High pressure remains over the region, bringing a prolonged period of hot weather, most notable west of the mountains. Breezy Santa Ana winds will continue through Monday; highest winds will be near the coastal-facing mountain slopes with an elevated fire weather risk. Confidence is increasing that cooler weather enters the picture by the end of the week, but details in how cool we become and if any wet weather arrives is still uncertain.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Weaker Santa Ana winds have been observed this morning, mainly below 35 MPH. This pattern has contributed to very hot temperatures this morning for areas west of the mountains. Valley and coastal locations are close to 95-100 degrees. Subtle increases in onshore flow and a weakening of the high pressure system overhead will allow increased onshore flow closer to the coast, bringing a few degrees of cooling each day. By Wednesday, confidence starts to increase to see highs below 100 degrees for the valleys and coastal areas of Orange and San Diego Counties. 850mb temperatures increase by Wednesday and Thursday with a thermal ridge poking into the Desert Southwest, leading to an increase in temperatures over the mountains and deserts a few degrees from what we have seen this weekend. Nights will still remain warm for many areas in the lower to mid 70s for the lower deserts and places west of the mountains. Please make sure to be in areas of A/C and check on those without effective cooling.
Models begin to diverge on our next story starting Friday into next weekend. Cluster analysis starts to break down the ridge on Friday, leading to greater onshore flow and cooling for places from the foothills to the coast. Highs for coastal areas and valleys will lower mainly into the 80s and 90s by this time with a better chance to see lows below 70 degrees.
As the ridge weakens, a trough is expected to enter the PacNW around Friday or Saturday. Model guidance is continuing to struggle on where exactly this weather system progresses and how amplified it becomes. A deeper trough across California would lead to more significant cooling next weekend with some model ensembles showing light amounts of precipitation around Sunday or the following Monday (October 12th). Others show the trough staying further north, which would still bring cooler weather, but keep us on the drier side. Would not be surprised to see a sort of mesh between these depictions to the forecast in the coming days, where cooler weather arrives but dry conditions continue.
041730z, Coast/western valleys: SKC and VFR through the period. There is a 20-40% chance E/SE winds gusting 10-20 kts could reach parts of the coast this morning through 19z Sun, including at KSAN and KCRQ (highest chance at KCRQ). Winds turn onshore W/NW by late morning.
Inland Valleys/Foothills/Mountains: E/SE winds increase and expand westward to valleys this morning, peaking through 20z with gusts to 15-35 kts. MOD UDDFS expected over coastal slopes. Winds gradually turn westerly this afternoon through the valleys as the sea breeze moves inland. Winds will weaken and return to being light and offshore (easterly) after 03z Mon.
Otherwise, Clear skies through the TAF period.
No hazardous marine conditions are expected through Thursday.
Ca, Extreme Heat Warning until 8 PM PDT Thursday for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.
Beach Hazards Statement from Tuesday afternoon through Friday evening for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
