Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 222359 AAA
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
459 PM PDT Wed Mar 22 2017
...update for new aviation discussion...
Possible precipitation with isolated thunderstorms will occur
into tonight. A dry and breezy northerly flow may bring a warming
trend from Thursday into Friday. But from Friday night through
Saturday precipitation is again possible with cooler temperatures.
Then early next week decreasing clouds will occur as high pressure
The latest radar imagery showed the cold front stretched across
the southeastern portion of San Luis Obispo (SLO) County and
across Santa Barbara County... just to the east of Gaviota. There
were good build ups along the front and a few behind it in SLO
County with the strongest cell near Buttonwillow along the front
and another east of Paso Robles near Shandon. Rainfall rates have
been about a tenth of an inch per hour with the frontal passage
and just a bit more with the stronger storms. There was a funnel
cloud reported with the Buttonwillow storm earlier in the day near
Santa Maria and small hail and gusty winds are also possible.
Widespread instability continues across the region and across the
coastal waters through this evening. LIs are negative 2-3 with
CAPE values 300-500 J/KG in many areas... but they become negative
LIs of 5-7 with CAPE values of 500-800 J/KG in the Ventura County
mountains this afternoon and evening with values just a little
less favorable in the Los Angeles County mountains. Moisture is a
bit limited but with breaks in the clouds providing a little extra
heating there should be increased enhancement of the storms as
the front moves across through Ventura and Los Angeles Counties.
The vertical wind profile does not favor deep rotation but terrain
may provide enough curvature to the profile to have another funnel
Rainfall totals will be a tenth to a quarter inch with up to a
half inch or so near thunderstorms. As the colder airmass comes
in behind the front the higher elevations will get a dusting of
snow. The snow level will begin near 6000 feet and drop to near
5000 feet overnight with one to three inches of snow possible
above 6000 feet.
As the wind shifts to the northwest-north direction winds will
become gusty in Santa Barbara County in the traditional sundowner
canyons and locations. The winds will generally remain below
advisory criteria but there may be periods when they approach
Skies will clear and temperatures will warm on Thursday and Friday
as a weak ridge of higher pressure builds into the region. Increasing
onshore flow may keep coastal areas a few degrees cooler on Friday
though the flow will likely boost the temperature a few degrees
in the Antelope Valley due to downslope flow. Thursday will likely
be the warmest day north of Point Conception due to the
increasing clouds ahead of the next weather system blocking the
Friday afternoon sunshine.
The next chance of precipitation comes to the region by late
Friday. The models are not in sync regarding the exact timing of
the system... with a possibility of the precip coming Friday
afternoon north of Point Conception versus late on Friday. However
the trend is for less rainfall overall with this next system and
to bring it in earlier rather than later. So areas to the north
will have the best chance of rain by the Friday evening commute
and those to the south of Point Conception will have the best
chance of rain Friday night into Saturday morning.
Skies will slowly clear on Saturday and some precipitation may
linger in the Los Angeles County mountains.
Conditions will be warmer and drier on Sunday as a weak ridge
moves into the region... which is followed by a weak trough on
Monday and a slight chance of light showers. There continue to be
significant differences in the models beyond Monday however...
with the possibility of a stronger ridge over the region or a low
pressure center that drops down to the east of the region. The
second solution provides a possibility of unsettled weather for
Tuesday and Wednesday. Have kept the forecast on the warm and dry
side but this discrepancy will bear watching.
At 2303Z, there was no marine inversion present at KLAX.
Generally hi confidence in the 00Z TAFs. VFR conditions are expected
at all the airfields thru Thu afternoon. There is a slight chance of
thunderstorms around KWJF and KPMD thru about 02Z this evening, with
a 20 percent chance of MVFR conditions. Gusty w to nw winds will
affect several airfields thru this evening, and some airfields Thu
afternoon, including KSBA, KOXR, KCMA, KSMO, KLAX and KLGB. Gusty w
to nw winds will affect KWJF and KPMD thru Thu.
KLAX...Generally hi confidence in the 00Z TAF. VFR conditions are
expected thru Thu evening. Gusty w winds will affect the airfield
thru this evening, and again Thu afternoon and early evening.
KBUR...High confidence in the 00Z TAF with VFR conditions expected
through Thu afternoon.
Isolated thunderstorms are possible early today across the
northern waters initially, then across all coastal waters late
morning through the early evening hours. Any thunderstorm that
forms will be capable of producing locally gusty winds and rough
seas, dangerous lightning, heavy rainfall with reduced visibility,
Gusty NW winds will reach SCA levels tonight through Thursday.
There will be a few gale force gusts between San Nicolas Island
and Santa Rosa Island during this time. The winds will weaken late
Thursday night into Friday.
CA...Beach Hazards Statement in effect through Thursday afternoon
for zones 39>41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for
zones 645-650-670. (See LAXMWWLOX).
Small Craft Advisory in effect until 4 PM PDT Thursday for
zone 655. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 PM PDT Thursday for
zones 673-676. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
A weak rain event is expected Friday night and Saturday, with
minimal impacts. High surf and strong rip currents are likely
Friday into Sunday.