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.
(tdy-Mon), 05/943 AM.
***UPDATE***
Mid and high level clouds sent by Hurricane Marie will spread into the area today. As for rain impacts, the high resolutions models are generally in agreement that rain will start early Sunday morning and last into the evening. Rain is expected to be focused over Los Angeles County, mostly likely the eastern portion. Rain totals are favored to be 0.25 inches or less for most areas in LA county, except high amounts in the foothills of the San Gabriel Valley (0.5 inches likely) and the eastern San Gabriel Mountains (locally around 1.0 inch). Rain totals will generally be 0.10 inch or less for Ventura County northward. Rain rates will be light to moderate, topping out around 0.25 in/hr for most locations. Local heavier showers with rain rates briefly 0.33-0.50 in/hr will be possible, especially for the eastern San Gabriel Mountains.
***From Previous Discussion***
Hurricane Marie was 850 NM due south of Los Angeles, and is forecasted to travel in the northwest to north direction over the next several days while weakening. Marie will remain well offshore of the California Coast, but will still be able to send some weather impacts to SoCal this holiday weekend and possibly beyond. Some of 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.
We will begin seeing mid to high clouds increase from the south this afternoon into evening, a prelude of unseasonably unsettled weather setting up for late tonight and especially into Sunday focused in LA and Ventura Counties, but possibly spreading into Santa Barbara County at times.
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 is a very rare pattern for our part of the country, especially in early September, as a strong (for early September), favorable part of a jet stream peaking near 120 kt interacts with the tropical moisture (precipitable waters may reach incredible values of 2 inches across LA and Ventura Counties) with improving mid-level lapse rates to support scattered mainly light to moderate showers. However, there is a 5 percent chance of excessive rainfall with minor flooding in embedded heavier showers or thunderstorms (5-15 percent chance) focused across the LA County into eastern Ventura County. While any embedded heavier showers or thunderstorms will mostly be moving at decent pace, any stalled or training cells could produce rainfall in excess of a quarter of an inch in an hour. Rainfall totals as a whole will be less than a half of an inch (probably under a quarter of an inch where most people live), focused across LA and possibly eastern Ventura County, isolated higher amounts will be possible, especially coastal facing mountains. The roads will be quite slick with any wetting rainfall due to the build up of oils over the last many 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 will warm some with continued humid conditions potentially posing moderate Heat Risk, especially near the coast where balmy ocean temperatures continue down south. Isolated showers or even a thunderstorm or two may continue into Monday as lingering impressive moisture near 1.5 in precipitable water will overlap with better destabilization sunshine.
(Tue-Fri), 05/301 AM.
Extremely low forecast confidence for Tuesday and beyond as what will likely be the remnants of Marie plays tricks with our model guidance.
Exactly when and how Marie or its moisture merges with an unseasonably far south jet stream will determine what version of weather and associated impacts we receive.
Two main scenarios seem to be emerging: 1) The remnants of Marie remain well offshore (80 percent chance). Even if this occurs continued moist south to southeast flow main bring light showers or isolated thunderstorms focused across interior mountains to deserts at times. This scenario has the greatest chance (50-60 percent chance) of a mid-week heatwave, potentially warranting heat products.
2) The remnants of Marie make a somewhat closer pass (20 percent chance), and bring widespread at least light to moderate rain in the Tuesdayish timeframe, especially Santa Barbara and San Louis Obispo Counties.
Please stay tuned if heat and/or rain may impact your plans next week as things will change.
05/1637z.
At 1600Z at KLAX, the marine layer was 1300 feet deep. The top of a weak inversion was 2600 feet with a temperature of 20 degrees Celsius.
For 18Z TAF package, high confidence in CAVU conditions for all sites through this evening. Overnight, moderate confidence in current forecasts as tropical moisture moves in, bringing the threat of light showers and could wreak havoc with stratus formation.
KLAX, Moderate confidence in 18Z TAF. CAVU conditions are expected through this evening. Overnight and through Sunday, there is a 30-40% chance of MVFR CIGs. Light showers are expected to develop Sunday morning. No significant easterly wind component is expected.
KBUR, Moderate confidence in 18Z TAF. CAVU conditions are expected through this evening. Overnight and Sunday morning, there is a 20-30% chance of MVFR CIGs. Light showers are expected to develop Sunday morning.
05/937 AM.
For the Outer Waters, moderate confidence in current forecast. There is a 20-30% chance of Small Craft Advisory (SCA) level winds through tonight. 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. High confidence in winds and seas remaining below SCA levels through tonight. 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 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.
05/937 AM.
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 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, NONE.
