Scientific Forecaster Discussion
Southwest California area forecast discussion
206 PM PDT Thursday Mar 26 2015
high pressure and well above normal afternoon temperatures are
expected through Friday. Temperatures will cool several degrees
Saturday and Sunday as a weak upper level trough moves through.
Another ridge will warm temperatures back up a few degrees early
next week and keeping temperatures above seasonal normals.
Short term (fri-mon)...
the upper level ridge responsible for the very warm conditions is
just about right over the forecast area but will shift eastward the
next couple of days. High temperatures behaving fairly well this
afternoon with a good share of 90 plus readings so far. The sea
breeze has already cooled temperatures down in some coastal spots. Winds
have not been an issue as our offshore gradients have not been too
strong and with the lack of upper level support...just some gusts in
the 30s in the usual favored spots for northeast winds. Speeds have
picked up slightly in the last couple of hours but that shouldn't
last much longer.
Lax-dag surface pressure gradients are forecast to be stronger
onshore tomorrow afternoon to bring a stronger sea breeze. The
combination of this and a very small decrease in thickness values
will cool coastal and nearby valley temperatures a few degrees
tomorrow...slightly more cooling along central coastal zones.
Meanwhile temperatures will warm slightly in the Antelope Valley. Even
though tomorrow's records are more reachable than today's...not
expecting many records to be broken. The best chances according to
what's forecast for now appear to be in Long Beach (forecast high of
88...record is 86)...Ojai (91 and 89) and Paso Robles (87 and 83).
By Saturday the upper high axis will be centered over Arizona while socal
will be in southwesterly upper level flow ahead of the dry and weak
trough that will slide through on Sunday. This will cool afternoon
temperatures on Saturday even further...but still will be well above
normal. Some additional cooling expected Sunday. Also a chance of
overnight stratus returning to the central coast and also around
Long Beach but confidence is low at this time. Ridging returns on Monday for
a slight bump up in high temperatures. Also a better chance of coastal
stratus Sunday night-Monday morning mainly Long Beach and possibly
up around lax.
Long term (tue-thu)...
not much day to day change over the extended period. No significant
ridging or troughing or warming or cooling forecast by the models.
The upper flow remains essentially zonal through the period with
just minor ripples passing through. Only impact will be some high
clouds...some northwest winds central coast and a possible weak sundowner
Wednesday behind a upper level ripple that passes by to our north
Tuesday night. Temperatures still remain above normal through the
period. Will likely see some marine layer stratus in this pattern as
well...mainly coastal l.A. County.
With the month of March coming to an end on Tuesday and no rain
forecast...downtown Los Angeles will end up over an inch and a half
below normal for March precipitation. The March normal is 2.53
inches and only .87 inches has been recorded this month. Not exactly
the Miracle March we needed to address our rainfall shortage.
At 1711z...the marine layer depth at klax is 1100 feet with a very
weak inversion up to 1400 feet with a temperature of 25 degrees
celsius. VFR conditions are expected through Friday morning due to
continued offshore flow.
Klax...good confidence in VFR conditions through Friday.
Kbur...good confidence in the 18z taf depicting VFR conditions.
Good confidence that winds will remain below Small Craft Advisory levels through Friday.
Winds are likely to reach Small Craft Advisory levels across the northern two thirds
of the outer waters Friday night and continue through the weekend.
Seas will be fairly steep and rough across the inner waters
today...but they will remain below advisory levels for hazardous
Beaches...a long period southern hemisphere swell will begin to
move into the coastal waters Friday...with surf and currents
increasing over the weekend. Expect elevated surf and strong rip
currents and longshore currents on beaches with good south exposure
Friday through the weekend...and most likely extending into early
next week. Sneaker waves will be possible as very long period swells
often produce long lulls in wave activity between sets.
high rip current risk (see laxsrflox).