Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 022053 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 200 PM PDT TUE SEP 2 2014 .SYNOPSIS... FAIR WEATHER WILL PREVAIL THROUGH EARLY NEXT WEEK. A LOW PRESSURE SYSTEM TO THE NORTH WILL BRING SOME COOLING WEDNESDAY WITH LITTLE TEMPERATURE CHANGE THURSDAY. LOW CLOUDS WILL EXTEND INTO MOST VALLEYS DURING THE NIGHTS THROUGH THURSDAY DUE TO A DEEPER MARINE LAYER...AND THERE WILL BE LOCALLY GUSTY WINDS IN THE MOUNTAINS AND DESERTS...MAINLY IN THE LATE AFTERNOONS AND EVENINGS. HIGH PRESSURE FROM THE SOUTHEAST WILL BUILD A LITTLE FRIDAY THROUGH THE WEEKEND TO BRING SLIGHT WARMING AND FEWER LOW CLOUDS...THEN SOME COOLING WILL RETURN EARLY NEXT WEEK AS THE HIGH WEAKENS. MONSOONAL MOISTURE WILL APPROACH EARLY NEXT WEEK...BUT MOST LIKELY THE MOISTURE WILL BE INSUFFICIENT FOR THUNDERSTORMS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... SKIES WERE CLEAR THIS AFTERNOON...WITH AREAS OF STRATUS OVER THE COASTAL WATERS. STRATUS SHOULD MOVE INTO COASTAL AREAS EARLY THIS EVENING BASED ON LOCAL WRF AND MOS GUIDANCE...THEN SPREAD INTO MOST OF THE VALLEYS OVERNIGHT DUE TO THE MARINE INVERSION BASE OF 1700-1800 FT MSL. TEMPERATURES WERE SLIGHTLY LOWER THAN MONDAY...EXCEPT ALONG THE SAN DIEGO COUNTY COAST WHERE IT 1-3 DEGREES WARMER...POSSIBLY DUE TO THE EARLIER CLEARING. A LOW PRESSURE TROUGH WILL GRADUALLY DEEPEN AND EXPAND OVER OREGON AND NORTHERN CALIFORNIA WEDNESDAY THROUGH THURSDAY WHILE THE HIGH PRESSURE RIDGE WILL EXTEND FROM SONORA EAST THROUGH THE SOUTHERN PLAINS/GULF STATES. HEIGHT FALLS WILL HELP MAINTAIN A RELATIVELY DEEP MARINE LAYER...THOUGH THE MODELS SHOW THE INVERSION WEAKENING. TEMPS ALOFT WILL CONTINUE TO LOWER AND BRING TEMPERATURES AVERAGING ABOUT 5 DEG F BELOW NORMAL WED/THU...MORE IN SOME OF THE VALLEYS AND WESTERN FOOTHILLS. SOME LOCALLY WINDY CONDITIONS WILL OCCUR AS ONSHORE PRESSURE GRADIENTS LOCAL WRF SHOWS SOME LOCAL SUSTAINED SURFACE WINDS OF 25 KNOTS IN THE WINDIEST DESERT/DESERT SLOPE LOCATIONS FOR WED AND THU LATE AFTERNOONS/EVENINGS...SO GUSTS COULD REACH 45 MPH. THIS WILL ONLY IN PLACES THAT NORMALLY GET WINDS LIKE THIS SUCH AS THROUGH/EAST OF SAN GORGONIO PASS...SO WE DO NOT PLAN ON A WIND ADVISORY RIGHT NOW. HIGH PRESSURE ALOFT OVER THE SOUTHERN US WILL BUILD WEST A LITTLE BIT FRIDAY AND HAVE AN AXIS FROM NORTHERN BAJA CALIFORNIA EAST TO TEXAS OVER THE WEEKEND. THE TROUGH WILL CONTINUE OVER NORTHERN CALIFORNIA...BUT HEIGHT RISES HERE WILL MEAN THE HIGH WILL DOMINATE AND RESULT IN WARMING AND A MORE SHALLOW MARINE LAYER FOR LESS EXTENSIVE NOCTURNAL STRATUS. THE UPPER HIGH SHIFTS SOUTH A BIT EARLY NEXT WEEK AS LONG-WAVE TROUGHING FORMS OVER THE INTERMOUNTAIN WEST AND NORTHERN PLAINS...SO SOME COOLING COULD OCCUR HERE THEN...MAINLY INLAND. A POSSIBLE TROPICAL SYSTEM TO OUR SOUTHWEST WILL LIKELY NOT BRING MUCH MOISTURE HERE...BUT SOME MOISTURE FROM THE SOUTHEAST WILL MOVE UP AROUND THE WEST SIDE OF THE UPPER HIGH. HOWEVER...THE WESTERLIES WILL PREVAIL JUST TO OUR NORTH...SO MOST LIKELY WE WILL JUST HAVE ENOUGH MOISTURE FOR CUMULUS BUT NOT ENOUGH FOR THUNDERSTORMS. THUS...OUR FORECAST IS FOR DRY WEATHER CONTINUING THROUGH EARLY NEXT WEEK. && .AVIATION... 022000Z...COAST/VALLEYS...VFR CONDITIONS WILL CONTINUE THROUGH EARLY THIS EVENING. STRATUS...WITH BASES AROUND 1800 FT MSL AND TOPS NEAR 2400 FT MSL...WILL DEVELOP ALONG THE COAST THIS EVENING AND PUSH AROUND 30 STATUTE MILES INLAND BY 10-12 UTC WEDNESDAY MORNING. VISIBILITY AT OR BELOW 1-3 STATUTE MILES DUE TO FG/BR WILL BE POSSIBLE WHERE STRATUS NEARS HIGHER TERRAIN. LOW CLOUDS WILL CLEAR TOWARDS THE COAST BY LATE WEDNESDAY MORNING. MOUNTAINS/DESERTS...VFR CONDITIONS PREVAILING THROUGH THE NEXT 24 HOURS...WITH ISOLATED BREEZY WESTERLY WINDS GUSTING TO 35 KT THROUGH MOUNTAIN PASSES AND DESERT MOUNTAIN SLOPES LATE THIS AFTERNOON AND EVENING. && .MARINE... 100 PM...NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH SATURDAY. && .SKYWARN... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY. && .SGX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...MAXWELL AVIATION/MARINE...JJT

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