29/232 AM.
Seasonably warm temperatures today will shift to dangerously hot by Friday through the weekend as the next heat wave arrives. Some cooling is expected next week though temperatures will remain above normal. Dangerous surf conditions are expected at beaches this week south of Point Conception due swells from a tropical storm west of Mexico.
(tdy-Fri), 29/845 AM.
***UPDATE***
The forecast is well on-track, and no changes have been made to the ongoing forecast.
***From Previous Discussion***
The marine layer is making a return along many coastal areas this morning as weak troughing develops over the West Coast. However, temperatures will remain seasonably warm today and tomorrow before high pressure over Arizona expands west Friday and through the weekend. Models have been very consistent over the last week showing 500mb heights rising to 600dam (at or above the 99th percentile) over the interior California deserts by Saturday and possibly as far west as the coast. The extreme pressure being exerted from aloft will force temperatures at the surface to rise to around 10 degrees above normal in many areas, resulting in significant heat stress, especially in areas that have limited or no access to cooling sources. Current forecast highs are near or exceeding record temperatures in many areas, especially Friday and Saturday. Temperatures along the Central Coast are cooler compared to other areas but even there forecasts are close to or exceeding daily records.
One positive aspect is that humidities have been decreasing as tropical moisture remains east and south of the area. This is allowing overnight temperatures overnight to cool a few degrees, providing some relief. However models are strongly suggesting increasing moisture aloft later this week and weekend during the peak of the heat wave, which will further exacerbate the heat stress over the area.
A large south swell from Hurricane Genevieve will further enhance large wave and potentially deadly rip currents for some area beaches. See Beaches discussion below and associated coastal hazard products for details.
(Sat-Tue), 29/400 AM.
A slow cooling trend is expected to begin Sunday though temperatures will still be 5-10 degrees above normal and increasing moisture aloft will limit overnight cooling and keep humidities higher than normal. And in addition, high pressure aloft will continue to dominate the weather pattern along the West coast all of next week, meaning highs will remain above normal for the foreseeable future.
29/1200z.
At 1150Z at KLAX, the marine layer was 1500 feet deep. The top of the inversion was 4200 feet with a temperature of 24 degrees Celsius.
For 12Z TAFs, high confidence in KPRB, and KPMD and KWJF. Low to moderate confidence elsewhere as timing of return of CIG/VSBY restrictions could be +/- 2 hours of current forecasts.
KLAX, Low to moderate confidence in TAF. Timing of flight category changes could be +/- 2 hours of current forecasts. There is a 30% chance that MVFR CIGs will return by 08z, increasing to 80% by 11z. No significant easterly wind component is expected.
KBUR, Moderate confidence in 12Z TAF with a 60-80% chance of MVFR cigs possible after 10Z.
28/814 PM.
For the Outer Waters, moderate to high confidence in current forecast. Local gusts to 35 knots will affect the outer waters through around midnight. Otherwise, through Sunday, high confidence in a combination of Small Craft Advisory (SCA) level winds and seas. There is also a 20-30% chance of Gale force winds across western sections of PZZ670/673 Wednesday evening.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Through Sunday, there is a 60-80% chance of SCA level winds in the afternoon and evening hours.
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 Sunday. The only exception will be the western half of the Santa Barbara Channel with a 60-80% chance of SCA level winds through late tonight then a 30-50% chance of SCA level winds Wednesday through Sunday in the late afternoon and evening hours.
Seas are expected to hover near 8-10 feet across the waters away from the coasts much of the week. There is a steep (short period) NW swell/wind wave from the persistent winds. In addition, a southerly swell from Hurricane Genevieve will continue across the coastal waters through this weekend. This south swell may impact south facing harbors, including Port San Luis.
Ca, Extreme Heat Warning in effect from 10 AM Friday to 8 PM PDT Sunday for zones 38-88-343>345-351>353-355>358-368>376-378-379-548. (See LAXNPWLOX). High Surf Advisory in effect until 5 PM PDT Saturday for zones 87-354-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect from 5 PM this afternoon to 3 AM PDT Saturday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect through Saturday afternoon for zones 340-346. (See LAXCFWLOX). Heat Advisory in effect from 10 AM Friday to 8 PM PDT Sunday for zones 341-342-347>350-354-362-366-367-377. (See LAXNPWLOX). Heat Advisory in effect from 10 AM Thursday to 10 AM PDT Friday for zones 378-379. (See LAXNPWLOX). Heat Advisory in effect from 10 AM Thursday to 8 PM PDT Sunday for zone 380. (See LAXNPWLOX). Extreme Heat Warning in effect from 10 AM Thursday to 8 PM PDT Sunday for zones 381>383. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zones 670-673-676. (See LAXMWWLOX).
