National Weather Service Forecast Discussion

Dicussion provided by the National Weather Service Forecast Office located in San Diego, California

000
FXUS66 KSGX 111627
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
827 AM PST Mon Dec 11 2017

.SYNOPSIS...
High pressure aloft and weak offshore flow at the surface will
likely keep the weather warm and dry through at least this
weekend. Locally gusty northeast to east winds will occur in the
coastal foothills, slopes and in the passes and canyons. Skies
should be mostly clear except for passing high clouds at times.

&&

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

Morning visible satellite shows scattered high clouds (associated
with an upper low over Baja) continuing to stream into the
region. The 12Z sounding from Miramar continues to show a very dry
profile up through 500 mb and then the high level moisture shows
up above that level. The sounding also shows weaker easterly winds
in the low to mid levels of the atmosphere, at only around 5-10
kt. This lack of upper level support and some weakening in the
offshore pressure gradients (down to 7.0 mb from San Diego to Las
Vegas whereas it was 10.0 mb at this time yesterday) has resulted
in much weaker Santa Ana winds this morning. Northeast to East
wind gusts of 20-30 mph and locally 40-45 mph are being reported
in the coastal foothills/slopes and passes/canyons while wind
gusts are mainly 10 mph or less elsewhere.

Water vapor satellite shows an upper level ridge over the Great
Basin and the aforementioned upper level low over Baja. The weak
offshore flow and dry atmosphere will continue to bring warmer
than normal weather (highs mostly 5-15 degrees above normal) to
the region today through much of the week, and possibly into the
weekend and early next week as well, with models not indicating
any significant trough moving down into Southern California.
Thus, rain or cooler weather is not expected through early next
week. There really isn`t even a hint of the marine layer coming
back to the coast except for possibly Friday when there may be a
brief return of onshore flow as the upper level ridge gets pushed
west and a trough moves down through the Inter-mountain West.
However, models show the offshore flow returning on Saturday and
continuing possibly into next Monday. The offshore flow should
remain weak, with strongest winds of 10-20 mph with 30-35 mph
gusts and locally up to 45 mph in the coastal foothills/slopes and
passes/canyons.

&&

.AVIATION...
111530Z...SCT-BKN clouds AOA FL200 and unrestricted vis through
Tuesday morning.

&&

.MARINE...
No hazardous marine weather is expected through Friday.

&&

.FIRE WEATHER...
Although the offshore/Santa Ana winds will be much weaker today
through at least Thursday, day-time humidity for everywhere
except coastal areas will be very low (down to 5-10 percent each
day) with very poor overnight humidity recovery. Strongest winds
will be in the coastal foothills/slopes and passes/canyons where
winds of NE to E winds 10-20 mph with gusts to 30-35 mph and
locally 45 mph can be expected. Elsewhere, wind gusts will mainly
be 15 mph or less. Red Flag Warnings not anticipated as winds will
be too weak, with strongest winds pretty localized. However,
elevated fire weather conditions will continue.

&&

.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...Harrison
AVIATION/MARINE...JJT

NWS SGX Office Area Forecast Discussion