Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 252044

Area Forecast Discussion
National Weather Service San Diego CA
145 PM PDT Wed Apr 25 2018

High pressure aloft will bring one more warm day Thursday before
temperatures trend downward over the weekend. A deep trough of low
pressure over the Pacific will move inland across California through
Saturday and Sunday bringing cooler weather, a deeper marine layer,
and gusty west winds in the mountains and deserts.



1 PM temperatures today were the same or 1-2 degrees lower than
yesterday in most areas west of the mountains. In contrast, the
lower deserts were hotter, with temperatures 3 to 5 degrees higher
than yesterday. PSP was 100 degrees at 1 PM, which was 5 degrees
higher that 24 hours ago.

Thursday will be similar to today with marine layer clouds in the
coastal zones and western valleys retreating back to the coast
through midday. Temperatures will be a degree or two lower west of
the mountains, but the triple digit heat will linger one more day in
the lower deserts. Records are out of reach though...the record high
at PSP Thursday is 109.

Friday through Sunday: A transition to stronger onshore flow and
cooler weather will take place as shortwaves circulating around a
deep closed low off the NorCal coast deepen the trough along the
West Coast. Most of the shortwave energy will pass by to the north,
as will the rain, but the trough will bring gusty west winds, cooler
weather and a deeper marine layer Friday through Sunday. It will
turn quite windy each afternoon and evening in the mountains and
deserts, especially in the east-west passes including the I-10 and I-
8 corridors. A low end Wind Advisory may be needed in these areas.
Low clouds will reach the inland valleys, but most areas should see
clearing during the day due to the weak inversion from the infusion
of cooler air aloft. Temperatures will be lower this weekend with
most areas at or slightly below average.

*From Previous Discussion*

Long Range Outlook for next week: The model spread is quite large
next week which makes it difficult to pinpoint which days will have
the best chance for showers. The GFS advertises a deep cold upper
low stalling over the Southwest Monday-Wednesday, while the ECMWF
delays this upper low until Wednesday and Thursday. This uncertainty
is too large to introduce rain chances at this time.


252000Z...Coast/Valleys...Predominantly SKC apart from SCT low
clouds over the coastal waters through 02Z. After 02Z Thursday, low
clouds will creep back inland, reaching 20-25 mile inland by 12Z
Thursday. Bases should be near 1000 ft MSL, with local visibility of
1/4 mile or less where low clouds and terrain intersect. Visibility
at KSAN, KCRQ, KSNA, and KONT should remain 5 SM or better. Low
clouds should clear to the coast between 15Z and 18Z Thursday.

Mountains/Deserts...SKC, unrestricted visibility and light winds
through Thursday afternoon.


No hazardous marine conditions through Thrusday. Stronger onshore
flow will bring breezier northwest winds to the coastal waters
Friday through early next week. Look for gusts near 20 kt during the
afternoons for areas outside of 20 nm, strongest winds near and
south of San Clemente Island. Choppier seas should accompany the
winds, with a 5-8 ft (7-9 sec) wind swell affecting the same areas
Saturday into early next week.


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





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