DISCUSSION
FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

This morning, diurnal drainage winds have pushed the marine layer low clouds offshore in San Diego County but they are slowly making a return to the coastal areas and will cover much of the coastal zones by about 8 am. Yesterday afternoon was about as warm as Thursday in the lower deserts but cooler in and west of the mtns.

The relatively cooler conditions will continue through Tuesday in response to a trough of low pressure moving inland to our north and displacing the high pressure ridge to the south and east. The trough will bring cooler drier air in southwest flow aloft, effectively ending the threat of afternoon thunderstorms. It will also bring stronger onshore flow and increase the marine layer presence west of the mtns, with an increase in coastal low clouds during the nights and mornings. With the stronger onshore flow, we will see west winds gusting 25-40 mph in mtn passes and on desert slopes this afternoon and evening.

Temperatures begin to rise again as the trough moves off to the north east into the northern Rockies and the high pressure ridge becomes centered over Texan and expands into the desert southwest once again. The position and westward expansion of the high will not only raise temperatures generally and reduce the marine layer presence west of the mtns, it will also allow for monsoonal moisture to begin moving back into SoCal. It's still too soon to say with any confidence which day will be the one when we see a return of afternoon tstms.

AVIATION
270945
Coast
Low clouds are expected to move onshore this morning with more uniform coverage than previous nights. Marine layer clouds are expected to cover coastal areas and parts of the western valleys overnight. Bases will be around 800-1200 feet MSL with local vis reduced 1-5SM on higher coastal terrain and in western valleys. Low clouds scatter out Saturday by 15-18Z. Cloud formation is expected to be limited across Orange County with patchy conditions in San Diego County.

Mountains/Deserts... Similar to yesterday, slightly stronger winds expected after 21Z Sat, gusting to 25-35 kt through Sat evening. MOD up/downdrafts in lee of mountains.

MARINE
No hazardous marine conditions are expected through Wednesday.

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

SGX WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...None.