Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
940 PM PDT Friday Sep 19 2014
a slow moving trough will continue to bring cooler weather and a
deep marine layer through Sunday. Patchy drizzle is possible again
late tonight and tomorrow morning. A warming trend and shallower
marine layer is expected Monday through Wednesday as high pressure
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
The marine layer is a little deeper than last night but the stratus
coverage is not nearly as widespread. Only scattered low clouds
cover the coastal waters this evening. Still expect the clouds
increase overnight and spread into the valleys...but the advancing
upper low could disrupt the coverage so it may not be the uniform
cloud deck that we saw this morning. 00z WRF still outputting light
quantitative precipitation forecast so there may be areas of drizzle again tomorrow morning.
Water vapor image shows the upper trough west of pt Conception this
evening. It will move east tonight...then briefly stall over pt
Conception Saturday before ejecting northeast toward Nevada Saturday
night and Sunday. The nam4 and cansac generate still generate small
quantitative precipitation forecast over the sbd/riv County mountains Saturday afternoon with the passage
of the upper vorticity maximum...so will hold onto the slt chance for
rain showers/thunderstorms there. The wrfems and hrrr models are dry.
The low moves across Nevada Sunday with a small increase in heights and
a few degrees of warming. Greater warming and a shallower marine
layer Monday-Wednesday from weak ridging building over the southwest. The
GFS shows some increase in precipitable water Wednesday as low level
winds shift southerly...but precipitation is not expected.
Long range outlook late next week...the GFS and Gem forecast a deep
trough to move into the West Coast Thursday through Saturday which
would bring cooling...a deeper marine layer and gusty mountain and desert
winds. The outlier is the European model (ecmwf) which holds onto weak ridging into
the weekend. There is a 100dm height spread between the models which
is significant. Have trended toward European model (ecmwf) since it has been
performing better than the GFS lately...and have tempered the
cooling somewhat in the Thursday-Sat time frame.
200300z...low clouds will move ashore through the evening with
bases 1500-2000 feet mean sea level and spread into inland valleys overnight.
Tops will be around 3000 feet. Local visible 3-5sm in far inland
valleys. Scatter out Saturday by 17-19z. Otherwise...skies will be
clear and visible unrestricted through Saturday.
On Saturday afternoon in the mountains there will be some cumulus
based around 8000 feet and a very small chance of thunderstorms over
the mountains of Riverside/San Bernardino counties.
800 PM...no hazardous marine weather is expected through Wednesday.
spotter activation will not be needed this weekend.