AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
259 PM EDT WED AUG 31 2005
.SYNOPSIS...NUMEROUS SHOWERS AND THUNDERSTORMS ONGOING ACROSS THE
FORECAST AREA THIS AFTERNOON. 18Z SURFACE ANALYSIS SHOWS A WEAK
BOUNDARY..."FRONT"...JUST TO THE NORTH OF MONTGOMERY AL EASTWARD TO
MACON GA NORTHEAST TO COLUMBIA SC. THIS IS THE LOCATION OF THE
TIGHTEST DEWPOINT GRADIENT AND THE LIKELY LEADING EDGE OF THE DRY
AIR AS THE CUMULUS FIELD CUTS OFF JUST BEHIND...NORTH...OF THIS
"FRONT". THIS BOUNDARY IS PROVIDING SOME LIFT COUPLED WITH THE WARM
MOIST AIRMASS IN PLACE OVER OUR AREA TO SPARK THESE SHOWERS AND
THUNDERSTORMS.
.SHORT TERM...TONIGHT THROUGH SATURDAY...
OVERALL AGREEMENT IN THE SHORT TERM BETWEEN THE NAM AND GFS IS
BETTER THAN NORMAL. HOWEVER THE TWO MODELS DISAGREE ON THE EVENTUAL
PROGRESSION OF THE BOUNDARY THROUGH OUR CWA AND MOVEMENT TO THE
SOUTH. BOTH MODELS AGREE THAT A RATHER NOTICEABLE CHANGE IN OUR
AIRMASS WILL BEGIN TO OCCUR FRIDAY AND INTO THE WEEKEND. BUT
BEFORE THAT HAPPENS...THE BOUNDARY WILL APPROACH THE FORECAST AREA
TOMORROW. THE GFS IS THE MOST PROGRESSIVE OF THE MODELS CALLING FOR
A CLEAR PASSAGE THROUGH THE FORECAST AREA AND INTO THE FLORIDA
PENINSULA BY FRIDAY AFTERNOON. THE NAM SEEMS TO WANT TO STALL
THE BOUNDARY SLIGHTLY FROM CTY TO JAX ON FRIDAY UNTIL A WEAK WAVE
DEVELOPS ON THE TAIL END OF THE BOUNDARY. THIS SOLUTION WOULD
OBVIOUSLY MEAN KEEPING POPS AROUND LONGER IN THE SHORT TERM PERIOD
IN OUR SE ZONES...AND KEEPING THEM HIGH. WILL SPLIT THE DIFFERENCE
HERE AS IT IS RARE TO SEE A CLEAN PASSAGE OF ANY BOUNDARY THIS TIME
OF YEAR IN THE FORECAST AREA.
TONIGHT...SHOWERS AND THUNDERSTORMS WILL CONTINUE AT ISSUANCE OF
FORECAST LIKELY UNTIL JUST AFTER SUNSET WHEN THEY WILL BEGIN TO
WANE...BUT COULD POSSIBLY CONTINUE AFTER MIDNIGHT ACROSS OUR EASTERN
ZONES WHERE HIGHER POPS ARE LEFT IN. WILL WORD THE ZFP FOR GREATEST
PRECIPITATION THREAT IN THE EVENING HOURS. LOW TEMPERATURES WILL BE
SLIGHTLY COOLER THAN LAST NIGHT AS MORE AREAS ARE GETTING A COOLING
SHOWER IN THE AFTERNOON AND EVENING. STILL LOW TO MID 70S WHICH
MATCHES WELL WITH BOTH NAM AND GFS GUIDANCE.
THURSDAY...WITH THE AGREEMENT BETWEEN THE GFS AND NAM THAT THE
BOUNDARY IS AT LEAST PROGRESSIVE THROUGH MY ALABAMA AND MOST OF MY
GEORGIA ZONES...WILL BE ABLE TO HAVE LOWER POPS IN ALABAMA AND
PORTIONS OF GA AND FL. HOWEVER...THERE WILL BE A TIGHT GRADIENT IN
POPS OUT AHEAD OF THE BOUNDARY ACROSS THE BIG BEND OF FLORIDA AND UP
TO VALDOSTA GA. ONCE HEATING COMMENCES TOMORROW...COULD SEE A GOOD
AMOUNT OF COVERAGE ACROSS MY SE ZONES AS WELL. TEMPERATURES WILL BE
CONFIGURED TO BE HIGHER IN MY WESTERN ZONES WHERE LESS PRECIP AND
CLEARER SKIES WILL BE EXPERIENCED. THURSDAY NIGHT SHOULD SEE THE
PRECIP DIMINISH AS THE BOUNDARY MOVES ON INTO EXTREME SOUTH CENTRAL
GA. POPS DROP SOME MORE AND WILL BE REMOVED FOR DHN AND ABY BUT
CONTINUED AT SLIGHT CHANCE TO CHANCE ELSEWHERE. MIN TEMPS LOWEST UP
IN MY NE ZONES AS THERE WILL BE CLEARER SKIES AND LOWER DEWPOINTS
THERE.
FRIDAY...BUYING THE GFS NEARLY CLEARS OUT MY WHOLE CWA OF MOIST
UNSTABLE AIRMASS BY THE START OF THE AFTERNOON HOURS. HOWEVER...I
SUSPECT THE FRONT WILL LINGER AROUND A BIT AND WILL KEEP A SLIGHT
CHANCE TO CHANCE POP CONFIGURATION FOR MY FOUR EASTERN FLORIDA
COUNTIES ONLY AS THEY WILL BE CLOSEST TO THE BOUNDARY...ALL OTHER
ZONES WILL HAVE POPS TO LOW TO MENTION. TEMPERATURES ARE EXPECTED TO
BE QUITE WARM...RISING INTO THE LOW TO MID 90S MOST PLACES WHERE
PLENTY OF INSOLATION WILL BE OBSERVED UNDER PARTLY CLOUDY
SKIES...ESPECIALLY FROM PFN UP TO DHN AND ABY.
SATURDAY...OUT OF DEFERENCE TO THE NAM STILL TRYING TO LINGER SOME
MOISTURE AROUND WILL KEEP A SLIGHT CHANCE POP IN FOR DIXIE AND
LAFAYETTE COUNTY WITH THE REMAINDER OF THE AREA DRY. PWS REALLY
BEGIN TO DROP OFF AT THIS POINT IN THE PERIOD AND SKIES WILL LIKELY
BE BETWEEN MOSTLY CLEAR AND PARTLY CLOUDY ACROSS THE AREA.
TEMPERATURES WILL COOL JUST SLIGHTLY BELOW FRIDAY'S NUMBERS BACK
INTO THE LOW 90S AREA WIDE. SHOULD BE A GREAT WEEKEND.
.LONG TERM...SUNDAY THROUGH WEDNESDAY...
LONG TERM PERIOD STARTS OFF WITH SHORTWAVE TROF EXITING THE
NORTHEAST WITH A STRONG RIDGE BEGINNING TO MOVE INTO THE MID SECTION
OF THE COUNTRY. THE SURFACE RIDGE MOVES INTO THE UPPER OHIO RIVER
VALLEY. THIS WILL INDUCE A NORTHERLY FLOW FOR US HERE THAT WILL HELP
TO FURTHER DRY OUT OUR AIRMASS AND EVENTUALLY PROVIDE FOR SOME
SLIGHTLY COOLER TEMPERATURES. WITH THE DRIER AIRMASS...POP CHANCES
WILL BE LOWER THAN CLIMATOLOGY UNTIL THE END OF THE PERIOD.
FOR THE LONG TERM FORECAST CYCLE HAVE DECIDED TO LEAN AGAIN ON THE
GFS SOLUTION AS IT HAS COME INTO EVEN BETTER AGREEMENT WITH THE
REMAINING GLOBAL MODELS.
SUNDAY...RIDGE BEGINS TO APPROACH AND WITH NORTHERLY FLOW COMMENCING
OVER THE REGION FELT IT BEST TO LOWER POPS FOR SUNDAY. MEX GUIDANCE
DOESN'T EVEN MAKE IT TO 15 PERCENT FOR ANY LOCATION IN THE CWA. GFS
PWS DROP TO NEAR 1 INCH ACROSS GA AND AL WITH 1.25 INCHES IN FLA
DURING THE DAY ON SUNDAY. THE DRY ADVECTION IS ALSO GOOD INDICATION
THAT PRECIP CHANCES WILL BE VERY LOW AND WORTH REMOVING MENTION OF
THEM IN THE ZONES AT THIS POINT. TEMPERATURES ARE THE NEXT CONCERN.
DESPITE THE DRIER AIR ADVECTING IN...WON'T BE FULLY IN PLACE UNTIL
MONDAY SO SHOULDN'T SEE A CORRESPONDING TEMPERATURE DECREASE UNTIL
MONDAY. SO WILL SEE ONE MORE DAY OF TEMPERATURES IN THE LOW 90S
BEFORE COOLING DOWN INTO THE UPPER 80S.
MONDAY...THE GFS IS INDICATING A WAVE DEVELOPING ON THE TAIL END OF
A SURFACE TROF OVER THE CARIBBEAN. THE 06Z DGEX IS A LITTLE FURTHER
SOUTH WITH THIS FEATURE. THE COMBINATION THOUGH OF THIS LOW AND THE
RIDGE TO THE NORTH WILL SLIGHTLY INCREASE OUR NORTHEAST FLOW. THIS
WILL BRING IN SOME MOISTURE FROM THE ATLANTIC THAT WILL NECESSITATE
BRINGING BACK IN 20 POPS TO THE FORECAST. TEMPS WILL DECREASE A
CATEGORY TODAY FOR MAX TEMPS. MIN TEMPS WILL CONTINUE A COOL DOWN
INTO THE UPPER 60S.
TUESDAY...AFOREMENTIONED WAVE CONTINUES TO MOVE TOWARD FLORIDA. DGEX
ACTUALLY MOVES THE SYSTEM INTO THE EASTERN GOMEX BY THIS TIME.
CONSIDERING THE DIFFERENCE IN PLACEMENT OF THE TWO MODELS...WILL NOT
GO WITH ONE OVER THE OTHER. WILL TREND TOWARD MORE MOISTURE BEING IN
THE AREA AND INCREASE POPS SLIGHTLY SOUTH AND SHOW AN INCREASING
TREND IN WINDS AND CLOUDS. TEMPERATURES WILL DROP INTO THE MID 80S
ACROSS THE FORECAST AREA UNDER A COMBINATION OF THE STRONG
NORTHEASTERLY FLOW AND THE CLOUD COVER THAT WILL BE MOVING IN FROM
THE SE. THIS CLOUD COVER MAY HURT TUESDAY MORNING'S LOWS THAT ARE
FORECASTED TO BE IN THE LOW TO MID 60S IN THE MEX GUIDANCE.
THEREFORE...I TRENDED 1 TO 2 DEGREES ABOVE GUIDANCE FOR THIS
POSSIBILITY.
WEDNESDAY...AFTER READING THE PREEPD FROM NCEP THIS
MORNING...SUPPORT THEIR REASONING FOR THIS FAR EXTENDED PORTION OF
THE FORECAST. SIMPLY PUT...WE DON'T HAVE THE SKILL YET TO FORECAST
THE GENESIS OF A TROPICAL/SUBTROPICAL SYSTEM THIS FAR OUT IN THE
EXTENDED. HOWEVER...WE CAN CERTAINLY NOTICE TRENDS IN THE MODELS AND
LEAN OUR FORECAST IN THAT DIRECTION. WITH THAT BEING SAID...THE 06Z
DGEX BRINGS THE CLOSED SURFACE LOW VERY CLOSE TO THE PANHANDLE COAST
BY WEDNESDAY AFTERNOON. THE GFS IS NOT INDICATING THE SYSTEM GETTING
AT ALL CLOSE TO THE FLORIDA PANHANDLE. IN FACT...THE UPPER AIR
STEERING FLOW ACTUALLY SUGGESTS THAT THIS SYSTEM WOULD TREND FURTHER
TO THE WEST THAN IS CURRENTLY INDICATED BY THE DGEX...PLUS THE 12Z
GFS TAKES THIS SYSTEM WELL SOUTH AND WEST OF OUR AREA. JUST FAR TO
MANY VARIABLES TO ACCOUNT FOR AT THIS POINT IN TIME TO GIVE A
PRECISE FORECAST. SO AS SAID ABOVE FOR TUESDAY...WILL TREND POPS UP
SLIGHTLY ACROSS THE AREA AND INCREASE CLOUD COVER SLIGHTLY...BECAUSE
THERE WILL BE ADDED MOISTURE...BUT WILL NOT JUMP ALL OVER
THIS...BECAUSE THE MODELS HAVE A TENDENCY TO FLIP FLOP FROM ONE DAY
TO THE NEXT. THERE WAS A LITTLE CONTINUITY BETWEEN YESTERDAY'S RUNS
AND TODAY AND WITH NCEP PLACING IT ON THEIR PROG CHART...THERE IS
SOME SUPPORT FOR TRENDING TOWARD A SLIGHTLY WETTER THAN NORMAL
FORECAST. TEMPERATURES SHOULD MODERATE WITH A SOMEWHAT TROPICAL
AIRMASS EXPECTED EITHER WAY.
&&
.MARINE...WINDS AND SEAS CONTINUING TO DIMINISH WITH OUR OFFSHORE
BUOYS COMING IN AT 4 FEET AT 18Z. WILL CONTINUE TO SEE TREND DOWN IN
SEAS. NO HEADLINES PLANED FOR THE WATERS THROUGH THE FORECAST
PERIODS. WINDS AND SEAS MAY COME UP A LITTLE INTO THE FIRST PART OF
THE WORK WEEK...BUT NO HEADLINES EXPECTED.
&&
.FIRE WEATHER...RH VALUES WILL BEGIN TO DROP AS WE MOVE INTO THE
WEEKEND...BUT STILL EXPECTED TO REMAIN ABOVE CRITERIA FOR ANY
HEADLINES. NO CONCERNS ANTICIPATED THROUGH THE FORECAST PERIOD.
&&
.
