A broad low pressure system will continue to deepen the marine layer and keep temperatures below average for the next several days. Morning low clouds through the coastal basin each day with a chance for a few fully overcast days at the coastline. Strong winds will continue through the weekend for deserts and desert slopes, peaking today and slowly weakening over the next several days.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Visible satellite imagery reveals a battle early this afternoon between the typical retreat of low clouds toward the coastline and a robust coastal eddy pushing the other way. As a result, low clouds may linger through the afternoon at the immediate SD County coastline. Regardless of how that plays out, cool and breezy conditions will dominate the region this weekend along with increased cloud cover for the coastal basin as an unseasonably deep upper trough over the PNW makes its presence known. Temperatures will be around 5 degrees below average at the coast and 5 to 15 degrees below average for inland areas today. For Sunday, those values drop to 5 to 10 and 10 to 20 degrees below average, respectively. In fact, temperatures may still be slightly overdone as models are struggling to deal with this anomalously cool pattern for late June. Additionally, a deepening marine layer may allow for drizzle at the coast and locally into valleys Sunday morning.
The main story for the deserts this weekend will be the wind. West-southwest winds are expected to peak in strength this evening with widespread gusts 35-55 mph and local gusts exceeding 65 mph along desert slopes and through the San Gorgonio Pass. See the Wind Advisory for more details. Winds will be slightly weaker on Sunday as the core of the upper trough begins to progress eastward toward the High Plains.
Models are in strong agreement that reinforcing shortwaves will keep the longwave troughing pattern in place over the western CONUS through next week. This will keep temps cool through the forecast period with strong marine layer influence for the coastal basin and breezy conditions for the deserts. A shortwave is expected to round the base of the trough sometime late Monday into Tuesday. There is some discrepancy in the exact track and strength of this shortwave, but it may briefly reinforce already elevated winds for the deserts. The longwave trough is expected to slowly diminish in strength by late next week, allowing for a slow warming trend. Even so, the mean of the ensembles indicates temperatures and upper heights will remain at least slightly below average through next weekend.
271745z, Coast/Valleys, Slow to no clearing looks increasingly possible along the immediate coast this afternoon. Most likely time for any clearing will be 20-23Z Sat. Low clouds will begin to move inland after 00Z Sun with bases 2000-3000 ft MSL, reaching KONT/KSBD by 07Z. VIS reductions along mountain foothills where clouds meet terrain. Low clouds expected to clear the valleys 17-19Z Sun, with 60% chance of only partial and intermittent clearing along the immediate coast Sun afternoon.
Mountains/Deserts, West winds increase after 21z Sat. Peak gusts of 35-55 kt expected on the desert slopes into the deserts with local gusts to 65 kt through the San Gorgonio pass. MOD up/downdrafts in lee of mountains. Winds decrease and become more localized 06-09Z Sun.
Breezy NW winds occasionally gusting over 20 kt this afternoon and evening near San Clemente Island may create hazardous conditions to small craft. Otherwise, no additional hazardous marine conditions are expected through Friday.
Ca, Wind Advisory until 5 AM PDT Sunday for Apple and Lucerne Valleys.
Wind Advisory until 11 PM PDT Sunday for San Diego County Deserts.
Wind Advisory until 2 AM PDT Monday for San Gorgonio Pass near Banning.
PZ, None.
