Frost Advisory 3, NWS Los Angeles, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
232 PM PST Thu Jan 26 2017

.SYNOPSIS...
Temperatures across the region will warm each day into Monday
while overnight readings will continue to be chilly. There will
be gusty and possibly damaging offshore winds Friday through
Monday. The next chance of rain comes in the Wednesday or
Thursday timeframe.

&&

.SHORT TERM...(TDY-SUN)

Temperatures are up today compared to yesterday thanks to some
locally breezy north to northeast winds, but overall we remain
noticeably below normal. A short wave trough will move through
eastern California tonight...depositing plenty of cold air to
spawn a strong 1048 mb surface high over the Great Basin. The
surface high will remain parked through Monday and will only
gradually weaken each day after Saturday. With the shortwave
exiting to the east by Friday, the flow aloft will be oriented
north-to-south...favorably providing upper level support for
offshore winds. As a result, a moderate to strong Santa Ana wind
event for Los Angeles and Ventura County is on track beginning
late tonight, peaking on Friday, then gradually weakening into
early next week. During the Friday peak, fairly confident that
warning-level gusts over 60 mph will occur in the mountains and
the Santa Clarita Valley, and the High Wind Watch for those areas
are being converted to a warning as a result. With the flow well
under 50 KT at 950 mb, felt the valleys and coasts would be
better represented by strong advisories instead of warnings.
regardless, winds this strong will probably bring some trees down
especially considering the soil effects from the recent rains.
Used a simplified approach for the timing of the warnings and
advisories with a start time of 1 AM for everything...which
matches our NWS San Diego neighbors. This start time is good for
the mountains but way too early (mid-morning ramp up more likely)
for the other areas. When the warnings expire, a wind advisory
will certainly be needed to carry through Saturday. Winds will
remain gusty Saturday night into Sunday and some areas will
probably need additional wind advisories.

A ridge of high pressure currently 600 miles offshore will
gradually expand into central California by Sunday which will
warm the air mass. Along with the persistent offshore flow,
coastal and valley areas will noticeably warm each day, likely
going above normal by Saturday or Sunday and peaking on Monday.
Interior areas should cool a touch tomorrow, but then warm up
thanks to the building ridge. Night temperatures will remain cold
outside of the windy areas, and frost/freeze concerns should
continue through at least Saturday morning. Minimum temperature
forecast for tonight is very tricky for coastal and valley areas,
and completely dependent on where the winds pick up over night.

.LONG TERM...(MON-THU)

Temperatures should peak on Monday with weak offshore flow and a
strong ridge of high pressure. The high pressure will retreat to
the southeast on Tuesday as surface pressure gradients quickly
swing onshore. Temperatures will lower as a result to the surprise
of no one. Still eying a potential storm system for Wednesday or
Thursday. A deep low pressure system is on target to form 900
miles west of northern California Tuesday night, then push to the
northeast Wednesday and Thursday. The associated frontal band will
move down the coast, but with the northward track of the low, the
frontal band should weaken quickly along the way. All areas have a
shot of rain, with SLO and SBA Counties having the best chance.
Any amounts should be light however and no where near what we got
used to over the last couple of weeks.

&&

.AVIATION...26/1800Z.

At 1800Z, there was no marine layer or marine inversion at KLAX.

High confidence in 18Z TAF package as skies will remain clear
through the TAF period.

KLAX...High confidence in 18Z TAF. There is a 40% chance of east
winds exceeding 7 knots Friday morning and although there is yet
no mention of possible low level wind shear for Friday morning,
there is a 30 percent chance of low level wind shear at some
point on friday.

KBUR...High confidence in 18Z TAF. There is a chance of light to
moderate LLWS/turbulence Friday morning (after 10Z).

&&

.MARINE...26/200 PM...

For the Outer Waters, good confidence in current forecast. Small
Craft Advisory (SCA) levels conditions will develop across the
Outer Waters today as a large (10+ foot) swell moves into the
area. For Friday night through Monday, winds and seas are
expected to be below SCA levels.

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, winds are expected to remain below
SCA levels through Monday, but SCA level seas are expected this
afternoon through Friday. For the waters south of Point
Conception, seas are expected to remain below SCA levels through
Monday. However, gusty northeast winds are expected on Friday and
to a lesser extent on Saturday. At this time, moderate to high
confidence in SCA level northeast winds on Friday from Ventura
south to Santa Monica and over the San Pedro Channel. The winds
will be a bit weaker on Saturday, but there is a decent chance of
another round of SCA level northeast winds.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 10 PM PST Friday for zones
      34-35. (See LAXCFWLOX).
     Frost Advisory in effect from 2 AM to 9 AM PST Friday for
      zones 35-39. (See LAXNPWLOX).
     High Surf Advisory in effect until 10 AM PST Friday for zones
      40-41-87. (See LAXCFWLOX).
     Wind Advisory in effect from 1 AM Friday to 6 PM PST Saturday
      for zones 40-41-44-45-547. (See LAXNPWLOX).
     Freeze Warning in effect from 2 AM to 9 AM PST Friday for
      zone 44. (See LAXNPWLOX).
     High Wind Warning in effect from 1 AM to 10 PM PST Friday for
      zones 46-53-54-88. (See LAXNPWLOX).
PZ...Small Craft Advisory for hazardous seas in effect until 9 AM
      PST Friday for zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(SUN-THU)
Gusty northeast winds will continue over Los Angeles and Ventura
Counties on Sunday. A weak storm system could impact the region
Wednesday or Thursday.

&&

PUBLIC...Kittell
AVIATION...Sweet
MARINE...Sweet
SYNOPSIS...Kj

weather.gov/losangeles