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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

FXUS66 KLOX 192109

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
209 PM PDT Wed Jun 19 2019

.SYNOPSIS...19/1252 PM.

Low clouds have cleared the valleys and continue to cover most
beaches this afternoon. Strong onshore winds will keep low clouds
over the coasts and valleys the next several days. There will be 
slow and limited afternoon clearing each day with possible drizzle
in the morning. Temperatures will cool through Friday and warm 
slightly into the weekend as there will be better clearing.


.SHORT TERM (TDY-SAT)...19/208 PM.

The Eastern Pacific High moves in to the area from the west today.
The ridging will last until Thursday afternoon when another trof 
will extend into our area from the northeast. By Monday that trof
has moved off to the east and a large upper-level low establishes
about 250 miles west of Seattle with a trof extending south 
through mid-California. The trof will push southward into our area
on Tuesday and Wednesday.

Very few changes from earlier discussions in this persisting
pattern. Weak high pressure aloft continues over the center of 
the state today with 588 DM heights over the CWA. Moderate 
onshore flow both to the east and north will become strong in 
afternoon, especially in Antelope Valley. It will continue to be 
slightly unstable over the mountains but only expecting some 
cumulus build ups and limited showers because of low moisture. 
The coasts and valleys will stay 5 to 10 degrees below normal, 
while higher than normal heights will bring interior temps 3 to 6 
degrees above normal.

The ridge will be replaced with broad cyclonic flow on Thursday as
a cold upper low pushes into the Great Basin. The onshore flow
is forecast to increase as the gradients tighten. This increase, 
along with the slightly lowering heights and weak lift from the 
cyclonic flow will produce a great environment for morning 
drizzle. It would not be surprising if more than a few areas 
received a few hundredths of an inch of measurable precipitation 
from the drizzle. The foothill areas will likely see the heaviest 
drizzle due to the extra kick from the orographic lift. Max temps
will fall a few degrees across the interior due to the lowering 
heights. The cloudy coasts will see little temperature change but
the valleys will cool even further. The Antelope Vly will likely 
see advisory level wind gusts in the afternoon and early evening.

Friday should be a near repeat of Thursday except that there will
be even lower heights and perhaps more drizzle. Look for slow to 
no clearing. It will be the coolest day of the next 7 with max 
temps across the valleys and interior 12 to 18 degrees below 

Very weak ridging is expected Saturday and the winds will trend
offshore helping the marine layer clouds clear earlier and
allowing afternoon high temperatures to rise a few degrees.

.LONG TERM (SUN-WED)...19/208 PM.

By Sunday, temperatures will be near normal across the interior 
but will still be 5 to 10 degrees below normal across the coasts 
and valleys. Another trof will arrive Monday, this time from the 
northwest.  We'll have westerly zonal flow aloft on Monday as 
we're just south of the trof, then the lower heights work their 
way south through Wednesday. The low will bring back the strong 
onshore flow, less clearing and cooler coastal temperatures.



At 1703Z, the marine layer depth was around 2800 feet deep at 
KLAX. The top of the inversion was near 4800 feet with a 
temperature around 23 degrees Celsius.

Moderate confidence in the current forecast. The satellite picture
trends definitely show better clearing patterns in the marine
clouds and even coastal sections in LA county look good for
clearing within the next 2 hours. There is still some doubt about
clearing in the coastal sections of Ventura and southern Santa
Barbara counties, however. The valley and desert TAF sites are
well on their way toward clearing. Tonight, onshore flow will
begin to increase along wih an anticipated deepening marine layer.
Therefore, ceilings will be a bit higher at many TAF sites,
however clearing trends will be slower and some coastal sites will
remain cloudy on Thursday. Mountain obscuration will be a concern
through Thursday.

KLAX...VFR conditions are expected this afternoon, followed by
MVFR ceilings tonight and Thursday. 

KBUR...VFR conditions are expected this afternoon, followed by
MVFR ceilings tonight and Thursday.


.MARINE...19/144 PM.

Winds and seas will likely remain below Small Craft Advisory 
levels through at least Thursday. There is a 50 percent chance 
for advisory level seas and winds across the northern most outer 
waters Friday afternoon and evening, and a 30 percent chance of
advisory level winds each afternoon and evening through the 





No significant hazards expected.