Acton Weather

954
FXUS66 KLOX 191659
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
959 AM PDT Sun May 19 2019

.SYNOPSIS...19/812 AM.

Today will be cloudy with showers and a slight chance of
thunderstorms. Monday will be breezy and mostly dry, with a chance
for lingering showers and snow in the mountains. Showers are
possible again Tuesday. Cool temperatures are expected into next
week.

&&

.SHORT TERM (TDY-TUE)...19/930 AM.

***UPDATE***

Showers overall have remained fairly light to moderate and
steady, with foothills receiving locally higher amounts. This due
to the topography giving some extra lift and acting like a sponge
to squeeze out some higher amounts. As of mid morning, there were
some rainfall reports across the Santa Barbara South Coast and
adjacent foothills between 0.75 to near 1.5 inches. SLO County
received anywhere between 0.25 to around 0.75 inches, except the
usual outlier of Rocky Butte which did receive around an inch so
far with this storm. Ventura and L.A. Counties have received
decent amounts so far as well generally between 0.25 to 0.50
inches with some foothills receiving between 0.50 inches to near
an inch in the Ventura County Mountains.

Latest NWS Doppler radar indicated the bulk of showers moving
south of L.A. County into Orange County. However, there will
continue to be some lingering showers across the forecast area
through today. The upper low which was located north of San
Francisco will begin to drop across Central California this
afternoon. Although the main upper low will remain to the north of
the area, 500mb temps will lower to -23 degrees C well south into
L.A. County and with afternoon heating and some breaks in the
clouds, some instability is expected, especially over the
mountains this afternoon. There will be a slight chance for
thunderstorms to develop across SLO County and interior areas of
SBA County due to the proximity of the upper low. There is also a
secondary area expected across the southeastern portion of the
forecast area mainly affecting L.A. County due to a jet streak
approaching the San Diego/OC Counties. Again, with low temps this
cold this time of year with the high Sun angle, thunderstorms
could develop just about anywhere, but best chances will be across
the mountains, eastern L.A. County and SLO County late this
morning and afternoon/evening hours.

There will be a secondary area of showers moving across areas N of
Point Conception this evening and have raised POPs slightly, and
scattered hit and miss showers are expected to continue across
much of the forecast area through tonight. A Winter Wx Advisory
will remain in effect for the L.A./ Ventura County Mountains
through 3 AM Monday morning. Snow levels are expected to lower to
between 5500 and 6000 ft. Mainly between 1-3 inches expected
between 5500-7000 ft. 3-5 inches above 7000 ft. Gusty winds are
expected to pick up through this afternoon across portions of the
Antelope Valley and a wind advisory remains in effect through 8 pm
this evening.

***From Previous Discussion***

A cold for this time of year 540 DM upper low sits to the NW of
San Francisco. A cold front is over SBA county and is moving to
the east. A powerful jet streak which is very noticeable on
satellite is sweeping to the south of the area and is aimed
squarely at San Diego county.

It will be a very showery morning as the front and a post frontal
trof zip through the area. TSTMs are possible over VTA/LA county
and the inner waters as the front and the jet streak interact. The
best chc of TSTMs will be over srn LA county and the adjacent
waters where the jet streak will be nearest.

The upper low will move to the SE and into the San Joaquin vly. 500
mb temperatures drop to near -25 degrees Celsius. This will
increase the instability enough to bring convective showers and a
slight chance of thunderstorms to interior sections. Rainfall
totals should range between 0.25 and 0.75 inches, except local
totals up to 1.00 inch possible across San Luis Obispo/Santa
Barbara counties and near thunderstorms.

Initially, snow levels will start near 7000 feet, but will  lower
rapidly behind the front, eventually lowering to between 5000 and
6000 feet during the afternoon and evening hours. A winter
weather advisory is in effect until 300 am Monday. Total snow
accumulations 1 to 3 inches between 5500 and 7000 feet, and 3 to 5
inches above 7000 feet. Southwest winds will be gusting between
35 and 50 mph across portions of the mountains, Antelope Valley,
and interior valleys through this evening.

Cool NW flow and a very weak ridge will move into the area in the
wake of todays front. It will lead to a decrease in clouds and dry
conditions with the only exception being the North Slopes near
the Kern county line where upslope flow will bring clouds and
showers. Max temps will rise some but will still be well below
normal. There will be near advisory level winds through the i-5
corridor.

The forecast for Tuesday`s system continues to evolve and now most
mdl solns are moving the upper low more to the east edging it
closer and closer to a pure inside slider. Right now it does not
look totally dry and will likely produce some instability showers
esp over the mtns. Max temps will not change much from Monday`s
readings and will remain well under seasonal norms.

.LONG TERM (WED-SAT)...19/338 AM.

The odd weather pattern will continue for the Wednesday through
Saturday period. Tuesdays upper low will retrograde and then spawn
an upper low which will expand to cover the state. It will then
sit and spin through the duration of the period.

The low will be centered over Fresno and the flow patter will keep
any over water trajectories away from the forecast area so this
will not be a big rain maker. The cool air aloft will destabilize
the atmosphere and this combined with short waves running around
the upper low will provide for a chc of showers over the area esp
over the mtns.

Max temps will continue to range about 10 degree below normal
through the period.

&&

.AVIATION...19/1128Z.

At 1030 at KLAX...There was no marine layer nor an inversion.

Low confidence in TAFs. Flight cats will change frequently as
front approaches and moves through the area. Steady rain is likely
through 18Z scattered showers will persist through 00Z. There is a
20 percent chc of a TSTM north of Pt Conception and a 10 percent
chc south. There is a 30 percent chc of VFR conds after 00Z at
sites with MVFR cigs fcst.

KLAX...Low confidence in TAFs. Flight cats will change frequently
through 18Z and then settle down after. Steady rain is likely
through 18Z scattered showers will persist through 00Z. There is a
10 percent chc of a TSTM through 20Z. There is a 20 percent chc
of an east wind component of 9 kt through 16Z.

KBUR...Low confidence in TAFs. Flight cats will change frequently
through 18Z and then settle down after. Steady rain is likely
through 18Z scattered showers will persist through 00Z. There is a
10 percent chc of a TSTM through 20Z. There is a 30 percent of
SCT conds after 00Z.

&&

.MARINE...19/904 AM.

A cold front will move across the waters today with a slight
chance of thunderstorms and a possibility of waterspouts. Behind
the front there will be an extended period of strong west to
northwest winds.

For the Outer Waters... Small Craft Advisory (SCA) level
conditions will develop this afternoon and continue through at
least Wednesday. There is a sixty percent chance of gale force
winds at times Monday night through Tuesday night.

For the Inner Waters north of Point Conception... There is a forty
percent chance of SCA level winds this afternoon and evening and
then they are likely during the afternoon and evening hours
Monday through Wednesday.

For the Inner Waters south of Point Conception... SCA level winds
will develop today and continue through at least early Wednesday.
There is a thirty percent chance of gale force winds at times
Monday night through Tuesday night.

&&

.BEACHES...19/906 AM.

A large swell will generate increasing surf through at least late
Monday along west and northwest facing shores. The largest surf
will affect the Central Coast where a High Surf Advisory (HSA) is
in effect through at least early Tuesday. The surf will diminish
on Tuesday but will remain close to or above advisory level...
then increase again by Wednesday. It is possible that the advisory
may be extended through at least Thursday for the Central Coast.
There is a forty percent chance that a Beach Hazard Statement may
be needed for the Ventura and/or Los Angeles County beaches
sometime during the week.

This large surf will generate widespread and dangerous rip
currents along local beaches. There is an increased risk of ocean
drowning. Rip currents can pull swimmers and surfers out to sea...
wash people off beaches and rocks... and capsize small boats near
shore.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 3 AM PDT Tuesday for zones
      34-35. (See LAXCFWLOX).
     Winter Weather Advisory in effect until 3 AM PDT Monday for
      zones 53-54. (See LAXWSWLOX).
     Wind Advisory in effect until 8 PM PDT this evening for zone
      59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Wednesday for zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 3
      PM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

Gusty advisory level west to northwest winds will be possible at
times Tue.

&&

$$

PUBLIC...Kaplan/Rorke
AVIATION...Rorke
MARINE...Kj
BEACHES...Kj
SYNOPSIS...Phillips

weather.gov/losangeles