Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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143 FXUS66 KLOX 070518 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 1018 PM PDT Thu Jun 6 2024 .SYNOPSIS...06/227 PM. Fairly widespread low clouds and nighttime fog will affect areas near the coast each day into next week, with areas of partial clearing during the afternoon. While temperatures will be a few to several degrees below normal close to the coast with onshore flow, temperatures will be considerably warmer over interior sections. Precipitation is not expected over the region through at least the middle of next week. && .SHORT TERM (THU-SUN)...06/827 PM. ***UPDATE*** Gradients started trending onshore today which led to a cooling trend in most areas and some gusty west winds across the interior. A slow cooling trend will continue Friday but still above normal in the mountains and far interior valleys. Meanwhile, at the coast the same old story. A solid but shallow marine layer is already pushing into the coastal areas with some patches of dense fog. Stratus will eventually push into the lower valleys overnight with some dense fog there as well. And again clearing to within a few miles of the coast by around noon. ***From Previous Discussion*** Little change in this overall pattern is expected for the remainder of this week and this weekend. One exception will be the anticipated modest cooling trend, from day-to-day, over interior sections in response to the eastward-translation of the aforementioned midlevel ridge. Correspondingly lowering heights aloft will be the result of generally weak midlevel waves suppressing the ridge over the region, with a more prominent midlevel trough setting up along the California coast this weekend. However, dry profiles aloft are expected to prevent precipitation development through the weekend. Before daily high temperatures settle to values within a few degrees above normal this weekend across interior sections, very warm conditions are once again expected on Friday across the Antelope Valley and nearby foothills. Also of note, the strong onshore pressure gradient is expected to drive daytime enhancements in southwest winds across the Antelope Valley and nearby foothills, where local wind gusts to 40-45 mph will be possible each day. However, without stronger upper support, Wind Advisories appear generally unlikely but cannot be ruled out (10-30 percent chance of issuance). .LONG TERM (MON-THU)...06/228 PM. Only gradual change is expected in the overall weather pattern going from the weekend into next week. Within the base of the previously mentioned prominent upper trough, an upper low is expected to gradually close off and drift southward near or just off the coast of Southern California through early next week. Thereafter, it may slowly advance eastward or northeastward later in the week. This will occur within a semi-blocking pattern over the southwest states, responsible for the limited overall change in weather conditions. Midlevel ridging extending northwest from the southern Rockies to the central Great Basin will correspond to strong heating over interior sections and a strong onshore pressure gradient. This will cause the marine layer to be entrenched over coastal areas and nearby valleys, with widespread nighttime stratus and patchy fog partially clearing each afternoon. Temperatures each day will range from the 60s near the coast, to the 70s over coastal valleys, to the 80s and 90s over interior sections -- warmest over the Antelope Valley. If the upper low were to track directly over the area, there is some potential for cooling aloft to disrupt the strength of the thermal inversion surmounting the marine layer. If this were to occur, a deepening moist layer could cause overnight and morning drizzle near the coast -- especially early next week. Diurnal cumulus development may also occur over the mountains, if the upper low were to track directly over the area. And then with the departure of the upper low by the middle of next week, temperatures could increase by a couple degrees, though uncertainty regarding the track of the upper low extends to the strength of the marine layer and temperatures. Regardless, measurable precipitation is not expected without greater midlevel moisture content. Also, diurnally-enhanced southwest wind gusts are expected over interior areas each afternoon -- especially for the Antelope Valley. && .AVIATION...07/0306Z. At 0008Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was at 4300 ft with a temperature of 25 degrees Celsius. Overall for the 00Z TAF package, high confidence in KWJF and KPMD...and moderate confidence for all other coastal and valley TAF sites. There is a 20% chance for brief cigs at KPRB around 12Z. Lower confidence for coastal and valley sites is due to uncertainties in the marine layer. Timing of flight category changes through the TAF period could be +/- 2 hours of current forecasts. KLAX...Moderate confidence in 00Z TAF. For tonight, high confidence in return of cigs, but lower confidence in flight categories. No significant easterly wind component is expected. KBUR...Moderate confidence in 00Z TAF. Timing of return of IFR/MVFR conditions could be +/- 2 hours of current 06Z forecast. There is a 20-30% chance for LIFR conditions. && .MARINE...06/1017 PM. For the Outer Waters, moderate to high confidence in current forecast. Tonight through Saturday morning, high confidence in winds and seas remaining below Small Craft Advisory (SCA) levels. From Saturday afternoon through Sunday night, there is a 50-60% chance of SCA level winds. For Monday and Tuesday, high confidence in winds and seas remaining below SCA levels. For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, high confidence in winds and seas remaining below SCA levels. For Sunday, there is a 30-40% chance of SCA level winds in the afternoon and evening hours. On Monday and Tuesday, high confidence in winds and seas remaining below SCA levels. For the Inner Waters south of Point Conception, high confidence in current forecast. Today through Tuesday, winds and seas are expected to remain below SCA levels. Through the weekend, dense fog, with visibility of one mile or less, will continue to impact the coastal waters north of Point Conception during the night and morning hours. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory remains in effect until 8 PM PDT Friday for zones 382-383. (See LAXNPWLOX). PZ...NONE. && $$ PUBLIC...MW/Cohen AVIATION...Phillips MARINE...RAT/Phillips SYNOPSIS...Cohen weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox