Scientific Forecaster Discussion
fxus66 klox 261843
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
1143 am PDT Wed Jul 26 2017
partly cloudy skies will persist into next week, with an overnight
marine layer along the coast. Some remnants of Hilary may reach the
region by next week. Early next week, monsoonal moisture should
bring possible thunderstorms and showers to the Ventura and Los
Angeles mountains and deserts. The temperatures are forecast to be
around normal this week, with a slight warming trend next week.
The latest satellite imagery indicates an upper-level ridge of
high pressure centered along the Texas-New Mexico border. The high
will build across the area into Friday, weakening onshore flow
and thinning the marine layer. The marine layer stratus coverage
could be very patchy to non-existent across the South Coast, with
slightly better coverage along the central coast. With weakening
onshore flow and a thinning marine layer, a warming trend will
develop across the area over the next several days.
Monsoonal moisture will continue to gradually exit the region.
With only isolated showers and thunderstorms yesterday, the dry
forecast stance continues for this afternoon and evening. An
isolated shower cannot be ruled out over eastern Los Angeles
County, but any rainfall will likely not measure or amount to
much. The best chance for any convective showers remain outside
of the forecast area.
*** From previous discussion ***
Friday will be the warmest day of the next 7...but not by much.
Look for another degree of warming. There will be a smattering of
triple digit heat in the desert and warmest mtn locations but
since we are in the warmest part of the year Max temps will really
only be 2 to 4 degrees above normal and even less than that
across the coastal areas. There will still be morning low clouds
but they will be gone by mid morning.
Both the 00z and 06z runs of the GFS swing Hurricane Hilary
northward weaken it dramatically and then run the remnants over
Southern California Monday night or Tuesday. This probably will not happen as
the GFS ensembles greatly favor a westerly track. The ec has
consistently favored the westerly track as well. This westerly
track is the one used for this forecast. But will monitor it
because stranger things have happened.
Not much action for the weekend. A little trof moves into the Pacific
northwest and this shifts the upper high a little to the east which will
reduce the hgts and increase the marine layer. Both of these
factors will knock 1 to 3 degrees off of the Max temps compared to
On Sunday hgts rebound slightly and some non coastal areas will
see 1 or 2 degrees of warming. There is a slight chc that some
monsoon moisture or tropical moisture may make it into the area.
There is a 20 percent chc of a mtn or desert thunderstorm in la County to
cover this possibility.
Low confidence in the Monday and Tuesday forecast. It all depends
on what happens to Hilary and/of the remnant moisture. For now
just a have pretty Standard Summer forecast in place with normal
temps...morning clouds along the coast and a slight chc of mtn and
desert tstms during the afternoon and early evening.
At 1701z, the marine layer depth was 1260 feet. The top of the
inversion was 4000 feet with a temperature of 23 degrees celsius.
Good confidence in the 18z tafs. Expect similar marine cloud
coverage tonight and Thursday morning in spite of a slight
shallowing of the marine layer to around 1000 feet and IFR
conditions. The valley tafs will not likely see any marine clouds
and the Antelope Valley will have another round of gusty
afternoon winds today.
Klax...good confidence in 18z taf. There is a 30 percent chance of
marine clouds arriving plus or minus two or more hours from the
Kbur...high confidence in 12z taf. There is a 15% chance of IFR
For the outer waters, good confidence in current forecast. Winds
and seas will remain below Small Craft Advisory (sca) levels
through Thursday night. On Friday and Saturday, there is a chance
of Small Craft Advisory level winds across pzz670/673. Winds should decrease below
Small Craft Advisory levels across all the outer waters on Sunday.
For the inner waters, good confidence in current forecast. For all
the waters, winds and seas are expected to remain below Small Craft Advisory levels
Hurricane Hilary is expected to slowly weaken today. In spite of
the weakening trend, it will generate a southeasterly swell that
will impact Southern California beaches this weekend. The
southeasterly swell will move into the coastal waters early
Friday, then peak on Sunday. High surf conditions as well as
strong rip currents will be likely across south-facing beaches
this weekend. Isolated damaging sets of surf and beach erosion
cannot be ruled out for the south-facing beaches of Los Angeles
and Ventura counties.
California...beach hazards statement in effect from Friday morning through
Tuesday evening for zones 40-41-87. (See laxcfwlox).
Hazard potential outlook...(fri-tue)
a significant surf event could develop late Thursday as swells
from Hurricane Hilary arrive at the Southern California beaches.
High surf and strong rip currents will occur from Friday through