FXUS66 KSGX 290436
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 PM PDT THU AUG 28 2008

.SYNOPSIS...THE MARINE LAYER WILL CONTINUE NIGHT AND MORNING LOW
CLOUDS AND FOG ALONG THE COAST. MONSOONAL MOISTURE WILL BRING A
SLIGHT CHANCE OF THUNDERSTORMS FRIDAY AND SATURDAY. SOME OF THESE
THUNDERSTORMS MAY MOVE INTO THE VALLEYS AND COAST ON SATURDAY. A
TROUGH OF LOW PRESSURE WILL BRING DRIER AIR AND MUCH COOLER WEATHER
SUNDAY THROUGH LABOR DAY. TEMPS WILL SLOWLY WARM NEXT WEEK BUT
REMAIN NEAR SEASONAL AVERAGES.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.SHORT TERM...TONIGHT THROUGH SUNDAY...
GOOD ONSHORE GRADIENTS THIS EVENING WITH ABOUT 6 MB SAN-TRM AND 6 MB
SAN-DAG. THE 00Z KNKX SOUNDING PLACES THE MARINE INVERSION AT ABOUT
1500 FT...SO STRATUS SHOULD MAKE IT INTO THE WESTERN VALLEYS BY
MORNING. MONSOONAL MOISTURE SLOWLY BEGINS TO WORK ITS WAY INTO THE
FORECAST AREA TOMORROW AFTERNOON AS A WEAK UPPER HIGH SHIFTS TOWARDS
NV/AZ. HOWEVER IT LOOKS LIKE WE WILL STILL BE IN THE TRANSITION ZONE
BETWEEN THE MOISTER AIR TO THE SOUTH AND THE DRIER AIR TO THE NORTH
FOR MUCH OF THE DAY. LOWERED THE CHANCE OF TSTORMS OVER THE NORTHERN
MOUNTAINS TOMORROW AS IT LOOKS LIKE INSTABILITY AND MOISTURE WILL BE
LACKING THERE...BUT KEPT A SLIGHT CHANCE IN FOR THE THE SOUTHERN
MOUNTAINS.

AN INVERTED TROUGH MOVING THROUGH THE AREA FROM THE EAST WILL BRING
A CHANCE OF SHOWERS AND/OR THUNDERSTORMS EVERYWHERE ON SATURDAY
MORNING. THE MOST LIKELY SCENARIO INVOLVES LOTS OF MID AND HIGH
LEVEL CLOUDS STREAMING OVERHEAD ACCOMPANIED BY BRIEF SHOWERS. BY THE
AFTERNOON...TSTORMS ARE EXPECTED TO REDEVELOP OVER THE MOUNTAINS AND
DESERTS. SOME OF THESE COULD AGAIN DRIFT WEST OF THE MOUNTAINS. MID
LEVELS WIND ARE FAIRLY STRONG ON SATURDAY WHICH MAY ULTIMATELY LIMIT
THE AMOUNT OF THUNDERSTORM ACTIVITY.

A STRONG UPPER LEVEL TROUGH OF LOW PRESSURE WILL MOVE INTO THE WEST
COAST ON SUNDAY AND RAPIDLY PUSH THE MONSOONAL MOISTURE TO OUR EAST.
THERE STILL COULD BE A FEW AFTERNOON TSTORMS...BUT THEY SHOULD BE
CONFINED TO AREAS EAST OF THE MOUNTAIN CRESTS. THE SEA BREEZE IS
EXPECTED TO RAMP UP ON SUNDAY AFTERNOON AS AN IMPRESSIVE 993 MB
SURFACE LOW DEVELOPS OVER SOUTHERN NV. THIS WILL LIKELY CAUSE GUSTY
WINDS IN THE MOUNTAINS AND DESERTS DURING THE AFTERNOON AND EVENING.
THE STRONG ONSHORE FLOW WILL ALSO CAUSE THE MARINE LAYER TO DEEPEN
SIGNIFICANTLY...POSSIBLY TO 3000 FT BY MONDAY MORNING. 500 MB
HEIGHTS DROP 100 M OVER OUR NORTHERN AREAS BETWEEN SUNDAY AND MONDAY
AFTERNOON...SO TEMPS WILL BE NOTICEABLY COOLER...POSSIBLY SEVERAL
DEGREES BELOW NORMAL. THE DRY AIR...LOW 500 MB HEIGHTS...AND LOW
THICKNESS VALUES COULD CAUSE SOME AREAS TO GET QUITE CHILLY MONDAY
NIGHT AND SUNDAY MORNING.


.LONG TERM...MONDAY THROUGH WEDNESDAY...
GFS MODEL INDICATES WEAK OFFSHORE FLOW FOR TUESDAY AS SURFACE HIGH
PRESSURE MOVES INTO THE GREAT BASIN IN THE WAKE OF MONDAYS UPPER
TROUGH. THE GOOD NEWS IS THAT THE THERMAL TROUGH IS EXPECTED TO
REMAIN NORTH OF OUR AREA...SO THAT SHOULD KEEP THINGS FROM REALLY
HEATING UP HERE. ONSHORE FLOW AND DRY WEST TO SOUTHWEST FLOW ALOFT
WILL CONTINUE FAIR WEATHER AND SEASONABLE TEMPS WITH NIGHT/MORNING
LOW CLOUDS AND FOG THE LATER HALF OF NEXT WEEK.

&&

.AVIATION...
290320Z...MARINE LAYER MOVING ONSHORE WITH CEILING ALREADY AT KCRQ
AND KSAN. MARINE LAYER WILL CONTINUE TO SPREAD UP TO 20 MILES INLAND
OVERNIGHT WITH BASES NEAR 1K FT MSL...AND TOPS AOB FL020. VIS WILL
DROP IN MANY AREAS TO 3-5SM IN FOG/HAZE AFTER 08Z THROUGH ABOUT 18Z
FRI MORNING...BUT WILL FALL BELOW 3SM NEAR THE INLAND EXTENT OF THE
STRATUS LAYER AND ON HIGHER TERRAIN BETWEEN 10Z AND 15Z FRI. EXPECT
CLEARING BACK TO THE COAST BY AROUND 18Z FRIDAY MORNING.

ABOVE THE MARINE LAYER VIS WILL BE UNRESTRICTED AND SKIES MOSTLY
CLEAR EXCEPT FOR SCATTERED TO LOCALLY BROKEN CLOUDS ABOVE FL120.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...SCV
AVIATION/MARINE...ECC

NWS ON THE WEB AT WEATHER.GOV/SANDIEGO














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