Marine Weather and Tide Forecast for Potrero, CA

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

New Aviation and Marine Discussion...

This afternoon...a low pressure system to our southwest continues to bring widespread mid and high clouds to SoCal, along with onshore flow and slightly lower temperatures. The marine layer has been disrupted by this system and there is no significant inversion and very few low clouds, mostly over the coastal waters. As this system moves inland over northern Baja this evening and tonight, the onshore flow will strengthen briefly producing westerly winds locally gusting 35 to 45 mph in the mountains and deserts.

For late tonight into Friday morning...a surface high will move into the Great Basin, briefly setting up offshore flow. Gusty north to northeast winds will develop early Friday morning, peak during the day and weaken Friday evening. Gusts of 35 to 45 mph are expected in and below the Cajon Pass, along and below the coastal slopes of the Santa Ana Mountains, and in northern and eastern portions of the Coachella Valley. The offshore flow will also bring about 5 degrees of warming to the areas west of the mountains but the deserts could be about 5 degrees cooler than today. High temperatures on Friday will be mostly in the 70s for the coast and valleys to around 80 for the western valleys and inland coastal areas with high temperatures for the lower deserts in the lower to mid 80s.

The offshore winds will weaken on Saturday and a transient ridge of high pressure ahead of a low pressure system, developing south of the Gulf of Alaska, will bring daytime temperatures about 5-10 degrees higher than Friday. High temperatures are expected to range from the lower 70s near the coast to the lower to mid 80s for the Inland Empire with the lower deserts around 90.

Warming will continue for inland areas on Sunday under southwest flow aloft ahead of the low pressure system moving southward off the CA coast. High temperatures on Sunday will likely be 5 to 10 degrees above average for most areas. Sunday high temperatures will range from the lower 70s near the coast to the lower to mid 80s for the Inland Empire with the lower to mid 90s for the lower deserts.

For Monday through the middle of next week...Model solutions have not yet begun to converge on a solution so forecast details are quite uncertain. The low pressure system will move inland over CA by Wed or Thu. We can say with reasonable confidence that conditions will be cooler and breezier with increasing clouds. Almost half the ensemble members across model platforms indicate the potential for measurable precipitation but timing and amounts are uncertain.
At this time, the National Blend of Models indicate a 15%-25% chance of measurable precip between next Tue and Thu.

AVIATION
170430Z
Coast/Valleys/Coastal Slopes
Patchy low clouds based 1500-2000 ft MSL are currently developing over coastal areas. Low clouds spread into San Diego/Orange County valleys and the southern Inland Empire by 06-09z, though coverage should remain patchy and intermittent for all areas. Greatest chance for BKN cigs will occur now through 09z in San Diego County. Thereafter, flow turns offshore with any remaining low clouds clearing out of land areas by 12-15z.
North to northeast winds become elevated to strong starting 09-12z along coastal slopes in San Bernardino County. Then, winds spread through/downwind of the Cajon Pass into the Inland Empire and Santa Ana mtns. Gusts 35-45 mph expected, locally to 50 mph through wind prone passes and coastal slopes. MOD up/downdrafts in lee of mountains. Winds weaken and eventually diminish Friday afternoon.

Desert Slopes/Deserts...Elevated to strong westerly winds are currently gusting up to 30 to 40 knots in the High desert, along desert slopes and through mountain passes. Winds will shift to northerly and weaken from 06-12z. The exception will be the northern Coachella Valley where northerly winds will remain strong into early Friday afternoon. MOD up/downdrafts in lee of mountains.

MARINE
No hazardous marine conditions are expected through Monday.

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



SGX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory from 5 AM to 5 PM PDT Friday for Orange County Inland Areas-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-Santa Ana Mountains and Foothills.

Wind Advisory until 2 AM PDT Friday for Apple and Lucerne Valleys.

PZ...None.