High temperatures inland areas will remain around 15 to 20 degrees above average with some record daily temperatures for heat continuing to be tied or broken, mainly for the mountains and deserts but occasionally for the inland valleys as well. Night and morning coastal low clouds spreading into the far western valleys at times. Cooling will spread inland early next week, but with high temperatures for next Tuesday still around 5 to 10 degrees above average.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Another day, another set of daily high temperature records broken at Big Bear, Idyllwild, Palomar, and Campo. Marine layer low clouds have returned to the coastal areas this evening with clear skies elsewhere. The marine layer depth on the 00Z KNKX sounding is roughly the same as 00Z yesterday, so expect similar inland extent of low clouds tonight into Wednesday morning. A weak upper level low currently around 325 mi southwest of San Diego will lift north around the west side of the upper ridge and into So Cal tonight into Wednesday. This will mainly generate stronger onshore winds across the mountains and deserts Wednesday afternoon and evening. Gusts will be around 30-40 mph in the usual wind- prone passes and desert mountain slopes. Otherwise another warm and potentially daily high temperature record breaking day is in store with highs 15-20 degrees above normal inland and 5-10 degrees above normal near the coast.
Upper level high pressure will remain over the region for Thursday through the weekend. High temperatures will climb a couple degrees each day through Friday as onshore flow weakens and the marine layer becomes more shallow, with widespread high temperatures close to 20 degrees above normal away from the coastal areas and western valleys. By Friday, marine layer clouds become patchier and confined to the coastal areas.
Minor cooling begins over the weekend as weak troughing starts to develop along the west coast. There remains uncertainty in the position and amplitude of the trough early next week. For Sunday, around 51% of the global ensemble members have a deeper trough further west, maintaining warmer weather here, another 23% have the the trough much further west, also resulting in warm weather continuing. Around 26% have weak troughing and the ridge breaking down/shifting east faster, allowing for a little more cooling. Current temp forecast leans towards the warmth and well above normal temperatures hanging on. There is higher confidence early next week with the trough progressing westward into the West Coast. More ensemble members are now showing precipitation towards the middle of next week, though ensemble mean precipitation from the GEFS, EC, and their AI counterparts are generally less than 0.50" and skewed by a a couple very wet members. Nbm probabilities of 0.25" or greater for Tue-Thu morning range from around 25-35% for the mountains westward.
250430z, Low clouds based 900-1400 ft MSL are moving onshore from the coast, filling into inland valleys by 06-08z. With cigs, BR/FG to reduce vis 0-3SM mainly in eastern inland valleys (i.e. KRNM) and inland foothills, vis 3-6SM in BR along I-15 corridor (in SD co.) and 5-6SM in BR/HZ at times for coastal sites. Before sunrise, 12- 14z, bases lower to 500-1000 ft, reducing vis to 0-3SM along I-15 corridor and 4-6SM at the coast until bases rise again and clouds scatter out 16-18z Wed morning. Low clouds with similar bases are expected to develop at the coast 02-05 Thu.
Elsewhere, mostly clear and VFR conditions will prevail through Wednesday afternoon.
No hazardous marine conditions expected through Saturday.
Ca, None. PZ, None.
