Area Forecast Discussion

SYNOPSIS

21/1215 PM.

Hotter than normal conditions will dominate the foreseeable future. The hot daytime and warm night conditions will bring elevated risks for heat illness. Thursday through Sunday will generally be the hottest of the next seven days. Gusty north winds expected Wednesday through Friday.

SHORT TERM (TDY-FRI)

21/129 PM.

Very warm conditions materialized on the Central Coast today, thanks in large part to the decaying tropical system just to the west crushing the marine layer and cooling onshore flow. These features should return back to normal tomorrow.

A huge area of high pressure, currently centered over Nebraska and affecting most of the western and southern United States, will dominate our weather for several days. The core of the high will wobble to the south tomorrow, then towards the west Thursday through Saturday and eventually settling over New Mexico and Arizona. Meanwhile, the prevailing mid-level flow will shift from southerly today to northerly by Thursday. These two ingredients will drive a significant warm up that will weakly start tomorrow, but really kick in Thursday. High temperatures of 97 to 107 will be common for most valleys and lower mountains by Friday, with highs of 85 to 95 over inland coastal areas. Beaches will be a mixed bag depending on how the marine layer responds, but with warmer than normal water temperatures, it will remain rather muggy and unpleasant.

Decided to convert all of the Extreme Heat Watches to Heat Advisories, except for the Antelope Valley which is now in a low- end Extreme Heat Warning. Most of these heat hazards are in effect from Wednesday through Monday. One could justify some localized Warnings in the Advisory for a day or two, but went with a long- duration Advisory to simplify the message. While high temperatures will generally only be 10 degrees above normal, there are other factors in play for the Heat concerns. Minimum temperatures will also be 5 to 10 degrees above normal, except 10 to 15 degrees above normal for the mountains and foothills. This means that the overnight relief that many depend on to cool their homes and their bodies will be less than usual. The other factor considered is the duration. We look locked into above normal temperatures for the foreseeable future, including this imminent heat up that will last a good 5 days. With all that considered, the risk for heat illness is high, especially for sensitive groups like the very young, the very old, those without air conditioning, and those active outdoors.

There will be a little wind to deal with as well, mainly over southern Santa Barbara County, the I-5 Corridor, and the western Antelope Valley Wednesday through Thursday or Friday Night. Expecting northwesterly to north gusts of 30 to 50 mph in those areas. A Wind Advisory was issued for southwest Santa Barbara County where the winds will be the strongest of the bunch.

LONG TERM (SAT-TUE)

21/139 PM.

The high pressure area will continue to dominate the southwest United States through most of next week, which means warmer than normal conditions will persist. The ensemble projections favor stronger onshore flow starting Saturday which would signal some drop in termperatures. The high pressure system changes little however, and the mid-level flow does shift back to southerly which will pull some tropical moisture back into the area at least over the weekend. This tends to keep the marine layer at bay and makes it feel warmer than it is. We also might see a shower or two in the mountains. With all that said, expecting little change to the general heat concerns through Sunday or Monday. After that there is a range of outcomes in the finer details, but it will remain warm, with another potential heat up towards the end of next week.

AVIATION

21/1802Z.

Around 18Z at KLAX, the marine layer was 1800 ft deep. The top of the inversion was at 3500 ft with a max temperature of 22 C.

High confidence in VFR TAFs for KPMD, KWJF, and KPRB. There is a 10 percent chance of LIFR-IFR conds at KPRB 08Z-17Z Wed.

High confidence in the remaining TAFs through 03Z, then low to moderate confidence. There is a 30 percent chance of IFR/LIFR cig/vis 04Z-18Z Wed for the coastal TAFs, and a 20 percent chance 10Z-15Z Wed for KBUR and KVNY.

KLAX...High confidence through 06Z, then low to moderate confidence in TAF. There is a 30 percent chance of 2SM OVC005 conds 07Z-18Z Wed. No significant east wind component expected.

KBUR...High confidence through 09Z, then moderate confidence in TAF. There is a 20 percent chance of 2SM OVC005 conds 07Z-18Z Wed.

MARINE

21/1157 AM.

Northwest winds will strengthen to Small Craft Advisory (SCA) levels this afternoon, and will likely continue into the weekend. Chances also increase for SCA level west to northwest winds across the western half of the Santa Barbara Channel each afternoon and evening. Additionally, there is a 30% chance of Gale Force wind gusts across the outer waters Wednesday afternoon through at least Thursday, and 20% chance into the western portion of the Santa Barbara Channel Wednesday afternoon and evening.

A series of moderate period southerly swells will move through the waters through the week and likely beyond, along with a long period southern hemisphere swell arriving late this week. These swells may impact south facing harbors, including the Port San Luis area.

BEACHES

21/148 PM.

Over the eastern Pacific, Hurricane Fausto, located 700 NM SW of southern Baja, will move WNW between 15 to 20 N latitude through at least the next 5 days. This system is bringing an elevated South-Southwesterly swell into the region. Therefore, High Surf Advisories and Beach Hazards Statements are in effect through Tuesday night.

After a brief break, an incoming long period, southern hemisphere swell will arrive later this week/Thursday night and will contribute to continued hazardous beach conditions late this week and weekend. Additional Beach Hazards Statements will likely be needed during this time.

Looking beyond the forecast period, a series of tropical systems are forecast to develop off the coast of Mexico and move to the northwest, likely producing multiple rounds of southerly swells over the next couple of weeks.

LOX WATCHES / WARNINGS / ADVISORIES

CA...Heat Advisory remains in effect from 10 AM Wednesday to 8 PM PDT Monday for zones 38-88-342>345-348-351>353-355>358-368>382-548. (See LAXNPWLOX). High Surf Advisory in effect until 11 PM PDT this evening for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect until 5 PM PDT this afternoon for zones 340-346. (See LAXCFWLOX). Heat Advisory remains in effect from 10 AM Wednesday to 8 PM PDT Thursday for zones 349-350. (See LAXNPWLOX). Wind Advisory in effect from 6 PM Wednesday to 6 AM PDT Thursday for zones 349-351. (See LAXNPWLOX). Extreme Heat Warning in effect from 10 AM Thursday to 8 PM PDT Monday for zone 383. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 673-676. (See LAXMWWLOX).