Slight chance of showers over the San Bernardino Mountains this afternoon. Upper level high pressure will slowly build in from the east this week, bringing gradual warming, a shallower marine layer, and dry weather. Shower and thunderstorm chances return for the mountains Thursday through Saturday with subtle cooling as the upper high shifts east.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
Current temperatures are running a few degrees warmer than yesterday inland, though still generally near or slightly below average for this time of year. High based cumulus have developed over the mountain ridges, but are struggling to develop into deep vertical clouds at this time. A similar inversion at 15,000 feet was observed in yesterdays sounding and cells were able to develop later in the afternoon despite this. A shower or thunderstorm can thus not be ruled out this afternoon locally over the highest peaks of the San Bernardino County and Riverside County mountains. The marine layer is about 3000 feet deep as of this morning and is expected to become slightly shallower into the middle of the week. Patchy fog expected during the nighttime hours in inland valley spots where clouds intersect terrain.
The broad center of the 500mb ridge drifts into the Desert Southwest this week, increasing temperatures a few degrees per day through mid- week. High temperatures for inland areas likely peak Thursday (90s to low 100s), with similar temperatures lingering through at least the weekend. Through the forecast period, lower desert temperatures largely appear unaffected by the ebb and flow of the ridge, with highs consistently 108-111F throughout the week.
As the center of the ridge migrates toward the Four Corners region, southeasterly flow will bring increasing mid-level moisture and shower/t-storm chances for the mountains through Saturday. Beyond Saturday, model clusters diverge into two general solutions: a ridge over the Northwest, which would keep the warmer than average temperatures around, and a ridge over the Central US, which could return temperatures back to near average.
170000z. Coast/Valleys, Aside from a few intermittent patches of clouds near central coastal San Diego County, clear skies prevails into the evening hours. Low clouds are expected to begin to redevelop and push ashore after 03z Monday, with CIGs filling in across San Diego County between 05-07z, eventually spreading inland and northward into Orange County by 09-12z. Low clouds clearing back to the coast around 15-17z Monday morning.
Mountains/Deserts, VFR conditions prevail through the TAF period. SCT-BKN cu AOA 10,000ft MSL over the desert slopes and High Desert this afternoon will dissipate by 03z.
Gusty northwest winds 20-23 knots near San Clemente Island expected Monday afternoon. Otherwise, no hazardous marine conditions are expected through Thursday.
Ca, None. PZ, None.
