Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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059 FXUS66 KLOX 051801 AAA AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1101 AM PDT Fri Jul 5 2024 updated aviation discussion .SYNOPSIS...05/957 AM. A long-lasting and extreme heatwave will affect the region through much of this week, with a high risk for dangerous heat illness and fast-growing fires. Today will be the hottest in the coastal and valley areas, with Saturday the hottest over the interior areas. Peak high temperatures will reach 95 to 105 degrees in many areas away from the coast, and upwards of 105 to 115 across valleys and mountains. All-time records will be threatened. Dense fog will affect the immediate coastal areas. && .SHORT TERM (TDY-SUN)...05/1016 AM. ***UPDATE*** The long lasting and extreme heat wave continues. Today and Saturday have all the ingredients to be the hottest and most dangerous in terms of heat-illness and fire risk. PLEASE avoid hiking in the mountains and the hills through this weekend and stay away from anything that could spark a fire. High pressure aloft is peaking around 595 dekameters. Onshore pressure gradients will be near neutral for much of today. North- to-south gradients continue to trend offshore, and it is this gradient in particular that has behaved like this for nearly all of our all-time record hot days. All systems are go for widespread triple-digit heat inland of the coastal plains and significantly hotter than yesterday. Several calendar day records are sure to fall today, with a few all-time records threatened today or Saturday (Lancaster, Palmdale, Paso Robles). The coastal areas will be the hardest to predict, as the shallow marine layer remains and is not showing any signs of going away. As a result, the most likely outcome is for the beach areas to stay in the 70s with a very sharp gradient going inland reaching 100 degree temperatures within 5 to 10 miles of the ocean. A few changes were made this morning. Added Palos Verdes to the Heat Advisory as they will mostly in the hot layer above the shallow marine layer. Lowered the temperatures along the immediate coasts of southeast and northwest Santa Barbara County. It will be very hot just a few miles inland, and rather warm at the beaches, but steady onshore flow at the coast should keep the moderating marine layer around. Also added a Wind Advisory for southwest Santa Barbara County for tonight as the winds look similar to the 40 to 50 mph gusts from last night. Will look into the current end times for the Excessive Heat Warnings and Heat Advisories. They all look good through Saturday, but the coastal and valley areas may need to end a little earlier than their currently scheduled end times. ***From Previous Discussion*** Well, today is the day - the hottest day of the prolonged period of dangerously hot weather. Make sure to limit time outdoors in the sun and stay hydrated to avoid any heat illness. Some low clouds and fog were hanging out along the coasts early this morning, though very patchy in nature. Onshore pressure gradients between KLAX and KDAG were weakening, while N-S gradients were becoming increasingly offshore. Therefore, the marine layer clouds are expected to burn off rather quickly this morning. Temps at 950 mb are expected to rise quite a bit today due to all of this. This will allow for plenty of heating -up to 20 degrees compared to yesterday`s high temperatures, and 15 to 20 degrees above normal for this time of year. As a result, today has the best chance for several locations to break daily high temperature records. Saturday`s maximum temperatures will be similar to today`s, though a few degrees cooler at the coasts and coastal valleys due to increasing onshore trends through the weekend. Exact temperatures at the coastal locations on Saturday will depend on when the increasing onshore trends start up, leading to less confidence in the heat advisories for coastal areas on Saturday. Even less confidence in the advisories on Sunday as temperatures in the mid 70s to mid 80s would be below advisory criteria. While the onshore flow will reach interior areas on Sunday, temperatures will still be at or above 110 in the deserts and far interior valleys of SLO County, and above 100 degrees in the warmer locations in the L.A./VTU valleys. Therefore the Excessive heat warnings will likely still be needed across those locations. The increase in onshore winds there in the afternoon, particularly across the interior mountains and Antelope Valley, will increase the fire risk in those areas. .LONG TERM (MON-THU)...05/440 AM. Unsurprisingly, hot weather continues through the extended period due to the high pressure aloft hanging out to the north and east of the region. The onshore flow starts weakening again on Monday resulting in a few degrees of warming both Monday and Tuesday across the region, except the deserts and mountains which will change little if at all due to the stationary high. Then, conditions are expected to be very similar Tuesday through Thursday. The deserts and far interior areas of SLO County will continue to scorch with highs near or above 110 and warmer coastal valley highs will reach around 105 each day. Lower confidence with coastal temperatures due to the uncertainty with the marine layer and possible eddy development over the southern coastal waters, but highs there should be up to 4-8 degrees above normal all week. && .AVIATION...05/1800Z. At 17Z at KLAX, the marine layer was 700 feet deep. The top of the inversion was at 3300 feet with a temperature of 34 deg C. Moderate to hi confidence in the 18Z TAFs. Most airfields will be VFR thru the fcst period. Low clouds should move back into coastal airfields from KOXR southward at some time tonight and persist into Sat morning, with IFR/MVFR conds. There is also a 30% chance of LIFR conds at KSMX late tonight and early Sat. Timing of the onset and any dissipation of the low clouds may be off +/- an hour or two. There will also be some MVFR to even local IFR vsbys early in the TAF period for the coast and vly airfields of L.A. County due to haze. Some more haze is possible (50% chance) late tonight into Sat morning for KBUR and KVNY with MVFR vsbys. KLAX...Moderate confidence in the 18Z TAF. MVFR vsbys due to haze should end around 20Z. Tonight, there is a 40% chance that IFR cigs will arrive as early as 04Z. Cigs are expected to improve to MVFR around 14Z. Timing of onset and dissipation of the low clouds may be off +/- an hour or two. There is a 20% chance of an east wind component of 7-8 kt from 10Z-17Z Sat. KBUR...Moderate to high confidence in the 18Z TAF. VFR conds should prevail for most of the fcst period. However, MVFR vsbys in haze is expected until about 20Z and again tonight from about 09Z-15Z. && .MARINE...05/821 AM. In the Outer Waters, Small Craft Advisory (SCA) level winds will continue in the southern zones (PZZ673/PZZ676) thru Sat morning. In the northern zone (PZZ670), SCA conds are likely (70% chance) this afternoon thru tonight. For the most part, expect winds to remain below SCA levels Sat afternoon thru Tue night. However, there is a 30% chance of SCA level NW winds in the far outer waters and from near Pt. Conception to NW of San Nicolas Island, especially during the late afternoon thru late evening hours. For the Inner Waters N of Pt. Sal, SCA conds are likely (70% chance) this afternoon/eve. There is a 30% chance of SCA level winds Sat afternoon/eve. SCA conds are not expected Sat night thru Tue night. For the Inner Waters south of Pt. Conception, there is a 30% chance of SCA conds late this afternoon and evening in western portions of the Santa Barbara Channel, mainly from Santa Cruz Island to the SBA County south coast from Pt. Conception to Gaviota to Refugio State Beach. Otherwise, conds will be below SCA levels for the southern inner waters thru Tue night. Areas of dense fog will affect the coastal waters this morning. Please reference the Marine Weather Statement for additional information. && .BEACHES...05/820 AM. A moderate southerly swell will affect the Southern California coastal waters through Sunday, with a 15-17-second period this weekend. While surf is not expected to be particularly high, surf heights upwards of around 6 feet at times are anticipated at beaches exposed to southerly swell -- especially the LA and Ventura County beaches. The significant wave energy with the long-period swell will combine with the elevated surf to create dangerous conditions at area beaches, with powerful and dangerous rip currents expected. This is especially the case for the south- facing beaches of LA and Ventura Counties. A Beach Hazards Statement is in effect through the weekend to address these concerns. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning remains in effect until 6 PM PDT Wednesday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 6 PM PDT Monday for zones 88-342-348-351-352-356>358-369>375-380. (See LAXNPWLOX). Heat Advisory in effect until 6 PM PDT Sunday for zones 341-347-355-367-368. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 6 PM PDT Saturday for zones 349-350. (See LAXNPWLOX). Wind Advisory in effect from 6 PM this evening to 3 AM PDT Saturday for zones 349-351. (See LAXNPWLOX). Beach Hazards Statement in effect through Sunday evening for zones 354-362-366. (See LAXCFWLOX). Heat Advisory remains in effect until 6 PM PDT Sunday for zone 548. (See LAXNPWLOX). Red Flag Warning in effect until 6 AM PDT Saturday for zones 342>345-349-351>353-376>378-381. (See LAXRFWLOX). PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Saturday for zones 673-676. (See LAXMWWLOX). && $$ PUBLIC...Lund/DB/Kittell AVIATION...Sirard MARINE...DB/Sirard BEACHES...Sirard SYNOPSIS...RK weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox