Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 242034

Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Mon Oct 24 2016

Scattered showers and isolated thunderstorms will continue through
this afternoon under the trough of low pressure and instability
aloft. The low pressure system will move east tonight, and fair
weather will return and continue through Thursday with a gradual
warming trend. Some low clouds and fog will occur at times near the
coast Tuesday through Thursday. There is a chance of rain Friday as
another trough of low pressure develops, along with cooler weather.
Some clouds will occur next weekend.



Numerous thunderstorms occurred earlier today, especially in Orange,
western Riverside and SW San Bernardino Counties. Maximum Unstable
CAPEs exceeded 1000 J/kg in the 850-700 mb layer which was quite
moist, contributing to total precipitable water amounts of around
1.2 inches, though outside of areas receiving rain, the layer below
850 MB was dry. 120-knot jet was to our southwest, with good
diffluence over our area. Well over 1000 lightning strikes have
occurred over our forecast area in the past 24 hours, and some power
poles have been damaged due to lightning strikes, especially San
Bernardino County. Scattered showers and thunderstorms were
occurring at early afternoon, mainly north of San Diego County. With
an upper low about 120 miles to our SW, we could have some more
precip through late this afternoon, though no lightning strikes are
currently to our southwest. There does continue to be good MU CAPE
aloft though. After the trough axis passes trough around 03Z
tonight, precip should be gone. Ridging over the western US should
bring a gradual warming trend Tue-Thu with 80s in the valleys
Wed/Thu and 90s in the lower deserts, though coastal areas will be
only in the lower to mid 70s due to onshore flow which should bring
some stratus/fog, especially Tue and Wed nights.

Mean troughing continues off the West Coast for the next week, and a
strong deep trough will develop the second half of next week. The
effects of the trough will be greatest to our northwest where
moisture will be more abundant, and dynamics will be better. When a
shortwave moves through California on the east side of the trough
Friday, we could have some precip in our forecast area. The trough
could send more waves through California over the weekend through
early next week, but we will be at the SE fringe of the moisture, so
precip amounts will not be great, most likely under 1/2 inch. Some
moisture from Hurricane Seymour, now at 15N/110W, could interact
with the trough as well as the remnants will eventually move north
off the Baja California coast around Friday.


242015Z...Isolated showers and a chance of thunderstorms will
continue this afternoon. Cloud bases will be as low as 5000 feet msl
in showers, but mostly in variable layers above 8000 feet. Vis
locally reduced 3-5 sm in heavier showers. Precip coverage and
chances will continue to decrease through the afternoon, ending
after 00Z, with skies gradually thinning of clouds tonight. Patchy
low clouds with bases around 1500 ft MSL could return to the coast
overnight tonight, but confidence is low to moderate and will depend
on if/when the higher clouds dissipate. Better stratus return is
expected for Tuesday night.


Slight chance of thunderstorms will continue through this afternoon,
with chances ending tonight. The biggest threat is still cloud-to-
water lightning. The Marine Weather Statement highlights this threat
through 5 pm PDT. Otherwise, no hazardous marine weather is expected
through Friday.


Slight chance of thunderstorms will continue through this
afternoon,with chances ending tonight. Isolated lightning strikes on
the beaches are possible during this time. The beach hazards
statement for lightning remains in effect through 5 pm PDT.


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




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