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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

FXUS66 KLOX 181137

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
437 AM PDT Mon Jun 18 2018

New Aviation Discussion

.SYNOPSIS...18/322 AM.

A ridge of high pressure building over the region through the
middle of this week will bring significant warming away from the
coast. Night to morning low clouds will become confined to coastal
areas during this time with fair skies elsewhere.


.SHORT TERM (TDY-WED)...18/314 AM.

The cool air and mixing assoc with ydys trof greatly weakened the
marine inversion and low clouds have been mostly wiped out across
SLO and SBA county. Low clouds still cover the csts/vlys and cstl
slopes of VTA/LA county. The clouds are very thin and the eddy is
gone so the coasts will clear while the vlys will have partly
cloudy skies as the bkn stratus deck transforms to a sct strata
cu deck with the late morning sunshine. Ydys upper low is now in
Idaho and hgts will rise to 585 DM. The sunshine and higher hgts
will combine with weaker onshore flow and will allow for 5 to 10
degrees of warming today but since ydy was so cool...max temps
will still be 5 to 10 degrees blo normal.

The SBA to SMX grad goes offshore tonight as high pressure pushes
into the east pac. This will produce a sundowner which will mostly
affect the western portion of the SBA south coast. There will be a
few advisory level gusts but for the most part this event will be
just below advisory levels. The marine layer will reform but will
be lower and low clouds will mostly affect the coastal areas (but
not southern SBA county due to the north winds.

High pressure begins to nose in from the SW on Tuesday and hgts
climb to 591 DM. Offshore trends will continue. Max temps will
shoot up 6 to 12 degrees and will reach normals at the coasts and
above normal inland.

Stronger high pressure presses into the north Tuesday night. There
will be an advisory level sundowner and the winds will also affect
the city of SBA a little more although the strongest gusts will
still be to the west. Low clouds will remain confined to the coast
trapped under a strengthening and lowering inversion.

The high moves over the Mexico/CA border Wednesday and hgts climb
further to 594 DM. The marine layer will preclude much additional
warming at the coasts but inland will see another 3 to 6 degrees
of warming and max temps in the vlys will be 6 to 9 degrees above

.LONG TERM (THU-SUN)...18/323 AM.

The GFS and the EC agree that the large high pressure system will
sit atop Srn Ca during the Thu/Fri time period. It looks like the
Wed to Fri days will be very similar to each other.

At the surface, the onshore gradient winds and coastal eddy will 
continue. There will be a shallow marine layer across the coasts 
each night through morning. The capping inversion will be very 
strong and it might make it tough for the low clouds to clear at 
the beaches. There will be huge difference in afternoon maximum 
temperatures: beach temps will be near normal...valley temps will
be 5 to 10 degrees above normal, and inland temps will 8 to 12 
degrees above normal. The overnight minimum temperatures will also
rise to above normal and there will likely be a small zone at the
top of the inversion where minimum temperatures could be substantially
above normal. Due to a combination of very warm lows and highs there
could be some heat advisories on Thursday and or Friday.

A trof moving out of the Pac NW will knock the ridge down. Hgts
fall but not much only to 591 DM. So inland temps will cool a few
degrees but will remain well above normal. Both the EC and GFS
agree that there could be a large eddy which will produce a very
large southerly surge up the Central Coast. If this comes true
there will be more marine stratus and cooler coastal temps. Not
quite buying to this whole hog yet but will have to keep an eye on



At 0815Z at KLAX...the marine layer was 4000 feet deep. The top 
of the inversion was at 4900 feet with a temperature of 12 C.

Moderate confidence in TAFs for coastal and valley terminals 
through 00Z. There is a chance of MVFR cigs/vsbys at coastal and 
valley terminals south of KSBA including KLAX and KBUR thru 20Z. 
Low clouds expected scatter out within two hours of TAF. Low 
confidence after 00Z due to uncertainty in timing and flight 
category for coastal terminals (except high confidence in KSBA). 
Weak LLWS possible for KSBA between 00Z and 06Z. 

High confidence otherwise and elsewhere.

KLAX...Moderate confidence in TAF thru 00Z followed by low 
confidence due to uncertainty in timing and flight category of 
low cigs/vsbys. There is a chance of MVFR cigs/vsbys thru 20Z.

KBUR...Moderate confidence thru 00Z followed by generally high 
confidence. There is a chance of MVFR cigs/vsbys thru 19Z. There 
is a 20 percent of IFR cigs/vsbys as early as 09Z.


.MARINE...18/322 AM.

Low end SCA conds likely beginning late this afternoon or early 
evening for the Outer Waters as well as the Inner Waters adjacent 
to the Central Coast. SCA conds will become more likely and a bit
stronger for the same areas late Tuesday through Thursday or 
Friday. In fact there is a 30 percent of Gale winds at some point
during this period. Local SCA winds are also likely at times for 
western portions of the E Santa Barbara Channel during this time. 

A moderate eddy with winds gusting locally up to 20 knots is
possible for the Inner Waters south of Point Conception each 
morning beginning Tuesday.


PZ...Small Craft Advisory in effect from 2 PM this afternoon to 9
      PM PDT this evening for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect from 2 PM this afternoon to 3
      AM PDT Tuesday for zones 670-673-676. (See LAXMWWLOX).



No significant hazards expected.