textproduct: San Diego

SYNOPSIS

Unusually warm temperatures continue today, with highs ranging from 8 to 12 degrees above average. A gradual cooling trend will follow for Sunday through Tuesday/Wednesday, bringing temperatures around 5 degrees above average for midweek. The upper level ridge moves back west towards Las Vegas and restrengthens in the latter half of the week. There is increasing confidence that this setup could provide the hottest temperatures of the Summer thus far.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

The stubborn subtropical ridge remains anchored over the eastern Four Corners this afternoon. The influence of this feature continues to be the headline for the forecast, as above normal temperatures are expected to persist into next week. The ridge has been very gradually nudging east over the last day or so, and will continue to do so through early next week. While it will remain quite hot, a very subtle cooling trend continues into Tuesday, with high temperatures falling about a degree each day. However, for today, high temperatures remain about 10 degrees above normal, topping out in the upper 90s to low 100s for the inland valleys, upper 80s and low 90s for the western valleys, and 105-117 degrees in the deserts. The weak easterly flow aloft with the ridge setup is also keeping moisture slightly elevated, leading to the continually mild nighttime temperatures. The cumulative combination of the high temperatures and warm nights keeps HeatRisk elevated despite subtle cooling compared to a few days ago, with widespread moderate (level 2/4) HeatRisk in and west of the mountains, with major (level 3/4) HeatRisk in the deserts. As the ridge slowly nudges eastward and the gradual cooling trend ensues into Tuesday, HeatRisk follows suit, with slight improvements each day. The Extreme Heat Warning (for the deserts, Inland Empire, and San Diego County mountains) and Heat Advisory (everywhere else) remains in effect through 8 PM Monday evening.

As the ridge begins to nudge eastward through the next few days, this opens the door for some monsoonal influences to sneak in. While the subsidence will not be as strong, PWATs aren't overly impressive. The general expectation is for afternoon cumulus development over the mountains for Sunday-Tuesday. PoPs continue to be quite meager with Sunday having the best "shot" at seeing any showers over the mountains (~5% or less).

Tuesday into the end of next week...

With the upper ridge displaced some towards the front range of the Rockies and the southwestern Great Plains on Tuesday/Wednesday, high temperatures will be moderated compared to what we're expecting this weekend, but will still run about 5 degrees above normal. Even worse, Tues/Wed will be the "coolest" days of the week, as ensemble clusters all agree that the ridge will slowly migrate back west through the Desert Southwest and strengthen in the latter half of the week. The ridge looks to become centered over Las Vegas by Saturday, with some ensemble members taking the strength up to 600dm at 500mb. This setup could very well bring the hottest afternoon temperatures of the Summer so far, with some daytime temperature records potentially being challenged. Palm Springs currently has a 20-30% chance of seeing highs >120 degrees next Saturday, with the Inland Empire having about a 20% chance of seeing highs >110 degrees. Additional heat headlines are looking increasingly likely for the second half of next week.

AVIATION

251800Z....Coast/Valleys...Low clouds have cleared out to the coast with a few clouds sticking around at 1,500ft MSL. VFR conditions are expected until 03-05Z Sunday when low clouds are expected to move back on shore. Low cloud bases will be 1000-1500ft MSL with a tempo group for cloud bases at 800ft MSL at CRQ. Vis restrictions will be possible where clouds intersect terrain. Low clouds clear 16-18Z Sunday.

Mountains/Deserts...VFR conditions prevail through the TAF period with cumulus building over the mountain this afternoon AOA 20k ft MSL.

MARINE

Calm conditions over the weekend with waves 2 to 4 feet and afternoon wind gusts near 15 kts or less through Monday. Waves increase in the outer waters mid to late week with waves expected around 5 to 7 feet.

BEACHES

A 2 foot southerly swell with 12 second periods will continue to bring elevated surf 4-6 feet with sets to 7 feet to beaches through this evening. Sunday, a long-period southwesterly swell will replace the current swell, keeping surf around 3-5 feet with sets to 6 feet through Sunday evening. Monday and Tuesday, the southerly swell will increase to 3 feet with a period 17 seconds, elevating surf once again to 4-6 feet with sets to 7 feet. Highest surf is expected along south-facing beaches. High rip current risk will last through the upcoming week.

In addition to elevated surf, tides are expected to increase to a height of 6.0 to 6.5 feet MLLW by Sunday and continue at that height through most of the week. The combination of surf and tides will result in minor coastal flooding during high tides.

SGX WATCHES/WARNINGS/ADVISORIES

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

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

Extreme Heat Warning until 8 PM PDT Monday for Apple and Lucerne Valleys-Coachella Valley-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Deserts- San Diego County Mountains-San Gorgonio Pass near Banning.

PZ...None.