Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 252130 CCA
AFDSGX

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

corrected

.SYNOPSIS...
Monsoonal moisture will continue scattered afternoon and evening
thunderstorms today. Slow warming and drying for Wednesday
through Friday. For Saturday through early next week...monsoonal
moisture will return with slight inland cooling and with a chance
for renewed afternoon and evening thunderstorms...mostly for the
mountains and deserts.

&&

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

Moderate instability and high atmospheric moisture (PWAT 2")
remains in place and will be responsible for scattered
thunderstorms over our mountains and deserts through this evening.
Low level winds remain fairly light which will contribute to a
flash flooding threat due to slow moving heavy rain producing
cells. Stronger mid level winds may cause cells to not be very
long lasting though. Convection will likely diminish before
midnight this evening.

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...
251952Z...Coasts/Valleys...Stratus with bases 1500-2000 ft MSL with
tops to near 2500 extending locally inland south of KCRQ, then
stratus re-developing after 26/01Z and spreading to KRNM and just
west of KONT overnight. Bases will remain around 1500-2000 ft MSL
with tops to 2500 ft MSL. Otherwise SCT-BKN cloud layers AOA 10000
ft MSL through this evening. At KSAN the risk of solid low clouds
tonight is moderate-high, and confidence in little if any clearing
the remainder of the afternoon is moderate.

Mountains/Deserts...Isolated to scattered showers/thunderstorms
developing over the mountains and deserts til 26/01Z. Bases will
likely be 8000 ft MSL with tops to 35000 ft MSL. Strong
up/downdrafts and local gusty surface winds will be possible
near storms. Otherwise SCT-BKN cloud layers AOA 10000 ft MSL
through this evening.

&&

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

&&

.BEACHES...
A south swell generated by Hurricane Hilary may produce high surf
along south facing beaches Friday through early next week.
Confidence in forecast surf heights is low as this will largely
depend on the intensity and track of the hurricane over the next few
days.

&&

.SKYWARN...
Skywarn activation is requested for San Diego, Western Riverside,
and Southwestern San Bernardino Counties due to scattered
thunderstorms over the mountains and deserts this afternoon and
evening. Spotters are asked to submit storm reports via amateur
radio, social media, or telephone.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...Brotherton
AVIATION/MARINE...Small


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