textproduct: San Diego

SYNOPSIS

An upper ridge will build into the region starting today creating a warming trend along with sunny conditions through this week. Any morning marine layer clouds will likely vanish by Thursday morning as flow switches to offshore. Record high temperatures expected for several locations Thursday and Friday. Flow turns weakly onshore for the weekend, which may provide some relief to coastal areas. However, most of Southern California remains hot and dry through the weekend. Another (potentially stronger) ridge will begin to take shape by early next week with more record high temperatures currently in the forecast.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Visible satellite shows scattered cumulus sticking around in portions of the coastal basin early this afternoon. Onshore flow will keep temperatures seasonable through today, even as an upper ridge begins to build into the region. However, the ridge will start to make its presence known by Wednesday as morning marine layer clouds begin to lower and high temperatures increase to 5 to 15 degrees above average.

By early Thursday, building surface high pressure over the intermountain west will reverse the direction of our flow to offshore. Offshore winds are expected to gust 25-35 mph along coastal slopes, through passes, and locally into valleys. Thus, any remaining marine layer clouds will quickly vanish on Thursday morning. This in combination with 500 mb heights approaching 590 dm will set the stage for record highs across most of Southern California both Thursday and Friday. A few monthly record could even be threatened as highs in the coastal basin climb to 20-30 degrees above normal. Highs in the mid to upper 90s for inland valley zones and upper 80s to near 90 for the coast. NBM probability of exceeding 85 degrees is 80% for downtown San Diego both days.

Onshore flow and a slight weakening of the ridge arrive for the weekend, which should provide slight cooling relative to Friday for the coastal basin. However, 500 mb heights will remain well above normal through the weekend with mean heights staying well above 580 dm. Temperatures 10 to 20 degrees above normal (locally 25 degrees above normal inland) will still be enough to break some record highs for inland areas.

Looking toward next week, the vast majority of the guidance ushers in another upper ridge from the west. Therefore, there is high confidence in well above normal temperatures and dry conditions to continue through next week. In fact, there is some indication that temperatures next week could be even higher than what is forecast for this week. However, exactly how hot it will be and for how long is still to be determined.

AVIATION

101745Z...SCT-BKN 2000-3000 ft MSL low clouds will stick around the coastal basin through around 20Z, this afternoon with partial clearing (best chance across the Inland Empire). Some of these clouds may stick around into the afternoon/early evening in Orange County. Low clouds expected to return with more widespread coverage after 02Z this evening across much of the coastal basin. Cigs starting near 2500 ft MSL 02-06Z Wed, lowering thereafter near 1000- 2000 ft MSL though some may be locally lower near 800 ft MSL. Skies clearing valleys to coast 16-19Z Wed.

Mostly clear with high clouds AOA 20K ft MSL over the mountains and the deserts Tuesday into Wednesday. West winds 20-35 kts at times along desert slopes through this afternoon.

MARINE

No hazardous marine conditions are expected through Saturday.

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 Thursday to 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.

PZ...None.