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Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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979 FXUS66 KLOX 281733 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1033 AM PDT Fri Jun 28 2024 .SYNOPSIS...27/1153 PM. Slight cooling is expected into Friday as high pressure aloft weakens. Gusty northwest winds will affect southwestern Santa Barbara County and the Interstate 5 Corridor tonight. Warmer weather is expected over the weekend as high pressure returns, and above normal temperatures will continue through next week. && .SHORT TERM (TDY-SUN)...28/1033 AM. ***UPDATE*** Confidence continues to increase in a dangerous heatwave affecting Southern California next week, and an Excessive Heat Watch has been issued for interior areas across portions of Southern California. The forecast has been updated to account for the issuance of the Excessive Heat Watch. Otherwise, no changes have been made to the ongoing forecast. ***From Previous Discussion*** An onshore flow pattern remains in place across the area early this morning. Slight cooling will continue into today as the tail end of upper-level trough of low pressure moving through the northern Intermountain Region will brush the area and slightly increase onshore flow. Night through morning low clouds and fog, which have struggled to form over the last several nights and mornings, are becoming more entrenched along the Central Coast of California this morning, while an eddy circulation near Santa Catalina Island still struggles to form stratus clouds around it. The increase in northwest flow over the offshore coastal waters and parallel to the southern California coastline should permit the eddy circulation to become a little more vigorous. With the shallow marine layer depth along the Central Coast, there is a high-to-likely (40-60 percent) chance of dense fog developing along the Central Coast this morning. A dense fog advisory might be needed for the Central Coast later this morning. 500 mb heights start to climb across the region over the weekend as an upper-level ridge of high pressure over north Texas this morning strengthens and expands westward. A warming trend is forecast for Saturday and Sunday across the region, most pronounced away from the coast. Onshore flow will weaken some, but still remain intact into early next week. A persistent marine layer depth will keep at least patchy low cloud coverage for some coastal areas, but the marine layer depth will be forced to thin some. A warming trend is well reflected in the forecast, but with 950 mb temperatures to reaching around 35 degrees Celsius across the warmest areas, dangerously hot conditions are not forecast at this time. Temperatures will warm to about 5 to 10 degrees above normal for this time of year, though. Closer to the coast, temperatures will remain around normal for this time of year with a continued marine influence continuing and keeping the sea breeze cooling the land mass during the afternoon hours. .LONG TERM (MON-THU)...28/406 AM. The strong upper-level ridge will pull away farther to the east for early next week and allow for a piece of an upper-level trough of low pressure over the Gulf of Alaska to brush the area and increase onshore flow. A little better onshore push should occur into the valleys and foothill area and bring some cooling for Monday. Low cloud coverage should increase some and possibly extend a little farther inland as the marine layer depth deepens some. By late week, the story for the weather pattern will change as a strong high pressure system over the Central Pacific Ocean this morning will build into the West Coast. A hot air mass will develop over the region as 500 mb heights potentially reach 600 decameters over the northern California where the ridge center could end up being anchored. Looking at the latest ensemble forecast members, there is a moderate-to-high chance of widespread dangerously hot weather developing across the region for the latter half of next week. EPS ensemble means suggest high temperatures means climbing through next Saturday. NBM values remain in the forecast for high temperatures for late next week, but as the ridge builds east into Nevada, a southeast flow aloft could develop and open the door for monsoonal moisture to sneak in. This could create some more cloudiness and keeps overnight low temperatures warmer than normal across the region. Minimum temperatures break away from NBM values toward the latter part of the forecast period away from the coast. In addition, the marine layer induced low cloud pattern could become very patchy in nature or even non-existent as the middle level clouds and warmer temperatures will mess with low cloud formation. The increase in subtropical moisture could also develop more typical afternoon and evening showers and thunderstorms with a monsoonal flow pattern. EPS ensemble members suggest precipitable water means climbing close to 1.00 at KLAX. A very slight (10 percent) chance of showers and thunderstorms has been added to the forecast for the mountains and desert on Thursday and Friday, breaking away from WPC and NBM values for late week. && .AVIATION...28/1653Z. At 16Z at KLAX, the marine layer was 2200 feet deep. The top of the inversion was at 4500 feet with a temperature of 22 Celsius. Moderate confidence in all sites becoming VFR today by 19Z. High confidence in VFR conditions through Saturday at KWJF KPMD. There is a chance of ceilings at KPRB (20%) KSBA (50%) KBUR (60%) KVNY (40%) tonight into Saturday. All other sites, high confidence in ceilings. Moderate confidence in any ceilings tonight being in similar categories as last night (persistence). KLAX...Moderate confidence in VFR conditions through at least 04Z. Moderate confidence on MVFR ceilings occurring tonight. Low confidence on timing with ceilings starting as early 06Z and as late 14Z. High confidence in any southeast winds staying under 06 knots. KBUR...High confidence in VFR conditions through at least 04Z. There is a 60% of BKN008-012 ceilings forming tonight as early as 08Z and as last as 14Z. High confidence in seasonal winds. && .MARINE...28/931 AM. The moderate threat of dense fog (visibilities one mile or less) continuing through the afternoon and returning tonight along the Central Coast. Moderate confidence that visibilities will be up everywhere else. Moderate confidence the Small Craft Advisories (SCA) winds and/or steep seas will continue through most of tonight from the Central Coast to San Miguel Island. This will be a low-end event however, and conditions may stay just under criteria, but it will still be unpleasant out there. Elsewhere, high confidence in fairly benign conditions through at least Saturday. High confidence in northwest winds increasing once again later Saturday Night and lasting through Monday Night. There is a moderate threat for Gales for the offshore waters from the Central Coast to Point Conception Sunday through Monday. There is also a low but present threat of these winds pushing deep enough into the Santa Barbara Channel to need a Small Craft Advisory. There is a potential for winds to be stronger than the most recent event. As a result of these winds, choppy seas should be expected everywhere. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Watch in effect from Tuesday morning through late Friday night for zones 38-88-343>345-353-376>379-381>383. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Cohen/Hall AVIATION...Kittell MARINE...RK SYNOPSIS...jld/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox