06/410 AM.
Tropical Cyclone Marie, which will remain well offshore of SoCal, will bring impacts to the region through at least early next week. Rain is favored early Sunday morning into the evening, focused over Los Angeles and portions of Ventura Counties. A significant southerly swell will create hazardous surf conditions at some coasts.
(tdy-Tue), 06/408 AM.
Ahead of jumping into unseasonably unsettled weather for many areas, we want to continue to emphasize the ongoing large and potentially deadly surf and rip currents focused across south and southwest facing beaches with minor flooding also possible at the coast. If entering the ocean, we recommend swimming near a life guard. This threat continues through at least Tuesday, please see associated coastal hazards for details.
Still squarely in our climatologically dry season, we will likely see anything but that today, especially Los Angeles and eastern Ventura County. Hurricane Marie was 770 miles south southwest of Los Angeles continue on a steady northwest track. Marie will remain well offshore while continuing to weaken over the next several days, although it is partially responsible for the unseasonably wet conditions today and potentially into times next week.
Showers were already expanding in coverage across far southern California with expanding and cooling cloud tops indicative of organizing showers offshore to our south. With the unsettled weather now on our doorstop we have increasing confidence of widespread rainfall covering at least much of Los Angeles and Ventura Counties. Rain will likely start early to mid morning across many of these areas with increased likelihood of embedded moderate to heavy showers and isolated thunderstorms (5-15 percent chance) with a 5-10 percent chance of excessive rainfall leading to minor flooding in steep terrain (especially near recent burn scars) and in urban areas. Ingredients that give us moderate confidence in this scenario include Mid- level lapse rates increasing to modest values of 6 deg C/km with a very strong (for this time of year) and favorable portion of a jet streak will combined a tropical airmass (with near record precipitable water values near 2 inches) that we are unaccustomed to in Southwest California.
Rain totals of a tenth to third of an inch will be common where most consistent banding of showers and isolated thunderstorms occur, which is still looking likely in Los Angeles into eastern Ventura County. Isolated totals in excess of 0.5-1 inch is possible especially coastal foothills or where training of heavier showers occurs. There is a 5-10 percent chance of rainfall rates of 0.25-0.5 inches per hour (much of which could fall in about 30 minutes), which would cause some flooding issues, especially sensitive areas. In addition to minor roadway flooding concerns, roads could become slick and dangerous due to the buildup of oil after many dry months.
A weak impulse acting on lingering low level moisture may instigate isolated to scattered additional showers this evening or even early overnight. Otherwise clearing is expected and areas with decent rain could see patchy dense fog develop by early Monday morning. A boundary lifting back north later Monday and especially into Tuesday may support another round of light to moderate showers just about anywhere. Cannot rule out an isolated thunderstorm focused across interior mountains.
Heat impacts will continue to be on the increase through Monday or Tuesday with moderate heat risk likely in some areas due to added humidity elevated overnight low temperatures and daytime highs also increasing where we get decent daytime sunshine.
(Wed-Sat), 06/411 AM.
Moderate confidence that we will see a warming trend into Wednesday with moderate to high heat impacts possible Wednesday into Thursday or Friday with increasing potential of at least some heat products in this window. The position of the ridge by Thursday may be favorable for monsoon moisture or injection of tropical moisture from the south. So it will likely be quite humid with weak morning offshore flow potentially delaying the sea breeze, potentially bringing dangerous heat impacts close to coast. This type of pattern could support isolated showers or thunderstorms focused across the interior.
Below normal confidence Friday into next weekend as the ridge may break down pretty quickly or be somewhat stubborn. Either way it does look somewhat likely that troughing off the coast may reestablish at times, keeping the door open for additional tropical or monsoon moisture to shuttle into southwest California.
06/0704z.
At 06Z at KLAX, the marine layer was 600 feet deep. The top of an inversion was 800 feet with a temperature of 25 deg C.
High confidence in VFR conds KSBA and north with a 10-20 percent chance of IFR/LIFR cigs/vsbys for KSMX through 16Z.
Moderate confidence in rain timing and coverage elsewhere although vis in particular could dip to near 2sm in any brief heavier showers. There is also a 5-15 percent chance of a thunderstorm in all TAFs that have shra with the best potential between 18Z-00Z.
Deep tropical moisture could support low clouds at just about any level, especially in or following brief heavier showers, although VFR to MVFR cigs should prevail.
KLAX, Moderate confidence in TAF. Rain timing may be off by 2 hours with MVFR to occasionally IFR vis and mainly VFR to MVFR cigs in any heavier showers. East wind component of 3-6 kts possible near the onset of rain around 12Z through 18-20Z with a 10 percent chance of briefly reaching 8 kts.
KBUR, Moderate confidence in TAF. Rain timing may be off by 2 hours with MVFR to occasionally IFR vis and mainly VFR to MVFR cigs in any heavier showers.
06/1204 AM.
For the Outer Waters, moderate to high confidence in current forecast. This afternoon through Monday, there is a 60-80% chance of SCA level winds. For Tuesday and Wednesday, high confidence in winds and seas remaining below SCA levels. On Thursday, there is a 30-50% chance of SCA level winds.
For the Inner Waters north of Point Sal, high confidence in winds and seas remaining below SCA levels through Thursday.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Through Wednesday, high confidence in winds and seas remaining below SCA levels. On Thursday, there is a 30-50% chance of SCA level winds across western sections.
Tropical moisture will stream over the area Sunday through Tuesday, bringing the threat of showers to the coastal waters. There is a 15% chance of thunderstorms Sunday afternoon for the waters south of the Channel Islands. A large southeast to south swell will also impact the area, causing increased currents and surges in the vulnerable harbors.
05/809 PM.
Significant coastal impacts are expected across Southern California beaches this Labor Day weekend. A large southeast to south swell from Hurricane Marie will move into the coastal waters this weekend with swell heights of 5-7 feet and a period around 13 seconds.
High surf conditions are expected on south-facing beaches of Ventura and Los Angeles counties, peaking at 5-8 feet with local sets to 10 feet through Monday. The Santa Barbara South Coast will be largely protected from this swell, but there are some small windows of southeasterly and southwesterly energy that could cause boosts in the waves. HIGH SURF ADVISORIES remain in place for Los Angeles and Ventura Counties, with BEACH HAZARDS STATEMENTS (a step below high surf advisories) in effect for Santa Barbara and San Luis Obispo Counties.
High tides will also be increasing through early next week. Due to a variety of reasons, the actual observed tides have been running about 6 inches above predictions for sometime now. The south swell will likely boost that enhancement. As a result, high tides should exceed 7 feet by Monday. Adding large tides with the south swell will result in a moderate risk for coastal flooding over the vulnerable south-facing shores. Areas of most concern include Avalon, Long Beach (Alamitos Peninsula), and Oxnard to Malibu (including Point Mugu). COASTAL FLOOD ADVISORIES remain in effect for Los Angeles and Ventura Counties where the best combination of tides and waves will occur, but Santa Barbara and San Luis Obispo Counties could also see some isolated issues.
Ca, Coastal Flood Advisory in effect until 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect until 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect through Tuesday evening for zones 340-346-349-350. (See LAXCFWLOX). PZ, Small Craft Advisory in effect from 3 PM this afternoon to 9 AM PDT Monday for zones 670-673-676. (See LAXMWWLOX).
