textproduct: San Diego

SYNOPSIS

High temperatures near average today and tomorrow with stronger onshore on Thursday: southwest to west winds for the mountains and deserts gusting to 35 to 45 mph. Winds turn offshore on Friday with northeast winds along and below the coastal slopes of the mountains gusting to 35 to 45 mph. Warmer with weaker winds for the weekend with high temperatures warming to around 5 to 10 degrees above average for Saturday/Sunday. Then cooler and breezy early next week as a low pressure system moves toward the California coast, but there remains a large amount of uncertainty in how this system progresses.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Current satellite and 500mb analysis reveals upper level flow is turning more quasi-zonal as the trough from the disturbed weather earlier this week departs. As a result, temperatures this afternoon will be about 5 degrees warmer than yesterday, but is also fairly seasonable temperatures for mid April. This zonal setup is going to be fairly short-lived as the next trough (currently pushing into eh Pacific Northwest) is progged to dig southeastward through the Great Basin and northern Rockies Thursday into Friday. This trough and a slough of mid/upper level clouds on Thursday knocks temperatures back down a few degrees compared to today.

Of most highlight from this trough late week will be the wind, with strengthening onshore flow on Thursday, followed by offshore winds late Thursday into Saturday. The elevated onshore flow Thursday afternoon will be felt most in the mountains/passes, adjacent deserts, and the high deserts. Wind gusts 35-45 mph expected in these areas, with localized areas up to 55 mph in the mounains and vulnerable mountain passes. With gusts upwards of 40-45 mph in the High Deserts, a Wind Advisory has been issued here from 11 AM Thursday through 2 AM Friday. As the upper trough pushes southeastward and surface high pressure spills into the Great Basin, winds will quickly switch to offshore, forcing north to northeasterly wind gusts of 35-45mph in and below mountain passes, locally up to 55 mph within passes. Timing of the flip to offshore looks to be overnight Thursday into Friday morning, with the peak gusts late Thursday morning to around noon. Gusts look to wane by the afternoon hours, with another weak push of easterly offshore winds Saturday. The offshore winds bring in warmer and drier air to the inland valleys, with high temperatures 5-10 degrees above normal by Friday, continuing into Saturday.

The forecast becomes much more uncertain early next week as global ensembles continue to struggle with the resolution of a large upper trough set to near the California coast Monday into Tuesday. Regardless of the track of this low, temperatures will remain on the cool side to start next week with elevated onshore winds likely. Depending on the track of this storm, some light precipitation may be brought to southern California, but details will have to continue to be refined in the coming days.

AVIATION

151730Z...Coasts...Low clouds based around 2000 ft MSL are currently lingering over southern SD County (vcty KSAN). Scattering out by 1830Z with SKC expected through this evening. Patchy low clouds based 1500-2000 ft MSL expected to redevelop over nearshore waters and coastal areas after 06Z Thu. Coverage will remain patchy through Thursday morning. Chances for BKN cigs at TAF sites: 70% at KSAN, 50% at CRQ, 60% at KSNA.

Otherwise...mostly clear and VFR conditions today through tonight.

MARINE

Wind gusts to reach around 20 kts near San Clemente Island Thursday afternoon and evening. Otherwise, no hazardous marine conditions are expected through Sunday.

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory from 11 AM Thursday to 2 AM PDT Friday for Apple and Lucerne Valleys.

PZ...None.