FXUS62 KEYW 080837 AFDEYW FLORIDA KEYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KEY WEST 415 AM EDT SAT JUN 7 2003 OBSERVATIONS/TRENDS... THE ATLANTIC SURFACE RIDGE AXIS AT 06Z EXTENDED WEST TO THE FLORIDA PENINSULA...FROM JUST NORTH OF GRAND BAHAMA ISLAND TO JUST NORTH OF PALM BEACH. SE TO S WINDS AT 10-15 KT AT ISLAND AND C-MAN SITES ON THE REEF AND BAY WERE VERIFYING AS EXPECTED. LATE STARTING SECONDARY CONVECTION FIRED IN THE STRAITS SOUTH OF DRY TORTUGAS BEFORE MIDNIGHT...OCCURRING ALONG NORTHBOUND BOUNDARIES FROM EARLIER CUBAN DIURNAL CONVECTION. THESE STORMS IN TURN SINCE MIDNIGHT HAVE PRODUCED ADDITIONAL OUTFLOWS THAT HAVE TRAVELED BOTH EAST AND NORTH...AND LEAD TO THIRD-ROUND CONVECTION OVER THE LOWER KEYS AND GULF WATERS. SOME NEW SHOWERS ARE ALSO FORMING IN MIDDLE KEYS NEARSHORE WATERS... AND EAST OF NORTH KEY LARGO. DEWPOINTS ARE IN MID-UPPER 70S. FORECASTS... AT THE SURFACE...THE ATLANTIC RIDGE IS STILL SHOWN BY MODELS TO PERHAPS SHIFT SOUTH CLOSER TO THE KEYS AND BREAK DOWN MONDAY AFTERNOON THROUGH MUCH OF THE DAY TUESDAY...BRINGING A LIGHT PRESSURE GRADIENT AND HARD-TO-FORECAST WIND DIRECTIONS TO THE KEYS. THEN...TUE EVENING AND MORE RELIABLY WED AND THU...CONTINUING THROUGH NEXT SAT...THE SURFACE RIDGE RE-ESTABLISHES ITSELF WESTWARD TO NORTH FLORIDA...BRINGING A STEADIER SE WIND FLOW BACK TO THE KEYS. THE SPECIFICS OF LOW LEVEL WIND FLOW WHILE THE RIDGE HAS BROKEN DOWN MON AFTERNOON THROUGH TUE AFTERNOON MAY ALLOW OVER-ISLAND TCU/CB LINES TO FORM AND BRING SHOWERS AND TSTMS TO KEYS SITES. MIDDAY THROUGH AFTERNOON WOULD BE THE FAVORED HOURS IF THAT HAPPENS...SO I WILL NOT MAKE MENTION OF ANY FAVORED TIME PERIOD FOR PRECIP WITH THIS FORECAST PACKAGE. AT UPPER LEVELS...WITH 500 MB RIDGE OVERHEAD OR NEARBY...THERE NORMALLY WOULD SEEM TO BE LITTLE LARGE SCALE LIFT FOR PRECIP ENHANCEMENTS. HOWEVER...THE CENTER OF THE UPPER HIGH IS FORECAST BY MODELS TO MOVE SW OVER THE KEYS TODAY...AND LIE OVER THE WESTERN GULF WITH A RIDGE TO THE KEYS BY MON-TUE-THROUGH FRI. AS A RESULT OF THIS SHIFT OF THE HIGH ALOFT...BOTH AT 500 MB AND DOWN AT LOWER LEVELS TOO...THERE IS SOME EVIDENCE THAT STEERING FLOW FOR MAINLAND AFTERNOON TSTMS MAY BECOME FOCUSED SOUTH TOWARD THE UPPER KEYS MON AFTERNOON AND S TO SW TOWARD MID AND LOWER KEYS TUE. ALSO OF NOTE... MON AND TUE...MODELS TAKE LOW AND MID LEVEL UVV FIELDS SW OVER THE MAINLAND AND TO THE UPPER KEYS. THE MONDAY EVENT OF UVV'S MAY BE RELATED TO A WEAK VORTICITY MAXIMUM MOVING SOUTH FROM AN ATLANTIC TROUGH...AROUND THE EASTERN EDGE OF THE UPPER HIGH AS IT SHIFTS TO OUR WEST. TODAY...SE TO S MARINE WINDS OUGHT TO DROP THIS AFTERNOON TO 10 KT OR LESS AS THE ATLANTIC RIDGE STARTS TO WEAKEN TO OUR NORTH. PREVIOUS FORECASTS WILL BE ADHERED TO...MENTIONING MAINLY MORNING THREAT OF PRECIP FOR LOWER/MID KEYS...AND ANY TIME WITH SLIGHTLY HIGHER POP OF 40 PCT FOR UPPER KEYS. TONIGHT...STEERING FLOW IS SEEN TO WEAKEN AND TURN MORE E TO W THIS EVENING OVER CUBA. TSTMS MAY DRIFT INTO STRAITS IN LATE AFTERNOON... BUT I WILL STICK WITH LOWER POPS AT 20 PCT FOR LOWER AND MID KEYS IN HOPES OUTFLOWS FOCUS MORE TOWARD THE WEST...AND NOT MENTION ANY TIMING WITH THESE LOW POPS. WILL LEAVE UPPER KEYS FORECAST ALONE WITH 30 PCT POPS. MARINE WINDS MAY NEAR OR LESS THAN 10 KT...STILL MAINLY SE TO S ACCORDING TO GFS...ETA HAS A PERIOD ERRATIC WINDS TONIGHT AS OFTEN IT DOES WITH RIDGE BREAKDOWN. MON-TUE...I WILL LEAN MORE TOWARD GFS FOR WIND DIRECTION. ETA SOMETIMES IS TOO BRASH WITH ITS E AND W MOVEMENT OF COL REGIONS BETWEEN THE GULF AND ATLANTIC RIDGES...AND IS DOING THAT NOW WITH COL PLACEMENTS FROM THE GULF TO WELL EAST OF THE KEYS AT VARIOUS TIMES. STILL...FROM LATE MON INTO AT LEAST EARLY TUE...EVEN THE GFS SHOWS WINDS VARYING OVER THE KEYS...SO VARIABLE 5-10 KT MARINE WINDS WILL BE ADVERTISED. WITH SURFACE WINDS GOING LIGHT LATE MON...WE MAY SEE LOWER AND MIDDLE KEYS TCU/CB LINES OVERHEAD. AND...STEERING MAY BRING AFTERNOON AND EVENING MAINLAND CONVECTION TO THE UPPER KEYS. THIS SAME STORY MAY PLAY OUT AGAIN TUE AFTERNOON AND EVENING. WILL DELETE MENTION OF EARLINESS OF SHOWERS FOR MID AND LOWER KEYS. WED-SAT...UPPER TROUGH IS SHOWN TO BE IN SE GULF FRI AND SAT. AT THIS POINT...EXTENDED GFS HOWEVER IS SIMILAR TO PREVIOUS RUN... WITH THE SURFACE RIDGE KEEPING A SE FLOW OVER THE KEYS 10-15 KT. TEMPS/POPS... EYW BB 89/80/89/80/89 30/20/30/20/30 MTH BB 92/80/92/80/92 30/20/30/20/30 .EYW...NONE. C.B.