Slight chance of showers and thunderstorms over the mountains and high desert this afternoon. High pressure will begin to expand across the area through the upcoming week. This will lead to a warming trend over the next few days with temperatures remaining slightly above normal thereafter. This will also lead to a drier weather pattern with a shallower marine layer closer to the coast each night and morning.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
A trough is draped across the State, leading to temperatures slightly below normal today. This pattern of greater onshore flow and cooler weather also allowed for a deeper marine layer that covered inland valleys of Orange and San Diego Counties earlier this morning. We'll give the monsoon another try later this afternoon as some mid-level moisture is seen from this morning's sounding. Cumulus building over the mountain ridges into the high desert may be able to produce a few showers or weak thunderstorms, accompanied by locally gusty winds.
High pressure off to the east will slowly expand across the region by Sunday into the middle of next week. This will bring a drying trend on Sunday, with chances for any showers across the mountains near 10 percent or less. Temperatures for Sunday will be very similar to those of today. Models continue to show high pressure expanding and strengthening over our area by Monday to around Wednesday or Thursday of next week. Temperatures will increase 2-4 degrees each day away from the coastal regions, where moderate to locally major heat risk is possible for inland valleys and desert regions. The strengthening weather system will also push the marine layer down further, limiting the marine layer to cover areas near the coast each night and morning.
Model ensembles show fair agreement on the high pressure system sticking around the Desert Southwest into the latter half of next week. The elongated form of the high will eventually become amplified over the region later in the week. How much amplification and exact location of the high is still to be determined. Depending on it's position, it may be able to entrain some monsoonal moisture back into our region as early as Thursday, possibly lingering into next weekend, which would trigger showers/storms for the mountains and deserts.
152330z. Coast/Valleys, Very patchy low clouds are starting to develop over nearshore waters this afternoon. Low clouds will expand and slowly push into coastal San Diego County starting 01-03z. Clouds slowly push inland and northward into Orange County overnight, reaching up to 20 miles inland by 12z. Bases will be slightly lower than last night, around 1500-2000 ft MSL. Clouds may briefly push into the western Inland Empire 13-16z, with a 40-50% chance for cigs at KONT. Minor vis reductions (3-5SM) possible for elevated inland valleys (KONT, KRNM). Clouds clear toward the coastline 15-18z Sun with VFR conditions expected for Sunday afternoon.
Mountains/Deserts, VFR conditions prevail through the TAF period. SCT-BKN cu AOA 10,000ft MSL expected this afternoon with a slight chance (10-20%) for TSRA over the Riverside County mountains and in the high deserts.
Gusty northwest winds 20-23 knots near San Clemente Island expected Sunday and Monday afternoon. Otherwise, no hazardous marine conditions are expected through Thursday.
Ca, None. PZ, None.
