Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
838 am PDT Friday Jul 25 2014
high pressure to the east will bring seasonally warm Summer weather
through next week. Middle and upper-level moisture will bring a slight
chance of thunderstorms...mainly over the mountains in the
afternoons. The marine layer will keep coastal areas cooler with
areas of night and morning low clouds and fog. The marine layer will
be a little deeper through the weekend...then a little shallower
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Isolated thunderstorms developed early this morning over San Diego
County and were drifting slowly northward with mostly light
rainfall...except where cells have repeated over the same area in
southern San Diego County. These isolated spots could have up to
one-half inch. The convection appears to have helped clear out the
marine stratus earlier than expected in some areas. Weak onshore
gradients were in place. The 12z Miramar sounding had a Ten Degree c
inversion based near 2000 feet with weak southerly flow below.
A heat advisory remains in effect for the lower deserts today due to
heat and humidity...although maximum temperatures will likely be a few degrees
lower today. Continued slight cooling into the weekend should keep
maximum temperatures below heat advisory criteria inland...although it will
remain quite warm.
The strong subtropical high will remain centered over New Mexico
through early next week. South to southeast flow aloft around the high will
continue to steer monsoonal moisture and pockets of weak to moderate
instability over socal through the weekend. Most of the moisture is
expected to be above 10k feet so any convection is not expected to
produce widespread heavy rainfall. Instead...the main threat will be
the occasional cloud-to-ground lightning strike and gusty
downdrafts. Nocturnal thunderstorms cannot be ruled out anywhere...
but should be isolated. The main thunderstorm threat will be in the
mountains each afternoon/early evening.
Upper-level winds will become SW early next week with some drying
and a reduction in the thunderstorm threat. Another push of
monsoonal moisture could develop later next week according to the
latest GFS run but the 00z European model (ecmwf) looks drier.
For the coast...onshore flow should maintain a shallow marine layer
with areas of night and morning low clouds and fog. Hires models
show the eddy continuing through Sat...then weakening so expect the
marine layer to decrease...but maintain over coastal areas next
251530z...coast/valleys...isolated to scattered thunderstorms will
move north over San Diego County and SW Riverside County through
18z. The thunderstorms will most likely miss ksan and kcrq but will
affect ksee and krnm at times with isolated lightning strikes and
local visible 3 Michigan in rain showers. Otherwise...areas of broken ceilings 1000-1500 feet
mean sea level tops to 1700 feet mean sea level will mostly dissipate by 17z along the
Orange County coast...with areas of broken-overcast clouds at/above 7000 feet
mean sea level through this afternoon. Some stratus will occur again tonight
along the coast with moderate confidence of timing after 05z. Bases
will again be 1000-1500 feet mean sea level with tops to 1700 feet mean sea level.
Mtns/deserts...isolated to scattered thunderstorms will occur today
in San Diego County/West Riverside County mountains...and after 18z in SW
San Bernardino County mtns/deserts. Local visible 3 Michigan in rain showers. Bases of
the broken-overcast clouds will be at/above 7000 feet with isolated tops to
35000 feet mean sea level. Most thunderstorm activity will dissipate by 02z
tonight. There is a chance of thunderstorms again Saturday.
830 am PDT...isolated thunderstorms could produce a few cloud to
water lightning strikes over the coastal waters this morning.
Despite the thunderstorms...winds should remain mostly light. We
predict no hazardous marine weather tonight through Wednesday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...heat advisory until 9 PM PDT this evening for the Coachella
Valley...San Diego County deserts.