Gale Warning 23, NWS Los Angeles, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
939 AM PDT Tue May 16 2017

.SYNOPSIS...
An unseasonably cool upper trough will persist over the West
Coast through the middle of the week...bringing below normal
temperatures and extensive night through morning low clouds. and
patchy drizzle in the foothills. A ridge of high pressure will
bring a warming trend to the area late this week with much warmer
temperatures expected over the weekend.

&&

.SHORT TERM...(TDY-THU)

We are in between troughs now with yesterday's upper low near the
CA/NV/AZ border and the next system currently in the Pac NW.
Inversion was weaker this morning in the wake of yesterday's
upper low passage and cloud coverage mostly confined to eastern LA
County and more solid north of Pt Conception. In the middle from
srn SB to wrn LA County northwest flow is keeping skies pretty
clear. Onshore flow is a little weaker today and with overall less
clouds temps should climb at least a few degrees especially in
the valleys where we had some showers yesterday. Still, there is
enough low lvl moisture that with some daytime heating we'll
likely see the stratocu over LA county continue and possibly
expand.

***From previous discussion***

Another strong upper low is progged to move south out of Idaho
tonight into the four corners region by Wednesday. This upper low
remain east of the area, but cause stronger northerly winds to
develop tonight into Wednesday. gusty NW winds across the outer
waters will continue to bring a decent eddy in across SOCAL bight
allowing for more low clouds to spin up across LA/VTU Counties to
the coastal slopes. Patchy drizzle will be possible across the San
Gabriel Valley foothills and Coastal slopes early Wednesday
morning due to the deep most layer. Also, northerly flow across
the San Joaquin Valley should push some clouds up against the
northern slopes of the Ventura County Mtns. A few light showers
will be possible around the hills above the Grapevine tonight into
Wed morning. Wind advisories will likely be needed for several
areas Wednesday including the usual Sundowner areas in Santa
Barbara County, LA/VTU County Mtns and Antelope Valley, and
possibly the Central Coast. Skies are expected to clear out by
Wednesday afternoon for most area except for some lingering clouds
across much of LA County and a few low clouds across the Central
Coast. The warming trend is expected to continue for most areas
2-6 degrees, still just below normal for this time of year, but
highs will range up into the 70s for most areas, while some
coastal areas remain in the mid to upper 60s. Some cooling
expected along the eastern portion of the forecast area including
the Antelope Valley due to the proximately of the upper low.

Not expecting much in the way for low clouds Wed night into
Thursday morning, as a ridge of high pressure will be sitting off
the Eastern Pac with a fairly strong upper low over the Central
Plains. Broad NW to N flow will persist over the forecast area
while weak surface offshore flow develops Thu morning. The
combination of heights and thickness levels rising with the weak
offshore flow will cause high temps to continue to trend up over
the next few days, significantly on Fri/Sat. Highs will finally
be around normal for this time of year with warmest valleys
reaching the lower to mid 80s on Thursday.

.LONG TERM...(FRI-MON)

The upper ridge will continue to build over the state through
Saturday while offshore flow strengthens slightly. Temps are
expected to soar upward several degrees, peaking Saturday in most
areas with highs in the lower to mid 90s in the valleys and 80s
to the upper 80s for the interior coastal areas. Winds should not
be strong enough to justify a Wind Advisory at this point. Cooling
should begin along the coast Sunday as light onshore flow
returns, but likely one more day of interior warming. Then cooler
for at least coast/valleys Monday with additional onshore flow and
possible return of low clouds near the coast. Not much cooling
expected for the Antelope Valley on Mon.

&&

.AVIATION...16/1545Z...

At 1545Z, there was no marine inversion at KLAX, but there was a
deep moist layer up to around 6000 feet.

Overall, moderate confidence in 18Z TAF. SCT-BKN skies will
prevail through the afternoon for most coastal/valley TAF sites
with VFR conditions anticipated this afternoon. For tonight,
stratus should return to Central Coast and to the coastal/valley
areas of Ventura/LA counties with MVFR conditions likely.

KLAX...moderate confidence in 18Z TAF. SCT-BKN cloud deck will
prevail through the afternoon with flight categories ranging from
MVFR to VFR. For tonight, moderate confidence in return of MVFR
CIGs, but low confidence in timing (could be +/- 4 hours of
current 09Z forecast).

KBUR...moderate confidence in 18Z TAF. SCT-BKN cloud deck will
prevail through the afternoon with flight categories ranging from
MVFR to VFR. For tonight, moderate confidence in return of MVFR
CIGs, but low confidence in timing (could be +/- 4 hours of
current 11Z forecast).

&&

.MARINE...16/800 AM...

For the Outer Waters, moderate to high confidence in current
forecast. High confidence in Small Craft Advisory (SCA) level
winds continuing through Friday. For this afternoon/evening, there
is a 20% chance of gusts reaching Gale force levels, but a 50%
chance of Gale force winds on Wednesday and Wednesday night (and a
Gale Watch remains in effect for this time frame).

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, moderate confidence in development
of SCA level winds each afternoon/evening today and Wednesday
with a 40% chance of the SCA level conditions continuing through
Thursday. For the waters south of Point Conception, moderate
confidence in development of SCA level winds each
afternoon/evening today and Wednesday with a 40% chance of the
SCA level conditions continuing through Thursday. For the
southern Inner Waters, the strongest winds will occur across
western sections.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9
      PM PDT this evening for zones 645-650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Thursday for
      zone 670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Wednesday for
      zones 673-676. (See LAXMWWLOX).
     Gale Watch in effect from Wednesday afternoon through late
      Wednesday night for zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(THU-MON)
Temperatures will warm to well above normal levels by the
weekend.

&&

PUBLIC...MW/Kaplan
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kaplan

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