Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 260419
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
819 PM PST Sat Feb 25 2017
A couple of weak weather systems will bring and a chance of rain
and mountain snow tonight and early Sunday, with a chance of
showers continuing through Monday. High pressure will bring clear
skies and a warming trend to the region Tuesday through much of
next week, with above normal temperatures expected Thursday and
Cold upper level low pressure system off the coast of Monterey
will continue to dive southeastward across Southwest California
overnight. Thick shield of mid and high level clouds streamed
into the area this afternoon and evening ahead of this system.
A few sprinkles will be possible this evening with this shield
of mid level clouds. Light to moderate rain is expected to spread
into SLO/SBA counties within the next few hours, likely impacting
LA/Ventura counties later tonight into the early morning hours on
Sunday. During this time, snow levels are expected to fall to
between 3500 and 4500 feet, with light snow showers possible along
I-5 near the Grapevine and the foothills of the Antelope Valley.
NAM/RAP models showing steepening lapse rates and CAPE values as
high as 300 J/kg over the coastal waters off the Central Coast, so
introduced a slight chance of thunderstorms for this area
The main trough axis quickly shifts east of the area on Sunday,
however ample low level moisture and onshore flow will continue to
bring a chance of showers the remainder of the day Sunday into
Sunday night. The best chance of showers will be across LA County
(including Hollywood). During this time, snow levels are expected
to increase to between 4500 and 5500 feet. Rainfall amounts
tonight through Sunday night are generally expected to range
between 0.25 and 0.50 inches, with local amounts up to 0.75 inches
possible in the mountains. Snow amounts through Sunday night are
expected to range between 1 and 4 inches, mostly above 4000 feet.
*** From previous discussion ***
A cooler air mass should linger into early next week as a trough
of low pressure over British Columbia phases with a trough near
35N and 145W and moves over the region. Additional shower chances
should linger into at least Tuesday as the troughs combine while
dampening. Additional rainfall amounts between Sunday night and
Tuesday should be a tenth of an inch or less. Any extra snowfall
will amount to an inch or less. South of Los Angeles County, San
Diego and Orange Counties will be in a more favorable flow pattern
and higher rainfall total should be expected across Extreme
Another trough could move into the region on Wednesday and bring
mainly clouds and possibly showers to the northern slopes of the
mountains, but ridging aloft should take ahold over the area for
the latter part of next week and into the weekend. Warmer and
drier conditions along with the possiblity of gusty Santa Ana
winds should develop between Thursday and Sunday. The warmest days
should be Friday and Sunday when offshore gradients and the ridge
position is in a favorable location respectively.
At 0000Z, there was no marine inversion at KLAX.
Moderate confidence with 00z tafs through 06z this evening. Then
low confidence as Cigs are expected to lower to MVFR and possibly
to IFR conds as approaching rain from the NW will move into
SLO/SBA counties later this evening, then overspread across VTU/LA
counties late tonight into Monday morning. 50 percent chance of
low mvfr cigs at all TAF sites once light rain begins,with 20-30
percent for IFR conds during the peak of the light rain occurring.
with highest chances between 09Z and 16Z. Moderate confidence in
TAF winds and rain timing and intensity.
KLAX...Moderate confidence in 00Z TAF. There is a 50 percent
chance of low MVFR cigs after 09Z with a 20 percent chance of
brief IFR cigs. There is a 30 percent chance that sustained east
to south winds will be 10 kt or greater sometime through 01z. then
once again from 12z to 23z Sunday.
KBUR...Moderate confidence in 00Z TAF. There is a 50 percent
chance of MVFR cigs after 10Z. Moderate confidence in TAF winds
and rain timing and intensity.
There is a 30 percent chance of Small Craft Advisory (SCA) levels
this evening into early tonight across the outer waters. Gusty
south to southeast winds are expected to develop across the
southern inner waters Sunday with gusts to around 20 kt and choppy
seas, especially across the San Pedro Channel.
There is a 70 percent chance of SCA conditions Tuesday into
Tuesday night as winds and seas approach SCA levels. There is a 70
percent chance of SCA conditions Wednesday night through Friday.
.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
No significant hazards expected.