Scientific Forecaster Discussion
fxus66 klox 142048
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
148 PM PDT Mon Oct 14 2019
Overnight low clouds and fog are expected along most coasts. A
ridge will warm temperatures through midweek, followed by a dry
trough to cool temperatures through the end of the week. Gusty
northerly winds will develop late in the week and continue into
Short term (tdy-thu)...14/147 PM.
An onshore flow pattern remains in place across the area beneath
an upper-level trough of low pressure overhead. Onshore pressure
gradients peaked earlier this morning and starting to weaken.
Onshore trends still remain versus the last 24 hours, but onshore
flow will continue to weaken into Tuesday.
The trough of low pressure overhead will exit the region tonight
and an upper-level ridge off the West Coast will build in quickly
aloft through Tuesday morning. A warming and drying trend is
expected for Tuesday as the flow pattern reverses to offshore.
Winds will largely remain below advisory levels, but a few
isolated gusts to 35-40 mph cannot be ruled out overnight tonight
and into Tuesday morning. Any typical low cloud coverage will
remain confined to the coastal areas, except for the Santa Barbara
A weak upper-level trough of low pressure near 20n and 135w will
phase with a stronger trough centered near 50n and 150w and force
broad troughing into the West Coast between Wednesday and
Thursday. Model solutions are good agreement with the middle and
upper-level synoptic pattern but disagree on how much moisture
will move south late Wednesday night and Thursday. The frontal
boundary looks to shear apart north of the area, but a mix of
clouds and sun look a bit more definite between Wednesday night
and Thursday night. The marine layer will deepen some and low
clouds and fog should push into the valley areas on Thursday
morning. Cooler temperatures look on tap for Thursday. There is a
chance that the marine layer could struggle to clear on Thursday
until late in the day. Pops have been nudged a tad higher along
the central coast in case that the frontal boundary holds together
or the possibility of measurable drizzle.
A northerly surface gradient will develop and tighten on Thursday
night and likely bring Post-frontal sundowner winds to southern
Santa Barbara County on Thursday night. Advisory level winds look
likely at this time.
Long term (fri-mon)...14/142 PM.
The northerly gradient will tighten further between early Friday
and Saturday. Moderate-to-high end advisory level winds look
likely to develop across southern Santa Barbara County and
through the Interstate 5 corridor. A cooler weather pattern will
likely linger into Friday with the Santa Barbara South Coast
likely being the warmest area due to compressional heating, but
temperatures will start to rebound into next weekend as high
pressure builds in.
Both European model (ecmwf) and GFS solutions and the gefs members agree very well
with the idea of ridging gradually building into the region
between Saturday and Monday. A warmer weather pattern looks likely
for early next week as offshore flow settles into the region.
An early peek at the gradients indicate a weak to possibly
moderate Santa Ana wind event early next week. Stay tuned as this
could be developing story.
At 1535z at klax, the marine layer was 2700 ft deep. The top of
the inversion was near 3500 ft with a temperature of 13 c.
Good confidence for Desert/Valley tafs. Moderate confidence in
coastal tafs. VFR transition may occur any time between 15z and
18z. For ksmx, there is a 40% chance of LIFR conditions after
06z. For klax and klgb, low clouds may arrive as early as 03z.
There is a 30 percent chance of marine clouds spreading up to
Ventura coastal locations after 11z.
Klax...moderate confidence in taf. VFR transition could occur
anytime between 16z and 18z. Good confidence in taf 18z-03z then
lower confidence as low clouds may arrive as early as 03z. Good
confidence in an east wind component under 5 kt.
Kbur....high confidence in ceiling and visibility unlimited taf.
High confidence that winds and seas will remain below Small Craft
Advisory (sca) criteria through Tuesday over all of the coastal
waters. Wind speeds are expected to increase over the waters along
the central coast and southward towards San Nicolas Island on
Wednesday afternoon. Good confidence in Small Craft Advisory level winds over
these waters on Wednesday night, then become strong Small Craft Advisory level to
possibly near gale force on Thursday and Friday. Good confidence
in these Small Craft Advisory level winds reaching the western portion of the Santa
Barbara Channel. Increasing confidence in a long-period, large northwest
swell arriving Thursday and lasting through at least the weekend.
Patchy dense fog is likely across the coastal waters north of
Point Conception through the morning.
Hazard potential outlook (thu-mon).
Gusty sundowner winds are expected for southern Santa Barbara
County Thursday through Sunday. Gusty northerly winds also
possible for the Interstate 5 corridor region Friday through