textproduct: San Diego

SYNOPSIS

Weak Santa Ana winds will continue this morning. Warmer today with high temperatures 10 to 15 degrees above normal west of the mountains. Inland areas will continue to warm on Sunday while coastal areas begin to cool, followed by only minor changes for Monday and Tuesday. Minor cooling Wednesday, then more significant cooling with a 15-30% chance of precipitation Thursday and Friday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Morning satellite imagery shows a small patch of low clouds over southern Orange County with just a few high clouds elsewhere. Surface pressure gradients remain weakly offshore, currently around -3.9 mb SAN-DAG and -9.9 SAN-TPH. Northeast to east winds are gusting to around 25-40 mph below the passes and canyons and will continue through the morning, gradually weakening as pressure gradients relax. Otherwise warmer today as upper level ridging builds in, especially west of the mountains where offshore flow will aid in warming. In general, highs will be around 10-15 degrees above normal for the coastal foothills westward, and around 3-6 degrees above normal elsewhere. A few locations in the valleys and inland Orange County could approach 90 degrees (30% chance of exceeding 90 degrees).

Onshore flow returns for Sunday with a coastal eddy spinning up. This will bring a resurgence of low clouds and fog at the coast, potentially dense over the higher coastal terrain as low clouds spread inland Sunday morning. The upper level ridge begins to shift eastward, and with an afternoon sea breeze this will bring cooling west of the mountains but slightly warmer conditions inland. A very weak short wave moves through on Monday for minor cooling and a slight deepening of the marine layer, followed by weak ridging on Tuesday before an upper level closed low begins to approach the West Coast on Wednesday. Overall minimal day to day temperature variations for the first half of the work week with high temperatures around 5-10 degrees above normal and marine layer low clouds extending into the western valleys each night and morning.

More uncertainty later in the week as ensembles begin to diverge in the track of the upper low. The faster end of the guidance is composed of about 43% of the ensemble space, bringing precipitation to So Cal as early as Wednesday night. On the opposite end, the slowest cluster, about 17% of the ensemble space, the onset of precipitation doesn't occur until Thursday evening and lasts into Saturday. Given the large spread in the timing, PoPs remain relatively low (15-30%) for each period Thursday morning through Friday evening. Almost every member of the global ensembles has at least some precipitation, so it's just a matter of narrowing down the window of when it will occur. Precipitation amounts also vary wildly, but that is to be expected 5-6 days out. For 48 hour period from 4 AM Thu through 4 AM Sat, the NBM has a 15-35% chance of total accumulations 0.25 inch or more for the mountains westward.

AVIATION

041200Z...Iso patches of low clouds 300-700 ft MSL have a 30% chance to impact coastal sites through 15Z this morning. Any cig/vis impacts are expected to be brief before scattering out again. Better chances for low clouds 400-800 ft MSL to impact coastal areas after 10Z Sun, best chances (50-60% chance) for southern SD Co vcnty KSAN.

Elevated north to northeast winds gusting 20-35 kts along coastal slopes, foothills, through passes, and locally into the Inland Empire continues through this afternoon, before gradually decreasing after 19Z today.

MARINE

No hazardous marine conditions expected through Wednesday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory until 1 PM PDT this afternoon for Orange County Inland Areas-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.

PZ...None.