Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 042015

Area Forecast Discussion
National Weather Service San Diego CA
115 PM PDT Mon Jul 4 2022

A gradual warming trend is expected through the coming weekend
with the warmest temperatures occurring Saturday and Sunday.
Temperatures across inland areas will climb by a few degrees each
day, while areas near the coast remain more moderated by marine
layer clouds and prolonged onshore flow each morning. The marine
layer becomes more shallow starting Thursday, with low clouds
struggling to develop away from the immediate coast and some of
the coastal valleys by the weekend. This will also allow for
coastal areas to warm up by a few degrees.



The upper level trough over the Eastern Pacific will weaken
slightly today and Tuesday, leading to slightly weaker onshore
flow. Westerly winds can still be expected during the afternoon
and evening hours both today and Tuesday with peak gusts of 30-40
mph, localized gusts to 50 mph below mountain passes and through
wind-prone valleys. Winds will get progressively weaker through
the week ahead as indicated by ECM/GFS modeled pressure gradients
between SAN-LAS, falling from nearly 9mb today to as low as 1-3mb
by the weekend.

The upper trough will still remain entrenched over the Eastern
Pacific, helping to maintain onshore flow and marine layer clouds
each morning this week. Today’s 12z sounding indicated a roughly
8C inversion based around 2500 FT MSL. The weaker trough as well
as upper ridging expanding into the area will cause the marine
layer to become more and more shallow through the week. By the
weekend, marine layer depth will likely only be a few hundred feet
above sea level, which will favor low clouds only developing
along and near the immediate coast. The relative lack of marine
layer clouds late this week will allow for the coast to see a
warming trend starting Thursday.

The upper level ridge over the Central US will gradually
strengthen and retrograde westward through the week, which in
conjunction with a weaker Pacific trough will lead to warming
temperatures for most inland areas through the week. Ensemble
guidance still favors a 500mb high peaking around 597dm and
centered over the Colorado Rockies, marking another very slight
shift eastward. The warm-up will be fairly steady through the
weekend, with most inland areas seeing high temperatures climb 2-4
degrees each day while the immediate coast remains fairly cool.
The coast will finally get in on the warming trend starting
Thursday as the marine layer becomes rather shallow. Temperatures
peak around 5-8 degrees above seasonal normals for most areas on
Saturday, with some desert locations seeing their hottest
temperatures on Sunday, also around 5-7 degrees above average.


042000Z...Coast/Valleys...Mostly clear skies with unrestricted vis
will prevail through this afternoon. Low clouds will move back
inland after 03Z, with bases around 2000 feet MSL. Clouds will
spread about 30-35 miles inland overnight, reaching KONT and KSBD
after 12Z. Patchy FU possible 04-05Z tonight due to fireworks vcty
KSAN. Low clouds will scatter out 16-17Z Tuesday.

Mountains/Deserts...Mostly clear with unrestricted vis through
Tuesday morning. W-NW winds with surface gusts 25-35kt over/east of
mtns and desert slopes this afternoon and evening, diminishing by
12Z Tuesday. Areas of moderate up/downdrafts and LLWS possible
over/east of the mountains with these winds.


Gusts around 20 knots will develop near San Clemente Island each
afternoon Monday through Wednesday. No hazardous marine weather
expected Thursday through Saturday.


Westerly winds will increase again over the mountains and into
the deserts later this afternoon and evening, with peak wind gusts
of 30-40 mph at times. Gusty winds will coincide with RH values
around 15-20% which will lead to some elevated fire weather
conditions for a few hours. Areas west of the mountains will
experience light winds and elevated RH with the marine layer in
place. The warming trend expected later this week will certainly
lead to lower RH across many inland areas, especially from the
Inland Empire into the mountains and desert foothills.


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




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