Weather

817 
fxus66 ksgx 071114 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
415 am PDT sun Sep 7 2008 


Synopsis... 
high pressure will weaken slowly bringing a slow cooling trend to 
seasonal temperatures through middle week. The marine layer will deepen 
and the coastal clouds will become more extensive during the nights 
and mornings over the next few days. Middle level moisture in southeast 
flow aloft will bring some afternoon clouds to the mountains the 
next few days with a slight chance of thunderstorms for Monday and 
Tuesday afternoons. 


&& 


Discussion...for extreme southwestern California including Orange... 
San Diego...western Riverside and southwestern San Bernardino 
counties... 


Short term (today through tuesday)... 
a trough of low pressure along the California coast will slowly 
amplify through Tuesday. This will bring slow cooling and steady 
slow deepening of the marine layer with night and mornign coastal 
stratus extending inland into the westernmost San Diego County 
valleys this morning and into lower portions of the inland valleys 
by Tuesday morning. Fog could be locally dense near The Mesas and 
other higher coastal terrain this morning. 


Middle level moisture continues centered around 600 mb in southeast 
flow aloft. While there's been sufficent moisture for clouds over 
the mountains the past few afternoons...thunderstorms have remained 
south of the border. While most models show little or no 
precipitation in the mountains the next few days...the local 
workstation version of the WRF with the NAM initialization does show 
increasing quantitative precipitation forecast on the desert slopes of the mountains the next few 
days. While this appears overdone...this may indicate just enough 
increase in moisture and instability along the desert slopes of the 
mountains to support a few thunderstorms Monday and Tuesday 
afternoons. 


&& 


Long term (wednesday through satursday)... 
weak upper troughing will move slowly southward along the California 
coast bring slowly cooling and drying. By late in the weekend...the 
trough may weeken with slow warming and a slow decrease in the 
marine layer depth. 


&& 


Aviation... 
071030z...marine layer is shallow...less than 1000 feet deep. Areas of 
stratus and fog will continue through 16z with bases at/below 800 feet 
mean sea level and visibilities below 1 mile at times over The Mesas and higher 
coastal terrain. Some local near zero visibilities will occur. Clearing 
will occur between 15z and 17z...though local scattered-broken conditions 
will occur near the immediate coast. The marine layer should deepen 
tonight...with stratus bases likely to be above 1000 feet mean sea level then. 


Above the marine layer...moderate amounts of middle-level moisture will 
result in scattered cumulus today...mainly after 18z...and with 
bases above 9000 feet mean sea level. Any thunderstorms should remain over Baja California 
California again. Otherwise...unlimited visibilities and ceilings are expected 
through Monday. 


&& 


Sgx watches/warnings/advisories... 
California...none. 
Pz...none. 


&& 


$$ 


Public...Martin 
aviation/marine...Maxwell 


National Weather Service on the web at weather.Gov/sandiego