrees warmer than Wednesday. The temperature increase will bring conditions near to slightly above normal for this time of year. Another area of low pressure looks likely to move across the US West Coast for the upcoming weekend. While there remains some timing differences between the global models, the trough will bring another round of cooler conditions, increase in westerly winds, and potential for light precipitation. Dry and warmer for next Monday, with high temperatures for inland areas still a few to around 5 degrees below average.

AVIATION

211800Z...Coast/Valleys...A band of low clouds based 2500-5000 feet MSL associated with a weak front containing waves of -SHRA will move from west to east across the coastal basin from 20-07Z. ISO -SHRA could briefly create MVFR vis and cigs 1500-2500 ft MSL as they pass over sites. Clouds mostly clear out from northwest to southeast after that band, first at Orange County coast and last inland San Diego County.

Mountains/Deserts...Southwest to west winds increase through late this afternoon with peak gusts 35-55 kts, strongest on ridgetops, along desert slopes, and through mountain passes. Isolated vis reduced by BLDU in the deserts and moderate/strong up/downdrafts in lee of mountains. Winds decrease tonight but remain breezy for the desert slopes and mtn passes, then gusty winds become more widespread again though not quite as strong for Wed afternoon.

MARINE

Westerly to northwesterly winds will increase Wednesday afternoon through late Wednesday night with gusts 20-25 knots likely for outer coastal waters. These winds could generate choppy and hazardous conditions. Winds diminish early Thursday morning before briefly increasing again in the outer coastal waters Thursday afternoon, with peak gusts around 20 knots. Otherwise, no hazardous marine conditions are expected through Saturday.

SKYWARN

Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.

SGX WATCHES / WARNINGS / ADVISORIES

CA...Wind Advisory from 2 PM this afternoon to 7 AM PDT Wednesday 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.

PZ...None.