No significant changes from the previous forecast. Model guidance for Integrated Water Vapor Transport (IVT) continues to highlight very early Wednesday morning into late Wednesday morning as the most impactful period, and rain rates may exceed 0.50"/hr at times. Given this is still 4-5 days out, timing will likely shift forwards or backwards, possibly by 12+ hrs, so it's important to follow the forecast closely as things change in the coming days. Regardless, heavy and persistent rain can be expected from late Tuesday evening into Thursday afternoon, with additional chances for Friday and Saturday. If planning on traveling for the Christmas holiday, ensure you are aware of any Flood Watches or Flash Flood Warnings in effect, avoid driving at night in heavy rain, have emergency supplies in your car or bag, and find alternative routes if roads are covered with water (Turn Around, Don't Drown!). Those living in mountain communities where the heaviest rainfall is expected will be especially at risk, as dirt roads may be washed away. Follow all guidance from local emergency officials.
Dry weather with above average temperatures inland will continue through Monday. Periods of patchy fog along the coast and in the valleys each morning through Tuesday. An Atmospheric River will bring widespread heavy rain and mountain snow above 8000 ft late Tuesday into Thursday (Christmas Day). Gusty southerly winds during this same period expected for much of the area, including the mountains, marine waters, and coast. There may be additional showers late week into next weekend but chances are lower.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
.UPDATE, No significant changes from the previous forecast. Model guidance for Integrated Water Vapor Transport (IVT) continues to highlight very early Wednesday morning into late Wednesday morning as the most impactful period, and rain rates may exceed 0.50"/hr at times. Given this is still 4-5 days out, timing will likely shift forwards or backwards, possibly by 12+ hrs, so it's important to follow the forecast closely as things change in the coming days. Regardless, heavy and persistent rain can be expected from late Tuesday evening into Thursday afternoon, with additional chances for Friday and Saturday. If planning on traveling for the Christmas holiday, ensure you are aware of any Flood Watches or Flash Flood Warnings in effect, avoid driving at night in heavy rain, have emergency supplies in your car or bag, and find alternative routes if roads are covered with water (Turn Around, Don't Drown!). Those living in mountain communities where the heaviest rainfall is expected will be especially at risk, as dirt roads may be washed away. Follow all guidance from local emergency officials.
Dry weather continues through Tuesday morning. A low pressure system and associated Atmospheric River brings increasing chances for widespread heavy rainfall late Tuesday into Thursday. Timing for heaviest rainfall is currently Tuesday night into Wednesday morning.
Wednesday morning through Wednesday night for Lytle Creek on the coastal slopes of the eastern San Gabriel Mountains, the chance for 3 inches or more of rainfall is 92-95%, with a 70% chance for 5 inches or more and a 30-35% chance for 6 inches or more. For early Wednesday morning through Thursday night, the chance for 8 inches or more of rainfall at Lytle Creek is 50-60%.
Probabilities of rainfall totals of 2 inches or more Tuesday night through Thursday night:
- OC/Santa Ana Mountains/San Bernardino Mountains: 90% - Inland Empire: 75-90%, highest west - SD Co Mts/Coast/Valleys: 50-75% - Deserts: 15-25% (lower deserts), 50-70% (high desert)
Probabilities of rainfall totals of 3 inches ore more Tuesday through Thursday night:
- OC/Santa Ana Mountains/San Bernardino Mountains: 70-85% - Inland Empire: 50-60%, highest west - SD Co Mts/Coast/Valleys: 25-55% - Deserts: 5-15% (lower deserts), 25-30% chance (high desert)
Most of the precipitation across southwestern California through Christmas morning is expected to fall as rain with snow levels remaining above 8000 feet. Snow levels may drop closer to 6000-6500 feet Friday and further into Saturday, but exact levels and locations remains uncertain.
210340z, Coast/Western Valleys, Low clouds have begun their nightly infiltration into southern San Diego Co and will move northwards into Orange Co after 05Z, then inland to 15-20 miles overnight. Clouds very likely to make it to vcnty KONT, with a 60% chance for CIGs at the airport itself by 10Z. Currently based at 1300-1600 ft MSL, bases lower slightly overnight after 08Z to 800- 1300 ft MSL, bringing VIS restrictions 4-6 SM to coastal mesas/highlands. Clouds scatter back to coasts 17-19Z, then moving back onshore after 22/02Z with similar bases/inland extent to tonight.
Otherwise, SCT-BKN high clouds with unrestricted VIS tonight and Sunday.
No hazardous marine conditions through Tuesday morning. South winds will strengthen late Tuesday in advance of a Pacific storm. Strong winds and building seas are expected as a result, with seas near 8- 10 ft and wind gusts upward of 30-35 kts.
Ca, None. PZ, None.
