04/225 PM.
Tropical Cyclone Marie, which will remain well offshore of SoCal, will bring impacts to the region over the weekend into early next week. Rain is favored late Saturday and Sunday focused over Los Angeles and Ventura Counties. Increasing southerly swell will create hazardous surf conditions at the coasts.
(Fri-Mon), 04/703 PM.
***UPDATE***
A small-scale perturbation on the eastern peripheral of Hurricane Marie will move northward due to mainly the interaction of large- scale troughing situated along the west coast. This activity is expected to arrive later Saturday into Sunday. Widespread light rain showers with areas of heavier rainfall is likely especially under any thunderstorm (5-15% chc) that develops. The best chc for numerous rain showers is across LA county. Generally expecting rainfall amounts under 0.25" across LA/VTA counties. Cannot rule out rainfall totals of 0.50"-0.75" in a few local spots.
Interestingly enough, a few CAMs are indicating that a "dry-slot" may develop across Ventura county which could reduce rain shower coverage a bit. This does seem like a reasonable possibility due to the eastward location of the aforementioned perturbation, and the well-defined shortwave rounding the base of the trough on Sunday. Not perfect timing and moisture profiles are somewhat limited over eastern SB county, but this may result in a better chance for showers and thunderstorms across that area. But confidence is still pretty low as short term guidance is bouncing around trying to handle this feature. Thus, have not made any significant chances in POPs across VT and SB counties. Still want to emphasis that confidence is pretty good with current precipitation forecast across LA County.
Have reduced high temperatures about 5 degrees across LA county due to widespread showers and cloud cover. Good consenus across guidance that LA Basin will likely struggle to get out of the low 80s on Sunday.
***From Previous Discussion***
Hurricane Marie is currently 950 NM due south of Los Angeles, and is forecasted to travel in the northwest direction over the next several days. Marie will remain well offshore of the California Coast, but will still be able to send some weather impacts to SoCal. The most significant hazards from Marie will be seen across the beaches where very hazardous ocean swimming conditions are expected for the Labor Day holiday weekend. Potentially deadly rip currents and high surf is expected for south-facing beaches. Please consider swimming near a lifeguard and follow their guidance. Additionally, moderate coastal flooding and coastal erosion is expected for vulnerable south-facing beaches. See the beaches section below for details on the coastal hazards.
As for the weather conditions over land, expect increased cloud cover, elevated humidity and periods of light to moderate rain. Rain will be possible as early as late Saturday, becoming likely (50-70% chance) at least for Los Angeles County early Sunday morning into Sunday night, with lower chances to the north. Mositure from Marie will funnel into the area along the bottom of a broad upper level trough, and PWATs may approach 2 inches in portions of the region. Lapse rates aloft however limit some of the convective potential, so despite the extremely anomalous amount of moisture rain totals are likely to mostly 0.25 inches or less, except for local amounts of 0.50 to 0.75 inches possible in Los Angeles and Ventura County (especially foothills) and near thunderstorms or heavier showers. There is a 5-15% chance of thunderstorms on Sunday focused over Los Angeles County. One impact of note is that roads will be quite slick with any wetting rainfall due to the build up of oils over the last several months.
Temperatures will feel warmer over the weekend with the additional humidity but still remain within a few degrees of normal. Overnight lows could be quite warm and only into the 70s for our southern coasts and coastal valleys where the topical mositure will be the greatest. Monday temperatures will warm a few more degrees but humidity and rain chances will decrease.
(Tue-Fri), 04/232 PM.
In the long term, there is uncertainty in the upper level pattern, especially mid week onward. Tuesday, there is moderate confidence in 500 mb heights rising over the region, along with continued warming temperatures to a few degrees above normal at the coasts and coastal plains, and a few degrees below normal farther inland. By Wednesay, Southwest California may become sandwiched between a ridge to the southeast and a trough (that will have entrained moisture from the remnants of Marie) to the west. This will keep the door open for additional tropical moisture. The associated southwest flow aloft may bring unsettled weather, although timing, location, and potential impacts are uncertain that far out.
05/0108z.
At 2343Z at KLAX, the marine layer was 1500 feet deep. The top of the inversion was 3000 feet with a temperature of 22 deg Celsius.
High confidence in desert TAFs. Moderate confidence in remainder of TAFs. MVFR conds are possible at KPRB 12-17Z Sat. Cigs could return to KSBP and KSMX as early as 03Z Sat, and brief, intermittant MVFR conds are possible at KOXR, KCMA, KBUR, and KVNY 06-17Z Sat. There isa 30% chance of no cigs forming at KSMO, KLAX, and KLGB, or cigs are brief/intermittent through the night.
KLAX, Moderate confidence in TAF. Timing of return of MVFR CIGs could be +/- 3 hours of current 11Z forecast. There is a 30% chance that CIG/VSBY restrictions do not develop overnight. No significant easterly wind component is expected.
KBUR, Moderate confidence in TAF, with a 20% chance of brief/intermittent CIGs of BKN0010-022 between 08-17Z Sat.
04/741 PM.
For the Outer Waters, moderate confidence in current forecast. Tonight through Saturday night, there is a 20-30% chance of Small Craft Advisory (SCA) level winds. For Sunday, there is a 60-80% chance of SCA level winds. For Monday through Wednesday, there is a 30-40% chance of SCA level winds.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, high confidence in winds and seas remaining below SCA levels. On Sunday and Monday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours. For Tuesday and Wednesday, high confidence in winds and seas remaining below SCA levels.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For a majority of the southern Inner Waters, high confidence in winds and seas remaining below SCA levels today through Wednesday. The only exception will be the western half of the Santa Barbara Channel where there will be 50-60% chance of SCA level winds late Sunday afternoon and evening.
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.
04/740 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 5-8 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 on Sunday and 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 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 from 6 AM Saturday to 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect from 6 AM Saturday to 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect from 6 AM PDT Saturday through Tuesday evening for zones 340-346-349-350. (See LAXCFWLOX). PZ, NONE.
