Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 260423
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
923 PM PDT Tue Jul 25 2017

.SYNOPSIS...
A westerly flow aloft will bring drying and more stable conditions
across Southern California for the balance of the week. By next
weekend, easterly flow aloft will bring a return of monsoonal
moisture for slight inland cooling and a renewed chance of afternoon
and evening thunderstorms...mostly near the mountains.

&&

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

Satellite imagery this evening showed marine stratus covering much
of the San Diego County coastal area, and extending inland up to 20
miles. convective clouds were dissipating and drifting north of the
CWA at 9 PM PDT. The 00Z Miramar sounding had stabilized
considerably from 12Z, but the PW was still high at 1.72 inch. The
profile had warmed aloft with a weak inversion near 15K FT. The
marine inversion base was near 1350 FT MSL. Rainfall today was
isolated, with only the Mt. Laguna area reporting any significant
rainfall. An isolated thunderstorm there left between 1.25 and 1.50
inches of rain earlier in the afternoon. Otherwise, it appears the
warming aloft and lingering cloud cover in some areas hindered more
widespread convective development.

No further thunderstorms activity is expected tonight. There is a
small chance for isolated convection along the higher mts on Wed,
but the forecast POPS are too low at this point for a mention of the
weather in the Zone Forecasts. Seasonally hot weather will continue
inland, with milder conditions along the coast for the next few
days. A forecast update was issued late this afternoon, and no
further updates are planned.

From previous discussion...

Drier westerly flow ensues on Wednesday dissipating the threat for
diurnally driven convection. For Wednesday through the
weekend...the high pressure ridge over the Southern Plains will
gradually retrograde over the Desert Southwest. The medium range
models are coming into better agreement that the high pres ridge
will generally dominate the weather pattern with hotter
temperatures inland and a shallower marine layer near the coast.

For early next week a southeasterly flow looks to set back up with a
series of weak waves in the flow bringing a return of the monsoonal
pattern with chances for diurnal thunderstorms once again. The EC is
also trying to pick up a chunk of moisture from Hurricane Hillary
which could enhance the potential for convection over the region
early next week as well as a return to more humid conditions across
the region. This will be an interesting pattern to keep an eye on
for SoCal indirect impacts.

&&

.AVIATION...
260300Z...Coasts/Valleys...Stratus with bases 1500-2000 ft MSL with
tops to near 2500 extending to KRNM and just west of KONT overnight.
The stratus deck may remain locked in at KCRQ and KSAN throughout
the day on Wednesday and have gone with this, though a few hours of
clearing is a possibility. High confidence tonight with moderate
confidence for Wednesday.

Mountains/Deserts...VFR will prevail with SCT clouds AOA 10000 ft
MSL. Very low risk of an isolated tsra developing during the heat of
the day on Wednesday.

&&

.MARINE...
A south swell from Hurricane Hilary will build into the local waters
Fri-Sat, likely peaking Sun-Mon, then lowering Tue-Wed. Swell will
be from 170 degrees at a period of around 14 seconds. Currently
swell height is forecast at around 5 FT, but ultimately will depend
on the track/strength of Hilary.

&&

.BEACHES...
A south swell generated by Hurricane Hilary will bring increasing
surf to the Southern California beaches Fri-Tue with highest surf
forecast to occur Sun-Mon. Current projections are for surf of 5-7
FT with sets to 10 FT along south facing beaches. A Beach Hazards
Statement has been issued Fri-Tue for the potential high surf.
Depending on the strength/track of Hilary, these surf heights could
change.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Friday morning through Tuesday
evening for Orange County Coastal Areas-San Diego County Coastal
Areas.

PZ...NONE.

&&

$$

PUBLIC...JAD/Brotherton
AVIATION/MARINE...Gregoria


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