Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
1130 am PDT Tuesday Oct 6 2015
..new aviation discussion...
High pressure will move in to warm temperatures to above normal by
midweek. Offhore winds will develop towards the end of the week to
add even a bit more heat to the forecast. A slight cooling trend
will begin on Sunday as the high pressure weakens and then low
pressure approaching by Tuesday will bring more clouds and cooling.
Short term (today-thu)...
*** middle morning discussion update ***
Middle morning temperatures are a few degrees warmer than yesterday in
most areas though Los Angeles County locations are not much warmer
at this time. The few clouds in the region are diminishing and
clear skies will prevail shortly.
This is in advance of significant warming that will occur during the
next few days. Current projections are for temperature increases of
twenty to twenty five degrees by Friday which will result in triple
digit temperatures in the interior valleys of Los Angeles County on
Friday and Saturday. Temperatures will gradually cool beginning on
Other than the hot temperatures... there may be some elevated
offshore winds Friday and Saturday and another chance of
precipitation on Tuesday. Will take a look at those issues
developing but for the short term heat is the focus.
*** Early morning discussion ***
Large upper low is slowly moving into Arizona. Far enough away to
keep the wrap around moisture to the east of l.A. County. Today will
be sunny save for a few afternoon cumulus over the mountains and valleys.
Heights will build in the wake of the low and maximum temperatures will rise up a
few degrees from ydys readings but will still be a degree or two below
The ridge continues to build in Wednesday and temperatures will
continue to climb. There is a decent chance of some marine layer
clouds forming as the inversion redevelops but with weak offshore
flow at the surface think there will be another night of clear skies.
Toasty warm on Thursday as the areas finds itself under a 592 dm
heights from a strong ridge poking into California from the SW. The inversion
will be strong enough to support some low cloud development in the
Long Beach lax area which will be least affected by the weak
offshore flow. The central coast will sizzle with many areas seeing
90 degrees or more as the best offshore flow will occur there. South
of Point Conception the coasts will be in the 80s and the valleys in
the low to middle 90s.
Long term (fri-mon)... offshore flow and 594 heights will occur both
Friday and Sat. The models have been going back and forth on how much
offshore flow there will be. Right now it looks strong enough to
produce some morning canyon winds but not so strong to warrant
advisories. All most all of the coasts and valleys will see maximum temperatures
in the 90s with a decent amount of triple digit heat in the valleys.
The only encouraging news about this heat wave is that locations
away from the offshore breezes will see good overnight cooling with
the dry air and 12+ hours of darkness. Fire weather concerns will be
heightened through this period.
The ridge breaks down some Sunday and maximum temperatures will fall a few
degrees but will still be well above normal.
And then an odd thing happens the upper low that is right now
exiting the state will come back having made a round about trip
through Arizona nm and northern Mexico. On Monday it will be several hundred
miles to the southwest of l.A. At this point it will not affect the
weather much. It might push a few middle level clouds up over the area
but other wise the slow cooling trend will continue as heights fall to
At one point both the ec and GFS agreed that this upper low would
bring buckets of rain to the area Tuesday night and Wednesday. Now
while the GFS is still rather wet during this time...the ec is
totally dry. The ec pushes the upper low further to the west. So it
will be interesting to see how both models handle this over the next
At 1800z...there was no marine inversion at klax.
VFR conditions are expected the taf sites for the next 24 hours.
There is a 30 percent chance of brief MVFR conditions over the la
County taf sites this afternoon and evening...especially the
Antelope Valley. A 20 percent chance of morning stratus exists for
the la coastal sites.
Klax...good confidence in VFR conditions through Wednesday. There is
a 20 percent chance of morning stratus Wednesday morning.
Kbur...high confidence in VFR conditions through Wednesday.
Marine... 06/830 am
Good confidence that winds and seas will remain below Small Craft Advisory levels
through Wednesday morning. There is a 20 to 30 percent chance that winds
and seas will reach Small Craft Advisory levels across the outer waters Wednesday afternoon
and evening...then Small Craft Advisory level winds are a bit more likely Thursday
afternoon and evening.