Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 182052 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 155 PM PDT TUE JUN 18 2013 .SYNOPSIS... UPPER LEVEL TROUGH WILL GRADUALLY MOVE INLAND ALONG THE WEST OVER THE NEXT 24 TO 48 HOURS...AND REMAIN IN PLACE THROUGH THE WEEKEND. AS A RESULT...EXPECT SOME ONLY MINOR FLUCTUATIONS IN THE MARINE LAYER AND TEMPERATURES THE NEXT SEVERAL DAYS...WITH NIGHT AND MORNING LOW CLOUDS ALONG THE COAST. GUSTY WEST WINDS WILL DEVELOP EACH AFTERNOON AND EVENING IN THE MOUNTAINS AND DESERTS. && .DISCUSSION...
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FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... WATER VAPOR IMAGERY SHOWS THE UPPER LEVEL TROUGH SLOWLY DRIFTING TOWARDS THE WEST COAST THIS EVENING...EVEN THOUGH THE UPPER LEVEL LOW REALLY HAS NOT MOVED MUCH IN THE LAST 4 HOURS. NEEDLESS TO SAY...THE UPPER LEVEL TROUGH IS STILL POISED ALONG THE WEST COAST THIS MORNING...WITH SOUTHERN CALIFORNIA IN THE DRY SOUTHWESTERLY TO WESTERLY FLOW ALOFT. AS A RESULT...SKIES ARE PREDOMINATELY SUNNY THIS AFTERNOON...WITH JUST SOME LOW CLOUDS PUSHING BACK INTO THE BEACHES. THAT THIS TIME...MOST LOCATIONS ARE WITHIN 3 DEGREES OF THIS TIME YESTERDAY...AND THE ONSHORE PRESSURE GRADIENTS ARE STARTING TO INCREASE. THE UPPER LEVEL SUPPORT AT 850 MBS IS 30 TO 35 KTS...WITH THE MAIN FOCUS OF THESE WINDS RIVERSIDE AND SAN DIEGO COUNTY. HOWEVER...THINK THE STRONGEST WINDS WILL LIKELY BE THROUGH AND BELOW THE BANNING PASS AND AREAS NORTH OF INTERSTATE 10. THEREFORE...A WIND ADVISORY WILL GO INTO EFFECT AT 2 PM THIS AFTERNOON FOR THE BANNING PASS. THIS UPPER LEVEL TROUGH WILL GRADUALLY MOVE INLAND OVER THE NEXT 24 TO 48 HOURS...WITH SOME MINOR COOLING POSSIBLE FOR INLAND AREAS. HOWEVER...EXPECT ONLY MINOR FLUCTUATIONS IN TEMPERATURES ELSEWHERE. AN EDDY WILL LIKELY REDEVELOP EACH NIGHT AS WELL...BUT NOT EXPECT MUCH GROWTH IN THE MARINE LAYER THE NEXT SEVERAL NIGHT. HOWEVER...THE NIGHT AND MORNING LOW CLOUDS AND FOG WILL CONTINUE TO BE POSSIBLE ALONG THE COAST AND INTO THE WESTERN VALLEYS OF SAN DIEGO COUNTY. THE GUSTY WEST WINDS WILL ALSO REDEVELOP IN THE MOUNTAINS AND DESERTS EACH DAY. ALTHOUGH THE UPPER LEVEL LOW WILL SHIFT INLAND ACROSS THE INTERMOUNTAIN WEST ON FRIDAY AND THIS WEEKEND...THE UPPER LEVEL TROUGH WILL LINGER ALONG THE WEST COAST. IT WILL BE SLIGHTLY WEAKER...SO INLAND AREAS MIGHT SEE SOME MINOR WARMING. HOWEVER...EXPECT ONLY MINOR FLUCTUATIONS IN TEMPERATURES ALONG THE COAST AS WELL AS IN THE MARINE LAYER. THERE ARE SOME MINOR MODEL DIFFERENCE FOR NEXT WEEK...AS THE 12Z ECMWF CONTINUES WITH THE IDEA OF WEAK TROUGHINESS OVER SOUTHERN CALIFORNIA...WHILE THE 12Z GFS SHOWS A MASSIVE RIDGE BUILDING INTO THE REGION FROM THE EAST. SINCE THE 12Z ECMWF TRENDED SLIGHTLY WEAKER WITH THIS TROUGH THOUGH...WILL START THE IDEA OF WARMING UP THE INLAND AREAS EVEN MORE THAN THE CURRENT FORECAST SHOWS.
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&& .AVIATION...
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182000Z...COAST/VALLEYS...PATCHY STRATUS...WITH BASES AROUND 1100 FT MSL AND TOPS NEAR 1500 FT MSL...WILL LINGER ALONG THE COAST THROUGH THE AFTN. LOW CLOUDS WILL FILL IN OVER COASTAL AERODROMES THIS EVENING...AND DEVELOP AROUND 30 SM INLAND BY MID WED MORNING WITH BASES AROUND 1500 FT MSL AND TOPS TO 2300 FT MSL. VIS 2-4 SM BR IS EXPECTED WHERE STRATUS NEARS HIGHER TERRAIN TONIGHT. STRATUS WILL CLEAR TOWARDS THE COAST AROUND 17 UTC WED MORNING. MTNS/DESERTS...WESTERLY WIND GUSTS TO 40 KT WILL DEVELOP OVER MTN RIDGES AND DESERT MTN SLOPES THIS EVENING THROUGH TONIGHT. LOCALLY STRONG UP/DOWN DRAFTS AND LLWS ARE POSSIBLE NORTH OF KPSP. OTHERWISE...CLEAR AND VFR CONDITIONS WILL CONTINUE THROUGH WED MORNING.
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&& .MARINE...
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PREVIOUS DISCUSSION... A SMALL CRAFT ADVISORY FOR NW WIND GUSTS TO 25 KT REMAINS IN EFFECT FOR THE OUTER COASTAL WATERS THIS AFTN THROUGH TONIGHT. THESE WINDS WILL CREATE A SHORT-PERIOD COMBINED SWELL UP TO 8 FT THROUGH THE PERIOD. CONDITIONS MAY BE HAZARDOUS TO SMALL CRAFT...AND WILL IMPROVE EARLY WED MORNING.
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&& .SGX WATCHES/WARNINGS/ADVISORIES...
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CA...WIND ADVISORY UNTIL 3 AM PDT WEDNESDAY FOR THE COACHELLA VALLEY. PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 AM PDT WEDNESDAY FOR THE WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND.
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&& $$ PUBLIC...PALMER AVIATION/MARINE...JJT

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