11/209 AM.
A significant and long lasting heat wave is expected to affect the region starting Thursday and extend well into next week with MODERATE to HIGH heat impacts likely.
(tdy-Fri), 11/330 AM.
Marine layer stratus coverage definitely less than the last couple days but not entirely gone yet. Gradients are trending offshore this morning and will continue in that direction until Thursday afternoon. Temperatures today will be warmer everywhere by 4-8 degrees but the biggest day to day change will be Thursday when offshore flow to the east peaks around 5mb. Despite the possible dense fog near the coast in the morning, the combination of 500mb heights near 590dam, thicknesses near 575dam, the offshore flow, and 950 temps approaching 30c will lead to widespread temperatures in the 90s across coast and valleys by afternoon, roughly 25 degrees above normal. Based on the current forecast many of the official climate sites will be very close to breaking daily records, and some may break them by 3 or more degrees. There will be some gusty Santa Ana winds during the morning and early afternoon hours but winds aloft are under 15kt so Santa Ana winds should mostly stay below advisory levels.
A very similar day Friday but with some competing factors. It will heat up quick due to the lingering offshore flow and hot temps the day before but gradients will be weakening through the day leading to an earlier arriving sea breeze. This probably won't impact inland areas but areas closer to the coast may top out near or slightly cooler than Thursday. In any case, daily records stand a strong change to be broken for a second straight day as records Friday are generally cooler than Thursday.
A little more noticeable cooling trend expected Saturday with onshore flow in place and increasing high clouds from a decaying system over the Pacific. Highs will be about 5 degrees cooler in general but could be as much as 10 degrees cooler depending on how thick the high clouds are. Either way, temperatures will still be 15-20 degrees above normal.
(Sat-Tue), 11/359 AM.
Potentially dangerous heat will be the theme through next week as even hotter temperatures arrive and the long duration heat wave stretches into its second week. After a minor drop in temperatures over the weekend as high pressure aloft weakens, another strong high will build over the area starting Monday with thicknesses topping out around 579dam Wednesday. Offshore flow is not expected to be as strong as the previous week but enough to delay the arrival of any cooling sea breezes until later in the afternoon. More daily temperature records will be threatened each day with highs well into the 90s across coast and valleys. May even start breaking monthly temperature records. In addition, the Antelope Valley may break a record next week for the earliest 90 degree day in the calendar year.
Given the unprecedented length and magnitude of this extreme heat wave, heat stress will be increasing each day, especially in areas that aren't used to the heat, like the coastal areas, where people may not have methods to cool off their homes. Try to complete outdoor activities early in the day or in the evening, and don't leave people or pets in cars.
There still are no chances for rain at least through next weekend (Mar 22).
11/1038z.
Around 0715Z, the marine layer depth was around 1300 feet deep at KLAX.
Moderate confidence in the current forecast. Higher confidence in the current forecast for valley and desert terminals. Less confidence in the current forecast for coastal terminals.
There is a high to likely chance of VLIFR to LIFR conditions at coastal terminals north of Point Conception and IFR to MVFR conditions south of Point Conception through at least 16Z this morning. Otherwise, VFR conditions are expected. Periods of moderate to occasionally strong low-level wind shear and turbulence are possible through the period at coastal and valley terminals, with the highest chance for terminals north of Point Conception.
KLAX, There is a 60 percent chance of IFR to MVFR conditions between 11Z and 16Z. If sub-VFR conditions do develop, the clearing time should be around 17Z. Any easterly winds should remain less than 7 knots. There is a 10 percent chance of moderate low-level wind shear and turbulence between 03Z and 09Z Thursday.
KBUR, VFR conditions are expected through the period, except for a 20 percent chance of IFR conditions through 15Z. There is a 20 percent chance of moderate low-level wind shear and turbulence between 02Z and 16Z Thursday.
11/338 AM.
Moderate confidence in the current forecast. Higher confidence in the forecast through Thursday morning, then lower confidence thereafter.
For the waters southwest through northwest of the Channel Islands and the nearshore waters along the Central Coast, borderline Small Craft Advisory (SCA) winds and seas will persist until at least early Friday morning, especially beyond 30 nautical miles offshore of the Central Coast to Point Conception to northwest of San Nicolas Island. During the afternoon and evening, widespread advisory level winds are expected. There is a 50-70 percent chance of SCA level winds across the nearshore waters along the Central Coast this afternoon and evening. There is a moderate to high (40-50 percent) chance of SCA level northeast to east winds for the nearshore waters each night and morning through Friday morning. Friday night into Saturday evening, there is a moderate (40 percent) chance of local Gale Force wind gusts for the waters past 30 nautical miles offshore north of Point Sal, with near SCA level seas returning once again.
Inside the southern California bight, winds and seas should remain below SCA levels through the period, except for a moderate (30-40 percent) chance of SCA level west to northwest winds developing each afternoon and evening through Friday evening across the Santa Monica Bay and into the San Pedro Channel, and in the Santa Barbara Channel. Overnight tonight and into Thursday morning, there is a low to moderate (20-30 percent) chance of SCA level northeast winds between Point Mugu to Pacific Palisades.
A shallow marine inversion in place will create at least patchy dense fog all of the waters this morning. There is a moderate chance that fog may become fairly widespread Wednesday night into Thursday morning.
Ca, Heat Advisory in effect from 10 AM Thursday to 8 PM PDT Friday for zones 88-340>342-346>352-354>358-362-366>375-548. (See LAXNPWLOX). Wind Advisory remains in effect until 9 AM PDT this morning for zones 352-353-376>378-381. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 1 PM this afternoon to 9 AM PDT Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Friday for zone 673. (See LAXMWWLOX).
