Scientific Forecaster Discussion
fxus66 klox 191743
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
943 am PST sun Nov 19 2017
temperatures will warm significantly this week with record heat
possible on Wednesday and Thanksgiving day.
A very chilly morning across the mountains and interior valleys
as light winds and a very dry air mass promoted strong radiational
cooling. Lancaster Airport reached a low of 22 degrees,
registering the first hard freeze of the season across our
forecast area. All freeze warnings and frost advisories allowed
to expire as of 9 am. Meanwhile, offshore breezes continued
through the night across some of the wind prone canyons of Los
Angeles and Ventura counties, keeping temperatures above 60
degrees in some foothill areas.
Surface offshore gradients a bit stronger this morning than
previously expected, with lax-Daggett gradient peaking at -5.7 mb
at 7 am. Despite this offshore gradient, winds have remained
below advisory levels due to lack of upper level support.
Strongest offshore winds focused this morning across the la
County mountains and Santa Monica Mountains, where local gusts
between 30 and 40 mph have been observed. In morning update, have
bumped up offshore winds a tad, and nudged Max temps upwards in
a few areas due to the slightly stronger offshore flow. The
combination of locally breezy conditions combined with warm and
dry conditions (with very dry fuels) will continue to bring
elevated fire danger across the region. Some weak northerly winds
will also impact the Santa Ynez Mountains and sba South Coast
tonight and again Monday night. Otherwise just looking at some
periodic high clouds drifting across the region today through
*** From previous discussion ***
The ridge grows on Monday. Flow is still offshore but it is about
a mb weaker in both directions. There are a grip of clouds
currently at 140w and while most of them will be deflected to the
north of the area by the ridge enough mid and high levels clouds
will slip through to create partly cloudy skies, sba and esp slo
counties may have an hour or two of mostly cloudy skies. Max temps
will jump a few more degrees. The biggest jumps in Max temps will
be across the interior where the cool air from saturday's
offshore push will modify and the central coast where there will
be better easterly flow.
On Tuesday the ridge spikes up and hgts soar to 591 dm or 13 dm
above normal. Offshore flow will continue and Max temps will soar
5 to 10 degrees. Almost all of the coasts and the vlys will have
Max temps in the 80s or 10 to 20 degrees above normal.
The ridge grows to 594 dm and offshore flow increases. There will
be some north winds in places like the I-5 corridor. Under sunny
skies Max temps will rise several more degrees and Max temps will
be in the 80s and lower 90s across all of the coasts and vlys
except maybe for the central coast north of the city of slo.
Hgts fall a few dm on Thanksgiving as the ridge tilts to the east.
Offshore flow weakens a touch also. Max temps should fall a degree
or two. The all time record Max temp for Thanksgiving is 90 and
right now it looks like that record will stand but its still not
out of the question. Skies will be clear and there will not be
much of any wind.
The ridge flattens out as a large upper low moves out of the Gulf
of Alaska. Gradients will reverse to onshore and there will be
cooling both Friday and Saturday. Max temps...however...will still
be a few degrees above normal.
At 1633z, there was a surface based inversion at klax. The top of
the inversion was at 1300 ft with a temperature of 18 deg c.
Clear skies and VFR conds expected across the region thru the pd.
There will be locally gusty NE winds thru and below passes and
canyons in the mtns and valleys of l.A./Vtu counties through
mid to late morning with local low level wind shear and moderate uddf.
Klax...high confidence in the 18z taf. VFR conds thru the pd.
Kbur...high confidence in the 18z taf. VFR conds thru the pd.
Moderate confidence in the forecast. A Small Craft Advisory has been issued for
zones 673 and 676 this afternoon and evening. There is a 30
percent chance for Small Craft Advisory speeds in the same areas Monday afternoon
and evening. Otherwise, Small Craft Advisory conds are not expected through Wed
morning. Small Craft Advisory level winds are likely across the southern two thirds
of the outer waters late Wed through Thu, and possible across the
northern outer waters.
Pz...Small Craft Advisory in effect from 3 PM this afternoon to 3
am PST Monday for zones 673-676. (See laxmwwlox).
Hazard potential outlook...(tue-sat)
no significant hazards expected.