Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 222047

Area Forecast Discussion
National Weather Service San Diego CA
145 PM PDT Mon May 22 2017

Continued hot in the Inland Empire and the Lower Deserts through
Tuesday with high pressure aloft. Cooler near the coast with night
and morning low clouds and dense fog. Cooling will spread farther
inland Wednesday, with further cooling Thursday and Friday as a
trough of low pressure moves inland. This trough may produce areas
of light rain or drizzle west of the mountains Thursday night into
Friday morning. Dry and warm over the weekend with weak high
pressure aloft.



A shallow marine layer kept coastal areas comfortably cool, while
farther inland it baked. At 1 PM the temperature was 71 at the San
Diego Airport (avg high 69), 87 at Ramona (avg 76), 90 (avg 81) at
Riverside and a blistering 105 (avg 95) at Palm Springs.

Tuesday will be the same, or perhaps even a little hotter in the
eastern valleys, mountains and deserts as weak ridging aloft
suppresses the marine layer slightly. The record at Palm Springs
Tuesday is 114, and the forecast high is 111. This early season heat
will elevate the heat risk in the lower deserts. Areas of low clouds
and dense fog will spread 10-15 miles inland again tonight, then
retreat back to the coast Tuesday morning.

The upper ridge weakens Tuesday night and low clouds will spread a
little farther inland Wednesday morning. Wednesday will be a little
cooler with the deeper marine layer lowering valley highs into the
80s. Not quite as hot in the lower deserts with highs around 106.

Thursday through Sunday...A Pacific trough moving inland will bring
stronger onshore flow and greater cooling Thursday and Friday. Most
of it`s energy will slide past to the north, but it will bring
strong winds to the mountains and deserts where Wind Advisories may
be needed. The marine layer will be much deeper with low cloud and
fog extending into the valleys Thursday morning, perhaps deep enough
for light rain or drizzle west of the mountains Thursday night into
Friday morning.

On Saturday high pressure aloft rebuilds along the West Coast
bringing warmer weather and temperatures a few degrees above average
by Memorial Day.


222002...Coast/Valleys...Through 23/0200 UTC, mostly SKC and P6SM
vis, except at/near portions of the beaches where BKN-SCT clouds
1000-1500 ft msl may linger. 23/0200-1600 UTC, low stratus/dense fog
likely re-developing about 10-15 sm inland with bases 300-600 ft msl
and tops 700-1000 ft msl, with areas of vis 1/4-2 sm. Confidence in
cig heights and vis for KSAN, KCRQ and KSNA TAFs is moderate with
moderate confidence in timing and high confidence in low stratus/fog

Mountains/Deserts...P6SM vis and mostly SKC through Tuesday morning.


A shallower marine layer will likely bring dense fog to the coastal
waters tonight into Tuesday morning, producing visibilities of 1 NM
or less.

Also, 20 kt northwest wind gusts will be possible over the outer
waters near San Clemente island each late afternoon and early
evening through Friday.


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





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