Area Forecast Discussion
Issued by NWS San Diego, CA

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629
FXUS66 KSGX 222134
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
130 PM PST Wed Nov 22 2017

.SYNOPSIS...
High pressure aloft combined with weak offshore surface flow will
bring another day of record setting temperatures Thanksgiving Day.
The weather will turn gradually cooler Friday through Sunday as the
high weakens. Increasing onshore flow will bring greater cooling
Monday along with gusty west winds in the mountains and deserts. A
moderate to strong Santa Ana weather pattern will return next
Tuesday.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

It`s been quite a day today with record highs already being broken
by early afternoon. A record high was set at the San Diego Airport
when the temperature reached 90 at 12:53 PM, shattering the old
recored of 84 set in 2015. Vista set a record of 95, breaking the
old record of 86 set in 2015. Big Bear Lake reached 71 this morning,
breaking the old record of 65 set in 1995. Riverside reached 95
breaking of 90 set in 1924. More records will fall today and we
anticipate a rather lengthy Record Event Report to be issued by 530
PM.

Pressure gradients were strongly offshore this morning (-12.0)
compared to yesterday (-9.7) resulting in stronger northeast winds
in the mountains and passes than on Tuesday morning. Sill Hill,
typically the windiest location in the county, peaked at 58 mph at
7:30 AM. Fremont Canyon hit 50 mph and Pleasants Peak reached 47
mph.

The forecast remains on track for another very warm, record breaking
day on Thanksgiving. See the CLIMATE section below for the numbers.
It won`t be quite as hot in the coastal zones or the western valleys
as the high aloft weakens slightly, but temps will only lower a
couple degrees, so it will still be a hot day. Mountains and deserts
will likely see no temperature change tomorrow compared to today.

The high weakens further Friday through Sunday, flattened by a
trough passing by to the north that will bring increasing onshore
flow and gradual cooling each day. Nevertheless, it will still be
very warm with temperatures 5 to 15 degrees above average. A shallow
marine layer may return as early as Saturday morning with low clouds
and pockets of fog possible at the coast, with greater likelihood of
that occurring on Sunday morning.

The trough axis moves across northern California Sunday afternoon
and then across the Great Basin Monday as a dry inside slider.
Surface high pressure fills in over the Great Basin behind the
trough Monday night, setting the stage for a moderate to locally
strong Santa Ana wind event Monday night through Tuesday. Model
trends of wind, humidity and temperature will be monitored closely
for the potential of critical fire weather conditions next week.

&&

.AVIATION...
222059Z...FEW clouds AOA 20000 ft MSL and P6SM vis through Thursday
morning.

&&

.MARINE...
No hazardous marine weather is expected through Sunday. Gusty
northwest winds over the outer waters will be possible late Monday,
possibly producing hazardous small craft conditions.

&&

.FIRE WEATHER...
Fire Weather concerns will be slightly lower Thursday due to the
lighter winds that are projected. Winds this morning ranged from 15
to 25 mph with gusts to 50 mph. Winds tomorrow are forecast to be
from 10 to 20 mph with gusts to 40 mph. Still very hot and dry
though with with lowest humidities of 10 to 15 percent Thursday
afternoon.

We will be watching model trends for a potentially stronger Santa
Ana wind event next Monday night and Tuesday as strong high pressure
builds over the Great Basin. This event shows the potential for
widespread critical fire weather conditions with strong winds and
low humidities Monday night through Wednesday.

&&

.CLIMATE...
Forecast high temperatures that could be near or exceed existing
record high temperatures on Thanksgiving Day.

Location       Forecast       Current Record
San Diego         85              86 in 1950
Vista             88              83 in 1975
Chula Vista       90              87 in 1924
Riverside         92              91 in 1995
Escondido         92              90 in 1949
El Cajon          94              86 in 1995
Ramona            92              89 in 1995
Alpine            89              86 in 1995
Big Bear Lake     69              68 in 1981
Idyllwild         75              75 in 1954
Palomar Mountain  76              75 in 1954
Campo             87              82 in 1995
Palm Springs      92              94 in 1950
Thermal           90              93 in 1950
Borrego Springs   89              88 in 1989

There will likely also be some record warm minimum temperature
records set...and a few additional high temperature records tied
or broken on Friday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER/CLIMATE...Moede
AVIATION/MARINE...Harrison



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