AREA FORECAST DISCUSSION

 
 FXUS66 KSGX 290440 CCA
 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 SUNDAY 
 NIGHT AND MONDAY 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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