textproduct: San Diego

SYNOPSIS

Above average temperatures will prevail through much of the forecast period. The warmest conditions are expected Monday, with a gradual cooling to within a few degrees of normal Tuesday through Friday. Night and morning low clouds and fog will be present each day along the coast and into portions of the valleys. A gradual warming trend is possible next weekend.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

High temperatures today are expected to be a few degrees warmer than yesterday along the coast and up to 10 degrees warmer further inland. Warming will continue into Monday with an additional 3 to 7 degree increase compared to today. This will bring high temperatures 10 to 20 degrees above average for inland locations Monday and 5 to 8 degrees above average along the coast. Areas of widespread moderate HeatRisk are expected in the Inland Empire and High Desert with major HeatRisk in the low deserts through Monday. Make sure to stay hydrated and seek shade when possible if working outdoors.

Temperatures on Tuesday will cool 5 to 12 degrees compared to Monday as the ridge aloft weakens and is pushed east by a shortwave trough passing from our southwest. The passing shortwave will strengthen onshore flow for Tuesday and Wednesday, increasing south to southeast winds in the deserts on Tuesday and westerly winds from the mountain slopes into the deserts on Wednesday. This passing feature is not expected to have moisture associated with it so dry conditions will prevail.

For Wednesday through Friday, most ensemble clusters are showing a weak troughing pattern prevailing over the US West Coast. This will maintain marine layer low clouds and fog for the coast and valleys and take high temperatures back to within a few degrees of normal. For next weekend, the majority of ensemble clusters keep the upper level pattern weakly troughy to zonal, with only 10 percent of solutions showing weak ridging developing by next Sunday. The forecast for next weekend follows the NBM which indicates a gradual warm up for Saturday and Sunday. There remains low confidence in just how warm it will get with the deterministic NBM again representing the highest percentiles of most other ensemble guidance.

AVIATION

101800Z...Coast/Valleys...Low clouds from this morning have retreated offshore by 18z this morning, with SKC and VFR conditions prevailing through this afternoon. Low clouds expected to push back ashore after 01z Monday this evening, with higher confidence in lower bases than last night. While CIGs along the coast may initially be 1000-1500ft MSL, bases should settle to 700-1200ft MSL by 06-09z. CIGs fill inland up to 20 miles by 06z as well, though lower confidence in reaching KONT (15%) than this morning. VIS reductions 4-6 SM in BR for higher coastal terrain, with locally 1-3 SM for interior valleys. Bases likely lifting back above 1000ft MSL by 14-15z, with full scattering back offshore by 16-17z.

Mountains/Deserts...SKC and VFR through Monday afternoon. Gusts 20 to 30 kts along desert slopes (up to 40 kts through the Banning Pass) Sunday evening.

MARINE

No hazardous marine conditions are expected through Thursday.

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 to 8 PM PDT Monday for San Bernardino and Riverside County Valleys-The Inland Empire.

Extreme Heat Warning until 8 PM PDT Monday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.