High pressure remains over the region, bringing a prolonged period of hot weather, most notable west of the mountains. Elevated fire weather risk continues through today with light Santa Ana winds easing throughout the day. An area of low pressure will move over the western part of the country by the end of the week. This will bring cooler weather and a deeper marine layer to our region, with low confidence on the weather system giving us any wet weather.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Another hot day is in store as high pressure remains over the Southwest. Valley and coastal locations soaring into the 90s again this morning as weak offshore winds hold across the area. Models show better onshore flow (west winds) closer to the coast and far western valleys over the next couple of days. Still thinking temperatures from today into Tuesday will be relatively similar. A subtle increase in temperatures will be seen at the coast as a thermal ridge expands northward Wednesday into Thursday. This will mainly be felt across the mountains and the deserts with highs increasing 3-5 degrees from where they are today. Low temperatures will still remain warm over the region with many places staying into the 70s overnight in the lower deserts and west of the mountains. Light offshore flow at night will be the main driver of low temperatures. Wind-sheltered valleys will lower into the 60s in some areas, while communities that see wind the whole night will stay in the mid 70s to near 80. Please continue to practice heat safety by finding places with A/C and checking on friends and family. The marine layer will also subtly build on Wednesday into Thursday, but confidence is lower on when low clouds and fog reach coastal areas. Forecast now shows fog possibly moving along the coast by Wednesday morning. Chances for low clouds and fog will increase Thursday into Friday, and most definitely by the weekend for much of the coastal basin.
Models are starting to come into better agreement on when a trough of low pressure enters the Pacific Northwest, sometime later on Friday into early Saturday. This system will help weaken the high pressure system over area. Height falls will lead to greater onshore flow and cooling. Highs from Thursday to Friday will drop another 1- 4 degrees, with the greater cooling occurring from Friday to Saturday with highs lowering another 5-10 degrees. Friday will see highs closer to 100 degrees for the lower deserts and inland coastal valleys, with 80s more common near the coast. Models start to diverge once again on where this trough will go and how far south it plunges across the western U.S. For now, another significant temperature drop is in the forecast from Saturday to Sunday with highs lowering another 5-10 degrees. On Sunday, there's around a 50- 50 chance of temperatures staying below 80 degrees for the valleys west of the mountains as well as the large cities of the high desert.
The path of the weather system will determine how cool we become and if we are able to see any precipitation along and west of the mountains. Global models continue to show large discrepancies on how this feature evolves. Taking a look at model ensembles, ECMWF brings a wetter pattern with about 3/4 of the guidance showing light precipitation while the GFS ensembles show a dry pattern with about 1/4 of ensembles showing light precipitation Sunday through possibly next Tuesday. Low confidence remains on any precipitation across the region, but confidence is much higher in seeing cooler and breezier weather, along with low clouds each morning west of the mountains.
051730z, SKC and VFR today and tonight. Local easterly breezes through 20Z gusting to 25 knots in foothills and eastern valleys. MOD UDDFS expected over coastal slopes.
No hazardous marine conditions are expected through Friday.
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.
