FXUS66 KSGX 192006
Area Forecast Discussion
National Weather Service San Diego CA
106 PM PDT Thu Jul 19 2018
Monsoonal moisture will slowly decrease through Saturday with
isolated afternoon and early evening thunderstorms
possible, mainly for the mountains and high desert areas. Drier
with a warming trend Sunday through Wednesday as strong high
pressure aloft moves into the southwest states, with the heat
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
At 1 PM, water vapor satellite showed a large upper-level ridge
stretching from northern New Mexico to central California, and an
upper-level low just west of central Baja. Radar showed the first
shower of the day just northwest of Big Bear. Additional isolated
showers and thunderstorms are possible over portions of the
mountains and deserts this afternoon, however storms are not
expected to be very strong due to unfavorable mid-level winds.
Isolated storms are possible over portions of the mountains and
deserts in the afternoons through Saturday, however mid-level
moisture will be decreasing from now through the weekend. High
temperatures will be near normal to just below normal through the
weekend as the aforementioned upper-level ridge pushes to the
The main focus for the weather in the extended will be a big warm
up and dry weather. The upper-level ridge to our east will build
west early to mid next week, with Tuesday expected to be the
warmest day of the week. H850 temperatures of 31-33 deg C and weak
offshore flow inland on Tuesday will create surface highs in the
80s and 90s for the mountains and coastal valleys, 100s for the
inland valleys and high desert, and 110-117 for the Coachella
Valley and lower deserts. A shallow marine layer and weak coastal
eddy should keep the coast not as hot, with highs in the low to
mid 80s. An Excessive Heat Watch remains in effect for inland
areas Monday through Wednesday. The ridge sticks around through
the end of next week, so the above normal highs may linger longer
than currently forecast. Overnight lows will also remain high for
some inland areas, with the lower deserts only dipping into the
low 90s Tuesday and Wednesday mornings. Low clouds and fog are
expected to develop each night along the immediate coast.
191850Z...Coast/Valleys...Clear with unrestricted vis this
afternoon. Low clouds will return to coastal TAF sites aft 06Z Fri,
spreading up to 15 miles inland by 15Z Fri. Expect bases around 1000
ft MSL and tops to 1600 ft MSL. Clearing to the coast between 15Z
and 17Z Friday.
Mountains/Deserts...There is a slight chance of thunderstorms this
afternoon with bases 8000-9000 ft MSL and tops to 35000 ft MSL. Any
TSTMS that develop will likely be accompanied by strong
up/downdrafts, LLWS and local surface wind gusts to 35 knots.
Otherwise, SCT-BKN clouds at or abv 8000 ft MSL with unrestricted
vis through tonight.
No hazardous marine weather is expected through Tuesday.
Swells from the South Pacific will begin to arrive at SoCal beaches
over the weekend and continue to impact local beaches through the
middle of next week. High surf conditions and strong rip currents
could occur, most likely Monday through Wednesday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
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
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