fxus66 klox 221131 

Area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
431 am PDT Mon Oct 22 2018 

Synopsis...22/312 am. 

Temperatures will continue to trend cooler to near normal for this 
time of year through mid week. High pressure will cause 
temperatures to turn significantly warmer again late this week 
with offshore winds expected. Areas of night through morning low 
clouds will return through at least mid week. 


Short term (tdy-wed)...22/304 am. 

Latest fog product imagery indicated widespread low clouds across 
the central coast and the Santa Ynez Valley as well as much of the 
l.A. County coast and coastal valleys early this morning. Latest 
amdar sounding around lax showed the marine layer around 2,000 ft 
deep which makes sense with the intrusion of stratus into the 

Synoptically, the upper level trough axis will linger across 
Southern California through Tuesday night before exiting east 
while a west to east elongated upper level ridge develops across 
the eastern pac west of southern and central cal. This ridge will 
begin to nudge eastward into the area by Wednesday. The upper 
ridge will then expand and strengthen further inland allowing 
more significant warming late this week with increasing offshore 
flow late this week. 

As for today, high temps will trend slightly cooler as onshore 
flow increases, but will not be strong by any means. However, 
boundary layer temps and 500 mb heights will continue to trend 
slightly lower allowing for the modest cooling from yesterday. 
Tuesday should be slightly warmer as the upper low begins to shift 
to the east. High temps for today and Tuesday will be around 
normal for this time of year for much of the forecast area. Some 
northerly winds will affect the sba South Coast this evening, but 
will remain well below advisory levels. There will continue to be 
night through morning low clouds affecting most coast and coastal 
valleys tonight into Tue morning and once again Tue night into Wed 
morning. Not as confident that low clouds will reach the sba 
South Coast due to the northerly winds this evening. However, 
there could be a southerly surge from Oxnard moving up the coast 
by sunrise or a few hours before. Some additional warming is 
expected on Wednesday as onshore flow weakens while the upper 
ridge starts to strengthen as it nudges in over the region. High 
temps should increase 2 to 5 degrees for the most part. Best 
warming across the valleys and inland areas. 

Long term (thu-sun)...22/326 am. 

Both the ec and GFS remain in good agreement with large scale 
features through the weekend. An upper level ridge will build in 
from the eastern pac. At the lower levels, northerly winds will 
develop Thursday and then shift to the northeast by Friday 
bringing more Santa Ana winds to the wind prone areas of Los 
Angeles and Ventura counties. At this time, winds are not looking 
to strong, but the high temps will rise significantly Thursday and 
Friday. Highs are expected to reach the mid to upper 80s for 
coast and coastal valleys with the offshore flow. There will be a 
chance that by Friday highs in some inland coast or coastal 
valleys locations will reach the lower 90s. Not much change on 
Saturday. Grads will be a little less offshore so there will be 
weaker morning canyon winds. Max temps will likely be unaffected 
and will be very close to friday's warm values. 

The ridge should begin to weaken on Sunday and there will be good 
onshore trends (much like yesterday this will lead to 3 to 6 
degrees of cooling across the coasts and vlys. 



At 11z at klax, the marine layer depth was around 2000 feet. The 
top of the inversion was at 3200 feet with a temp of 19c. 

Areas of low clouds in most coastal areas (except in coastal 
sections of vtu county), in the San Gabriel, San Fernando, the 
Salinas and Santa Ynez valleys. Conditions were mostly IFR to 
LIFR, except low MVFR across coastal sections of l.A. County. 
Expect skies to clear by mid morning in the valleys, and by late 
morning or early afternoon across the coastal plain. Expect 
widespread low clouds in coastal and most valley areas tonight, 
with generally IFR conds, except LIFR conds on the central coast 
and low MVFR across the l.A. County coast. 

Klax...moderate confidence in the 12z taf. Cigs are expected to 
clear by late morning or around noon. There is a 20% chance that 
cigs could drop into the IFR category for a few hours between 12z 
and 16z. There is a 20% chance that cigs could linger until 21z. 
There is a 20-30% chance that cigs will arrive as early as 04z 
this evening. 

Kbur...moderate confidence in the 12z taf. Cigs are expected to 
clear by mid morning. There is a 20-30% chance that cigs 
linger through 18z. There is a 20-30% chance that cigs will 
arrive as early as 07z this evening. 


Marine...22/431 am. 

For the outer waters, moderate to high confidence in the forecast. 
Small Craft Advisory (sca) conds are expected thru at least late 
tonight. Conditions should drop below Small Craft Advisory levels very late tonight 
thru Tue morning, the Small Craft Advisory conds are likely Tue afternoon thru Thu. 

For the inner waters north of pt Conception, moderate to high confidence 
in Small Craft Advisory conds this afternoon/evening. There is a 40%-50% chance of 
Small Craft Advisory level conds during the afternoon/evening hours Tue thru Thu. 

For the inner waters S of Point Conception, Small Craft Advisory conds are not 
expected through Fri, except there is a 20-30% chance of Small Craft Advisory 
level gusts across western portions of the sba channel during the 
late afternoon and evening hours Tue thru Thu. 


Lox watches/warnings/advisories... 
Pz...Small Craft Advisory in effect from 3 PM this afternoon to 9 
PM PDT this evening for zone 645. (See laxmwwlox). 
Small Craft Advisory in effect until 3 am PDT Tuesday for 
zones 670-673-676. (See laxmwwlox). 


Hazard potential outlook (wed-sun). 

A significant warming trend is possible late next week. 




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