Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 190416

Area Forecast Discussion
National Weather Service San Diego CA
916 PM PDT Sun Jun 18 2017

High pressure aloft over the Southwest will keep the weather hot
inland this week, peaking Tuesday and Wednesday, when a few records
could fall. Meanwhile, a shallow marine layer and weak onshore flow
will moderate the temperatures along the coast, with areas of night
and morning low clouds and patchy dense fog. The High will slowly
weaken after midweek, allowing cooling to spread farther inland
across the valleys. Continued hot over the deserts through next



Temperatures continued to slide today along the coast, while desert
areas soared well past the century mark. No records were broken, but
Palm Springs and Idyllwild tied their records for this date. Patchy
marine clouds persisted over the CA Bight this evening, and there
were thunderstorms over the Sierra, and about 600 miles WSW of San
Diego, but over SW CA...skies were clear at 8 PM PDT. Surface
pressure gradients were running 5-7 MBS locally KSAN to the deserts,
supporting gusty westerly winds through the desert passes. The 00Z
Miramar sounding had a 6.5 degree C inversion based near 1460 FT
MSL. Slight warming was indicated above 1600 FT, with the peak of
the inversion near 3K FT with a temp of 28 degrees C.

Expect the marine layer to prevail again tonight over coastal areas
with low clouds and some fog redeveloping. Skies should clear again
on Monday over coastal areas, but some areas of fog/low clouds could
begin to linger into the afternoons through midweek as onshore flow
builds under a colossal marine inversion. Temperatures are expected
to rise a few degrees on Monday, with further gains possible inland
into Wednesday. Based on forecast temperatures, the Heat Advisory
for Orange and San Diego Counties is not warranted for Monday and
may need to be adjusted back by 24 hours.

A strong high pressure ridge centered over CA today, is forecast to
shift SE, and strengthen over AZ on Mon, reach peak intensity at 597
DM on Tue, then slowly deflate and sink to the south Wed through
Fri. The 500 MB heights peak over the CWA on Tue, with the thickness
following on Wed. Heat Advisories/Warnings cover this period, and in
some cases extend through Thu. See LAXNPWSGX for details.

Throughout this event, a weak mid-level trough is evident along the
CA Coast, which should support the marine layer along the Coast.
This feature transitions into a closed system and drifts farther
offshore during the latter half of the week, leaving a weak ridge
along the coast on Friday.

For early next week...the ridge is oriented east-west along 30 N as
more substantial troughing develops along the West Coast,
suppressing the westerlies to the south. This will create more
seasonal June weather, with a deeper marine layer and cooler


190400Z...Coast...IFR conditions are expected to develop along the
coast through 15Z, with ceilings between 600 and 1,000 ft msl and
visibility restrictions of 3-6 SM. Local visibility restrictions of
2 SM or less in FG are possible along the coastal mesas and at KCRQ.
Rapid clearing is expect around 15Z. Clear Skies, unrestricted
visibility and light winds will prevail between 16Z Monday and 04Z

Valleys, mountains, deserts...Clear skies and unrestricted
visibility will prevail through 06Z Tuesday. For density altitude
concerns, KPSP and KTRM can expected highs between 116 and 119
degrees Monday afternoon.


Areas of night and morning dense fog will occur over the coastal
waters through at least Thursday. Otherwise, no hazardous marine
weather is anticipated, with mixed seas of 4 ft or less and light
southwest-northwest winds.


A south swell from 170-180 degrees at 14-16 sec will build over the
coastal waters Monday and Tuesday, peaking at around 4 ft on
Wednesday. The swell will slowly fade thereafter through Friday.
This swell will be accompanied by large tidal swings near 7 ft. The
combination of the two will bring strong longshore currents and
increase the chances for rip currents along the coast. A Beach
Hazard Statement has been issues for Monday through Thursday to
account for the risk of strong rip currents.


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


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 Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains.

     Heat Advisory from 11 AM Monday to 9 PM PDT Wednesday for Orange
     County Inland Areas-San Diego County Valleys-Santa Ana
     Mountains and Foothills.



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