Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
945 am PDT Wednesday Jul 30 2014
although a stray afternoon or evening thunderstorm may be possible
over the San Bernardino County mountains and deserts today...drier
conditions will prevail across most areas through Thursday...with
above average temperatures for inland areas. Subtropical moisture
will then spread back into the area for this weekend...with a chance
of afternoon and evening thunderstorms...mainly in the mountains and
deserts. Drier weather will then return early next week.
Otherwise...the marine layer and weak onshore flow will bring patchy
late night and early morning low clouds and fog near the coast.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Water vapor imagery shows high pressure over the Desert Southwest
and a trough off the West Coast this morning...with southwesterly
flow aloft over California. At this time...Southern California
remains more under the influence of this ridge...but water vapor
imagery does show a couple of difference disturbances moving through
this southwesterly flow aloft...which are tapping into the remnants
of Hernan. The 12z knkx sounding shows that precipitable water increased overnight
to 1.33 inches. Even though we are on the fringes of this
moisture...with the brunt remaining to our north and east...the 12z
NAM is also hinting at some instability across the San Bernardino
County mountains and deserts later today. Although the local WRF
does not back this up...some of the other high resolution models
do. For this reason...cannot rule out a stray thunderstorm over our
northern mountains and deserts today...and have updated the forecast
to reflect this trend. Otherwise...just looking at some hazy
conditions today...as some smoke from a cluster of fires in
the central Sierra drifted out overnight. Although coastal areas
will likely be a couple of degrees cooler today...thanks to a very
shallow marine layer...inland areas should warm a few degrees over
those of yesterday.
Drier and slightly warmer conditions should prevail across the
region tomorrow...as high pressure continues to build over region.
Models are hinting at subtropical moisture spreading back across
Southern California by this weekend. In fact...several show the
potential for a disturbance moving through either late Saturday
night or on Sunday. For now...our forecast keeps the best chances
of showers and thunderstorms over our mountains and deserts for this
weekend...but will need to take a closer look at the rest of the 12z
runs for consistency sake. Drier conditions will redevelop then for
early next week...with a gradual warming trend possible.
301524z...coasts/valleys...a couple patches of stratus near the
immediate coast of Orange County and the extreme southern San Diego
County coast...with bases around 800 feet above mean sea level and
tops around 1200 feet above mean sea level...will clear out through
1600 UTC. Otherwise...unrestricted visibility and few-scattered
clouds at or above 20000 feet above mean sea level through 31/0600
UTC. 31/0600-1600 UTC...patches of stratus may gradually develop
within 5-8 miles of the coast...with bases of 700-1000 feet above mean
sea level and tops around 1200 feet above mean sea level. Visibility
may locally be reduced to 1 mile or less. Confidence in stratus
occurrence at ksan...kcrq and ksna is low.
Mountains/deserts...some cumulus clouds with bases around 9000 feet
above mean sea level developing over the mountains during the
1800-31/0200 UTC time-frame...with a thunderstorm or two possible
over the San Bernardino County mountains and high deserts.
Thunderstorm tops could reach 35000 feet mean sea level.
Otherwise...few-scattered clouds at or above 20000 feet above mean sea
level through Thursday morning.
824 am PDT...no hazardous marine weather expected through
Sunday...although wind gusts may reach 25 knots near San Clemente
Island during the evening hours today and Thursday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.