Area Forecast Discussion
Issued by NWS Los Angeles, CA
FXUS66 KLOX 301140
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
440 AM PDT Thu Mar 30 2017
An upper trough will move into the Great Basin later today and
tonight. Behind this system, widespread strong to locally damaging
winds will affect much of the region later today through early
Friday, and there will be significant cooling. High pressure and
weak offshore flow will bring warmer weather to the region this
weekend. A fast moving trough passing north of the area will cause
cooling early next week.
Areas of low clouds have developed on the Central Coast and in the
Santa Ynez valley early this morning, and some clouds were getting
close to the Salinas Valley. Some stratus was also developing just
to the south of the Los Angeles County and patchy low clouds
could move into southern sections by daybreak. Otherwise, some
high clouds were drifting across the region. Low clouds should not
last too long this morning as a dry frontal system should wipe
out the marine inversion.
The main story will be the winds. The models have trended quite
a bit stronger with all parameters necessary for strong winds
across the region. Winds aloft will really increase later today,
with 850 mb winds peaking at around 60 kt near the I-5 corridor
and across southern Santa Barbara County this evening. The 2km WRF
actually shows 850 mb winds up to 75 kt, which is really quite
impressive. Also, widespread strong subsidence through a deep
layer will overspread the region, and there will be good cold
advection as well. Finally, a powerful 140 kt northerly jet will
be aimed toward or just east of the mountains this evening, an
ideal location for powerful winds. Expect High Wind Warning
level winds across the mountains of L.A., VTU and SBA Counties,
the Antelope Valley, the Santa Clarita Valley and the south coast
of SBA County. Wind gusts of 70 to 80 mph are expected in the
mountains, and 60 to 65 mph in the Santa Clarita Valley and on the
south coast of SBA County. Elsewhere, solid to strong wind
advisory level winds are expected in most areas.
Strong northwest winds will affect the Central Coast this
afternoon, with strong west winds near the L.A. and VTU County
coast. Then winds will turn northerly tonight. Especially
noteworthy is that strong north winds will likely again affect the
San Fernando Valley and coastal sections of L.A. County from
Malibu to the Hollywood Hills, down through the Westside. It is
also possible that mountain wave activity could produce brief
bursts of damaging winds in areas near Lake Casitas and near
the foothills in the San Gabriel Valley.
Winds will peak in most areas this evening through late tonight,
although sooner on the Central Coast. There will be significant
cooling today, with max temps down 8 to 14 degrees in most areas.
Low level flow will shift to a more north northeasterly direction
Friday morning. There is a chance that winds will linger into the
early afternoon Friday, so advisories may have to be extended in
some areas, or issued once the High Wind Warnings expire in other
areas. Skies should be mostly sunny on Fri. Max temps may edge up
slightly west of the mtns, but the air mass should be too cool
to allow for dramatic warming.
An amplifying upper ridge and weak to moderate offshore flow
should bring significant warming on Sat, with max temps back into
at least the lower 80s in the valleys and possibly the interior
coastal plain. There will be some gusty ne winds across L.A. and
VTU Counties, possibly to near advisory levels Sat morning.
Heights will lower a bit Sunday and low level flow will turn onshore
in the afternoon. This should bring slight cooling, especially to
the coastal plain, but temps will still be above normal. A broad
trough moving through the Pac NW will dig across the northern
Rockies on Monday, likely bringing additional cooling to the
region. On the latest runs, the EC is now sharper than the GFS
with the feature, and would result in more significant cooling
and breezy to windy conds. The 06z run of the GFS shows warming
for Tue and especially Wed as a ridge builds into the region from
the southwest. Confidence in the details of the forecast beyond
Monday is not particularly high.
At 1100Z at KLAX, there was no marine layer. There was a sfc based
inversion with a top near 1800 ft with a temperature of 20 deg C.
Good confidence in all VFR TAFs. There is a 30 percent chc of VFR
conds at KSMX by 15Z. Strong NW to N winds will affect all TAF
sites today. There is a high likelihood of mountain wave
activity. There will be mdt ocnl stg turbc over and around the
higher terrain from 18Z on.
KLAX...Good confidence in VFR TAF. There is a 30 percent chc of
30 to 35 kt crosswinds 00Z-09Z.
KBUR...High confidence VFR TAF. lgt ocnl mdt turbc sfc-150.
Very good confidence in gale warnings and small craft advisories.
The strongest winds will be in the western portions of all zones.
CA...High Surf Advisory in effect until 3 PM PDT Friday for zones
34-35. (See LAXCFWLOX).
Wind Advisory in effect from noon today to 9 PM PDT this
evening for zones 34>36. (See LAXNPWLOX).
Wind Advisory in effect until noon PDT today for zones
39-52>54-59. (See LAXNPWLOX).
High Wind Warning in effect from 2 PM this afternoon to 8 AM
PDT Friday for zone 39. (See LAXNPWLOX).
Beach Hazards Statement in effect through Friday afternoon
for zones 40-41-87. (See LAXCFWLOX).
Wind Advisory in effect from 2 PM this afternoon to 9 PM PDT
this evening for zone 40. (See LAXNPWLOX).
Wind Advisory in effect from 2 PM this afternoon to 8 AM PDT
Friday for zones 41-44-45-87-547. (See LAXNPWLOX).
Wind Advisory in effect from 2 PM this afternoon to 6 PM PDT
this evening for zone 46. (See LAXNPWLOX).
High Wind Warning in effect from 6 PM this evening to 8 AM
PDT Friday for zone 46. (See LAXNPWLOX).
High Wind Warning in effect from noon today to 8 AM PDT
Friday for zones 52>54. (See LAXNPWLOX).
High Wind Warning in effect from noon today to 3 AM PDT
Friday for zone 59. (See LAXNPWLOX).
High Wind Warning in effect from 2 PM this afternoon to 3 AM
PDT Friday for zone 88. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 PM PDT Friday for zone
645. (See LAXMWWLOX).
Small Craft Advisory in effect from noon today to 3 AM PDT
Saturday for zones 650-655. (See LAXMWWLOX).
Small Craft Advisory in effect until 1 PM PDT this afternoon
for zones 670-673-676. (See LAXMWWLOX).
Gale Warning in effect from 1 PM this afternoon to 3 PM PDT
Friday for zones 670-673-676. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
Gusty northeast winds are possible Saturday across LA/Ventura