Acton Weather

000
FXUS66 KLOX 162203
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
203 PM PST Fri Nov 16 2018

.SYNOPSIS...16/1059 AM.

Weak offshore flow will keep dry and fairly warm weather across
the region today. Onshore flow will return Saturday, bringing
some cooling and a return of night through morning low clouds and
fog to coastal and some valley areas. Temperatures will be near
normal in most areas Sunday through Monday. A couple of low
pressure areas could bring some rain to portions of the region
late Wednesday into Thanksgiving Day.

&&

.SHORT TERM (TDY-MON)...16/153 PM.

Gradients still lightly offshore but trending onshore and should
official be onshore by this evening. Temps cooled off as expected
and this trend also will continue into Saturday along with what
should be an expanded and deepening marine layer. Forecast
soundings indicate the marine layer rapidly rising through the
evening up to around 1500` by morning. This may be enough to
squeak into the valleys but the deepening and onshore push might
not happen soon enough for this to happen. Either way expect
another few degrees of cooling and at least some morning stratus
along the coast. Will see another round of increasing high clouds
as well as some upper level moisture moves in off the Pacific.

A weak trough moving through the northern Rockies Sunday will
cause surface pressures to rise over Nevada and generate a little
offshore push that will peak Monday. The NAM came in with a -4.1
LAX-DAG gradient for Monday which was 1-2mb stronger than the
previous models. However there`s still little if any support aloft
so just the gradient driven winds should stay well below advisory
levels. Sunday we`ll see temps rising a few degrees as a result of
the weaker onshore flow and then probably little change Monday. If
the stronger gradients pan out then Monday highs may end up being
a little warmer than currently forecast but only by a few degrees.

.LONG TERM (TUE-FRI)...16/202 PM.

The Monday ridge and offshore flow will transition pretty quickly
to troughing and onshore flow Tuesday. Models have been consistent
last few days scooting this upper low too far south to have much
impact other than to cool temps off a couple degrees with the
onshore flow.

Forecast gets infinitely more complex after Tuesday as models
continue to exhibit significant run to run variations leading to
even lower than usual confidence in the longer range, particularly
with the specifics. The operational GFS remains dry through the
end of next week, however many of the GEFS ensemble members
support the wetter ECMWF and NBM solutions for Wed and again
either Thu or Fri with a second system. So I agree with the idea
of going with pops in the 20-40 range all those days with the
highest chances across SLO and northern SB Counties. It doesn`t
appear that any of these system have much potential for heavy rain
this far south as moisture is pretty limited, and while the ECMWF
does show some decent PVA for Wed night associated with a sharper
trough it`s pretty quick moving and again not a ton of moisture
to work with. So chances can`t be ruled out for some heavier
bursts but right now the odds favor a fairly benign series of
systems coming through mid to late next week. As we get closer
we`ll be able to be more precise with the timing and amounts.

&&

.AVIATION...16/1821Z.

At 17Z, the marine layer was 300 feet deep, with an inversion
extending to 2600 feet and a temperature of 18C.

High confidence in VFR conditions through 03Z this evening.
Moderate confidence in low clouds reforming tonight into Saturday.
Low confidence in timing, exact coverage, and flight cats
however. LIFR to IFR cats are most probable at all coastal sites.
Moderate confidence that low clouds will stay out of KVNY KBUR. 20
percent chance of impacting KPRB.

KLAX...High confidence in VFR through 03Z. 70 percent chance of
low clouds tonight, with onset window of 06-12Z. If clouds form,
cats will be IFR or below, with a good chance of LIFR, and a few
hours of VLIFR dense FG possible. East winds are likely again
tonight, but moderately confident they will stay below 8 knots.

KBUR...High confidence in VFR conditions persisting with light
winds, except for a 5 percent chance of LIFR low clouds Saturday
morning.

&&

.MARINE...16/119 PM.

High confidence in winds staying below Small Craft Advisory (SCA)
through Tuesday. Patchy dense fog will be possible anywhere
through Saturday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...MW
AVIATION...Kittell
MARINE...Kittell
SYNOPSIS...DB/Sirard

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