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Area Forecast Discussion (AFD)

Issued by Los Angeles, CA (LOX)

                            
786 
FXUS66 KLOX 251128
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
328 AM PST Sun Feb 25 2018

.SYNOPSIS...

24/1009 PM

Winds will be breezy through early Sunday along the Central Coast
and portions of Ventura and Los Angeles Counties. After another night
of very cold temperatures in wind sheltered areas... afternoon temperatures
will be near normal on Sunday then cool to below normal through the
work week. Breezy winds and a chance of light precipitation return to
the region Monday and Tuesday... then again Thursday through Saturday.
Snow levels will be at or below some passes at times this week.

&&

.SHORT TERM (TDY-TUE)...

25/314 AM

Dry NW flow is overhead in the wake of the dry front that went
overhead yesterday. SFC high pressure has built into NV and there
is offshore flow from both the north and east. Winds are not too
impressive but the mtns will see low end advisory level gusts 
through mid morning. Today will be the warmest of the next week
with the offshore flow combining with unlimited sunshine to warm
things up to just a few degrees below normal.

A cold low pressure system currently over the Gulf of Alaska will
drop into Northern California on Monday, then sweep through 
Southern California on Tuesday. The mdls have come into fairly
good agreement on the track of the upper low. The cold low center
will be just north of Sacramento Monday afternoon it will then
move to the SSW to just west of Pt Conception by dawn Tuesday. By
Tuesday afternoon the low will be near San Diego. Rain will 
likely fall across SLO and western SBA counties Monday afternoon 
and evening. As the system moves into VTA and LA counties it 
weakens and the chc of rain will be reduced esp for the coastal 
section of VTA county. The mtns will see the best chc of showers 
across VTA and LA counties. This is a cold system and snow levels 
will start out at 4000 feet but will then drop to 2500 feet by 
Monday evening. There is a chance that 2 to 4 inches of snow will 
fall across the mountains areas bordering Kern county including 
the grapevine region of the Interstate 5 Corridor. The core of the
upper low is so cold that it will create enough instability to 
create TSTMs. The track of the upper low will create the slight 
chc of TSTMs across the SLO and Western SBA counties Monday 
evening and then across the southern portions of SBA/VTA/LA 
counties as well as the inner waters after midnight and through 
the morning.

Rainfall totals will be highly variable with about 0.33 inch on 
the upper end of the rain, but most of the area should be less 
than 0.20 inch range. 

Hgts fall to 540 DM and its pretty unlikely that there will be any
max temp readings in above 60 degrees either day.

.LONG TERM (WED-SAT)...

25/327 AM

Weak ridging builds in on Wednesday and it will clear the skies
out. The cold airmass (561 DM hgts) and the clear skies will
combine to again allow freezing temperatures over some coastal 
and valley areas. Max temps will increase a few degrees but will
still be near 10 degrees blo normal.

A much better organized system will affect the area Thursday
afternoon. The GFS and EC have not been in the best agreement but
at the moment the current mdls are in near lock step. They both
forecast Central Coast rain to start Thursday before noon. Rain
should spread over VTA and LA counties Thursday afternoon and
early evening. At this time it looks like the heaviest rain will
be across the coastal and vly sections and esp foothills of Srn
SBA county and VTA/LA counties late evening and into the predawn
hours Friday. Day 6 forecasts should always be taken with several
large grains of salt but its possible that this system could
produce an inch of rain for much of the area.

The GFS and the EC disagree starting Friday afternoon. The GFS
clears things out pretty quickly Friday afternoon, while the EC
keeps showery activity over the area through Saturday.  chances 
look to linger Friday night into Saturday with moist westerly flow
sticking around. Temperatures will remain below normal.

Thursday will be the coolest of the next 7 with many areas only
reaching the mid 50s. There will be some warming Fri and Sat but
max temps will remain well blo normal.

&&

.AVIATION...

25/1114Z

At 1030Z, there was a surface-based inversion at KLAX. The top of
the inversion was 1100 feet with a temperature of 11 degrees
Celsius.

Overall, high confidence in 12Z TAF package. Weak offshore flow
will keep all sites VFR through the TAF period. 

KLAX...high confidence in 12Z TAF. Easterly winds are expected to
remain at 6 knots or less through 20Z.

KBUR...high confidence in 12Z TAF. There is a chance of llws and
turbulence 12Z-20Z.

&&

.MARINE...

25/116 AM

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level winds will continue across the Outer
Waters through Thursday. There is a 40% chance of Gale force wind
gusts Monday afternoon and Monday night. 

For the Inner Waters, high confidence in current forecast. For the
waters north of Point Sal, 80% chance that SCA level winds will
continue each afternoon/evening from today through Tuesday night.
For the waters south of Point Conception, there is a 30% chance of
SCA level winds each afternoon/evening today through Monday night.
Additionally, there is a 50% chance of SCA level winds Thursday
afternoon/evening.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect until 9 AM PST this morning for zone
      44. (See LAXNPWLOX).
     Wind Advisory in effect until 10 AM PST this morning for
      zones 53-54. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST Monday for
      zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

A cold storm system will bring light precipitation to the area 
into early Tuesday. Snow is possible down to the 2,500 foot 
elevation, which would affect mountain pass travel, as well as 
gale force winds and dangerous sea conditions. There could be 
frost or freeze across the region Tuesday night and early Wed. 
Another storm is expected Thursday into Friday, with potentially 
moderate rain and a chance for flooding issues.

&&

$$

PUBLIC...Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kj

weather.gov/losangeles