textproduct: San Diego

SYNOPSIS

Monsoonal moisture will decrease into the weekend with a slight chance of showers and thunderstorms for the mountains and high desert for this afternoon. Above average high and low temperatures will continue through next week. Widespread moderate to locally major HeatRisk for the coast, valleys, and mountains except near the beaches and for the higher elevations in the mountains, with major to extreme HeatRisk for the lower deserts.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Outside of a few passing high clouds, most of the region is experiencing sunshine this afternoon. Cumulus clouds over San Gorgonio mountain have grown into showers and a thunderstorm. PWAT values in this mornings sounding have actually increased a bit from yesterday and thus there is still an outside (10%) chance for shower development where cumulus have already developed over the Peninsular Range later this afternoon.

As of 1 PM, about 50% of temperature observations read 100F or above through the Inland Empire with readings approaching 100F through the interior and foothill valleys of San Diego County. Temperatures near the coast remain closer to average with more comfortable mid 70s across the San Diego County Coast and low 80s across the Orange County coast.

This morning's marine layer was slow to develop and quite shallow - around 1000 feet deep with patchy cloud cover and locally lower visibilities in the valleys surrounding the I-15 corridor. This pattern should continue in the coming days as the ridge continues to squash the boundary layer.

Long range models are in solid agreement about keeping the upper level ridge strong and centered over the Desert Southwest for at least the next week, despite the jet stream flowing north of it across the Northwest. As a result, model guidance is foresting temperatures consistently 5 to 10 degrees above average across Southern California through the forecast period with little day-to- day change. Given we are in an already hot time of year, impacts from prolonged above normal heat will be more widespread. Most inland areas will experience moderate HeatRisk through next week with some areas of Major HeatRisk. The lower deserts will experience persistent Major HeatRisk through next week with temperatures forecast 110-115F everyday of the forecast period and low temperatures struggling to fall below 90F in some places.

Despite the favorable positioning of the ridge, thunderstorm chances are limited this weekend and increasingly less impressive next week with less moisture in store. Chances are subject to change however, especially next week, as the mid-level flow remains generally southerly with the upper level high pressure spinning to the east.

The Extreme Heat Warning continues for the lower deserts through next Friday and a Heat Advisory is now in place for the inland valleys and mountains (below 6000 feet in San Bernardino County) from Saturday morning through Monday evening. Take breaks in the shade, hydrate and seek A/C when possible!

AVIATION

211800Z...Coast...VFR conditions expected this afternoon with SCT high clouds AOA 20 kft. Patchy low clouds reforming after 08Z near the beaches, with low to moderate confidence in cigs near 400-900 ft MSL impacting coastal SD County TAF sites between 11-15Z Sat. Low clouds scatter thereafter.

Otherwise...FEW to SCT clouds above 20 kft MSL through Friday. Slight chance (10-15%) for ISO SHRA/TSRA over mtns from 20z Fri to 01z Sat.

MARINE

No hazardous marine conditions are expected through Tuesday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Heat Advisory from 10 AM Saturday to 8 PM PDT Monday for Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains- San Diego County Valleys-Santa Ana Mountains and Foothills.

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

PZ...None.