Area Forecast Discussion
Issued by NWS San Diego, CA

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994
FXUS66 KSGX 220529
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
929 PM PST Wed Feb 21 2018

.SYNOPSIS...
A slight chance of light showers will continue through early
Friday morning. Brisk winds are also likely Thursday, especially
in the mountains and deserts. A fair and warmer weekend is
expected before low pressure returns next week for more cold
weather and another chance of showers.

&&

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

...Update...

A few light showers affected the region today, focused over San
Diego County. Amounts were mostly less than a tenth of an inch.
There is a slight chance of showers overnight along the coast and
the coastal mountain slopes, though WRF has backed away on this
notion. The evening San Diego sounding did show a moist layer
centered on 7,000 FT, but the PW only came in at 0.38 inches.
Minor tweaks to POP/WX grids were made. Otherwise, no significant
changes to the forecast this evening. See previous discussion
below for further forecast details.

...Prev Discussion (Issued at 132 PM PST Wed Feb 21 2018)...

Isolated light showers continue to move east this afternoon.
Current temperatures are mostly in the 50s west of the mtns, and
winds continue onshore with few locations reporting gusts of 20
mph or greater.

The long wave pattern over the globe has the western U.S.
dominated by a longwave trough. Shortwaves will rotate through
Southern California within this longwave trough for at least the
coming week. The first wave bringing us the clouds and light
showers today will continue moving eastward into Arizona. Expect
light showers anywhere in the coastal basin and into the coastal
slopes of the mountains through this evening, tapering off
overnight. The second wave moves in from the north on Thursday,
bringing a similar precip scenario, but this wave has more dynamic
energy, so precip chances continue into early Friday along with
stronger west winds in the mtns and deserts. Both these waves
favor San Diego County for the best chances of measurable precip.
The snow level will be low, around 3500 to 4000 feet, but
accumulations will be very light. The winds will be quite strong
in the mountains and deserts Thursday and Thursday night. The
winds weaken and turn offshore Friday morning to flush out the
clouds and precip. Weak offshore flow will continue through the
weekend for fair weather, although with cool days and cold nights
(not as cold as our last two nights, however). Next week, a third
wave reaches the West Coast with more moisture than the previous
two. This has some promise for significant precipitation, but the
timing and strength discrepancies between models keep confidence
low. Either Monday or Tuesday we can expect gusty west winds and
precipitation.

&&

.AVIATION...
220445Z...SCT-BKN clouds with bases near 5000 ft MSL along the
coastal mtn slopes clearing overnight. Increasing clouds with bases
2500-4000 ft MSL with tops to 8000 ft MSL after 12Z. ISO-SCT light
showers developing after 14Z and continuing through at least Thu
evening.

SW to W winds increasing over the mountains and deserts with sfc
gusts 35 to 50 kt along the desert mountain slopes and adjacent
desert foothills after 20Z. UDDFS/LLWS/rotors likely over and east
of the mountains Thu afternoon and evening, including near KPSP.

&&

.MARINE...
No hazardous marine conditions are expected through Thursday
morning. West to Northwest winds with gusts 20-30 kt and combined
seas of 8-9 ft with steep waves will develop Thursday afternoon
through Friday evening. This will create hazardous boating
conditions. A Small Craft Advisory will be in effect from 2 PM
Thursday through 8 PM Friday.


&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 10 AM Thursday to 10 AM PST Friday for Apple
     and Lucerne Valleys-Coachella Valley-Riverside County
     Mountains-San Bernardino County Mountains-San Diego County
     Deserts-San Diego County Mountains-San Gorgonio Pass Near
     Banning.

PZ...Small Craft Advisory from 2 PM Thursday to 8 PM PST Friday for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 30 nm-Waters from San Mateo point to the Mexican
     Border Extending 30 to 60 nm out including San Clemente
     Island.

&&

$$

PUBLIC...Gregoria (Update)/PG (Prev Discussion)
AVIATION/MARINE...SS



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