Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
400 am PDT sun may 3 2015
A weak low pressure system off the California coast will move inland
through Southern California on Monday. This will bring cooling and
more night and morning low clouds and patchy fog as the marine layer
deepens and onshore flow strengthens. There is also a slight chance
of afternoon and early evening thunderstorms on Monday...mainly for
the mountains. Onshore flow will continue through Friday as a colder
low pressure system moves southward through the western states
bringing below average temperatures for inland areas...gusty west
winds in the mountains and deserts...and chances for mainly light
precipitation along and west of the mountains Thursday and Friday.
Dry and a little warmer for Saturday under weak high pressure.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Short term (today through tuesday)...
A weak low pressure system off the California coast will move to a
position southwest of Point Conception late today...then move inland
across Southern California Monday and into Arizona Monday night.
This will bring increasing onshore flow with inland cooling...
deepening of the marine layer...and gusty west winds in the
mountains and deserts. It will also bring a slight chance of showers
and thunderstorms Monday afternoon...mainly to the mountains with
greatest chances over the San Bernardino Mountains. Aircraft
soundings show the marine layer has deepened to around 2500 feet
with satellite imagery showing stratus extending inland into the San
Diego County valleys and into southern portions of the inland
Empire. Stratus should continue to spread into the inland valleys
early this morning. Night and morning coastal low clouds and fog
will extend into the far inland valleys and possibly onto the lower
coastal mountain slopes the next two nights.
Long term (wednesday through saturday)...
A cold...closed low pressure system will move southward into the
western states for Wednesday through Friday...then weaken and move
east on Saturday. This will bring additional inland cooling...
stronger onshore flow with periods of gusty west winds in the
mountains and deserts...and chances for mainly light precipitation
along and west of the mountains at times...mainly Thursday and
Friday. While the models are in better agreement with the general
pattern during this period...there remain differences with the
details which would most impact timing and intensity of any
precipitation. Weak high pressure will bring dry and a little warmer
weather for Saturday.
Coast/valleys...low clouds with bases between 1700 and 2300 feet mean sea level
and tops from 2200 to 2800 feet mean sea level will continue to build through 14z
Sunday. Coastal taf sites may see ceilings increasing to above 2000 feet
mean sea level by 16z. Visible restrictions of 3 sm or less will occur where low
clouds intersect higher terrain. Overcast-broken low clouds should clear to
the coast by 18z. After 18z...sct-few low clouds with bases near
2500 feet mean sea level will linger along coast...with sky clear prevailing inland.
Low clouds will likely return for coastal taf sites between 23z
Sunday and 04z Monday.
Mountains/deserts...unrestricted visible with few/scattered clouds between
10000 and 15000 feet mean sea level.
300 am...no hazardous marine weather is expected through Wednesday.
A trough approaching from the north will likely bring breezy
northwest winds Thursday and Friday...with Small Craft Advisory
300 am...an elevated southerly swell...near 4 feet...with a 20+ second
period arrived in the coastal waters this evening. This swell will
continue to build through the day on Sunday...reaching 4-5 feet for
late Sunday into Monday. As a result...surf of 6-10 feet with sets
to 12 feet will be possible along the southwest facing beaches of
Orange County and northern San Diego County through the day on
Monday. Surf will decrease slightly on Tuesday as the period falls
below 20 seconds...but significant reductions in surf are not
expected until Wednesday. In addition to the surf...powerful rip and
longshore currents...minor beach erosion...and minor tidal overflow
during the evening high tides will remain possible into Tuesday. A
high surf advisory has been issued for Sunday morning through late
Tuesday evening. Please see laxcfwsgx for further details.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...high surf advisory until 11 PM PDT Tuesday for Orange County
coastal areas-San Diego County coastal areas for the beaches.