textproduct: San Diego

SYNOPSIS

Continued hot weather today with high temperatures 15-20 degrees above normal inland. Cooler, windier, and cloudier conditions expected for the middle of next week. Slight chance (15-20 percent) of light precipitation on Wednesday for areas along and west of the mountains. Drier and warmer conditions for the end of next week with potential for Santa Ana winds.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Marine layer low clouds and fog are very patchy this morning. Fog may become locally dense where sufficient radiational cooling occurs, but this will be limited given the high cloud coverage. The upper level ridge across the southern tier of the US weakens slightly today, though this results in minimal changes to high temperatures. Highs will once again be around 15-20 degrees above normal across the region, with the greatest departure from normal in the valleys and lower elevation mountains. A coastal eddy develops tonight for more organized low clouds and fog, though the marine layer remains fairly shallow, limiting low clouds and fog to the coastal areas. Convection over the Sonoran Desert this afternoon and evening could produce a very early season gulf surge into the low deserts. The REFS has a 70-80% chance of dew points of 60F or higher over the southeastern Coachella Valley. If this occurs we could see some low clouds and light fog in this area Monday morning, or at a minimum some muggy conditions until the moisture mixes out in the afternoon.

The upper level high shifts much further east on Monday with weakly cyclonic flow developing across California. This brings greater cooling with highs closer to 10-15 degrees above normal inland and around 5-10 degrees above normal near the coast. Monday could be the first time in two weeks that no record high temperatures are broken. Greater cooling occurs Tuesday and Wednesday as a weak trough moves through, and high temperatures will finally return to normal. The marine layer deepens through this period with low clouds extending into the valleys Tuesday and Wednesday morning. Ensembles continue to trend drier with this system, especially over the southern part of the forecast area. For Wednesday, there is around a 15% chance of 0.10" or more for the coastal areas and valleys, and a 20-25% chance over the mountains. At this rate, the coastal areas and valleys will be lucky to see a few hundredths. West winds strengthen Tuesday and Wednesday across the mountains and deserts with gusts around 40-55 mph on the wind-prone desert mountain slopes and passes.

On Thursday, an upper level closed low moves east across the Pac NW with troughing continuing over So Cal. This will maintain cooler weather with a deep marine layer and breezy onshore winds. The trough associated with this low digs through the Great Basin into the Rockies on Friday with surface high pressure developing in its wake. While there is good ensemble agreement with the general pattern, the depth of the trough varies between members which results in some uncertainty in the strength of the Santa Ana winds. The CW3E wrf ensemble has around a 20% chance of a weak event on Friday. Surface pressure gradients remain offshore into Saturday and an upper level ridge builds in from the west, resulting in much warmer and drier weather.

AVIATION

290945Z...Patchy fog is developing in SD Co. coastal areas, including elevated coastal mesas up to 600 ft elevation. VIS down to 1/4SM in FG and 4-6SM in VCFG/BR. Around 50% chance for periods of VIS below 1SM and FG at KSAN/KCRQ. Lower confidence in FG development in OC coastal areas; timing likely after 12z. Clearing expected 16-18Z. Low clouds return to the coast with higher bases, 5000-1000 ft MSL, around 06-10z Mon.

Otherwise, partly cloudy skies with clouds AOA 20K ft MSL through the TAF period.

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...None. PZ...None.