FXUS62 KTBW 200627 AFDTBW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL 227 AM EDT SAT SEP 20 2008 .SHORT TERM (TODAY - MONDAY)...A MID LEVEL TROUGH OVER THE CENTRAL U.S./LOWER MS VALLEY WILL MOVE VERY SLOWLY EAST THROUGH THE PERIOD WHILE ANOTHER OFFSHORE THE FLORIDA EAST COAST WILL PERSIST THROUGH SUNDAY. AT THE SURFACE STRONG HIGH PRESSURE FROM NEW ENGLAND EXTENDING SOUTHWEST ACROSS THE MID ATLANTIC AND INTO THE DEEP SOUTH WILL REMAIN IN PLACE TODAY...THEN WILL MOVE NORTHEAST TONIGHT AND SUNDAY AS AN INVERTED TROUGH OFFSHORE THE FLORIDA EAST COAST MIGRATES WEST NORTHWEST TOWARD THE FLORIDA EAST COAST. THE COMBINATION OF THE SURFACE HIGH TO THE NORTH AND THE INVERTED TROUGH OFFSHORE TO THE EAST WILL MAINTAIN A DRY NORTHEASTERLY WIND FLOW ACROSS THE FORECAST AREA TODAY. SIMILAR TO YESTERDAY THE MODERATE NORTHEAST WIND FLOW SHOULD AGAIN HOLD OFF THE WEST COAST SEA BREEZE...AND WITH MODEL SOUNDING/CROSS SECTIONS DATA SHOWING LIMITED MOISTURE AND INSTABILITY AM EXPECTING ANOTHER UNSEASONABLY DRY DAY TODAY (POPS ~10% AT BEST) ACROSS THE ENTIRE FORECAST AREA UNDER PARTLY TO MOSTLY SUNNY SKIES. TONIGHT THROUGH MONDAY UPPER RIDGING WILL BEGIN TO NOSE ITSELF IN FROM THE EAST ACROSS THE SOUTHERN MOST PENINSULA AND STRAITS WHILE MID LEVEL TROUGHING REMAINS OVER THE SOUTHEASTERN U.S. AND THE AFOREMENTIONED INVERTED TROUGH TO OUR EAST MOVES WEST NORTHWEST TOWARD THE FLORIDA EAST COAST. AS THIS OCCURS MOISTURE LEVELS WILL BEGIN TO INCREASE (PW'S INCREASING INTO THE 1.7-1.9" RANGE ON SUNDAY THEN 2+ INCHES BY MONDAY) FROM SOUTHEAST TO NORTHWEST. THIS INCREASING MOISTURE COMBINED WITH INVERTED TROUGH AXIS AND WEAK IMPULSES ALOFT MOVING THROUGH THE BASE OF MID LEVEL TROUGH TO OUR NORTHWEST WILL HELP TO INCREASE CLOUDS AND RAIN CHANCES (POPS INCREASING TO 40-50%) ACROSS THE FORECAST AREA BOTH DAYS. TEMPERATURES WILL BE NEAR NORMAL THROUGH THE PERIOD WITH DAYTIME HIGHS IN THE MID/UPPER 80S WITH OVERNIGHT LOWS IN THE UPPER 60S NORTH...TO THE MID 70S CENTRAL AND SOUTH. && .LONG TERM (MONDAY NIGHT - FRIDAY)...THE ENTIRE PERIOD WILL FEATURE A WEAK UPPER LEVEL TROUGH EXTENDING FROM JUST OFF THE NORTHEAST U.S. COAST TO OVER THE FLORIDA PENINSULA. SIGNIFICANT JET ENERGY REMAINS CUT OFF WELL TO THE NORTH...SO THIS FEATURE SHOULD NOT HAVE A MAJOR IMPACT ON OUR WEATHER. 500 MB TEMPERATURES ARE FORECAST TO RANGE BETWEEN -6 AND -8 CELSIUS...WHICH IS PRETTY NORMAL FOR THIS TIME OF YEAR. AT THE SURFACE...A LARGE AREA OF STRONG HIGH PRESSURE IS FORECAST TO STRETCH FROM NEW ENGLAND...SOUTHWESTWARD THROUGH THE MID ATLANTIC AND SOUTHEASTERN UNITED STATES THROUGH FRIDAY. THIS WILL CREATE A RATHER TIGHT PRESSURE GRADIENT OVER OUR AREA...ESPECIALLY BEGINNING WEDNESDAY AND LASTING RIGHT THROUGH FRIDAY. WINDS MAY BE LIGHT ENOUGH ON TUESDAY FOR AFTERNOON SEA BREEZES TO DEVELOP RIGHT ALONG THE COAST...BUT THE REST OF THE WEEK SHOULD BE STRAIGHT NORTHEAST OR EASTERLY FLOW...WHICH IS NORMALLY A DRY PATTERN FOR THE WESTERN HALF OF FLORIDA. MOISTURE LOOKS PLENTIFUL ENOUGH ON TUESDAY FOR PRETTY GOOD COVERAGE OF AFTERNOON THUNDERSTORMS...ESPECIALLY IF WE CAN GET A SEA BREEZE TO DEVELOP. FOR WEDNESDAY THROUGH FRIDAY HOWEVER...THE GFS SUGGESTS DECREASING MOISTURE AND NOT MUCH CHANCE OF SEA BREEZE CONVERGENCE. MEX GUIDANCE SUPPORTS SCATTERED COVERAGE EACH DAY...HIGHEST SOUTH WITH 40 TO 50 POPS TUESDAY AND WEDNESDAY...BUT OTHERWISE BETWEEN 30 AND 40 PERCENT EACH DAY. WE ARE GETTING TOWARD THE END OF OUR WET SEASON NOW...AND AVERAGE RAIN CHANCES ARE RUNNING AROUND 30 PERCENT FOR MOST OF THE AREA. I WILL KEEP THE FORECAST CLOSE TO THE MEX... BUT WILL BLEND IN A BIT OF CLIMO AS WELL SINCE THE FORECAST SURFACE PATTERN USUALLY RESULTS IN DRIER THAN NORMAL CONDITIONS. TEMPERATURES WILL BE REAL CLOSE TO WHERE THEY SHOULD BE FOR THIS TIME OF YEAR...BASICALLY MID 80S NORTH...UPPER 80S CENTRAL AND PERHAPS REACHING 90 SOUTH. OVERNIGHT LOWS WILL RANGE FROM THE MID TO UPPER 60S NORTH TO THE LOWER TO MIDDLE 70S CENTRAL AND SOUTH. && .AVIATION...DRY CONDITIONS EXPECTED FOR THE NEXT 24 HOURS SO WILL KEEP TAFS VFR. THERE MAY BE SOME PATCHY FOG AROUND TOWARD SUNRISE...BUT NOT MENTIONING IN TAFS AT THIS TIME. && .MARINE...HIGH PRESSURE FROM NEW ENGLAND SOUTHWEST TO THE NORTHERN GULF WILL MAINTAIN A NORTHEAST WIND FLOW ~15 KNOTS WITH SEAS OF 3-4 FEET WITH A NOCTURNAL SURGE CLOSE TO EXERCISE CAUTION TONIGHT FROM TARPON SPRINGS NORTH TO THE SUWANNEE RIVER TODAY THROUGH SUNDAY WHERE THE GRADIENT WILL REMAIN THE TIGHTEST...WITH 10-15 KNOTS AND 2-4 FOOT SEAS EXPECTED ELSEWHERE. DURING EARLY NEXT WEEK A PROLONGED PERIOD OF ELEVATED WINDS AND SEAS APPEARS TO BE ON TAP (ESPECIALLY FROM WEDNESDAY ONWARD AS A STRONG REINFORCING RIDGE OF HIGH PRESSURE (1034MB) BUILDS FROM NEW ENGLAND SOUTH TO THE NORTHERN GULF WITH EXERCISE CAUTION OR LOW END SMALL CRAFT CONDITIONS A GOOD POSSIBILITY...SO STAY TUNED. && .FIRE WEATHER...SIMILAR TO YESTERDAY NORTHEAST TRANSPORT WINDS IN THE 10-15 KNOT RANGE COMBINED WITH HIGH MIXING HEIGHTS WILL SUPPORT HIGH DISPERSION INDICES ACROSS THE REGION TODAY...ESPECIALLY FROM THE NATURE COAST NORTH WHERE THE GRADIENT WILL REMAIN THE TIGHTEST. LINGERING DRY AIR (DEW POINTS IN THE UPPER 60S) COMBINED WITH TEMPERATURES CLIMBING INTO THE MID/UPPER 80S WILL AGAIN SUPPORT POCKETS OF LOWER HUMIDITIES BUT VALUES WILL REMAIN ABOVE CRITICAL LEVELS SO NO RED FLAG CONDITIONS ARE EXPECTED. && .PRELIMINARY POINT TEMPS/POPS... TPA 89 73 89 74 / 10 10 40 20 FMY 91 73 91 74 / 10 10 40 20 GIF 89 72 90 73 / 10 10 50 20 SRQ 89 71 89 71 / 10 10 40 20 BKV 88 69 89 70 / 10 10 40 20 SPG 89 77 88 77 / 10 10 40 20 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...NONE. GULF WATERS...NONE. && $$ SHORT TERM/MARINE/FIRE WEATHER...MCMICHAEL LONG TERM/AVIATION...JILLSON