Widespread moderate Heat Risk with areas of major Heat Risk will continue through today. Heat Risk will decrease for the weekend, with minor cooling. Even with the cooling, temperatures will remain above average into next week. Patchy marine layer low clouds and fog will be present at times, most likely to impact the coastal waters and immediate coast. Stronger onshore flow will likely spread marine layer low clouds and fog farther inland for the weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, NEW AVIATION AND MARINE DISCUSSION BELOW,
Low clouds and fog are developing over the coastal waters this morning but are being kept offshore by drainage winds enhanced by weak offshore pressure gradients. The low clouds and fog could move onto the beaches late this morning as a weak sea breeze develops. Otherwise, skies are clear under the extensive dome of high pressure now centered over southwestern AZ.
Today will be another day of record-setting temperatures with daytime highs in the 90s to low triple digits in the inland valleys, the 70s to low 90s in the coastal areas, the mid 90s in the upper deserts and near 110 in the low deserts. The mountains below 6000 ft will see temperatures in the 80s.
Temperatures begin to trend downward on Saturday as the upper level high weakens and gets displaced southeast while onshore flow strengthens. The temperature change will be most noticeable in the coastal areas a the onshore flow spreads cooler marine air, with low clouds and fog, a little farther inland. However, daytime temperatures will still be 10-25 degrees above seasonal averages.
Sunday will likely be cooler still as the ridge is replaced by weak troughing over SoCal and the onshore flow continues. Temperatures in the coastal areas will likely be in the 70s while the inland valleys will be in the 80s to low 90s. The lower deserts will be in the low triple digits and the high deserts will be in the low 90s. These temperatures are still 9-20 degrees above seasonal averages. Marine layer influence will likely spread even farther inland.
The ridge rebuilds over the western states for next Monday through Thursday, with a corresponding upward trend in temperatures. Current solutions indicate the ridge won't be as strong as it's been the last few days but we can expect several more days of unseasonably high temperatures.
A percentage of model solutions show the ridge weakening again next Friday, with stronger onshore flow combining to bring us some relief from the heat.
201100z, SKC across the area currently except for patchy FG lingering just offshore. FG may intermittently creep into coastal areas this morning. 30% chance for vis less than 1SM at KSAN and less than 20% at KCRQ, KSNA. Clearing 15Z-17Z. Similar story for Friday evening and overnight with patchy FG expected to intermittently reduce vis for coastal areas starting 03-06Z. Everywhere else, VFR conditions expected through the TAF period.
Very patchy fog over nearshore waters will continue to locally reduce vis to near 1 nautical mile through mid morning. There is greater confidence for areas of fog Friday evening and overnight with highest chances hear the coastline once again. Otherwise, no hazardous marine conditions are expected through Tuesday.
Ca, 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.
Extreme Heat Warning until 8 PM PDT Saturday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
