Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 191054
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
354 AM PDT Thu Jul 19 2018

.SYNOPSIS...
Monsoonal moisture will slowly decrease through Saturday with
isolated afternoon and early evening thunderstorms
possible...mainly for the mountains and high desert areas. For
Sunday through Wednesday...drier with a warming trend as strong
high pressure aloft moves into the southwest states with the heat
peaking Tuesday and Wednesday.

&&

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

.SHORT TERM (Today through Saturday)...
Early this morning...a weak upper level low pressure system is
centered just off the central coast of Baja with east/west
oriented high press across the eastern Pacific into the southwest
states with the ridge axis across central California into Nevada.
This upper level low pressure system will move slowly towards the
northwest through Saturday. The flow aloft across southwest
California will transition from easterly to southeasterly
today...southeasterly on Friday...and southerly on Saturday. There
will be slow drying of the lower level moisture in the lower
deserts through Saturday. Most areas will have little change in
high temperatures through Saturday...except for the lower deserts
which will warm as the lower levels dry.

Afternoon convergence boundaries for the north/south mountain
ranges will shift from the coastal slopes today...to the desert
slopes for Friday and Saturday. Isolated thunder is once again
possible today for the mountains and high desert areas for this
afternoon and early evening...but with very little coverage
similar to Tuesday and Wednesday afternoons. With the shift of the
convergence boundaries onto the desert slopes of the Riverside
and San Diego County mountains for Friday and Saturday...it may be
possible to more effectively tap the residual lower level
moisture in the lower deserts to supported isolated thunder on the
east slopes of the mountains for Friday and Saturday afternoons.
A slight chance of thunderstorms has been added for those areas.

&&

.LONG TERM (Sunday through Wednesday)...
Strong high pressure centered over New Mexico on Sunday will move
slowly westward and be centered over Arizona on Tuesday and over
southern Nevada on Wednesday with 500 mb heights peaking around
600 DM on Tuesday and Wednesday. This will bring a warming trend
from Sunday into Tuesday and Wednesday. A shallow marine layer and
weak onshore flow is expected to keep areas near the coast cooler
with the extended run of the local workstation WRF showing a weak
coastal eddy at times for Tuesday and Wednesday. High temperatures
will peak around 10 degrees above average on Tuesday and
Wednesday. An Excessive Heat Watch has been issue for Monday
through Wednesday except near the coast.

&&

.AVIATION...
190930Z...Coast/Valleys...Patchy stratus with CIGS of 1200-1700 ft
MSL and tops to 2000 ft MSL will be found near the coast through 15Z
and again after 06Z Friday. Otherwise, VFR will prevail with some
passing high clouds.

Mountains/Deserts...There is just a slight chance of thunderstorms
this afternoon with bases 8000-9000 ft MSL and tops to 35000 ft MSL,
strong up/downdrafts, LLWS and local surface wind gusts to 35 knots.
Otherwise, VFR will prevail under some passing high clouds.

&&

.MARINE...
A small pulse of Southern Hemisphere south swell will move into the
SoCal waters this weekend, but only at 1-2 FT. A larger pulse of 3-4
FT will arrive on Monday, lasting through the middle part of next
week with period of 18-20 seconds. However, significant wave
heights are forecast to remain below 7 FT.


&&

.BEACHES...
Two pulses of Southern Hemisphere swell will arrive to the SoCal
beaches, a small pulse of 1-2 FT this weekend followed by a larger
pulse at 3-4 FT beginning on Monday and lasting through the middle
part of next week. The larger pulse arriving on Monday, July 23rd
will create a hazardous surf zone with larger breaking waves
possibly to 7-10 FT on south facing beaches and strong rip currents.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch from Monday morning through Wednesday
     evening for Apple and Lucerne Valleys-Coachella Valley-
     Orange County Inland Areas-Riverside County Mountains-San
     Bernardino County Mountains-San Bernardino and Riverside
     County Valleys-The Inland Empire-San Diego County Deserts-
     San Diego County Mountains-San Diego County Valleys-San
     Gorgonio Pass Near Banning-Santa Ana Mountains and
     Foothills.

PZ...NONE.

&&

$$

PUBLIC...17
AVIATION/MARINE/BEACHES...Gregoria


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