Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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630 FXUS66 KLOX 111213 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 513 AM PDT Thu Jul 11 2024 .SYNOPSIS...10/102 PM. A long-lasting and extreme heatwave will continue across the mountains and interior areas through much of the week, as a strong high pressure system remains anchored over the region. A high risk of dangerous heat illness exists across the interior portions of the area. A cooling trend is expected by Friday and the weekend but temperatures will remain well above normal inland. && .SHORT TERM (TDY-SAT)...11/329 AM. The marine layer is about 900 ft deep. The E/W gradient is near neutral while there is weak onshore flow to the north. Low clouds cover all of the coastal sections. Burn off will be similar to Wednesday. There are some high clouds drifting in from the SE and skies may be partly cloudy at times. Heat is still the #1 issue. 596 dam hgts are over the area extending from a very warm 598 dam upper high centered over eastern NV. Excessive Heat Warnings for the valleys (max temps 95 to 106 | 6 to 12 degrees above normal) last through this evening. The Excessive Heat Warnings for the Mtns and Interior (max temps 110 to 110 | 8 to 12 degrees above normal) continue to today and beyond. Look for a similar low cloud pattern tonight with an early low cloud arrival for the immediate coasts north of Malibu. It will be warm again for the foothills, lower mtns and deserts, with lows in the 70s to around 80 expected. Slight hgt falls will occur Friday as the upper high moves to the east. The onshore flow will increase a little as well. More importantly there will be an increase in mid level clouds and moisture as the new position of the high shuttles some monsoon moisture into the area. These factors will combine to bring 1 to 2 degrees of cooling to the area. Enough to preclude any heat products for the vlys, but not enough to prevent bring temperatures out of Excessive Heat Warning criteria for the Mtns and Interior. The one possible fly in the ointment is the mid level clouds which if they come in thicker than fcst could lead to more dramatic cooling. The convective parameters are still too low to mention showers or TSTMs but there will likely some build ups over the LA and VTA mtns. The upper high moves to near the 4 corners region on Saturday. This puts it into a good location for some monsoon flow and aside from the relentless coastal low clouds in the morning skies will be partly cloudy. There is also enough afternoon instability to bring a slight chc of TSTMs to the eastern LA mtns and the Antelope Vly. More cooling is forecast for the interior due to the increased cloud cover. The heat warning remains in effect through the evening, but if the clouds are thick enough it may be cancelled early this will be the short range problem of the next two days. .LONG TERM (SUN-WED)...11/343 AM. Deterministic and ensemble means agree that a trof will push closer to the west coast Sunday and will linger there through Tuesday. At the same time the onshore flow will increase. The marine layer will deepen and will push further inland. Max temps will fall each day and by Tuesday most areas will be 2 to 4 degrees blo normal. The upper trof will nudge the monsoon moisture back to the east and the afternoon convection threat will fall below 10 percent. The strong onshore push in the afternoon will keep some west facing beaches cloudy through most of or even all of the afternoon. In addition there will be gusty near advisory level winds across the interior. On Wednesday it is likely that the upper high will push westward again and kick off a warming trend that may extend into the weekend. && .AVIATION...11/1212Z. At 11Z at KLAX, the marine layer was near 500 feet deep. The top of the inversion was at 2900 feet with a temperature of 33 C. High confidence in CAVU TAFs for KPRB, KVNY, KPMD, and KWJF. Good confidence in KBUR TAF, with a 15 percent chance of IFR CIGs for the overnight period. Low clouds and fog were widespread in coastal area from Ventura County northward, and have pushed into western portions of the Santa Ynez Valley, and the lower valleys of VTU County. Condition were LIFR to VLIFR. Skies should clear by mid morning, except clouds could linger into the afternoon right at the beaches. Across L.A. County, cigs were confined to areas within a few miles of the beaches, and have not pushed into any valley locations. Conds were mostly IFR to LIFR. Clouds should clear in most areas by mid morning, but they could linger into the afternoon at some beaches. Expect widespread low clouds in coastal areas tonight, and with a deepening marine layer, clouds should push into all of the Santa Ynez Valley, the San Gabriel Valley, and lower portions of the VTU County valleys. Conds will generally be LIFR to VLIFR. KLAX...Moderate confidence in TAF. There is a 20% chance that conds will worsen to 2sm br ovc005 between 13Z and 16Z. There is a 20% chance that cigs will not scatter out until as late at 18Z. There is a 20% chance that cigs will arrive as early as 07Z tonight. No significant east wind component is expected. KBUR...Good confidence in TAF. There is a 15% chance of 1/2sm fg VV002 conds after 11Z tonight. && .MARINE...11/502 AM. Overall, Small Craft Advisory (SCA) conds are not expected thru Mon night. However, there is a 20% chance of SCA level winds in the outer waters and far western portions of the Santa Barbara Channel this afternoon/eve. Dense fog will continue across much of the waters this morning, and is possible again tonight/Fri morning. Please reference the Marine Weather Statement for additional information. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning remains in effect until 9 PM PDT Saturday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 9 PM PDT this evening for zones 88-351-352-356>358-369>375-380-548. (See LAXNPWLOX). PZ...NONE. && $$ PUBLIC...Rorke AVIATION...DB MARINE...DB SYNOPSIS...MW/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox