06/236 AM.
A major and long lasting heat wave will to persist through at least Thursday with dangerously high temperatures, though some cooling is expected near the coast the next few days. Friday into Sunday, temperatures will trend cooler each day and there is a small chance of showers and thunderstorms due to moisture from Hurricane Rachel.
(tdy-Thu), 06/854 AM.
***UPDATE***
The hot weather continues today, though offshore pressure gradients are weaker by 1.2mb this morning so that should create at least some additional onshore push beyond what we saw yesterday. It's always tricky in these situations when there is a little onshore push determining how far inland that cooling will reach so confidence with specific locations is low. Most areas are starting off cooler, and in some cases as much as 10 degrees below yesterday at this time. So the upshot is that most areas should be at least 1-2 degrees cooler, with coastal areas as much as 4-8 degrees cooler. The Central Coast may be an exception because there is a light northeast flow aloft that may create some downslope warming off the Santa Lucias that would lead to some warming.
***From Previous Discussion***
This long lasting and dangerous heat wave will continue through at least Thursday.
7 records were broken ydy: DTLA (104 vs 101), Burbank (Tie at 102), Woodland Hills (106 vs 105), Long Beach Airport (Tie at 104), LAX (Tie at 101), Camarillo (99 vs 98) and Oxnard (98 vs 94).
It was the 4th consecutive day of max temps 100 degrees or higher at the DTLA site. This is the record for October and it looks like that record will be xtnd by 1 maybe two days.
Upper level high pressure will reside over Srn CA today through Thursday. Hgts will range from 588 dam to 590 dam. At the sfc there will be weak offshore flow in the morning and weak onshore flow in the afternoon. One thing to note is the mdls have not been handling the sfc pressure gradient forecast that well over the past three days and this has led to some forecast errors. So there is a little more uncertainty in the temperature fcst than usual.
Today's temps should be very similar to Mondays with mostly 90s for the coasts (mid 80s to lower 90s Central Coast) and 100 to 105 in the vlys. Wednesday will see 2 to 4 degrees of cooling for the csts and vlys south of Pt Conception as afternoon onshore flow increases, but the Central Coast will warm 3 to 5 degrees as the offshore flow increases up there. Inland temps will change little each day.
On Thursday look for 2 to 4 degrees of cooling as the morning offshore flow weakens and the afternoon onshore flow increases. This cooling will lower vly temps to 98 to 102 degrees. Despite the cooling max temps will remain 10 to 15 degrees above normal.
Marine layer clouds are making a slight return along the Central Coast and there will likely be some patchy dense fog overnight into the morning esp along the western SBA coast.
There are some marine layer stratus clouds hugging the Central Coast and nearshore area will likely be cloudy with patchy dense fog in the morning.
(Fri-Mon), 05/207 PM.
High pressure will start to break down by around Friday but highs will still be 6-12 degrees warmer than normal with warmer valley highs around 100 and Downtown in the low to mid 90s.
A more pronounced cooling trend is expected by Sat as high pressure weakens and a weak upper level low drops down the coast of California. That upper low may pull up moisture from Rachel, depending on Rachel's track, so there is a chance of showers by Sunday, mainly LA County.
06/0918z.
At 0834Z at KLAX, there was no marine layer. There was a sfc based inversion with a top at 1500 ft and a temp of 32 C.
Moderate confidence in TAFs for KSMX and KSBP. There is a 30 percent chc of a few hours of IFR cig/vis before VFR conds arrive and anther 30 percent chc that VFR conds do not arrive until 17Z.
High confidence in the remainder of the CAVU TAFs.
KLAX, High confidence in CAVU TAF. Good confidence that any east wind component will be AOB 6kt.
KBUR, High confidence in CAVU TAF.
06/751 AM.
Relatively quiet conditions are expected across the coastal waters through Friday. Localized Small Craft Advisory (SCA) gusts may occur each afternoon and evening between Point Conception and San Nicolas Island. Additionally there is a 40% chance for an SCA to be issued for the northern portion of the outer waters Wednesday afternoon and evening for increasing northwest winds. Night through morning dense fog may affect portions of the coastal waters adjacent to the Central Coast and south to San Nicolas Island.
Increasing northwest winds and 10+ foot seas are likely this weekend. Additionally, remnant moisture from current Hurricane Rachel will bring a chance of showers to the waters late this weekend into early next week, best chances south of Point Concpetion.
06/759 AM.
Southerly swell from Hurricane Rachel will impact the Los Angeles and Ventura Counties coastline including Catalina Island starting late tonight. A Beach Hazard Statement has been issued starting 4 PM today and will transition to an a Coastal Flood Advisory early Wednesday morning through Friday.
Initially, the swell direction will be SE (150-160) and become more southerly (170-190) Wednesday through Friday. Unlike previous events, morning and evening high tides will be similar in height ranging 6.5 to 7.0 ft. Coastal flooding impacts are anticipated to be greatest for Long Beach (especially Alamitos Peninsula), Catalina Island, and the Malibu/Zuma Beach coast.
Saturday into early next week, tides will be very high (7+ feet) and a combination of long period southerly and westerly swells are expected to impact our coastline over the weekend into at least early next week. Some uncertainty in exact coastal flooding and surf impacts, but there is a risk for significant impacts. Please continue to monitor the forecast going forward.
Ca, Extreme Heat Warning in effect until 8 PM PDT Thursday for zones 38-87-88-349>358-362-366>375-548-550. (See LAXNPWLOX). Beach Hazards Statement in effect from 4 PM PDT this afternoon through late tonight for zones 87-354-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect from 6 AM Wednesday to 11 PM PDT Friday for zones 87-354-362-366. (See LAXCFWLOX). Heat Advisory in effect from 10 AM Wednesday to 8 PM PDT Thursday for zones 340-346. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Thursday for zones 341>345-347-348. (See LAXNPWLOX). PZ, NONE.
