Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 241625 AAA

Area Forecast Discussion
National Weather Service San Diego CA
915 AM PDT Tue Apr 24 2018

.Morning Update...

Areas of fog and coastal stratus continue this morning and will burn
off to the coast through late morning. Expect a similar renewal of
coastal fog and low clouds this evening through Wednesday morning.
Areas of fog will again affect coastal areas and along the mesas
with visibilities as low as 1 SM. No significant changes were needed
to the forecast this morning.


Fair and seasonal weather will continue this coming week. The
marine layer will continue the coastal clouds nights and mornings.
Lower pressure aloft this weekend into next week will bring cooler
weather for all areas, extend the marine layer and increase
coastal clouds.



(Previous discussion below remains valid)

The coastal clouds moved ashore on schedule last evening, but have
since moved out of San Diego in puzzling fashion. That should be a
temporary hiccup and low clouds and fog will cover coastal areas
and some westernmost valleys by sunrise. The cloud bases are
higher, so the coverage of dense fog will be patchier and slightly
farther inland than it was yesterday morning. By late morning
these clouds will clear, but there will be variable high clouds to
occasionally filter the sun a bit. Temperatures will continue
above seasonal averages except at the immediate coast. Breezy
winds will develop late this afternoon through mountain passes and
into deserts, but with gusts mostly below 35 mph. Take a mental
picture of this description, because that`s what Wednesday and
Thursday will be like. If there is any trend, it would be slightly
greater coverage of coastal clouds each night and morning through
Friday, and slightly cooler daytime weather. A low pressure
trough will develop and move into Northern California this
weekend. That is projected to deepen the marine layer and bring
even cooler weather with daytime temperatures below average and
brisk winds in the mountain and deserts. A larger long wave trough
circulation over the West will ensure that cooler and cloudier
weather persists as we head into May. There are some hints by
some model guidance for rain Monday and beyond, but recent
performance in the guidance out one week has not been good. The
models keep kicking the rain can down the road an additional day.
The obvious effect is to lower confidence, so we wait for more of
that before forecasting the wet stuff. Until then, keep the
jackets handy.


2401610Z...Coast...Areas of BKN-OVC stratus extending up to 15 miles
inland with bases 700-1000 ft MSL with tops to 1400 ft MSL. Areas of
vis 3-5 miles will occur over higher coastal terrain. Stratus
clearing over land 16Z-18Z, and should clear for at least a few
hours along the immediate coast in the afternoon. Stratus will
develop again after 25/02Z and spread 15-20 miles inland overnight.
Bases will be near 800-1200 ft MSL. The risk of OVC low clouds at
KSAN again tonight is high, so the TAF low clouds forecast looks
good, but it could arrive somewhat earlier at KSAN.

Valleys/Mountains/Deserts...SCT clouds at/above 25000 ft MSL with
unrestricted vis through Wednesday morning.


Stronger west to northwest winds will develop in mainly the coastal
waters beyond 30 NM each afternoon and evening Friday through Sunday
with gusts between 20 and 25 knots possible.


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





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