Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 221736
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1036 AM PDT Sat Jul 22 2017

.SYNOPSIS...

For the next few days, a typical summer weather pattern will bring
night through morning low clouds and fog to the coasts and some of
the valleys. Temperatures will be near normal. There is a slight
chance of thunderstorms in the afternoons and evenings for the
deserts and mountains on Monday and Tuesday.

&&

.SHORT TERM...(TDY-MON)

Influence of the high pressure aloft to the east over the Plains
States will start to diminish as the high weakens and a weak
trough of low pressure near 37N and 130W will approach the North
Coast of California through Sunday night. Onshore pressure
gradients should increase slightly today ahead of the trough;
however, increasing 500 mb heights and warming 950 mb
temperatures should warm the air mass today. A bit better sea
breeze should push in this afternoon. The marine layer depth
should deepen slightly tonight and into Sunday morning. Coverage
may be expanded somewhat, possibly extending into the Ventura and
San Fernando Valleys by Sunday morning. This decision will wait
for additional data to arrive.

Model solutions are pointing toward a decent monsoonal surge on
Monday and Monday night. GFS and NAM-WRF solutions keep this idea
in mind and early frames of the NCEP high-resolution WRF NMM and
ARW core solutions are hinting at a similar solution. PoPs will
likely be increased over the area, possibly spilling over showers
and thunderstorm activity into coastal and valley areas for
Monday and Monday night. Precipitable water values in NAM-WRF and
GFS solutions increase to 1.50-2.00 inches. 850-700 mb mixing
ratios and dewpoint are impressive ranging up 8-10 g/kg and near
10 degrees Celsius. A warm, cloudy and humid air mass should
expected for Monday and Monday with the possibility of at least
embedded sprinkles at times.

*** FROM PREVIOUS DISCUSSION ***

More low clouds and fog can be expected for the coast and some
adjacent vlys Sun night into Mon morning, otherwise partly cloudy
skies can be expected across the region for the most part during
the period.

Hgts continue to lower and there will be more clouds so Monday`s
temps will continue to cool and will be 2 to 5 degrees blo
normal.

.LONG TERM...(TUE-FRI)

Southwest flow returns on Tuesday. The GFS has just enough
residual moisture to warrant a slight chc of TSTMs in the
afternoon but mostly likely it will be dry. Hgts will be the
lowest of the week and Tuesday should be the coolest day of the
week. There will probably be enough mid level clouds as well as
possible low level mixing to eliminate the low clouds for the
morning.

The upper high to the east of the area then grows and reasserts
itself into the area. The inversion will strengthen and the night
through morning low cloud patter will resume but only for the
coasts. Max temps will trend higher each day and it looks like
next weekend could be a warm one.

&&

.AVIATION...22/1645Z...

At 1645Z, the marine inversion at KLAX was based around 1600 feet.
The top of the inversion was 3800 feet with a temperature of 23
degrees Celsius.

Overall, moderate confidence in 18Z TAF package. High confidence
in return of stratus/fog to all coastal sites, but only moderate
confidence in timing.

KLAX...moderate confidence in 18Z TAF. Arrival of MVFR CIGs could
be +/- 2 hours of current 09Z forecast.

KBUR...moderate confidence in 18Z TAF. There is a 20% chance of
IFR CIGs developing 10Z-16Z.

&&

.MARINE...22/800 AM...

For the Outer Waters, good confidence in current forecast. Small
Craft Advisory (SCA) level winds will continue into this afternoon
and evening, before diminishing. For Sunday through Wednesday,
winds and seas are expected to remain below SCA levels.

For the Inner Waters, good confidence in current forecast. Winds
and seas are expected to remain below SCA levels through
Wednesday.

&&

.BEACHES...22/930 AM...

Significant surf may impact Southern California beaches beginning
late next week. This is due to a developing tropical cyclone off
the Mexican coast that could produce 25 to 35 foot swells off Baja
California. A moderately long period swell may impact the Southern
California coastline as early as next Friday and build into next
weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Sunday evening for
      zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zones 670-676. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for zone
      673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(MON-FRI)

A monsoonal flow pattern Monday will bring a slight chance of
thunderstorm to the mountains and deserts on Monday and Tuesday.
There is a possibility that shower activity could spill over into
the valley areas.

&&

$$

PUBLIC...Hall/Rorke
AVIATION...Thompson
MARINE...Thompson
BEACHES...Thompson
SYNOPSIS...Sweet

weather.gov/losangeles



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