Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000 FXUS66 KLOX 281155 AFDLOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 455 AM PDT Sun May 28 2017 ...Aviation discussion updated... .SYNOPSIS... An upper level ridge of high pressure and a lowering marine layer will support a warming trend through early next week. The high will be replaced by a weak upper level trough of low pressure by the middle of next week providing a cooling trend with more widespread night and morning low clouds for the coast and valleys. && .SHORT TERM...(TDY-TUE) Pleasant but rather dull on tap for the next three days. All mdls agree that a 582 DM ridge will persist over the area today and Monday with a trof moving into the area Monday night and lasting into Tuesday. Marine layer stratus is struggling to develop due to a weak inversion and offshore trends. The only exception is western SBA county where westerly flow has produced a backwards building stratus deck. Patchy stratus will develop towards dawn over the LA and VTA coasts and the San Gabriel Vly as continued radiational cooling increases the low level humidities close to 100%. Whatever the morning stratus pattern skies everywhere will be sunny by mid to late morning. The increasing hgts...offshore trends and abundant sunshine will all contribute to 3 to 6 degrees of warming across the area and most max temps will end up 2 to 4 degrees above normal. Not much change in the weather for Monday. The stratus may be a little better developed as the inversion will be stronger. Max temps will be up 1 to 2 degrees from todays readings. Tuesday will see the arrival of a weak trof along with an increase in the onshore flow both to the west and north. This will likely spin up an eddy. Look for significant increase in morning low cloud coverage esp for the vlys. Still the onshore flow and the inversion will not be strong enough to prevent total clearing Max temps will fall with the biggest drops in the vlys and the smallest inland. .LONG TERM...(WED-SAT) The GFS and EC agree that a fairly sharp (at least for this time of year) upper level trough will move across the forecast area on Wednesday. This system will continue to deepen the marine layer which will continue to cool the coasts and vlys. Lowering hgts will allow some cooling inland also. The PVA with this trof moves across during max heating and while it is still on the dry side there is a 20 percent chc of a TSTM. A little ridge will bring a decrease in marine layer coverage as well as a noticeable bump up in temps on Thursday. The forecast is a little muddled for Friday and Saturday as the GFS continues the ridge while the EC brings in a weak trof. The night through morning low cloud pattern should continue but to what degree will be dependent on which pattern actually develops. && .AVIATION...
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28/12Z. At 09z at KLAX... The inversion was based near 500 feet. The top of the inversion was near 4900 feet with a temperature of about 17 degrees Celsius. Overall... Moderate confidence in the current TAFs. LIFR/IFR conditions will develop at some coastal locations by 14z then will clear by 18z. There is a fifteen percent chance of LIFR/IFR conditions at KBUR and KVNY in the 13z-17z period and a ten percent chance at KPRB and KSBA in the 14z-17z period. LIFR/IFR conditions will likely develop at most coastal and adjacent valley locations after 29/04z. Otherwise and elsewhere VFR conditions will prevail. KLAX... Moderate confidence in the current TAF. There is a thirty percent chance of LIFR/IFR conditions in the 13z-17z period then a seventy percent chance in the 29/05z-17z period. Otherwise VFR conditions will prevail. No east winds above 7 knots are expected. KBUR... Moderate confidence the current TAF. There is a fifteen percent chance of LIFR/IFR conditions in the 13z-17z period then a sixty percent chance after 29/05z. Otherwise VFR conditions will prevail.
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&& .MARINE...
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28/200 AM. Small Craft Advisory (SCA) conditions continue across the Outer Waters into at least Tuesday though there will be periods during overnight and early morning hours when winds dip below SCA levels. SCA conditions will begin in the nearshore waters of the Central Coast this afternoon and continue into at least Tuesday. There will be periods during the overnight and early morning hours when conditions will dip below SCA levels. The stronger winds will spill into the western half of the Santa Barbara Channel each evening but not far enough to warrant a SCA for the entire channel. The elevated winds will create a short period chop over all waters including the Santa Barbara Channel and Santa Monica Basin in the Inner Waters. The winds peak Monday and Tuesday and there is a thirty percent chance that Gale Conditions form beyond 30 nm of the Central Coast.
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&& .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9 AM PDT Tuesday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Tuesday for zones 670-673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK...(TUE-SAT) No significant hazards expected. && $$ PUBLIC...Rorke AVIATION...Kj MARINE...Kj SYNOPSIS...Sirard weather.gov/losangeles

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