Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
900 PM PST Thursday Feb 11 2016
Synopsis... high pressure aloft will weaken Saturday and Sunday but
temperatures will still be well above average. Strong high pressure
will rebuild over California early next week bringing more
unseasonably warm weather Monday and Tuesday along with gusty Santa
Ana winds. Cooler Wednesday and Thursday with a slight chance for
showers as a low pressure trough moves inland across California.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Today was another unseasonably warm day with record highs in all
four climate zones. At the coast San Diego reached 84. In the
valleys...El Cajon set a record with 87. In the mountains...big bear
set a record high with 64. In the desert...Borrego reached 86.
The strong upper ridge over the western U.S. Will weaken slightly
Friday in response to a trough moving into the Pacific northwest.
500 mb heights of 585dm today fall to 582 dm Friday...and then to
580dm Saturday. Despite these modest falls...the height fields will
still be anomalously high and temperatures will be well above
average over the weekend. Pressure gradients trend weakly onshore
Saturday which should be the coolest day...most notably in the
coastal zones...but still well above average.
Gradients shift back offshore Saturday night into Sunday as the
trough axis moves east and high pressure builds in from the Pacific.
Initially the north-south oriented pressure pattern will support
gusty north flow and the strongest through the Cajon Pass and in the
Santa Ana Mountains. The winds become northeasterly Sunday night
through Tuesday as the surface high drifts eastward over Nevada and
Utah. Surface pressures are not all that strong with a 1028 mb high
over Great Basin producing only 10 mb offshore pressure gradients.
Nevertheless...this pressure pattern along with 850 mb winds of 15-
25 knots will support Santa Ana winds of 15-30 miles per hour with gusts of 45-50
miles per hour in the passes/canyons/foothills.
Temperatures: the Santa Ana winds and downslope warming will send
temperatures to record levels Monday and Tuesday with highs in the
80s and low 90s west of the mountains. Very warm in the mountains
and deserts too.
Long range outlook Wednesday through Friday...a Pacific trough will
move inland across south-central California bringing cooling and a
chance for showers. The 00z GFS pulls subtropical moisture into so-
cal Wednesday night and Thursday with precipitable waters increasing to 1.00-
1.25". Although the antecedent airmass will be quite dry...if this
moisture plume verifies we could actually see showers late Wednesday
120330z...few-sct clouds at or above 20000 feet mean sea level and unrestricted visible
through Friday morning.
730 PM...no hazardous marine weather is expected through Tuesday.
730 PM...a long-period swell from 290 degrees will arrive arrive
late Thursday...slowly build Friday...then peak Saturday at 9 feet/18
second. This will generate high surf of 4 to 8 feet Friday through
Sunday with highest sets north of Newport Beach and south of del
A high surf advisory will be in effect from 10 am Friday through 8 PM
Sunday. Swell and surf will subside Monday.
light offshore winds will continue through next Tuesday...although
Sunday and Monday will have stronger offshore winds of 15-25 miles per hour and
gusts 35-45 miles per hour in the favored passes/canyons and coastal foothills.
The Santa Ana winds combined with unseasonably warm weather and very
low relative humidities in the single digits to teens to elevate the
fire danger Sunday and Monday. Overnight humidity recovery will be
poor. Even though fuels have been dried the last several days...the
winds Sunday and Monday do not appear to be strong or
widespread enough to produce red flag conditions.
Humidity will start to increase Wednesday as onshore flow returns
and a trough approaches from the Pacific. This trough could produce
wetting rains late in the week.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...high surf advisory from 10 am Friday to 8 PM PST Sunday for
Orange County coastal areas-San Diego County coastal areas.