Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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374 FXUS66 KLOX 161551 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 851 AM PDT Fri Aug 16 2024 .SYNOPSIS...16/225 AM. A high pressure system over the region will weaken and move east over the coming days as an upper-level trough moves into the Pacific Northwest. A cooling trend with increased onshore flow will continue through the weekend, then some warming will develop over the early half of next week. && .SHORT TERM (TDY-SUN)...16/850 AM. ***UPDATE*** The forecast is well on-track, and no changes have been made to the ongoing forecast. ***From Previous Discussion*** Very benign weather will continue across Srn Ca for the 3 day short period. Over the next three days an upper high over the CA/AZ border will shift to the east while at the same time an upper low to the N will move southward. The effects over SRN CA will be a switch to SW flow aloft that will strengthen with time. 594 dam hgts this morning will fall to 588 dam by Saturday afternoon and then rebound slightly Sun. At the sfc there will be weak to moderate onshore flow to the east and weak occasionally offshore flow in the N/S direction. Marine layer cloud coverage is a little more robust that it has been over the last few nights. A weak eddy has spun up and there are some low clouds moving from Long Beach into the Oxnard. Low clouds should increase further tonight into Saturday morning as hgts lower. The low cloud coverage will shrink Sunday morning as the offshore flow from the north increases slightly. The onshore push to the east will be a little stronger today and this will cool the coasts a few degrees. Northerly flow however will bring warmer air into the interior where max temps will warm 3 to 4 degrees. Look for 2 to 4 locally 5 to 6 degrees of cooling Saturday as the hgts lower and onshore increases. Less marine layer, slightly higher hgts and a stronger offshore push from the north will bring a little warming to the area Sunday. Last evenings Sundowner event did not live up to expectations with gusts almost all in the 30 to 40 mph range. The winds will be weaker tonight and there is not threat of advisory winds. Monsoonal thunderstorm activity is not favored through the weekend, although the outer edge of a moisture surge may bring some high clouds to the region tomorrow afternoon. This moisture is expected to be too elevated to increase thunderstorm chances, which continues to be well under 10 percent. .LONG TERM (MON-THU)...16/309 AM. The latest deterministic mdls and ensembles are in good agreement on the general upper level pattern for the xtnd period. The upper high will strengthen and move to the west on Monday and Tuesday. On Wednesday and Thursday a PAC NW trof will move into the state and push the upper high back to the east. Hgts will climb each day through Tuesday and will peak around 595 dam on Tuesday afternoon. to 595 dam. Look for 2 to 4 degrees of warming each day. By Tuesday afternoon the only 70s will be right at the beaches with 80s and lower 90s across the rest of the coasts. The vlys will see max temps from 92 to 104 degrees. There will be plenty of triple digit heat across the far interior and lower mtn elevations as well. These temps are about 6 degrees above normal. While it will be warm these temps will only pose a moderate heat risk. There is a 15 percent chc that the current temp forecast is too low and there would be a need for heat products across the interior and some of the vlys. Lowering hgts and onshore flow will arrive Wed and continue into Thu. Look for 2 to 4 degrees of cooling each day. The significant high pressure will likely suppress most if not all marine layer clouds on Mon and Tue. The lowering hgts will bring an more conducive environment for low cloud formation Wed and Thu mornings. Monsoonal moisture transport into the region becomes a bit more likely on Tuesday. Even so, at this point the chance of actual convection remains less than 10 percent. && .AVIATION...16/1129Z. At 0730Z at KLAX, the marine inversion was 600 ft deep. The top of the inversion was 2100 ft with a temperature of 27 deg C. High confidence in generally CAVU 12Z TAFs for KPRB, KBUR, KVNY, KPMD, KWJF. Moderate confidence in the 12Z TAFs for KSBA and KCMA. There is a 20%-30% that some low clouds with LIFR conds could move into the airfields by 14Z and persist until about 17Z. Otherwise, MVFR vsbys are expected 13Z-17Z and again aft about 09Z tonight, except for a 30% chance of LIFR cigs aft 09Z at KCMA. Moderate confidence in the 12Z TAF for KOXR as low clouds and LIFR/IFR conds are expected (60% chance) to affect the airfield at times 12Z-17Z, and again aft about 09Z tonight. Moderate confidence in the 12Z TAFs for the LA coastal airfields. There is a 90% chance of IFR cigs 12Z-16Z at KLGB, a 50%-60% chance at KLAX and KSMO from about 13Z-17Z. Low clouds with IFR/MVFR conds should move back into these airfields (50% chance) aft about 09Z-11Z tonight. Moderate to high confidence in the 12Z TAFs for KSMX and KSBP. VFR conds are expected into tonight. There is a 40-50% chance of VLIFR conds at KSMX between 04Z-12Z tonight due to cigs/vsbys, and the arrival of cigs could be off by +/- 2 hours from TAF time. There is a 40% chance of IFR/MVFR cigs/vsbys at KSBP between about 09Z-12Z tonight. KLAX...Moderate confidence in the 12Z TAF. There is a 50%-60% chance of IFR cigs between 13-17Z. There is also a 50% chance of IFR/MVFR cigs moving in aft about 09Z tonight thru about 17Z Sat. No significant east wind component is expected. KBUR...High confidence in the CAVU 12Z TAF. && .MARINE...16/216 AM. For the outer waters from Point Piedras Blancas to San Nicolas Island, high confidence in SCA level winds for all the waters thru tonight, and for the waters west and south of Point Sal Saturday through Sunday night. There is a chance (30%-40%) of SCA wind gusts at times for all the outer waters Monday through Tuesday night. For the inner waters north of Point Sal, moderate to high confidence in SCA level winds and/or steep seas through late tonight. There is then a 30% chance of SCA conditions afternoons and evenings over the weekend, and a 20%-30% chance afternoons and evening Monday and Tuesday. For the Santa Barbara Channel, high confidence in winds below SCA levels through Saturday. There is then a 30% chance of SCA wind gusts at times for the western portions of the channel each late afternoon to evening Saturday night through Tuesday. In the eastern portion, high confidence in conditions remaining below SCA level through the period. For the southern inner waters, high confidence in conditions staying under SCA levels through Tuesday night. With a shallow marine layer, there is moderate confidence in patchy dense fog with visibilities under 1 nautical mile effecting the Central Coast waters and southern inner waters through this morning. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Monday for zones 673-676. (See LAXMWWLOX). && $$ PUBLIC...Rorke/Cohen AVIATION...Sirard MARINE...Sirard SYNOPSIS...Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox