textproduct: San Diego

SYNOPSIS

Hot conditions with well above average temperatures expected this week. Weak offshore flow is expected today and tomorrow, with east to northeast wind gusts 25 to 40 mph along and below the coastal slopes of the mountains. Some cooling is expected through the weekend into early next week. Even with the cooling high temperatures for inland areas still 10 to 15 degrees above average. Marine layer low clouds and fog will be largely absent from the coast this week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Update: Weak offshore winds are slowly starting to return to the coast at this hour, which has helped to push out the low cloud deck/fog bank along portions of the San Diego coastline this evening. These weak offshore winds should help to keep the marine layer mostly confined to just the coastal areas, with minimal coverage over land within 5 miles from the coast. Other than some passing high clouds, the rest of the region should observe mostly clear skies. The ridge overhead will continue to strengthen throughout the week, with the ridge peaking out in intensity by Thursday into Friday. Not only are temperatures exceptionally warm, given the time of year, but the duration of prolonged heat for widespread locations is what is making this an unprecedented heat wave, especially for this time of year. By Thursday, it is possible that there will be a few locations possibly breaking monthly records, and then again on Friday. We will finally begin to see some relief from this heat beginning this upcoming weekend; gradually cooling from west to east. This will occur as the ridge begins to finally weaken with more troughing influencing the region. Be sure to stay alert to any updates to our Heat Watches and Advisories at weather.gov/sgx/

Previous discussion submitted at 1116 AM:

A persistent anomalously strong upper level area of high pressure is expected over Southern California this week. The high is expected to be at its strongest Thursday and Friday, with the potential for 500 mb height records to be broken for the month of March. Most days this week have the potential for daily temperature records to be broken or tied, with the potential for monthly temperature records to be broken or tied Wednesday through Friday. See the climate section below for more information.

For today and Tuesday, weak east to northeasterly winds are expected. Peak gusts of 25 to 40 mph are expected on the coastal mountain foothills and below passes. Strongest winds are expected on Tuesday. Weak offshore flow, combined with the building ridge aloft will result in warmer conditions for the coast and valleys. High temperatures at the coast and western valleys will peak on Tuesday. Widespread moderate to locally major HeatRisk are expected. Reduce outdoor activities if possible between 10 AM and 5 PM, seek shade, and stay hydrated. On Wednesday, a weak coastal eddy could bring a few degrees of cooling for inland coastal areas into the western valleys with the mountains and deserts warming another 3 to 5 degrees.

The heat is expected to peak for most inland areas on Thursday or Friday. Widespread moderate to areas of major HeatRisk are expected. High temperatures will be 20 to 30 degrees above average for this time of year. Daily and monthly temperature records are expected to be broken or tied for locations like Ramona, Big Bear Lake, Idyllwild, Palm Springs, and Borrego Springs. Overnight lows will also be elevated, which will limit overnight relief from the heat. The currently forecast low temperatures for Idyllwild of 64 for both Friday and Saturday would be the earliest for such a warm low temperature at Idyllwild by almost three months, the current earliest date for such a warm low temperature being June 16th (2021).

Weakening high pressure aloft and onshore flow will begin to spread cooling inland as early as Saturday for place west of the mountains, with cooling spreading inland Sunday and Monday. Even with the cooling high temperatures for inland areas for Monday of next week still 10 to 15 degrees above average. Much of this week will see an absence of marine layer low clouds and fog, with the potential for clouds and fog to return late in the weekend or early next week.

AVIATION

170600Z...Coasts...Deck of low clouds around 200-300ft MSL lingering offshore of San Diego County this evening. Patchy low clouds remains possible out over the waters and just offshore through the overnight hours, with a low chance (<10%) of impacting any TAF sites. Similarly patchy low clouds are possible again along the coasts after 02z Wednesday.

Valleys/Mountains/Deserts...Offshore winds have largely waned this evening for the valleys, though north-northeasterly gusts 15-20 kts remain possible through the overnight hours for the mountains and passes. Offshore winds turn more easterly on Tuesday, with gusts to 20-25 kts possible after 12z Tuesday, mostly in and just below mountain passes.

MARINE

No hazardous marine conditions are expected through Friday.

BEACHES

A long period (17-19 second) south-southwesterly swell (190-200 degrees) builds overnight, bringing breaking waves of 3-6 feet, with sets up to 7 feet on south-facing beaches. Swell and associated surf decreases on Wednesday. Locally hazardous swimming conditions are expected. A Beach Hazards Statement contains more details.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement through Wednesday evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory until 8 PM PDT Friday for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.

Heat Advisory from 10 AM Wednesday to 8 PM PDT Friday for Riverside County Mountains-San Bernardino County Mountains- San Diego County Mountains.

Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Saturday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.