Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 200410
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
910 PM PDT Mon Jun 19 2017

.SYNOPSIS...
Building high pressure aloft will continue to increase afternoon
temperatures through mid week. A shallow marine layer will continue
to moderate the weather along the coast with areas of nocturnal
clouds and fog...lingering at some beaches much of the day. It will
be cooler to end the week as the high weakens and onshore flow
increases, but still seasonally warm inland. Summer officially
arrives at 9:24 PM on Tuesday.

&&

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

At 8 PM PDT...Low marine clouds were widespread over the coastal
waters and extended to the Beaches. The 00Z Miramar sounding had a 3
degree C inversion based near 1250 FT MSL. This was about 200 FT
lower than yesterday. The atmospheric column had warmed with a peak
temp of 29.7 degrees C at 3500 FT MSL. Local sfc pressure gradients
were onshore 6-8 MBS KSAN to the deserts, continuing to support peak
westerly wind gusts through the passes and into the deserts of 25 to
30 MPH.

Expect fog to develop over coastal areas tonight and it may become
dense late tonight into Tue morning, possibly affecting the commute.

A 596 DM High was centered over AZ this evening, and should reach
peak intensity on Tue with 500 MB heights surpassing 594 DM over the
SGX CWA. See below for expected high temps and climate information.
No forecast changes this evening.

From previous discussion...

113-122 deg F in the Coachella Valley and S. D. County Deserts
108-114 deg F in the High Desert
100-112 deg F in the Inland Empire
95-106 deg F in the mountains below 5000 ft
90-105 deg F in the inland valleys

for Tuesday and Wednesday (see climate section below for record
information). The Excessive Heat Warnings and Heat Advisories
remain in effect through mid week (See LAXNPWSGX for additional
details). The very hot weather weather will linger Wednesday, then
lowering heights aloft will drop temperatures a few degrees
Thursday and Friday. Unfortunately, models show the ridge
lingering near the region through the weekend, with a slight bump
in high temperatures Saturday through next Monday for the valleys
and mountains. Luckily for the coast, a shallow marine layer will
help to moderate temperatures, keeping highs near seasonal normals
through the week. Night/morning low clouds and fog is expected to
continue along the coast through the week, with lowest visibility
expected Tuesday and Wednesday morning due to the ridge aloft
peaking. Slight deepening will develop by the end of the week as
heights aloft lower.

The position of the high this weekend might be able to pull some
monsoonal moisture into the region. Right now, only one model is
showing precipitation over the mountain ridges, so will keep the
forecast dry for now. However, it will be something to keep an
eye on.

&&

.AVIATION...
200400Z Coast: A mix of IFR-VLIFR conditions are expected within 10
miles of the coast through 16Z Tuesday. Low cloud bases should be
between 200 and 600 ft MSL. There is a high probability of
visibility restrictions of 1 SM or less with FG over the coastal
mesas and at KCRQ, and a moderate risk at KSAN and KSNA. Conditions
will improve after 16Z, though a few patches of low clouds, with
bases between 400-800 ft msl may linger along the beaches into the
afternoon.

Valleys, Mountains and Deserts: Clear skies and unrestricted
visibility through Wednesday. High density altitude at KPSP and KTRM
with max temperatures between 118-122 F.

&&

.MARINE...
Areas of night and morning dense fog remain possible through
Thursday. Otherwise, no hazardous marine weather is anticipated,
with mixed seas of 4 ft or less and light-moderate northwest winds.

&&

.BEACHES...
Beach Hazard Statement for strong rips currents in effect through
Thursday. A mix of southerly and westerly swells Tuesday-Thursday
with large tidal swings (high tides 7 ft with low tides -1.0 ft)
will result in strong and dangerous rip/longshore currents.

&&

.CLIMATE...

...Sites Expected to Break or Tie High Temp (deg F) Records...


                        TUESDAY
               Forecast  Record  Year
Palm Springs     122      122    2016
Thermal          121      121    2016

                       WEDNESDAY
               Forecast  Record  Year
El Cajon          94       92    2001
Idyllwild         94       94    1970
Campo            106      105    2008
Palm Springs     122      118    1968
Indio            118      116    1981
Thermal          120      117    1968

                        THURSDAY
               Forecast  Record  Year
Palm Springs     119      119    1959

&&

.Fire Weather...
The Holcomb Fire was burning this evening at around 6000 FT in the
San Bernardino Mts. It was over 800 Acres and zero percent contained
at 9 PM PDT. Hot, dry conditions and gusty afternoon and evening
winds along the ridges, desert slopes and foothills will cause an
elevated wildfire risk in these areas over then next few days. Winds
of 20 to 25 MPH and minimum humidity values of 10-15 percent are
likley Wed/Thu afternoons.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 9 PM PDT Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

     Heat Advisory until 9 PM PDT Wednesday for Orange County Inland
     Areas-Riverside County Mountains-San Bernardino County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire-San Diego County Mountains-San Diego County
     Valleys-Santa Ana Mountains and Foothills.

PZ...NONE.
&&

$$

PUBLIC...JAD/JJT
FIRE WEATHER...JAD
CLIMATE...JJT
AVIATION/MARINE/BEACHES...Albright


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