Much cooler through Thursday. Gusty south winds will develop across the San Bernardino mountains and deserts Tuesday afternoon, followed by light to moderate showers late Tuesday into Wednesday, mainly along and EST of the mountains. Slight chance of showers continues into Thursday. Dry conditions and a little warmer Friday and Saturday. Potential for more widespread precipitation, gusty winds, and a return to cooler conditions Sunday and Monday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Evening update, Widespread high clouds are moving over the region this evening ahead of an upper level trough off the California coast. Surface dew points have increased into the upper 50s and low 60s along the coast with a few sites reporting patchy low clouds. A coastal eddy is forecast to develop overnight, which will aid in low cloud formation. Patchy fog is possible as the marine layer first redevelops, with improving visibility overnight as the marine layer deepens and low clouds spread into the valleys.
Previous discussion, Dry conditions are expected through much of Tuesday. A few light pre- frontal showers may develop Tuesday evening but the main band of rainfall is still on track to move through Wednesday morning through mid-afternoon. Light to moderate rain is expected in the rain band, rainfall rates will mainly range from 0.10-0.20" per hour, with a 10 percent chance of localized rainfall rates up to 0.40" per hour. Latest guidance has a more defined surge of precipitable water moving into the area from the southwest which has resulted in the precipitation forecast to trend up for some locations. For San Diego county and Inland Empire, rainfall totals are still expected to be 0.25" or less. For Orange County and eastern San Gabriels the forecast has trended up with the potential for rainfall totals to be 0.30-0.50". The probability of exceeding 0.5" is 20 to 40 percent for Orange County and around 60 percent for the eastern San Gabriels. The rain band is expected to move quickly from northwest to southeast, with only isolated light showers in the wake of the frontal passage mid-Wednesday morning for Orange County and Wednesday afternoon for San Diego County.
Snow levels during the highest chance of precipitation are expected to be 6500-7000 ft. Latest forecast has 1-3" of snow from Tuesday night through Thursday, for most locations. Due to the increase in expected precipitation, portions of the eastern San Gabriels are now expected to exceed 3 inches of snow, but those higher accumulations will be above 7000 feet. Additionally, gusty southwest to west winds are expected in the mountains and deserts. Winds will begin to increase Tuesday afternoon, peak Wednesday morning and diminish into Wednesday afternoon. Strongest winds are likely to occur on the desert mountain slopes and below passes Tuesday afternoon into Wednesday. Current forecast has peak wind gusts of 40 to 60 mph.
Lingering light rain is possible on Thursday as the long-wave trough progresses eastward. Any additional showers will be fairly isolated and mainly confined to the coastal mountain slopes. Nbm probabilities for rainfall totals exceeding 0.10" from Thursday morning into Friday morning are 10-20 percent for the coast and valleys and 20-40 percent for the coastal mountain slopes.
Weak transitory ridging follows the upper trough for Friday afternoon into Saturday, bringing a brief period of dry and slightly warmer weather. A more robust trough dropping out of the Gulf of Alaska will bring additional chances of precipitation and gusty winds beginning as early as Saturday evening. Wet and cool weather looks like it will continue through the middle of next week with the potential for much higher rain and snow amounts.
100500z. Coasts/Valleys, A shield of high clouds AOA 20 kft remains over Southern California this evening. Areas of low clouds based 500-1000 ft MSL over coastal waters have begun into coastal San Diego County. Clouds will slowly fill into most coastal areas up to 10-15 miles inland and rise above 1000 ft MSL by 12Z. Coastal areas should remain shrouded under low clouds as bases rise to 2000- 3000 ft MSL through the early afternoon. Low clouds may fluctuate between SCT and BKN through tomorrow afternoon as bases continue to rise to well above 3000 ft by evening. Low cloud cover will slowly fill into the entire coastal basin starting Tuesday evening into the overnight. A band of RA will move in from the west starting around 06Z Wed.
Deserts/Mountains, Mostly VFR conditions expected through the period with BKN high clouds AOA 20 kft. Winds pick up starting 21Z Tue - 00Z Wed along the northern slopes of the San Bernardino County mtns and into the High Desert. Winds gusting 35-45 kts with isolated gusts to 55 kts along wind prone mountain slopes and passes.
No hazardous marine conditions are expected today through Friday, however, there will be borderline marginal Small Craft Advisory conditions possible for portions of the inner waters of the SoCal Bight between 06Z and 18Z on the 11th (Wednesday).
Ca, Wind Advisory from 1 PM Tuesday to 1 PM PST Wednesday for Apple and Lucerne Valleys-San Bernardino County Mountains.
PZ, None.
