Warm conditions expected through the weekend. Moderate HeatRisk is expected across inland areas, with localized areas of Major HeatRisk in the low deserts over the weekend. The marine layer is expected to get shallower, staying confined to coastal areas and portions of the western valleys at times through much of this week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
High pressure aloft will build over the Pacific for the middle to end of the week. Through the forecast period the ridge axis is expected to stay to our west, but with California in it's periphery warming conditions can be expected. Above average high and low temperatures can be expected through the weekend. Areas of moderate HeatRisk are expected for the Inland Empire and the High Desert, with more localized areas of moderate HeatRisk in the far eastern San Diego county valleys and Inland Orange County. Widespread moderate with locally major HeatRisk expected in the low deserts on Saturday. Based on current forecast, high temperatures do not look record breaking but some low temperature records will be in jeopardy, especially for the mountains, coast, and valleys.
The position of the ridge could allow for some subtropical moisture to sneak into the southwestern United States by the end of the week. Ensemble members of both the GEFS and ECMWF show a notable increase in precipitable water into the low deserts Friday, with less but still elevated precipitable water Saturday and Sunday. The forecast looks to remain dry at this time so it looks like the main impact from this moisture surge would be tempering the highs across the deserts and an increase in high clouds. Current forecast for the low deserts is 108-112 degrees Friday and Saturday, but if the moisture surge materializes high temperatures would likely be lower than that.
There is some uncertainty with highs Sunday for the desert areas. Highs in the desert have the potential to be hotter on Sunday compared to Friday/Saturday if the moisture surge is significantly weaker. There is higher confidence that areas west of the mountains will cool a degree or two by Sunday. Conditions will cool a degree or so each day into early next week.
For much of this week the marine layer is expected to be on the shallower side, staying confined to coastal areas and western valleys at times. The marine layer may deepen slightly into early next week.
091800z, Coast/Valleys, Mostly clear skies expected this afternoon with patchy low clouds near 2000 ft MSL near VCTY KSAN at times. Low clouds expected to fill back into coastal areas after 03Z with coastal TAF sites impacted after 06Z Wed , slightly later in Orange County near 08-10Z with moderate confidence on timing. Higher confidence in cloud bases tonight slightly lower than this morning with most cigs near 1000-1500 ft MSL, locally lower. Vis 4-6 SM in BR over higher coastal terrain and parts of the Inland Empire.
Mountains/Deserts, VFR and SKC through Wednesday. S/W wind gusts near 25-40 kts at times 22Z Tue-06Z Wed, highest in the San Gorgonio Pass.
No hazardous marine conditions are expected through Saturday.
Elevated surf and rip current activity expected through Thursday afternoon. Surf peaks on Wednesday with surf 4-7 feet and sets up to 10 feet at south-facing beaches, then gradually diminishes late this week. See the Beach Hazards Statement for more details.
Ca, Beach Hazards Statement through Thursday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
