09/317 AM.
Tropical Cyclone Priscilla may send showers and thunderstorms into Los Angeles County today into early Friday, along with elevated humidity. Dry and seasonable weather is expected over the weekend, followed by chances of rain early next week as a storm system drops into the region.
(tdy-Sat), 09/343 AM.
Mositure from Tropical Cyclone Priscilla will reach the region today, resulting in elevated humidity and a chance of showers and thunderstorms focused across Los Angeles County, today into early Friday. The majority of weather activity over the Continental US due to Priscilla will be the the south and east of the region, as LA County is on the far western periphery of impacts. Showers and thunderstorms will become possible late this morning, focused over the eastern portion of LA County and the coastal waters off the coast of Orange County. Limited and elevated moisture initially, will make measurable rain difficult early today, and thus the greatest risk may be dry lighting and fire starts. This afternoon and evening, chances of showers and thunderstorms will increase, focused over the eastern San Gabriel Mountains. Tonight into early Friday, there is a slight chance of shower and thunderstorms across the majority of LA County and skimming the Ventura County line.
Rainfall totals are expected to generally be light if any (under 0.25 inches), with just a remote risk (< 5% chance) of any flash flooding or burn scar debris flows. The highest totals and risk of flooding will be for the eastern San Gabriel mountains, due to the higher elevation, thus anyone near the Bridge scar is advised to pay close attention to weather conditions. Overall however, most locations across LA County will see little to no rain through Friday.
For Ventura, Santa Barbara, and San Luis Obispo Counties, mostly benign weather is expected, with minimal marine layer stratus and temperature near or below normal. This weekend, cloud coverage may trend upwards, especially during the overnight to morning hours. Additionally, gusty north-northwest winds are expected along Central Coast, Southwest Santa Barbara County, the I-5 corridor, and the Antelope Valley, late Friday through Saturday night, with Wind Advisories possible on Saturday.
(Sun-Wed), 09/315 AM.
A low pressure storm system will drop down from western Canada and slide down just off the California coastline on Monday, then cutting across the state late Tuesday. The exact trajectory of the low will determine the rainfall totals. Some ensemble members favor a more westward trajectory of the low over the coastal waters, which would allow for greater moisture in the storm system and higher rainfall totals over the SoCal region. Confidence in some amount of rainfall with this storm is trending upwards with the latest model runs. There is now around a 70-80% chance of seeing rain across the entire region, however the highest chance for rain is still for San Luis Obispo and Santa Barbara Counties.
The bulk of the rain is likely to fall Monday night through Tuesday, with lingering rain chances through Wednesday. There is low confidence in exact rain totals, however there is the potential for storm total rain as high as 1.5-3 inches for San Luis Obispo and Santa Barbara Counties, and 0.5-1.5 inches for LA and Ventura Counties. Southwesterly flow may result in some terrain driven enhances of rain totals for mountain ranges, especially for the west or south- facing slopes. Alternatively, if the center of the low travels mostly over land opposed to the coastal waters, rainfall totals may end up largely under 0.5 inches across the region.
Strong onshore winds and low 500 mb heights will combine with possible rainfall and cloud cover, to yield a period of well below normal temperatures and unsettled conditions, Monday through at least Wednesday.
09/1019z.
Around 0730Z, the marine layer depth was around 2000 feet deep at KLAX. The top of the marine inversion was near 3700 feet with a temperature near 18 degrees Celsius. There was another inversion above up to 5000 feet.
Low to moderate confidnece in the current forecast for coastal terminals and terminals north of Point Conception. High confidence in the current forecast for Los Angeles County valley and desert terminals.
There is a low-to-moderate chance of MVFR conditions through 18Z this morning. The highest chances will be for terminals north of Point Conception. There is a slight chance of thunderstorms this afternoon and tonight at Los Angeles County terminals. After 03Z Friday, there is a low- to- moderate chance of LIFR to IFR conditions, highest for terminals north of Point Conception.
KLAX, There is a 20 percent chance of MVFR conditions through 16Z. Otherwise, VFR conditions are expected through the period. There is a 20 percent chance of a thunderstorm this afternoon and evening. There is a 10 percent chance IFR conditions after 10Z Friday. Any east winds are likely to remain less than 7 knots, but there is a less than 5 percent chance of significant easterly winds due to storm outflow should thunderstorms develop east of the terminal.
KBUR, VFR conditions are expected through the period. There is a 20 percent chance of a thunderstorm this afternoon and evening. No wind impacts are expected at this time, but there is a less than 5 percent chance of a significant wind impact due to storm outflow.
09/250 AM.
For the waters southwest through northwest of the Channel Islands and the nearshore waters along the Central Coast, conditions will very likely remain below Small Craft Advisory (SCA) levels through early Friday morning. Local gusts near SCA levels are possible south of Point Conception this evening. There is an increasing chance of SCA level winds on Friday with an imminent (80-100 percent) chance of SCA conditions by Friday afternoon and lingering through at least early Tuesday. There is a high-to- likely (50-70 percent) chance of GALES Friday evening through Saturday evening, highest from the waters near Point Conception south to San Nicolas Island. At least, widespread SCA conditions are to be expected between Friday evening and Saturday evening. Inexperienced boaters should seek or remain in safe harbor during this period.
Inside the southern California bight, conditions should generally remain below SCA criteria through Friday afternoon. Local SCA gusts with choppy seas are possible near Point Dume and across the San Pedro Channel this evening. There is a high-to-likely (50-70 percent) chance for SCA level winds Friday and Saturday, with highest chances across the western portion of the Santa Barbara Channel. There is low-to-moderate (20-40 percent) chance of GALES on Saturday afternoon and evening with a high (50 percent) chance of short-period hazardous seas developing across the Santa Barbara Channel.
Moisture associated with rapidly weakening Tropical Cyclone Priscilla off the Baja California coast will move north through today through Friday and bring a slight (10-20 percent) chance of showers and thunderstorms for the southern coastal waters, highest from south of Dana Point into the San Pedro Channel adjacent to Los Angeles and Orange Counties this afternoon through early Friday morning. Any thunderstorm that forms will be capable of producing locally gale force winds and rough seas, dangerous lightning, and heavy rainfall with reduced visibility, and even a waterspout.
Ca, NONE. PZ, Small Craft Advisory in effect from 9 AM Friday to 9 AM PDT Saturday for zones 645-670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 AM to 9 PM PDT Friday for zones 673-676. (See LAXMWWLOX). Gale Watch in effect from Friday evening through late Saturday night for zones 673-676. (See LAXMWWLOX).
