Marine Weather and Tide Forecast for El Segundo, CA

.SHORT TERM (TDY-TUE)...15/821 AM.

***UPDATE***

Latest satellite and surface observations indicate some stratus and patchy dense fog across the coastal plain and the San Gabriel Valley with clear skies elsewhere. Current sounding data indicates marine inversion AOB 1000 feet in depth. Some northerly winds, gusting 25-35 MPH, are observed across the mountains.

Forecast-wise for the immediate short term, no significant issues are expected. Admittedly, stratus/fog is a bit more widespread this morning than I was expecting yesterday. That being said, stratus and fog should dissipate by the afternoon with sunny skies for all areas. Given this more extensive marine push this morning, coastal temperatures will likely be a bit cooler than forecast early. So, have "knocked" them down a couple of degrees today which matches the trends shown by TEMP STUDY. Inland areas, away from the marine layer, should bump up a few degrees today. As for winds, the northerly winds will continue through the day, but speeds will remain below advisory levels.

Overall, current forecast has good handle on the immediate short term. Other than the previously mentioned tweaks to coastal temperatures, no updates, significant or otherwise, are anticipated. For the afternoon forecast suite, attention still remain laser-focused on a historic heat event this week for the entire area.

***From Previous Discussion***

The heat wave will start off with...Marine Layer? Indeed - a 500 ft deep marine propelled by an eddy has brought low clouds, fog and patchy dense fog the csts all the way to the city of SBA.
Some low clouds will also infiltrate into the San Gabriel Vly.
Increasing offshore flow (2 to 4 mb from the N and E) will make quick work of the clouds and skies should be sunny from mid morning on. The offshore flow will generate some NE winds esp across the Central Coast, while there will be local advisory level gusts the bulk of the winds will come in just below advisory levels. Meanwhile at the upper levels an east PAC upper high will begin to approach the coast and hgts will rise 586 dam. These hgts and the offshore flow will combine with the sunny skies to bring 4 to 8 locally 10 degrees of warming to the csts and vlys. The interior will only see 1 or 2 degrees of warming. The beaches will remain fairly cool with highs in the lower 70s, but the rest of the cstl areas will be in the mid 70s to mid 80s. The Vlys will soar into the upper 80s to mid 90s. These temperatures, while very warm, do not quite meet heat advisory criteria (people working or playing outdoors should still be mindful of heat stress).

The upper high moves closer to the cst on Monday and hgts rise to 588 dam. Offshore flow continues (the same 2 to 4 mb but reversed with the stronger component coming from the east). Look for 4 to 8 degrees of warming. This warming coupled with warmer than normal overnight low will bring moderate heat danger to all of the csts and vlys. Because of this a HEAT ADVISORY has been issued for those areas. People outside and in houses without air conditioning should take precautions to prevent heat related illness.

Tuesday and Wednesday will be the hottest days of this historic heat event. Hgts will climb to at least 591 dam which would tie the all time hgt value for March. There will be about three mb offshore flow from the N and E. This will bring 3 to 6 degrees of warming to the csts to all areas. This will bring cstl temps into the upper 80s and 90s (some beaches may only reach the lower 80s)
while the vlys sizzle up to the upper 90s to 103 degrees. About 20 percent of the ensemble solutions show temps a couple of degrees warmer than this forecast. These max temps are 20 to 30 degrees warmer than normal and stand a good chance of setting not only daily records but monthly records as well. Wednesday will see little change in temps except for some cooling at the beaches. An EXTREME HEAT WATCH is in currently in effect, but this will likely be upgraded this afternoon to warnings after inter office coordination.

BOTTOM LINE...If you or someone you know is at risk for heat related problems you should make cooling plans today or Monday.

.LONG TERM (WED-SAT)...15/207 AM.

There will be little change in the synoptic features on Thursday and max and min temps will remain very close to the record values of Tue and Wed. On Friday the upper high shifts a little to the SE and hgts fall some. This will also move the area of maximum synoptic subsidence (and thus compressional heating) away from the fcst area. In addition the offshore flow will weaken some.
These items will all add up to 2 to 4 degrees of cooling. This cooling will not be enough to offset the dangerous heat. The EXTREME HEAT WATCHES do continue through Friday evening and will very likely be converted to warnings with the afternoon forecast package.

Another 2 to 4 degrees of cooling on Saturday should be enough to eliminate the warning level heat risk but the vlys will likely still need heat advisories.

Given the unprecedented length and magnitude of this extreme heat wave, heat stress will be a real threat 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.

Long range AI mdls are mostly dry through the 28th, but they do show increasing chances rain over the north half of the state and a chc of light showers over portions of SoCal on the 25th or 26th.

AVIATION
15/1013Z.

At 0845Z at KLAX, the marine layer was 1000 ft deep. The top of the inversion was at 1800 ft with a temperature of 19 C.

High confidence in TAFs for KPRB, KSBP, KSMX, KBUR, KVNY, KPMD and KWJF.

Moderate confidence in the remainder of the TAFs through 18Z then high confidence. Flight cat transitions could be off by +/- 2 hours.

KLAX...Moderate confidence in TAF through 18Z due to +/- 2 hour potential timing differences of flight cat changes. Good confidence in TAF from 18Z-04Z followed by moderate confidence with timing of return of low clouds and a 30 percent chc of no low clouds at all. Good confidence that any east wind component will be below 7 kts.

KBUR...High confidence in VFR TAF.

MARINE
15/1201 AM.

Small Craft Advisory (SCA) conditions will linger into late Sunday night across the Outer Waters. Thereafter, conditions will likely remain benign through at least mid-week. Moderate chances for SCA winds starting Thursday or Friday across the northern waters.

For the Inner waters along the Central Coast, localized SCA level NW winds likely south of Port San Luis Sunday afternoon into the early evening hours. Otherwise, conditions are expected to remain benign through at least mid-week.

Inside the Southern California Bight, conditions are expected to remain below SCA levels for the foreseeable future.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Heat Advisory remains in effect from 10 AM to 8 PM PDT Monday for zones 87-88-340>342-345>358-362-366>376-378>380-548. (See LAXNPWLOX).
Extreme Heat Watch in effect from Monday evening through Friday evening for zones 87-88-340>342-345>358-362-366>376-378>380-548>550. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 PM PDT this afternoon for zone 676. (See LAXMWWLOX).