textproduct: San Diego

SYNOPSIS

Monsoonal moisture will maintain a slight chance of afternoon showers and thunderstorms for the mountains and deserts through Tuesday. A warming trend will continue through Thursday with widespread major to extreme HeatRisk for the lower deserts, valleys, and inland Orange County. Widespread moderate or greater HeatRisk except for mountain elevations above 7000 feet is expected to continue through next Saturday.

..UPDATED AVIATION DISCUSSION

This morning featured clouds in all levels of the troposphere. Patchy fog covered San Diego County west of I-15 earlier in the morning, making way to photogenic skies of cumulus, altocumulus, and cirrus embedded with a few virga showers (sprinkles were reported in inland parts of San Diego). While these clouds signal to plentiful mid-level moisture, the broad coverage in SD County might be delaying convection over the mountains and thus shower/tstorm activity until later in the afternoon. Meanwhile, cumulus clouds have been persistently building on the eastern slopes of the San Bernardino and Riverside County mountains with some showers developing. More showers and thunderstorms are likely over these slopes through around 7 PM this evening. Any thunderstorm that develops could bring heavy downpours and up to an inch of rain locally.

Temperatures this afternoon are generally running a few degrees cooler than yesterday, expecting to reach the mid-90s inland, 100- 105F in the IE and 106-110F in the lower deserts. Highs today are expected to be the noticeably the coolest for the week for the inland valleys and lower deserts.

Thunderstorm chances peak this afternoon as PWAT's fall through Wednesday, though isolated terrain driven shower/t-storm chances remain in the forecast for our mountains through Thursday as the mid- level flow remains southerly, tapping into modest mid-level moisture.

The ridge axis over the Desert Southwest shifts westward through the middle of the week and high temperatures peak Wednesday through Friday through Southern California. Highs are expected to reach the upper 90s to 105F in the inland valleys, 103-108F through the IE and up to 115F in the lower deserts.

Both the GFS and the ECMWF show a significant flattening of the ridge over the weekend, increasing confidence that temperatures will return closer to normal by early next week.

In the meantime, take breaks in the shade, hydrate and seek A/C when possible!

AVIATION

250600Z...Coast...Patchy low clouds 400-700 ft MSL expected to develop overnight, most likely to impact KSAN and KCRQ after 12Z. Low confidence in cigs reaching KSNA. Vis reductions 0-5 SM possible where cigs form. Any cigs and vis restrictions will clear around 15Z. Patchy low clouds will form again after 01-03Z along the coastal areas, mainly for southern San Diego County, with cigs around 800-1500 MSL, occasionally going broken throughout the rest of the forecast period.

Mountains/Deserts...Cumulus based around 9000 feet MSL with CB clouds with tops to 40000 feet and ISO TSRA over mountains and locally into adjacent deserts possible Tuesday afternoon. Any TS could produce gusty, erratic winds.

Otherwise...SCT to locally BKN clouds AOA 10-15 kfeet MSL becoming mostly clear after 03Z. Similar cloud cover Tue after 18Z.

MARINE

No hazardous marine conditions are expected through Saturday.

BEACHES

A 4-5 foot southerly swell (from 170 degrees) at 13-15 seconds will move into the area Wednesday and Thursday, leading to elevated surf for the south facing beaches of northern San Diego County and Orange County. Breaking waves of 4 to 6 feet expected, sets up to 8 feet possible at beaches that face due south. Surf gradually subsides on Friday.

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 Tuesday to 8 PM PDT Friday for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory until 10 AM PDT Tuesday for Orange County Inland Areas-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 from 10 AM Tuesday to 8 PM PDT Friday for Apple and Lucerne Valleys-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Mountains-San Diego County Valleys-Santa Ana Mountains and Foothills.

Heat Advisory until 8 PM PDT Friday for Riverside County Mountains-San Bernardino County Mountains.

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

PZ...None.