Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 200308
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
808 PM PDT Tue Mar 19 2019

.SYNOPSIS...19/250 PM.

Light to moderate rain and mountain snow will move across the
region late tonight through early Thursday with a slight chance of
thunderstorms on Wednesday. Snow will remain above pass level.
There is another chance of rain late Friday and Saturday. Afternoon
temperatures will be cooler than normal Wednesday through Saturday.

&&

.SHORT TERM (TUE-FRI)...19/807 PM.

***UPDATE***

Overall, the atmosphere is shaping up pretty nicely this evening
with the current forecast. Latest radar/surface obs indicate
showers gradually increasing across the area with this trend
expected to continue this evening and overnight. Amounts between
0.01 and 0.12 inches have been recorded so far across SBA county
with trace amounts elsewhere. There has been some lightning north
of the CWA, over Kern County, but no strikes in the CWA.

For this evening and overnight, shower activity will continue to
develop. As some unstable air moves into the area overnight, the
possibility of isolated thunderstorms will increase. Snow levels
will drop to around 5500 feet tonight. However, given the light
nature of the precipitation expected, do not anticipate any
significant winter weather issues.

Overall, the current forecast has a very good handle on the
immediate short term with only some minor adjustments to winds and
POPs this evening.

***From Previous Discussion***

Partly to mostly cloudy skies due to a mixed bag of high clouds,
mountain wave clouds, and coastal low clouds. The dense fog from
earlier this morning is not expected tonight, but hazy skies will
likely continue into the evening south of Santa Barbara.

A low pressure system currently centered 500 miles west of Los
Angeles will move over San Francisco tonight, then move little
through Wednesday before moving into Utah Thursday night. Showers
are likely everywhere sometime between tonight and Thursday
night, but it remains difficult to highlight which 12 hour period
will be wet or not. This is why PoPs are on the meager side. This
storm system does not have a lot of lift or moisture to work
with, so expect more showers than hours of steady rain and
generally light amounts. As result, impacts will be minimal for
this event. The potential for thunderstorms remains pretty much
anywhere however on Wednesday, especially closer to the coast.
This ingredient pushes the upper range of rainfall amounts and
intensities, resulting in fairly a large range of options. In
general, amounts are expected to range 0.01 and 0.25 inches over
Los Angeles County, and 0.10 and 0.50 inches over the other three
counties. Isolated amounts up to around 0.75 inches are possible
under heavier showers or thunderstorms. Rainfall rates should
generally stay under 0.25 inches per hour, but could top out at
0.33 inches per hour basically anywhere under a thunderstorm. The
threat for debris flows are minimal. Impacts will likely stay
confined to travel issues from wet roads. Snow levels should stay
in the 5,000 to 6,000 foot range, but could lower to 4,000 feet
Wednesday or Thursday morning. Could see a dusting of snow on some
mountain roads, but accumulations should stay above 5,500 feet.
With the amounts trending lower, will hold off on any Winter
Weather Advisories. There will be some gusty south winds as well,
into early Wednesday, which will shift to more west to
northwesterly by Thursday, but looks to stay under any Wind
Advisories at this point. Temperatures will be below normal to no
surprise.

Friday looks rain-free, with temperatures creeping up closer to
normal as a weak ridge forms aloft. Locally breezy west to
northwest winds should continue.

.LONG TERM (SAT-TUE)...19/138 PM.

A very weak upper level trough will pass through northern
California Saturday morning. The GFS and ECMWF remain at odds with
one another in terms of how far south any light rain will get, but
the GFS and a few of its ensembles are looking more like the
ECMWF. Up PoPs a little as a result, with all areas having a
slight chance or chance for rain. Regardless, any rain will be
minimal. Sunday through Tuesday look warmer as an upper level
ridge quickly forms behind the trough, and onshore flow weakens.
Above normal temperatures are looking likely under such a pattern.

Computer projections continue to show a trough forming over
northern California by Monday with a steady stream of moisture and
soaking rain. So far all the projections keep that stream parked
over northern California through at least Tuesday, keeping us dry.
That could change of course, and when or if that plume moves to
the south could result in rain of some significance.

&&

.AVIATION...19/2324Z.

At 2315Z, the marine inversion at KLAX was based at 1800 feet.
The top of the inversion was 2400 feet with a temperature of 15
degrees Celsius.

Overall, low confidence in 00Z TAF package. Main focus through TAF
period will be storm system. This system will bring light showers
to the area as well as various flight restrictions. At this time,
MVFR CIGs and VSBYs are likely at coastal/valley sites tonight and
Wednesday. However, low confidence in timing of flight category
restrictions.

KLAX...Low confidence in 00Z TAF. Arrival of MVFR CIGs could be
+/- 3 hours of current 03Z forecast. There is a 50% chance that
MVFR CIGs will extend beyond 20Z.

KBUR...Low confidence in 00Z TAF. Arrival of MVFR CIGs could be
+/- 3 hours of current 03Z forecast. There is a 50% chance that
MVFR CIGs will extend beyond 21Z.

&&

.MARINE...19/807 PM.

For the Outer Waters, moderate to high confidence in current
forecast. High confidence in Small Craft Advisory (SCA) level
southeasterly winds tonight across PZZ670/673 while there is
a 30% chance of SCA level winds across PZZ676. For Wednesday
through Friday, moderate confidence in winds and seas remaining
below SCA levels. For Friday night and Saturday, there is a
70% chance of SCA level northwest winds.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. High confidence in SCA level
southeasterly tonight. For Wednesday through Friday, moderate
confidence in winds and seas remaining below SCA levels. On
Saturday, there is a 60% chance of SCA level northwest winds.

For the Inner Waters south of Pt Conception, moderate to high
confidence in current forecast. There is a 40% chance of SCA
level southeast winds tonight. For Wednesday through Friday, high
confidence in winds and seas remaining below SCA levels. On
Saturday, there is a 50% chance of SCA level west to northwest
winds.

There will be the threat of isolated thunderstorms across all the
coastal waters tonight and Wednesday. Gusty and erratic winds,
brief moderate to heavy rainfall and dangerous lightning will be
possible. Additionally, there is the potential for isolated
waterspouts.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 11 PM PDT Wednesday for
      zones 34-35. (See LAXCFWLOX).
     High Surf Advisory in effect from 5 AM Wednesday to 3 PM PDT
      Thursday for zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
      zones 645-670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

High surf and dangerous rip currents are expected over the
weekend.

&&

$$

PUBLIC...Kittell
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kj

weather.gov/losangeles


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