Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 261636
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
936 AM PDT Mon Jun 26 2017

.SYNOPSIS...
Hot inland weather will continue today. Cooling will begin to
spread inland on Tuesday with near average high temperatures
returning on Wednesday and continuing into next weekend with minor
day to day differences. Patchy low clouds and locally dense fog
near the coast will increase in coverage and spread farther inland
on Tuesday night into Wednesday morning as the marine layer
deepens with the night and morning coastal low clouds and fog
extending into portions of the valleys through next weekend.

&&

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

A patch of fog was all there was this morning off Pt. Loma to Del
Mar, but while that patch dissipated, another one surged up from
Mexico. Some high clouds will continue to traverse the southern
sky, but all these clouds will pretty much go away today. Hot
weather is the big story as temperatures at the middle and lower
layers of the atmosphere are very high. That translates into
extreme heat and probable broken records this afternoon. Our
dominant high pressure ridge has begun to erode from the top and
that will continue as a low pressure trough pushes the ridge a
little southward through Wednesday. That will bring cooler weather
to all areas Tuesday and Wednesday and produce some locally strong
winds in the deserts (see fire weather info below). While the
marine layer will take time to develop, only a patch or two of
coastal fog is expected tonight. The marine layer aided by the
lower pressure aloft and a possible coastal eddy, will develop a
marine layer that should bring back a more uniform cloud deck
Tuesday night and beyond that will extend a little farther inland
each night and morning. But that cooling and clouding trend puts
on its brakes Thursday and little if any change is expected
heading into the weekend. Temps will get much closer to seasonal
averages by Wednesday.

&&

.AVIATION...
261530Z...Coast...From 16Z Monday to 09Z Tuesday, clear skies and
light winds will prevail along the coast and over the coastal
waters. A few patches of dense fog with a visibility of 1/2 SM or
less are possible between 09Z and 15Z Tuesday, but impacts at KSAN,
KCRQ and KSNA are not anticipated at this time. Clear skies and
unrestricted visibility will return between 15Z Tuesday and 00Z
Wednesday.

Valleys...Clear skies, unrestricted visibility and light winds will
prevail through 00Z Wednesday.

Mountains/Deserts...Breezy winds will develop over and east of the
mountain ridge this afternoon and evening resulting in moderate
up/downdrafts and LLWS. Otherwise clear skies and unrestricted
visibility are anticipated through 00Z Wednesday.

&&

.MARINE...
Patchy dense fog within 10 miles of the San Diego County coast will
burn off this morning, leaving clear skies for the afternoon. Patchy
dense fog within 20 miles of the coast is expected again Tuesday
morning.

Winds will remain west northwest over the coastal water through
Friday. Periods of stronger winds are possible this evening and
Tuesday evening in the vicinity of San Clemente Island, where local
gusts may approach 20-25 kt for a couple hours.

&&

.FIRE WEATHER...
Onshore flow will bring stronger and gusty southwest to west winds
to the desert slopes of the mountains into adjacent desert. The
winds in the high desert and north slopes of the mountains will
decrease late tonight and Tuesday, but continue strong and gusty
along the east slopes of the mountains into the lower deserts
through Tuesday night. Lowest daytime humidities will fall to
around 5 percent with poor overnight recovery. The combination of
strong gusty winds and low humidities will bring critical fire
weather conditions for the desert slopes of the mountains into
adjacent deserts. A Red Flag Warning has been issued. Winds will
weaken some Wednesday with slowly increasing humidity Wednesday
night and Thursday.

&&

.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 this evening for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

     Red Flag Warning from 1 PM this afternoon to 1 AM PDT Wednesday
     for Coachella Valley-Including The Palm Springs South Coast
     Desert District-Riverside County Mountains-Including The
     San Jacinto Ranger District Of The San Bernardino National
     Forest-San Diego County Deserts-Including The Anza Borrego
     Desert State Park-San Diego County Mountains-Including The
     Palomar And Descanso Ranger Districts of the Cleveland
     National Forest-San Gorgonio Pass Near Banning.

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

     Red Flag Warning from 1 PM this afternoon to 1 AM PDT Tuesday
     for Victor Valley-Apple Valley-Lucerne Valley-Johnson
     Valley.

     Heat Advisory until 9 PM PDT this evening for Orange County
     Inland Areas-San Diego County Valleys.

PZ...NONE.

&&

$$

PUBLIC/FIRE...MM
AVIATION/MARINE...BA



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