FNUS76 KSTO 121320
FWSSTO

SPOT FORECAST FOR SAN DIMAS ENGINE BURN OVER STUDY...CAL FIRE
NATIONAL WEATHER SERVICE SACRAMENTO CA
620 AM PDT MON SEP 12 2011

FORECAST IS BASED ON IGNITION TIME OF 1200 PDT ON SEPTEMBER 13
AND SEPTEMBER 15.
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER
SERVICE.

.DISCUSSION...
UPPER LEVEL LOW PRESSURE SITTING OVER CENTRAL CA AND NV WILL WEAKEN
SLIGHTLY ON TUESDAY AS IT BECOMES AN OPEN TROUGH. THIS TROUGH WILL
STILL CAUSE SOME INSTABILITY NEAR THE REGION. BEST INSTABILITY
WILL BE IN THE FOOTHILLS AND MOUNTAINS TO THE EAST OF THE BURNSITE
ON TUESDAY WITH A SLIGHT CHANCE TO CHANCE OF THUNDERSTORMS. NAM
MODEL SOUNDINGS SHOW WEAK INSTABILITY NEAR THE BURNSITE ON TUESDAY
AFTERNOON WITH LIFTED INDEX VALUES NEAR -1...BUT THE INSTABILITY IS
ELEVATED NEAR 10,000 FT ABOVE GROUND LEVEL AND HIGHER. VERTICAL WIND
PROFILE INDICATES LIGHT WINDS UP TO AROUND 15,000 FT SO INSTABILITY
MAY NOT MIX DOWN TO THE SURFACE OF THE BURNSITE. SURFACE WINDS ON
TUESDAY NEAR BURNSITE WILL BE LIGHT TO MODERATE.

THE UPPER TROUGH IS FORECAST TO WEAKEN AND MOVE EASTWARD BETWEEN
NEVADA AND THE FOUR CORNERS AREA BY THURSDAY. THUS...THE AIR MASS
WILL BE MORE STABLE WITH WEAKER WINDS ALOFT AND AT THE SURFACE.
CURRENT FORECAST HAS NO THUNDERSTORMS ON THURSDAY FOR NORTHERN
INTERIOR CALIFORNIA INCLUDING THE TERRAIN TO THE EAST OF THE
BURNSITE.


.TUESDAY THE 13TH...

SKY/WEATHER.........MOSTLY SUNNY OVER BURNSITE. SLIGHT CHANCE OF
                    THUNDERSTORMS DURING THE DAY IN THE UPPER
                    FOOTHILLS TO THE EAST OF THE BURNSITE.
MAX TEMPERATURE.....91-96.
MIN HUMIDITY........23-28 PERCENT.
WIND (20 FT)........
   SLOPE/VALLEY.....LIGHT WINDS BECOMING WEST 5 TO 10 MPH IN THE
                    AFTERNOON.
   RIDGETOP.........LIGHT WINDS.
MIXING HEIGHT.......500-1500 FT AGL INCREASING TO 5000-6000 FT AGL.
MIXING WINDS........SOUTHWEST TO WEST AROUND 5 MPH.

.THURSDAY THE 15TH...

SKY/WEATHER.........MOSTLY CLEAR.
MAX TEMPERATURE.....86-90.
MIN HUMIDITY........24-30 PERCENT.
WIND (20 FT)........
   SLOPE/VALLEY.....SOUTHWEST 1 TO 6 MPH.
   RIDGETOP.........LIGHT WINDS.
MIXING HEIGHT.......INCREASING TO 4000-5000 FT AGL
                    EARLY IN THE AFTERNOON.
MIXING WINDS........LIGHT WINDS.


FORECASTER...JBB
REQUESTED BY...BILL BAXTER
REASON FOR REQUEST...PRESCRIBED
.TAG 20110912.SANDI.01/STO

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