textproduct: San Diego

SYNOPSIS

Warmer conditions through Saturday with moderate HeatRisk for the coast and western valleys on Friday and Saturday. Night and morning low clouds and fog will stay confined to the coastal areas for the next few nights. There is a a slight chance of showers and isolated thunderstorms over the mountains Thursday afternoon. Cooler conditions expected Sunday and Monday, with potentially warmer conditions next Tuesday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Temperatures at 1 PM were running 10 to 18 degrees warmer than yesterday in the Inland Empire, 5 to 7 degrees warmer than yesterday for other inland locations, and were within a few degrees of yesterday for the coast. Most locations will see an increase in temperatures each day through Saturday, with high temperatures 5 to 7 degrees above average for inland locations and 7 to 12 degrees above average for the coast. Overnight lows will increase to the mid- 60s to 70 west of the mountains and in the upper 70s to low 80s in the low desert. Moderate HeatRisk is expected along the coast Friday and Saturday and in the low deserts for the second half of the week. Moderate HeatRisk has the most impacts on those sensitive to heat, especially those without cooling/hydration.

For Thursday, a closed low lingering to our south will start to move east. This low will draw moisture into Southern California from the southeast increasing chances for precipitation, mainly in the mountains. Latest high resolutions guidance indicates rainfall rates will mostly be 0.20-0.30 inches per hour, where thunderstorms develop rates could be closer to 0.50 inches per hour. There remains a 5-10% chance of thunderstorms over the mountains with the higher chances over the San Diego and Riverside County mountains.

For Sunday, an incoming trough of low pressure is expected to move inland across northern California. The low will dig south Monday and be to our east Tuesday or early Wednesday. There is good agreement that temperatures will cool 3 to 8 degrees between Saturday and Sunday and another 2 to 4 degrees for Monday. Additionally cloud coverage will increase. The trough looks like it will pull in moisture from our southwest, but there remains uncertainty in how much moisture will actually get pulled into Southern California. Ensemble members from both the GFS and ECMWF are showing increases in precipitable water and some potential for precipitation.

For next Tuesday and Wednesday, the forecast solutions diverge with 60% of solutions showing ridging and 40% maintaining weak troughing. Current forecast follows the NBM and shows a few degrees of warming each day Tuesday and Wednesday.

AVIATION

231900Z...Coast/Valleys...Low clouds based 1000-1500 feet MSL will gradually increase after 02Z Thu, becoming rather uniform after 10Z. Low clouds are not expected to reach KONT/KSBD. Low clouds will scatter out 16-18Z Thu.

Otherwise...mostly clear skies with unrestricted vis through Thu.

MARINE

No hazardous marine conditions are expected through Monday.

BEACHES

The combination of a 3 foot swell from 190 degrees on Sunday shifting to 160 degrees for Monday and Tuesday with a 12 to 15 second period coinciding with our bimonthly elevated high tides will increase chances for coastal flooding and erosion. Predicted high tides of 6.5 and 7.0 ft MSL will occur between 10 and 11 AM Sunday through Tuesday. The listed tide predictions have been corrected to reflect current trends in actual tide observations. Surf will be elevated, especially for south facing beaches with sets up to 5 feet on Sunday. Surf heights and direction of the swell remain uncertain for Monday and Tuesday and will be most influenced by the track of Tropical Cyclone Polo.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.