textproduct: San Diego

SYNOPSIS

A slight cooling trend begins today and continues through Wednesday, bringing temperatures down to around 5 degrees above average by midweek. Daytime temperatures rise again for Thursday through next weekend and we could see the highest temperatures of this summer so far by Saturday. Some monsoonal moisture aloft later in the week into the upcoming weekend may also provide a slight chance of afternoon showers and thunderstorms for our mountains and deserts.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

This afternoon...Temperatures range from a few degrees higher to a few degrees lower than at his time yesterday. There was a weak coastal eddy last night and low clouds from a shallow marine layer are persisting at the beaches of San Diego County. High resolution models indicate that a weak coastal eddy will likely return tonight.

A shallow marine layer will persist through the forecast period with night and morning low clouds mostly restricted to the coastal areas and western portions of the San Diego County valleys.

The large-scale pattern will remain quite stable, with high pressure centered over the southern Rockies/Desert Southwest and low pressure centered over the Gulf of Alaska. Through Wednesday, the high pressure over SoCal will weaken slightly in response to a vigorous shortwave trough moving inland to our north. The resulting height falls and weak cyclonic flow aloft will allow the marine layer to deepen a little and the low clouds to spread a little farther inland during the nights and mornings. Temperatures will be generally lower across the region but will be more noticeable nearer to the coast. By Wednesday, temperatures will range from a few degrees below normal in some locations west of the mtns to around 5 degrees above normal in the low deserts.

For Thursday through next weekend...The high pressure center will shift to the southwest and build over the Desert Southwest. This will bring significantly warmer conditions to SoCal, we are likely to see the highest temperatures so far this summer. Models indicate that Saturday will likely be the hottest day, with daytime temperatures ranging from 5-10 degrees above normal in the coastal areas to about 15 degrees above normal in parts of the inland valleys and deserts. Temperatures will range from the high 70s to the mid 80s near the coast, the low 90s to low triple digits in inland OC and SD County, low triple digits to about 110 in the IE, 80s to low 90 in the mtns, up to 113 in the high deserts and up to around 120 in the low deserts. The building high pressure will also make the marine layer shallower and restrict the low clouds to the immediate coast during the nights and mornings. The heat will likely abate slightly for next Monday as the high pressure weakens. Confidence in the coming high temperatures is relatively high due to the stable pattern and good agreement among model solutions.

AVIATION

271800Z....Coast/Valleys...Low clouds that filled in earlier this morning have since cleared out to the coast but will likely remain stuck to the beaches and immediate coastline through the afternoon. Any clouds that do clear out through the afternoon will redevelop and push back ashore after 00z Tuesday, with CIGs expected at the coastal TAF sites through the night. Bases look to generally be similar to last night, though perhaps a touch higher, around 1000- 1300ft MSL. Expected a similar inland extent of around 10-15 miles with VIS restrictions limited to coastal mesas and higher coastal terrain. Low clouds likely scatter back to the coasts around 16-17z Tuesday.

Mountains/Deserts...VFR prevails throughout the day with a few Cu based AOA 12,000ft possible over the mountains in the afternoon.

MARINE

Calm conditions into the early half of next week with waves 3 to 5 feet and afternoon wind gusts near 15 kts or less through Tuesday. Waves increase in the outer waters mid to late week with waves expected around 5 to 6 feet.

BEACHES

A persistent long-period southwesterly swell (2-3 feet at 17-19 seconds) keeps surf elevated at around 3-5 feet with sets to 6 feet into Wednesday. A Beach Hazard Statement remains in effect through 5 PM Wednesday for the elevated surf, rip current risk, and concern for minor tidal overflow.

By Wednesday afternoon/evening, a much higher amplitude swell associated with Hurricane Genevieve is set to build. Some uncertainty exists in exactly how strong this swell will be as it depends on the strength and track of Genevieve, but current guidance suggests the swell could be around 5 feet, with a period around 14 seconds. With this, breaking waves of 5-8 feet are expected, with set up to 9 feet for south-southwest facing beaches. The swell builds overnight Wednesday into Thursday, with highest surf expected on Thursday. With this, a High Surf Advisory has been issued for 5 PM Wednesday through 5 PM Saturday for dangerous swimming conditions brought about by large breaking waves and strong rip currents.

In addition to elevated surf, tides are expected to increase to a height of 6.0 to 6.5 feet MLLW for this evening's high tide and continue at that height through most of the week. The combination of elevated/high surf and tides will likely result in at least minor tidal overflow during the evening high this evening and Tuesday evening. More notable coastal flooding is likely for Wednesday through Friday when the high tides combine with the high surf brought with Genevieve's swell later this week. It is worth noting, that with the effects from this year's El Nino, observed tides have been consistently about 0.3-0.5 feet below many baseline predictions. A Coastal Flood Advisory has been issued for 5 PM Wednesday through 3AM Saturday for this risk of coastal flooding associated with the evening high tides.

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 afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.

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

Coastal Flood Advisory from 5 PM Wednesday to 3 AM PDT Saturday for Orange County Coastal Areas-San Diego County Coastal Areas.

High Surf Advisory from 5 PM Wednesday to 5 PM PDT Saturday for Orange County Coastal Areas-San Diego County Coastal Areas.

Extreme Heat Warning until 8 PM PDT this evening for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass near Banning.

PZ...None.