517 
fxus66 ksgx 152032 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
230 PM PDT Wednesday Oct 15 2008 


Synopsis...high pressure aloft and weak offshore flow will continue 
warm days west of the mountains through Friday. Upper level low 
pressure will bring more clouds and cooling this weekend. 


&& 


Discussion...for southwest California including San Diego... 
Orange...southwest San Bernardino and West Riverside counties. 


Short term (today-sat)...skies were clear except for a few high 
clouds. Early afternoon acars soundings indicated a near surface 
based inversion with NE winds to about 15 kts in the low levels and 
west to SW winds aloft. Offshore gradients with about -8 mb san-tph. 


A weak upper low will meander SW of San Diego as high pressure 
builds aloft into Friday. This will maintain clear skies except for 
a few high clouds at times. The low will get picked up by a trough 
in the NE Pacific with a vorticity maximum skirting past just to our west and north on 
Sat. The weakening offshore flow and high aloft will continue hot 
and dry days inland through Friday with maximum temperatures in the 90s in most 
inland valleys. There will still be local gusty offshore winds but 
they will generally be decreasing in strength and will remain below 
advisory strength. Clear and dry nights will allow excellent 
radiational cooling in areas protected from the winds. Areas with 
some winds and mixing such as the lower foothill locations will stay 
warmer each night. Patchy stratus could return to the beaches as 
early as Friday afternoon or evening. This should bring a little 
cooling to the beaches Friday afternoon. A shallow marine layer will 
develop by Sat morning. Maximum temperatures will drop about 10-15 degrees in 
most areas west of the mountains Sat with lowering heights and stronger 
onshore glow. If the upper low to our SW picks up more moisture then 
there could even be a few light showers late Sat...mainly in the northern 
areas. Will indicate some low level probability of precipitation but probabilities too low 
to include in the zones at this time. 


Local critical fire weather conditions will continue into Friday in the 
inland valleys and mountains due to low humidities. See the fire 
weather discussion below for details. 


&& 


Long term (sun-wed)...the trough will move through sun with flat 
flow or weak ridging Monday. Another trough should move past to the north 
Tuesday. While the marine layer will deepen...it should remain confined 
to the coastal areas and western San Diego inland valleys. Offshore flow 
could develop after the trough moves through toward the middle of 
next week...but the strength is uncertain. 


&& 


Aviation... 
152300z...clear. Weak locally moderate offshore flow through 
Thursday...becoming west to northwest onshore flow during the 
afternoon. Light to moderate up and downdrafts in the morning 
near the mountains. 


&& 


Fire weather... 
this afternoon...wind speeds have decreased significantly in all 
areas with the wind prone areas reporting gusts of 25 to 35 miles per hour. 
Weaker offshore winds will continue into Friday...mainly during the 
mornings for southern areas favored for easterly offshore flow. High 
pressure aloft will bring warmer daytime temperatures above seasonal 
averages through Friday. Combined with a very dry atmosphere...there 
will be several hours of relative humidities below 10 percent with 
little overnight recovery for some inland areas through Friday. In 
the coastal areas...a weak afternoon sea breeze could keep 
humidities above critical levels. For the weekend...a trough of low 
pressure moving inland through Southern California will bring 
cooling and higher humidities. 


A red flag warning is currently in effect for most of extreme 
southwest California...excluding the deserts...until Friday night 
due to long duration low relative humidities continuing through 
Friday although the winds will be weaker. 


&& 


Sgx watches/warnings/advisories... 


California...red flag warning for the mountains...inland valleys and Orange 
County coastal areas until 10 PM tonight and continuing for the 
mountains and inland valleys until 10 PM Friday. 


&& 


$$ 


Public...atkin 
aviation...small 
fire weather...pg