textproduct: San Diego

SYNOPSIS

After a cooler day today, a great warming trend is expected for the upcoming week, unfolding into a long duration heat wave. As high pressure moves over the area, highs will be 20 to 30 degrees above normal with moderate to high heat risk for all areas. The heat will peak later next week, with a gradual cooling trend thereafter.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

A weak trough to the north and weaker area of high pressure to the south has the led the marine layer to deepen. A coastal eddy over the California Bight has contributed to low clouds and fog near the coast this morning. Low clouds will dissipate some this afternoon over the water, then reform and move back further inland overnight.

An area of high pressure will begin to build off the coast by Sunday, where a long duration heat wave is expected to last through much of next week. Sunday temperatures will warm another 5 to 10 degrees across inland valleys west of the mountains with highs reaching into the 90s across the Inland Empire and lower deserts. The ridge will amplify further into Monday and Tuesday, centering over the region. Hot temperatures in the valleys will expand closer to the coast and foothills with plentiful 90s for western valleys and closer to 100 degrees across the lower deserts on Monday.

All regions will continue to warm another 2-5 degrees on Tuesday. By Tuesday, chances for 100 degrees are around 20-40% for the southern Inland Empire and northern Orange County, closer to 50-80% across the northern Inland Empire. Models show similar temperatures expected on Wednesday as 850mb temps climb to near 25C. The only places that may warm a few degrees would be across the mountains with areas near Big Bear Lake closing in on 80 degrees (their record high for March) and Julian and Idyllwild getting into the mid to upper 80s. Seeing that these places in the mountains will be this warm and even warmer by late week, please avoid any outdoor recreation in these areas each afternoon this week if at all possible.

The area of high pressure will peak in strength by Thursday and Friday over SE California into Arizona, billowing into a staggering 595 dm, very strong for this time of year. The hottest temperatures of the heat wave still look to occur during this time. Chances to see 100 degree temperatures will be around a 50-50 chance from El Cajon to Escondido to Anaheim with a general 30-60% chance across inland valleys east of the 5 and the 15 in Orange and San Diego Counties. The IE will see temperatures over 100 with about a 30-50% chance to see highs reach 105 degrees, especially near the city of San Bernardino. Mountain areas will continue to be hot with highs in the upper 80s to near 90 from Idyllwild to Julian to Lake Arrowhead. The immediate coast will be a tougher forecast in this pattern as weak / cool onshore winds off the cold ocean have a large influence on the exact temperatures. Some lucky beaches along San Diego County may stay in the 70s for much of the upcoming week making for some beautiful beach weather.

As the high slowly weakens and pushes into Arizona late week, hot temperatures will be last to cool across the Coachella Valley and Anza-Borrego desert. High heat risk will begin in this area on Thursday, lasting through Saturday, so please make sure to find air conditioned spaces and limit time outdoors. Not only will this area shatter record temperatures for the month of March, some may even break records for April! Since 1894, the hottest April temperature in Indo is 110 degrees. NBM gives this about a 75% chance of going over this value! Chances to break the April records at Palm Springs (112 degrees) is around 25% and around 80% at Thermal (110 degrees). Quite incredible for this time of year! Models are in fair agreement of a trough beginning to loom offshore by next weekend, bringing a gradual cooling trend first along and west of the mountains by next Saturday, then across all areas thereafter.

AVIATION

141800Z...Low clouds along the coast are lifting slightly and scattering out and should stay offshore through the afternoon. Low clouds out over the local waters with bases around 500-700 ft MSL will begin to push in after 02-03Z Sunday. Patchy fog with vis 4-5SM is expected to develop around KCRQ after 09z and KSAN after 12Z with a 45% of vis less than 4SM. Low clouds will begin to clear after 16- 18Z. Otherwise, VFR conditions will prevail with stronger westerly winds this afternoon confined to the usual passes and canyons with peak gusts around 20-25 kts. .

MARINE

No hazardous marine conditions are expected through Wednesday.

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 Monday 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- Santa Ana Mountains and Foothills.

PZ...None.