Above average temperatures will prevail through the remainder of the forecast period. Warmest conditions will be Sunday through Tuesay with areas of moderate HeatRisk expected in the valleys and High Desert and major HeatRisk in the low deserts. The marine layer and weak onshore flow will keep coastal areas cooler.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Coastal low clouds are making a morning surge today with visible satellite at 7 AM showing clouds moving from south to north up the coast. Clouds should clear inland areas by noon today. Areas of low clouds may linger along the immediate coast into this afternoon. Highs today are expected to be a few degrees warmer than yesterday along the coast and 7 to 11 degrees warmer than yesterday for inland locations.
An upper level ridge of high pressure will expand over California and strengthen early next week. This will bring temperatures 15 to 20 degrees above average for the far inland valleys, mountains, and deserts. Current forecast has moderate to major HeatRisk in the low desert, with minor to moderate in the valleys and High Desert Sunday through Tuesday. Ensemble guidance from the ECMWF and GEFS are more inline with the NBM on the latest runs, although the deterministic NBM guidance is running closer to the maximum values of the EC and GEFS ensemble guidance especially for Monday. The geographical proximity of the deserts to the center of the high pressure increases confidence in the temperature forecast for that area. There still remains some uncertainty on how warm it will get west of the mountains as prevailing onshore flow will spread cooler coastal air inland with the afternoon sea breeze.
By Tuesday, most of the ensemble guidance indicates the ridge aloft will weaken or move east, which will bring a few degrees of cooling to the area. The upper level pattern becomes more uncertain for Wednesday, with some solutions maintaining weak ridging and others showing weak troughing. Current forecast has a few additional degrees of cooling between Tuesday and Wednesday. Areas of at least patchy night and morning low clouds and fog are expected to be present along the coast potentially into portions of the western valleys at times through the forecast period.
070930z, Coast, Low clouds 1000-1400 feet MSL with tops to 1800 feet will continue to expand and cover most coastal areas through 14Z. Scatter out by 17Z, though patches of low clouds could persist intermittently along some beaches. More widespread and cohesive low clouds 1000-1500 feet MSL will move ashore after 02Z and locally inland overnight. There's a 20% chance of reaching KONT by 13Z Friday. Vis reduced 3-5SM along inland extent of clouds.
Valleys/Mountains/Deserts, Mostly clear and VFR today and tonight, with only SCT clouds around 10000 feet MSL over mountains 18-00Z. Strong westerly winds with gusts 25-35 kts develop after 23Z through mountain gaps into deserts, continuing into early Friday.
No hazardous marine conditions are expected through Monday.
Ca, None. PZ, None.
