DISCUSSION
FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

Temperatures this afternoon are running warmer than yesterday afternoon for most places away from the coast. The most noticeable rise has been in the Inland Empire where temperatures are 7 to 15 degrees warmer than yesterday afternoon. Another noticeable change from yesterday is in the low deserts where the shallow moisture surge does not seem to be hindering the temperature rise. Most spots in the northern Coachella Valley are already above 115 degrees as of 130 PM.

The heat for areas west of the mountains is expected to peak today, with a few degrees of cooling for most areas west of the mountains.
Even with that cooling, highs on Saturday will be 3 to 7 degrees above average for the coast and inland Orange County and 7 to 14 degrees above average for the valleys and mountains. Widespread moderate to major HeatRisk is expected west of the mountains but away from the coast through Saturday. Temperatures on Sunday are expected to "cool" an additional few degrees in the valleys and mountains. Moderate to locally major HeatRisk is still expected Sunday in the Inland Empire and in the mountains, with areas of moderate HeatRisk through Monday for most valley locations.
Temperatures for areas west of the mountains are expected to increase again Tuesday into the latter half of next week, with more widespread moderate to locally major HeatRisk.

The heat in the deserts will be persistent with highs on Saturday 12 to 15 degrees above average for the High Desert and 6 to 13 degrees above average for the low deserts. HeatRisk in the deserts is expected to stay major to extreme through the weekend and into much of next week. Local high resolution guidance continues to show shallow moisture surges making it into at least the southern portions of the Coachella Valley each morning. How much the moisture retreats for the afternoon heating of the day will greatly impact how high the thermometer goes. High resolution guidance is indicating a minor moisture surge Saturday with a more substantial surge Sunday. Global ensemble guidance is indicating that the atmosphere will dry out early next week, and without the moisture present temperatures could reach near record breaking levels in the lower deserts.

For the middle to end of next week, the position of the ridge of high pressure is still uncertain. If the ridge pushes further east, the southerly flow over Southern California will bring more moisture and a better chance for monsoon storms. Current forecast follows NBM with 10-12 percent chance of showers Thursday and Friday afternoon and evening. If monsoon moisture does in fact make it into the area, that will keep highs in the desert and mountains tapered down but will bring the potential for more heating west of the mountains.

AVIATION
052000Z
Coast
Low clouds lingering along beaches this afternoon, but otherwise clear skies. More low clouds redevelop and move inland again this evening 01-05Z, with bases 800-1200 ft MSL. Cigs may scatter out briefly overnight 04-09Z but return to BKN-OVC following that as the marine layer surges back inland. Clearing to the coast expected 16-20Z.

Otherwise, mostly clear skies with unrestricted VIS through tonight, and seasonable afternoon/evening winds winds. SCT cumulus at 10,000 ft MSL over the mountain ridges which will dissipate by sunset.

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

Excessive Heat Warning until 9 PM PDT Sunday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Mountains.

Excessive Heat Warning until 9 PM PDT Saturday for San Diego County Valleys.

Heat Advisory until 9 PM PDT Saturday for Orange County Inland Areas-Santa Ana Mountains and Foothills.

Excessive Heat Warning until 9 PM PDT Wednesday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning.

PZ...None.