Area Forecast Discussion
Issued by NWS San Diego, CA

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140
FXUS66 KSGX 251629
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
920 AM PDT Wed Apr 25 2018

.SYNOPSIS...
Weakening high pressure aloft will bring seasonal weather through
Thursday. From Friday through Sunday the weather will turn cooler as
a deep trough of low pressure moves inland across central
California.

&&

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

The ridge of high pressure that`s been over the West the last few
days will slowly buckle and drift east through Thursday. Until then
there will only be minor changes in our weather the next 48 hours
with a slight deepening of the marine layer and a couple degrees of
cooling along and west of the mountains. Desert temperatures will be
unchanged through Thursday with highs near 90 in the Upper Deserts
and near 100 in the Lower Deserts.

From Friday through Sunday we transition to a stronger onshore flow
pattern as spokes of energy from a deep closed low off the NorCal
coast rotate across California. Most of this energy will pass by to
the north of us, but the trough passage will bring gusty west winds,
cooler weather and a deeper marine layer Saturday and Sunday. 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. Gusty winds will be the greatest impact in the
mountains and deserts where low end Wind Advisories may be needed.
Temperatures will be lower this weekend with most areas at
or slightly below average.

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...
251500Z...Coast/Valleys...Low clouds with bases near 900 ft MSL
clearing to the coast by 18Z. Predominantly SKC this afternoon apart
from SCT low clouds over the coastal waters. After 02Z Thursday, low
clouds will creep back inland, reaching 20-25 mile inland by 12Z
Thursday. Bases should be near 1000 ft MSL, with local visibility of
1/4 mile or less where low clouds terrain intersect. Visibility at
KSAN, KCRQ, KSNA, and KONT should remain 5 SM or better.

Mountains/Deserts...SKC, unrestricted visibility and light winds
through Thursday afternoon.

&&

.MARINE...
No hazardous marine conditions through Thrusday. Stronger onshore
flow will bring breezier northwest winds to the coastal waters this
weekend and early next week. Look for gusts near 20 kt during the
afternoons for areas outside of 20 nm, strongest winds near and
south of San Clemente Island. Choppier seas should accompany the
winds, with a 5-8 ft (7-9 sec) wind swell affecting the same areas
Saturday into early next week.

&&

.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
AVIATION/MARINE...Albright



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