Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
900 PM PST Tuesday Nov 25 2014
Santa Ana conditions will continue through Thursday with warm
days...cool nights and gusty winds in the mountains and valleys.
High temperatures will be well above average through Thanksgiving.
Cooling Friday through Sunday with increasing onshore flow. Early
next week a Pacific storm is projected to bring rain to the region.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
There was a substantial drop off in the winds this evening with peak
gusts only in the middle 20s at 8 PM. There will be a diurnally driven
increase overnight through Wednesday morning when wind gusts will
peak between 35-45 miles per hour in the mountains and foothills. A similar
scenario will play out Wednesday night into Thursday...but the winds
Thursday morning will not be quite as strong.
Sunny skies and downslope flow west of the mountains will push
temperatures in the 80s in most coastal and valley areas Wednesday
and Thursday. Only the onset of the afternoon sea breeze will hold
temperatures in the 70s at the coast. The airmass will remain very dry
through Thanksgiving with no hint of any marine layer clouds.
The high amplitude ridge over the West Coast breaks down on Friday.
Increasing onshore and a cooler airmass will filter into Southern
California over the weekend. A shallow marine layer could produce
areas of dense fog over the coastal waters or beaches as early as
Friday morning...with progressively greater inland coverage of
stratus and fog through the weekend.
Long range outlook for next week: a Pacific low will move ashore
along the California coast Tuesday. Models vary as to its strength,
position and the amounts of precipitation it will generate. The 00z
GFS has scaled back on the precipitation amounts in so-cal and has also
delayed the onset of the rain to Monday night. The 12z European model (ecmwf) is a
little faster than the GFS and shows precipitation moving into the area
Monday afternoon. Will continue to evaluate through the Holiday and
get a better handle on the timing and intensity as it moves into the
higher resolution model window in a few days.
In the meantime...the climate prediction center precipitation
probability map shows above average confidence for above average
precipitation over California from Dec 01-05.
260500z...clear skies with unrestricted visible through Wednesday night.
Local surface east-northeast winds 15-30 knots with gusts 30-40 knots will
occur through/below passes/canyons and in coastal
foothills...mainly 08z-21z Wednesday with up/downdrafts. There will be
areas of low level wind shear at times...likely impacting ksna and kont in the
09z-18z Wednesday period.
900 PM...no hazardous marine weather is expected through Sunday.
winds will pick up again late tonight into Wednesday morning...with
gusts of 35-45 miles per hour along the coastal slopes...through and below the
passes and canyons...and into the coastal foothills of San Diego and
Riverside counties. A red flag warning continues through 6 PM
Wednesday for those areas. The winds will weaken on Thursday...with
only local gusts of 25-35 miles per hour...and so the red flag warning will
likely not be extended into Thursday. However...humidity will still
be in the low teens to single digits...resulting in elevated fire
weather conditions. Little to no overnight humidity recoveries will
continue. The red flag warning for inland Orange County...Santa Ana
Mountains/foothills and the San Bernardino National Forest has been
cancelled...as forecast models continue to trend weaker with the
winds for those areas for today into tomorrow...and so red flag
criteria is very unlikely to be met.
Onshore flow will return Thursday night into Friday morning...with
the marine layer returning by Friday night and deepening into
Saturday night. The return of onshore flow...the marine layer...and
cooler conditions will result in much higher humidities and a
diminished fire weather threat. Significant wetting precipitation is
possible for early next week as a storm system moves through the
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
California...red flag warning until 6 PM PST Wednesday for the Riverside
County mountains-including the San Jacinto Ranger district
of the San Bernardino National Forest...San Bernardino and
Riverside County valleys-the inland Empire...San Diego
County inland valleys...San Diego County
mountains-including the Palomar and Descanso Ranger
districts of the Cleveland National Forest.
Wind Advisory until 4 PM PST Wednesday for the San Diego County
mountains...San Diego County valleys.
Wind Advisory until 4 PM PST Wednesday for the San Bernardino
and Riverside County valleys-the inland Empire.