Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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436 FXUS66 KLOX 020311 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 811 PM PDT Wed May 1 2024 .SYNOPSIS...01/440 PM. Areas of night to morning low clouds and fog will be present near the coast for the remainder of this week. Otherwise, dry conditions and near-normal temperatures are expected through Friday. This weekend, a storm system will pass by to the north of the area. The main impacts across southern California will be areas of light precipitation late Saturday into Sunday, along with cooler temperatures and gusty winds. For next week, near-normal temperatures and dry conditions are expected. && .SHORT TERM (WED-SAT)...01/810 PM. ***UPDATE*** Gusty northwest winds continue to affect interior portions of the forecast area this evening, and are expected to persist through early Thursday morning. A Wind Advisory is in effect through 5 AM Thursday, with gusts up to 45 mph and isolated gusts to 50 mph at times. Increasing north winds will also affect the Ventura Mountains later this evening and overnight, with northeast winds over the interior Santa Barbara County Mountains. In both of these areas, peak gusts are likely to remain near or below 40 mph, although isolated gusts to 45 mph may occur at times. Otherwise, the forecast calls for low clouds and fog over the LA and Ventura County coast and valleys, extending along the eastern Santa Barbara South Coast. Last night the combination of stronger onshore gradients and a weaker inversion may have allowed the coastal eddy to spin low clouds well inland, over the San Gabriel Foothills, and extending into the western Santa Clarita Valley. At the same time, a band of dense fog formed over western Santa Barbara County from Lompoc into the Santa Ynez Valley. The dense fog is not expected to reoccur tonight, and with LAX to Daggett gradients trending weakly offshore overnight, do not anticipate inland progression beyond the coastal valleys of LA and Ventura Counties. For Thursday, look for good clearing from late morning onward, with near-normal temperatures from the mid 70s to the lower 80s in most areas. ***From Previous Discussion*** Northwesterly midlevel flow will persist for the remainder of this week between an upper trough being reinforced over the western states, and a midlevel ridge well offshore over the Pacific waters. The enhanced flow aloft combined with nocturnal drainage flow will support wind gusts of 45 mph overnight. A similar pattern will support gusty northwest winds over these areas Thursday night and Friday morning, though the chance for a Wind Advisory becoming needed over these areas is lower -- 30% chance. Otherwise, in general, dry conditions and mostly clear skies are expected across the region through the remainder of this week. An exception will be over coastal areas and nearby valleys, where neutral to slightly onshore pressure gradients will favor night and morning low clouds and fog in the marine layer. There will be a 30% chance for localized Dense Fog Advisories to become necessary in conjunction with this activity. Some change in these conditions is expected going into Saturday, as temperatures cool by a few to several degrees as midlevel heights fall in response to a deep upper cyclone moving southeast along the Pacific Northwest coast. Gusty west-southwest to west- northwest winds are expected area-wide on Saturday, as enhanced tropospheric flow in the southern periphery of this cyclone overspreads the area. While moisture will deepen over the area well in advance of this system for Saturday and Saturday evening, cooling aloft will tend to disrupt marine layer continuity and related fog development. However, low clouds and drizzle could occur within the deepening moist layer. .LONG TERM (SUN-WED)...01/215 PM. The aforementioned deep upper cyclone will track east-southeastward across the Intermountain West on Sunday. A shortwave trough pivoting around the southern semi-circle of the cyclone may bring sufficient ascent and midlevel cooling to yield a few showers over the area late Saturday afternoon through Sunday. Ample dry air aloft should keep precipitation amounts below one-tenth inch, and many locations may not experience precipitation. A light dusting of snow could occur over the highest elevations of northern VTA and LA Counties, though significant precipitation impacts with this system appear to be unlikely. However, temperatures will be noticeably cooler across the region on Sunday, with most locations only experiencing high temperatures in the lower to middle 60s -- around 10-15 degrees below normal in many areas. Looking further ahead, dry conditions are expected areawide for next week, as midlevel heights rise behind the departing upper cyclone and attendant shortwave trough. Local pressure gradients for next week are expected to turn more neutral to offshore in response to surface ridging north of the area -- beneath subsidence in the wake of the departing upper cyclone. While this pressure pattern will likely still facilitate diurnal wind fluctuations and sea-breeze development, the development of a pronounced marine layer fostering low-cloud and fog development appears unlikely through at least the middle of next week. As a result, clear skies and a warming trend are expected for early to middle parts of next week, with high temperatures rebounding to the mid and upper 70s in most areas Monday through Wednesday. && .AVIATION...01/2336Z. At 2300Z at KLAX, the marine layer was 1900 ft deep with an inversion top at 4300 ft with a temperature of 17 C. Low to moderate confidence in coastal TAF sites and KBUR and KVNY, with high confidence elsewhere. Timing of flight cat changes could be off by +/- 2 hours, and cigs may develop one category lower than forecast for coastal sites in Ventura and L.A. counties. There is a 30% chance of no cigs developing for KSBA, KBUR, and KVNY, and a 30-40% chance of IFR cigs overnight for KSMX. KLAX...Low to moderate confidence in the 00Z TAF. Timing of flight cat changes could be off by +/- 2 hours, and there is a 20% chance of cigs as low as BKN008. High confidence in any east wind component remaining less than 6 kt. KBUR...Low to moderate confidence in the 00Z TAF. Timing of flight cat changes may be off by +/- 2 hours, with a 30% chance of no cigs developing tonight, and a 30% chance of IFR cigs developing overnight. && .MARINE...01/157 PM. For the outer waters, wind are currently below Gale Force at most location. This lull is expected to be short lived, with a 70% chance of gales redevelop this afternoon and tonight. Another lull in wind is possible Thursday morning, followed by an 80% chance of gales Thursday afternoon and night. At least SCA wind are expected much of the time through Sunday, and Sunday afternoon and night there is a 40% chance of gales returning. SCA level seas are expected through Friday night followed by a 40-50% chance of SCA seas on Sunday and Monday. For the inner waters N of Pt. Sal, SCA level winds are likely to continue through tonight, followed by a 80% chance of returning during the afternoon/evening Thursday and Friday (25% chance of brief gales during these times), and a 40% of SCA winds Saturday afternoon/evening. SCA winds are then likely (70% chance) Sunday and Monday. Current SCA level seas will subside Thursday night, followed by a 20% chance of returning Sunday and Monday. For the Santa Barbara Channel, SCA level winds will affect the western portions of the the channel this afternoon and evening, with a 20% chance of reaching the central/eastern portions. Thursday onward, SCA level winds are generally expected to only impact the extreme western portions of the channel, until Saturday afternoon. Saturday afternoon through Sunday night there is a 40-50% chance of widespread NW SCA winds for the entire channel, with the potential (20% chance) for gales on Sunday. For the southern inner waters, there is a 20% chance of SCA level W to NW winds near Anacapa Island this evening. Otherwise conditions are expected to remain below SCA levels until Saturday afternoon. Saturday afternoon through Sunday there is a 40-50% chance of widespread NW SCA winds for all the inner waters, with the potential (20% chance) for gales on Sunday. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory in effect until 5 AM PDT Thursday for zones 378-381. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone 645. (See LAXMWWLOX). Gale Warning in effect until 3 AM PDT Friday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Cohen/Smith AVIATION...Smith MARINE...Schoenfeld/Lund SYNOPSIS...Cohen/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox