Area Forecast Discussion
Issued by NWS San Diego, CA

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154
FXUS66 KSGX 260426 AAA
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Wed Apr 25 2018

.SYNOPSIS...
High pressure aloft will bring one more warm day Thursday before
temperatures trend downward over the weekend. A deep trough of low
pressure over the Pacific will move inland across California through
Saturday and Sunday bringing cooler weather, a deeper marine layer,
and gusty west winds in the mountains and deserts.

&&

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

No significant changes were made to the forecast this evening. It
was another hot day today in the deserts with Thermal reaching 103
degrees, which was still 4 degrees shy of the daily record.
Meanwhile at the coast low clouds will spread further inland tonight
due to a little stronger and deeper marine layer.

Thursday will be similar to today with marine layer clouds in the
coastal zones and western valleys retreating back to the coast
through midday. Temperatures will be a degree or two lower west of
the mountains, but the triple digit heat will linger one more day in
the lower deserts. Records are out of reach though...the record high
at PSP Thursday is 109.

Friday through Sunday: A transition to stronger onshore flow and
cooler weather will take place as shortwaves circulating around a
deep closed low off the NorCal coast deepen the trough along the
West Coast. Most of the shortwave energy will pass by to the north,
as will the rain, but the trough will bring gusty west winds, cooler
weather and a deeper marine layer Friday through Sunday. It will
turn quite windy each afternoon and evening in the mountains and
deserts, especially in the east-west passes including the I-10 and I-
8 corridors. A low end Wind Advisory may be needed in these areas.
Low clouds will reach the inland valleys, but most areas should see
clearing during the day due to the weak inversion from the infusion
of cooler air aloft. Temperatures will be lower this weekend with
most areas at or slightly below average.

*From Previous Discussion*

Long Range Outlook for next week: The model spread is quite large
next week which makes it difficult to pinpoint which days will have
the best chance for showers. The GFS advertises a deep cold upper
low stalling over the Southwest Monday-Wednesday, while the ECMWF
delays this upper low until Wednesday and Thursday. This uncertainty
is too large to introduce rain chances at this time.

&&

.AVIATION...
260415Z...Coast/Valleys...Areas of BKN/OVC stratus will gradually
spread inland from the coast tonight, reaching 20-30 miles inland by
12Z Thu. KSAN, KCRQ and KSNA will have cigs at times, and KONT could
have a low cig around 12Z-15Z Thu. Bases will be mostly 1000-1500 ft
MSL with tops to 1800 ft MSL. Areas of vis 2-4 miles will occur in
the valleys, with local higher terrain obscured. Most coastal areas
will clear 16Z-19Z Thu, with stratus developing again Thu evening.

Mountains/Deserts...SCT high clouds will prevail at times at/above
20000 ft MSL with unrestricted vis through Thu evening. Local
surface wind gusts 25-35 knots from the west will occur late Thu
afternoon/evening over the desert mountain slopes and through San
Gorgonio Pass.

&&

.MARINE...
No hazardous marine conditions are expected through Thursday.
Stronger onshore flow will bring strengthening west to northwest
winds to the coastal waters Friday through Monday with gusts around
or slightly above 25 knots in the afternoons and evenings, mainly
beyond 30 NM from the coast. Choppy seas should accompany the winds,
with a 5-8 ft (7-9 sec) wind swell.

&&

.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...Moede/JMB
AVIATION/MARINE...Maxwell



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