Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 291652

Area Forecast Discussion
National Weather Service San Diego CA
950 AM PDT Wed Mar 29 2017

...Very strong winds Thursday afternoon through evening in the
mountains and deserts...

Sunny and warm today with high pressure aloft and weak offshore
flow. On Thursday a strong low pressure trough moving across the
Great Basin will bring strong westerly winds to the mountains and
deserts. Cooler Friday as the winds shift northeast behind the
trough. Mostly sunny and Warm over the weekend under weak high
pressure, but low pressure will bring cooler weather early next week.



Temperatures rose quickly after sunrise today, and were 4-8 degrees
higher than yesterday morning in most areas. Clear skies and weak
offshore flow will propel temperatures into the 80s west of the
mountains except near the coast.

The ridge axis aloft today will drift southeast tonight and our
offshore flow will transition to a progressively stronger onshore
flow pattern through Thursday afternoon as a deep trough over the
Pacific Northwest tracks across the Great Basin. Strong winds
rounding the base of the trough and an elevated inversion just above
the ridgetops will support mountain wave development Thursday
afternoon. Model cross-sections show waves surfacing down the lee
slopes into the Coachella Valley and San Diego deserts Thursday
afternoon and evening. Surface winds of 20-30 mph are likely with
peak gusts of 50-60 mph on the slopes and some parts of the desert
floor. Wind damage is possible. Blowing dust and sand will restrict
visibilities. Rotors are likely in the vicinity of Palm Springs
airport. A High Wind Watch in effect for most of the mountain and
desert areas.

The wind will quickly switch to the north late Thursday night behind
the trough, and gusty offshore north-northeast winds will follow
through Friday morning.

*From Previous Discussion*

High pressure will gradually build in for the weekend with
moderating temperatures and lighter winds. Another weak trough
slated for Monday and Tuesday next week will bring another cooldown
and another possible strong wind event. It is spring afterall!


291515Z...Coast and Valleys...Locally gusty N-NE winds will create
pockets of LLWS through and below the Cajon Pass through 18Z. Clear
skies and light afternoon sea breezes will prevail this afternoon.
Predominantly FEW AOA 20,000 ft msl tonight, though there some
potential for patchy fog or low stratus with bases AOB 1,000 ft msl
along the San Diego County coast between 10 and 15Z Thursday.

Mountains and Deserts...FEW AOA 20,000 ft msl and light winds will
prevail through 15Z Thursday. Westerly winds and mountain wave
activity will increase after 15Z, peaking around 00Z Friday. This
will create strong up/downdrafts and LLWS over the deserts and along
the desert slopes, especially between 21Z Thursday and 04Z Friday.
Impacts from LLWS and gusty winds are possible for KPSP and KTRM.


No hazardous marine weather is expected through Thursday morning.
The passage of a cold front will bring NW winds 15-25 kt and
increasing seas Thursday afternoon into Friday. Strongest winds will
likely be found 10 miles offshore and beyond Thursday Evening.
Highest combined seas are anticipated overnight Thursday into
Friday, with a 3-6 ft seas inside of 30 miles building to 7-10 ft
near and south of San Clemente Island. Winds and swell should
decrease over the weekend, before increasing again early next week.


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


CA...High Wind Watch from Thursday afternoon through late Thursday
     night for Apple and Lucerne Valleys-Coachella Valley-
     Riverside County Mountains-San Bernardino County Mountains-
     San Diego County Deserts-San Diego County Mountains-San
     Gorgonio Pass Near Banning.




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