Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000 FXUS66 KLOX 231122 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 422 AM PDT Mon Apr 23 2018 .SYNOPSIS...22/901 PM. There will be overnight and morning coastal low clouds and fog for several days this coming week otherwise conditions will be warm and dry. Temperatures will cool a bit Friday and Saturday as a weak weather system moves across the region. && .SHORT TERM (TDY-WED)...23/259 AM. Weak ridging along with onshore flow have combined to produce a fairly widespread stratus deck this morning. Aircraft soundings out of KLAX show the marine layer is 700 feet deep which is shallow enough to keep the clouds out of all of the valleys except for the lower portions of the San Gabriel Vly. It is also shallow enough to create some dense fog which will last through mid morning. The inversion is strong enough to prevent clearing at a few beaches this afternoon. The stronger onshore flow will create cooler temps across the coasts and to a lesser degree in the vlys. Inland temps will change little. Just a few little changes Tuesday. The ridge is a little weaker so the marine layer will be a touch deeper and will extend a little deeper into the vlys. Max temps will cool a little as well. An upper low approaches northern CA on Wednesday. It will push the ridge a little more to the east. Hgts...though...really do not change much. The lift from the trof should lift the low clouds into the vlys. The inversion will be a little weaker and this will allow the morning stratus to clear a little quicker. Max temps will not change much from Tuesday and will be a few degrees above normal. .LONG TERM (THU-SUN)...23/318 AM. EC and GFS agree that the upper low will not move much on Thursday. Things will be in pretty static pattern and like Wednesday there will be a deep stratus pattern extending deep into the vlys. Hgts and pressure grads do not change much and max temps will be similar to Wednesday`s. The EC and GFS begin to disagree on the movement and evolution of the low on Friday but the disagreement if more of a Northern CA problem as there is not too much difference between the two mdls for SoCal. Look for a troffier pattern with lower hgts. The deep marine layer will continue but the lower hgts will usher in a cooler trend and max temps will fall to a degree or two blo normal. Very large disagreement for the forecast next weekend. The EC brings a tight cut off 552 DM upper low over Sacramento while the GFS has only a weak trof over the state. The EC seems a little exuberant and based the weekend forecast on the GFS. Saturday will be like Friday but by Sunday there should be enough cool air mixing up north to prevent the stratus from forming across the Central Coast. The cooler air will also bring max temps down 2 to 4 degrees across the 4 county forecast area. && .AVIATION...
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23/1040Z. At 1035Z, the marine inversion at KLAX was based around 900 feet. The top of the inversion was 2700 feet with a temperature of 22 degrees Celsius. Overall, low confidence in coastal TAF sites and high confidence in inland TAf sites. Currently, LIFR/VLIFR conditions prevail at coastal TAF sites and these conditions should dissipate by late morning. For tonight, high confidence in return of stratus to coastal TAF sites, but low confidence in timing and flight category. For inland sites, high confidence in VFR through the period (although there is a 20% chance of IFR/LIFR conditions developing late at KBUR/KVNY) KLAX...Low confidence in 12Z TAF. Conditions will bounce between IFR and LIFR 12Z-20Z. Stratus could dissipate up to two hours earlier than current 20Z forecast. For tonight, high confidence in return of stratus, but low confidence in timing (+/- 3 hours of current 03Z forecast) and flight category (50/50 chance of either MVFR or IFR conditions). KBUR...High confidence in 12Z TAF. There is a 20% chance of IFR/LIFR conditions developing after 06Z tonight.
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&& .MARINE...23/137 AM. For the Outer Waters, high confidence in current forecast. Winds and seas will remain below Small Craft Advisory (SCA) levels through Wednesday. On Thursday and Friday, there is a 70% chance of SCA level winds. For the Inner Waters, high confidence in current forecast. For the waters north of Point Sal, winds and seas will remain below SCA levels through Wednesday. On Thursday and Friday, there is a 70% chance of SCA level winds in the afternoon/evening hours. For the waters south of Point Conception, winds and seas will remain below SCA levels through Wednesday. On Thursday and Friday, there is a 60% chance of SCA level winds, especially across western sections. Areas of dense fog will impact all the waters this morning with reduced visibilities. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (WED-SUN). No significant hazards expected. && $$ PUBLIC...Rorke AVIATION...RAT MARINE...RAT SYNOPSIS...Kj is the U.S. government's official web portal to all federal, state and local government web resources and services.