December 18, 2017
Temp
 
56.9 °F
 
Dew Pt.
 
23.3 °F
 
Humidity
 
27%
 
Pressure
 
1021.1 hPa 
  rising slowly
Wind
 
2.0 mph 
    E
Rain
 
0.00 in 
  0.00 in/hr
UV index
 
---  
 
Solar rad.
 
100 W/m²
 
Today

Today: Sunny, with a high near 73. North northeast wind around 5 mph becoming calm  in the morning.
Sunny

Tonight

Tonight: Mostly clear, with a low around 50. North northeast wind around 5 mph becoming calm  in the evening.
Mostly Clear

Hi 73 °F Lo 50 °F
000
FXUS66 KLOX 181422
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
622 AM PST Mon Dec 18 2017

.SYNOPSIS...
Gusty northeast winds across portions of Ventura and Los Angeles
Counties will diminish this morning, then tranquil weather is
expected through Tuesday. High temperatures will be near to
slightly above normal through Tuesday. It will be chilly tonight.
An upper trough passing to the north of the region may bring some
showers to northern areas and the mountains Wednesday. Gusty north
winds are expected late Wednesday into Wednesday night, followed by
gusty northeast winds Thursday. Offshore flow will continue into
the weekend.

&&

.SHORT TERM...(TDY-WED)

With the exception of some high clouds streaming into the region
from the northeast, skies were clear across the forecast area early
this morning. Today should be a mostly sunny day. Gusty northeast
winds continued to affect much of Ventura County, the mountains
of Los Angeles County including the Santa Monica Range and the
Santa Clarita Valley. A wind advisory remains in effect in these
areas through mid morning, but winds will be in the low end of the
advisory range, and nothing like the winds observed on Sunday.
Winds should diminish below advisory levels in most areas by mid
morning. After a chilly morning, with areas of frost on the Central
Coast and freezing temps in the Santa Ynez and Cuyama Valleys, it
should warm nicely in most areas today. Max temps should be 5-10
degrees higher than those on Sunday in the mtns, deserts, and
interior valleys, and a few degrees higher than those on Sunday
elsewhere. The exception will be across portions of the coastal
plain, mainly near the coast, where max temps should be about the
same.

The upper ridge building across the region today will flatten out
tonight and Tuesday as an upper low approaches the Pacific
northwest. With clear skies, light winds, and continued very dry
conditions, tonight will again be rather chilly and frost
advisories may be needed for the Central Coast and possibly the
Ojai Valley. Freezing conds are possible in the Santa Ynez Valley.
Do not expect any low clouds tonight as gradients will remain
weakly offshore. Pressure gradients turn onshore Tuesday
afternoon  and heights/thicknesses begin to fall. Expect a few
degrees of cooling in all areas west of the mtns on Tue, with
little change or possibly slightly warming in the mtns and
deserts as 850 mb temps rise a bit.

The upper low will move into the Pac NW Tue night, then drop into
the Great Basin on Wed with the trough axis extending south
southwestward into forecast area. Expect low clouds to develop on
the Central Coast and across coastal sections of L.A. and VTU
Counties Tue night, possibly pushing into some valley locations.
The southern end of a surface front associated with the trough
could bring some showers to areas north of Point Conception
Wednesday into Wed evening, and possibly to the northern slopes of
the mtns of VTU County and northwestern L.A. County Wed afternoon
and evening. Skies will be partly cloudy elsewhere. There will be
several degrees of cooling in all areas Wed. Gusty northwest to
north winds are expected to develop across much of SBA and SLO
Counties and through the Interstate 5 Corridor during Wed
afternoon.

.LONG TERM...(THU-SUN)

The EC and GFS have been showing plenty of run to run
inconsistencies during the past several days, but for the past
two or three runs, then have been a bit more consistent. Strong
subsidence and cold air advection will spread across the region
Wed evening, and northerly winds aloft will increase. N-S pressure
gradients will sharpen across SBA County and across nrn VTU and
L.A. Counties as well. This will bring strong and gusty northwest
to north winds to much of SBA County and the mtns of L.A. and VTU
Counties Wed night, likely requiring wind advisories. Gusts to 60
mph are possible in the more wind prone locations in and below the
Santa Ynez mountains, and through the Interstate 5 Corridor.

The low level flow will become more northeasterly Thursday
morning, and KLAX to KDAG gradients will become moderately
offshore. Expect gusty northeast winds to develop across much of
Ventura County and a good portion of L.A. County Thu morning.
Max temps on Thu may be up a bit west of the mtns due to
compressional warming, but there will be several more degrees of
cooling in the mtns, deserts and interior valleys, with max
temps well below normal. Frosts and freezes are possible in wind
sheltered areas Wednesday night and Thursday night.

The GFS and EC show some differences Fri and Sat. The GFS shows
ridging across the area both days, with offshore flow, but mainly
sub-advisory level winds and some warming. The EC is similar on
Fri though a bit cooler, then shows a cold upper trough digging
southwestward through the Great Basin, with much lower heights
and cooler conds across the region. The GFS keeps heights rather
high across the region on Sun, but shows very steep offshore
gradients, greater than 9 mb offshore between KLAX and KDAG. Both
models indicate a fair amount of northeast wind across the region
on Sunday, but how strong the winds will be and how cool it will
be are still rather uncertain at this point. Confidence remains
low in the extended forecast.

&&

.AVIATION...18/1140Z

At 1045Z at KLAX, there was no marine layer. There was a sfc based
inversion with a top of 500 feet and a temperature of 17 degrees C.

VFR conditions are expected throughout the period, except for a chance
of MVFR conditions in smoke at Santa Barbara and Ventura county
terminals. Periods light to moderate wind shear and turbulence are
possible at all terminals through 20Z.

KLAX...High confidence in TAF through 10Z. There is a 20 percent
chc of IFR cigs 10Z-17Z.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...18/300 AM

Outer waters...Good confidence in no Small Craft Advisory (SCA)
conditions through Wednesday morning and low end SCA conditions
Wednesday afternoon through Thursday.

Inner waters south of Point Conception...Good confidence that
conditions will remain below SCA levels through Friday.

There will continue to be areas of smoke from the Thomas Fire
over portions of the Coastal Waters.

&&

.FIRE WEATHER...18/400 AM.

18/300 AM.

Gusty winds will diminish across the region this morning. However, it will
remain very dry today.

There will be a return of more extensive onshore flow on Tuesday with
moderate humidity recovery across coastal and valley areas. Another upper
level trough will dig through California on Wednesday, with a weak cold
front bringing a slight chance of rain to areas north of Point Conception.
For areas south of Point Conception, including the Thomas Fire area,
there will be cooler temperatures, higher humidities, and increasing
west to northwest winds through the day on Wednesday. By late Wednesday
afternoon into Wednesday night, northwest to north are expected to peak
as upper level wind support, cold air advection, and north-south pressure
gradients align. Wind speeds across the Santa Barbara county mountains
and south coast will have the potential to be fairly similar to
Saturday morning`s event, with sustained winds in the 20 to 35 mph range,
and gusts generally ranging between 40 and 55 mph, except isolated gusts
to 60 mph across favored ridgetops. Gusty north winds could continue
into Thursday across much of Santa Barbara county. While humidity
levels will likely remain above 15 percent with this event, there
is still the potential for critical fire weather conditions
across the Santa Barbara county mountains and south coast
considering the potential for strong winds and continued very dry
fuels.

Later in the week into next weekend, confidence remains low for the
potential Santa Ana wind pattern as computer models continue to widely
fluctuate on the timing, duration, and strength of the Santa Ana
winds.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect until 9 AM PST this morning for
      zones 34-35. (See LAXNPWLOX).
     Freeze Warning in effect until 9 AM PST this morning for zone
      36. (See LAXNPWLOX).
     Hard Freeze Warning in effect until 9 AM PST this morning for
      zone 38. (See LAXNPWLOX).
     Wind Advisory in effect until 9 AM PST this morning for zones
      40-44>46-53-54-88. (See LAXNPWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK...(WED-SUN)
Critical fire weather conditions are possible with gusty
Sundowner winds Wednesday night and gusty offshore winds
Thursday and Friday. Frosts and freezes will be possible in
sheltered areas Wednesday night and Thursday night.

&&

$$

PUBLIC...DB
AVIATION...ASR
MARINE...Rorke
FIRE...Gomberg/DB
SYNOPSIS...DB

weather.gov/losangeles

NWS LOX Office Area Forecast Discussion