Scientific Forecaster Discussion
fxus66 klox 221604
Area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
904 am PDT Mon Oct 22 2018
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 light to moderate offshore winds expected. Areas of night
through morning low clouds will continue through at least mid
Short term (tdy-wed)...22/903 am.
The low clouds along the central coast and in la County will clear
to the beaches by 11, but will linger at the coast most of the
day. Temperatures are, in general, slightly cooler than yesterday
so far but will finish nearly the same. Sub-advisory strength
sundowner winds are still expected along the sba co South Coast
***From previous discussion***
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 1530z, the marine inversion at klax was based around 2000
feet. The top of the inversion was 3600 feet with a temperature
of 18 degrees celsius.
Overall, moderate confidence in 18z taf package. High confidence
in VFR conditions for all sites through this afternoon. For
tonight, high confidence in return of stratus/fog to coastal sites
and moderate confidence in stratus/fog reaching coastal valleys.
Klax...moderate confidence in 18z taf. High confidence in VFR
conditions through this evening. For tonight, high confidence in
return of IFR conditions, but low confidence in timing (could be
+/- 3 hours of current 08z forecast).
Kbur...moderate confidence in 18z taf. High confidence in VFR
conditions through this evening. For tonight, low confidence in
return of IFR/LIFR conditions as well as timing.
For the outer waters, moderate confidence in current forecast.
Through tonight, high confidence in Small Craft Advisory (sca)
level northwest winds. For Tuesday through Thursday, there is a
60% chance of Small Craft Advisory level winds developing.
For the inner waters north of Point Sal, moderate confidence in
current forecast. Small Craft Advisory level winds are expected this afternoon and
evening. For Tuesday through Thursday, there is a 50% chance of
Small Craft Advisory level winds each afternoon and evening.
For the inner waters south of Point Conception, high confidence in
current forecast. There is a 20% chance of Small Craft Advisory level winds across
the western half of the Santa Barbara Channel during the late
afternoon and evening hours Tuesday through Thursday.
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.