textproduct: San Diego

SYNOPSIS

Monsoonal moisture will increase today and Friday with a slight chance of afternoon showers and thunderstorms for the mountains and deserts. There will be some drying on Saturday, followed by the potential for a slight increase again early next week. High temperatures will remain around 5 degrees above average for inland areas into next week with low temperatures 5 to 10 degrees above average for inland areas.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

A weakening Mesoscale Convective Vortex (MCV) from earlier convection over AZ has moved into far Southeast California. Outflow from this system has helped kicked off convection over the San Diego County mountains, while further north we've only seen some cumulus clouds so far. Expect scattered thunderstorms over the mountains this afternoon with locally heavy rain, gusty winds, and small hail. Showers and thunderstorms will diminish this evening. Otherwise warm and humid weather continues today with highs around 5 to 8 degrees above normal inland. The Heat Advisory remains in effect for the Inland Empire through this evening.

The upper high begins to shift eastward as an upper level trough approaches the west coast. Overall this will lead to some drying Friday and Saturday though temperatures will only fluctuate a degree or two each day. Showers and thunderstorm chances lower to around 15-20% Friday afternoon, then less than 10% for Saturday afternoon. There is the potential for moisture to increase slightly on Sunday and Monday, though there is still some spread in the ensembles. For now we look to be on the fringes of the moisture, with the best chances of any afternoon storms limited to far southern San Diego County Sunday, perhaps shifting north into the remaining mountain ranges on Monday.

For much of next week, the upper high will remain centered over southern AZ/NM with the ridge axis extending west into So Cal and weak south to southwesterly flow aloft. Monsoonal moisture remains marginal for only low chances of showers and thunderstorms. Otherwise expect a minor warming trend for the middle of the week with widespread high HeatRisk in the low deserts and moderate HeatRisk elsewhere.

AVIATION

201800Z...Coast...Low clouds based 800-1200 ft MSL push onshore to coastal areas around 02z Fri, remaining very patchy and intermittent through 12z as high clouds disrupt their development. These low clouds briefly fill in coverage up to 15 miles inland through 16z Fri, then scatter out. Reduced VIS 0-5SM where clouds intersect terrain along elevated valleys.

Otherwise...SCT to locally BKN clouds above 15 kft MSL through Friday. BKN cumulus at 10 kft MSL towering over mountains and high desert with a 15-20% chance of TSRA 21-02Z. Gusty, erratic winds around any TSRA.

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...Heat Advisory until 8 PM PDT this evening for San Bernardino and Riverside County Valleys-The Inland Empire.

Extreme Heat Warning until 8 PM PDT Sunday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.