000
FXUS62 KTAE 171858
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
300 AM EDT FRI OCT 17 2008

.SYNOPSIS...
19Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING AN AMPLIFYING UPPER
LEVEL PATTERN THIS AFTERNOON ACROSS THE CONUS. FROM WEST TO EAST
WE STILL FIND LONGWAVE RIDGING COVERING MUCH OF THE WESTERN U.S.
AND SOUTHWEST CANADA. NORTHERN STREAM FLOW THEN DIPS INTO AN
AMPLIFYING LONGWAVE TROUGH ACROSS THE MID-SECTION OF THE
COUNTRY...WITH THE TROUGH AXIS NOW APPROACHING THE MS RIVER VALLEY.
THE OVERALL FLOW THEN FLATTENS OUT AS IT EXITS THE EASTERN SEABOARD
INTO THE WESTERN ATLANTIC. CURRENTLY OVERHEAD THE FORECAST AREA WE
FIND THE UPPER LEVEL RIDGING THAT HAS BROUGHT THE FAIR AND WARM
WEATHER TO THE AREA THE PAST SEVERAL DAYS BEGINNING SETTLING
SOUTHWARD IN RESPONSE TO THE APPROACHING HEIGHT FALLS TO THE
NORTHWEST.

AT THE SURFACE...WEAK HIGH PRESSURE IN THE VICINITY IS SHIFTING
SOUTH AS A COLD FRONT APPROACHES FROM THE NORTH. COLD FRONT IS
CURRENTLY LOCATED FROM THE SOUTH CAROLINA COAST BACK THROUGH
CENTRAL GA AND THEN SOUTHWEST IN SOUTHERN AL/MS. CLOUD-SHIELD IS
QUITE THICK ALONG THIS BOUNDARY WITH A LARGE AREA OF SHOWERS FROM
NEAR ATLANTA TO MONTGOMERY. THIS SHOWERS AND THICKER CLOUDS WILL
CONTINUE TO DROP SOUTHWARD TOWARD OUR NORTHWESTERN ZONES INTO THE
EVENING HOURS.

&&

.SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...
SLOW MOVING COLD FRONT LOCATED TO OUR NORTH AND NORTHWEST WILL
INCREASE ITS FORWARD PROGRESS SOUTHWARD AS MID-LEVEL
TROUGHING/ENERGY OVER THE MID-SECTION OF THE COUNTRY AMPLIFIES INTO
THE LOWER MS VALLEY AND SOUTHEASTERN STATES TONIGHT.

FRONT PUSHES SOUTHEAST ACROSS THE FORECAST AREA TONIGHT REACHING A
POSITION FROM AROUND VALDOSTA TO PERRY AND OUT INTO THE EASTERN
MARINE LEGS BY SUNRISE SATURDAY MORNING. FRONT IS SOMEWHAT MOISTURE
STARVED AS ANY INFLUX OF GULF MOISTURE HAS BEEN BRIEF. HOWEVER...AS
THE SHORTWAVE AMPLIFIES INTO THE SOUTHEAST DURING THE OVERNIGHT...
LARGE SCALE LIFT ASSOCIATED WITH THE RESPECTABLE HEIGHT FALLS SHOULD
BE ENOUGH TO SUPPORT A BROKEN BAND OF SHOWERS ALONG AND AHEAD OF
THE FRONTAL PASSAGE. DEEP LAYER Q-G FORCING AHEAD OF THE SHORTWAVE
WITH THESE MID-LEVEL HEIGHT FALLS IS MAXIMIZED ACROSS OUR NORTHERN
ZONES AND FURTHER NORTH. THEREFORE THE INHERITED FORECAST
PHILOSOPHY WILL NOT CHANGE WITH HIGHEST POPS ACROSS OUR SE ALABAMA
AND NORTHERN GA ZONES. SHOWERS SHOULD ARRIVE THIS EVENING INTO THE
EARLY MORNING HOURS ACROSS OUR NORTHERN AND WESTERN ZONES AND THEN
CONTINUE FURTHER SOUTHEAST AFTER MIDNIGHT. INSTABILITY CONTINUES TO
BE ONLY MARGINAL AT BEST WITH LATEST SREF PROBS STILL SHOWING 0% FOR
EVEN 500 J/KG OVER THE LAND. HOWEVER...CAN NOT RULE OUT AN ISOLATED
THUNDERSTORMS...ESPECIALLY ALONG THE EASTERN PANHANDLE COAST...BUT
MOST ACTIVITY SHOULD BE IN THE FORM OF SHOWERS. IT SHOULD BE NOTED
THAT EVEN WITH THE LIKELY POPS ACROSS THE FAR NORTH...NOT LOOKING
FOR A WASHOUT OF A NIGHT IN ANY LOCATION AS THE SHOWERS THAT DO
OCCUR SHOULD BE BRIEF IN NATURE AND AMOUNT GENERALLY NO MORE THAN
ONE OR TWO TENTH OF AN INCH OF ACCUMULATION AT BEST.

GFS/NAM/ECMWF ALL SHOW THE COLD FRONT EXITING RAPIDLY TO THE
SOUTHEAST OUT OF THE FORECAST AREA DURING THE FIRST HALF OF
SATURDAY MORNING. GLOBAL MODELS SHOWING A VERY QUICK DRYING THROUGH
THE COLUMN AS THE MID-LEVEL SHORTWAVE AXIS PASSES THE AREA.
THEREFORE LOOKING FOR A RAIN FREE DAY REGIONWIDE AFTER A POSSIBLE
QUICK EARLY MORNING SHOWER/SPRINKLE DOWN TOWARD PERRY OR CROSS CITY.
THEREFORE MORNING CLOUDS ALONG THE FRONT OVER THE SOUTHEAST HALF OF
THE AREA WILL BEGIN TO CLEAR WITH SKIES BECOMING PARTLY TO MOSTLY
SUNNY BY AFTERNOON. A COOLER AND DRIER AIRMASS WILL ARRIVE DURING
SATURDAY BEHIND THE FRONT WITH 850MB TEMPS DROPPING TO BETWEEN 7
AND 11C FROM NORTH TO SOUTH. THE COOLER AND DRIER AIR COMBINED WITH
A 10-15 MPH NORTHERLY FLOW WILL PROVIDE A MORE FALL-LIKE FEEL TO
YOUR SATURDAY AFTERNOON THAN WHAT HAS BEEN EXPERIENCED AS OF LATE.
HIGH TEMPERATURES STRUGGLING TO REACH" onClick="return popup(this, 'notes')">REACH THE LOWER 80S SOUTHEAST AND
THE UPPER 70S TO NEAR 80 ELSEWHERE.

MID-LEVEL SHORTWAVE ENERGY EXITS OFF THE SOUTHEAST COAST SATURDAY
NIGHT WITH MID-LEVEL RIDGING REBUILDING ALONG THE GULF COAST
THROUGH THE REMAINDER OF THE SHORT-TERM PERIOD. STRONG 1025-1030MB
SURFACE RIDGE ACROSS THE OHIO/MIDDLE MS VALLEYS WILL ALSO BUILD
SOUTH AND EAST THROUGH THE PERIOD TO A POSITION FROM THE EASTERN
SEABOARD TO THE NORTHEAST GULF OF MEXICO. THE RESULT WILL BE FAIR
AND SEASONABLE WEATHER WITH TEMPERATURES GENERALLY A FEW DEGREES
BELOW NORMAL. LOW TEMPERATURE FORECASTS ARE GOING TO BE ON THE
DIFFICULT SIDE BOTH SATURDAY AND SUNDAY NIGHTS. AIRMASS IS ON THE
COOL AND DRY SIDE...HOWEVER A FAIRLY TIGHT GRADIENT ON SATURDAY
NIGHT SHOULD KEEP RADIATIONAL COOLING FROM REALLY TAKING HOLD AND
DROPPING TEMPS TO LOW. MODELS STILL SHOW A FAIRLY TIGHT GRADIENT
SUNDAY NIGHT...HOWEVER ON THESE SECOND NIGHTS BEHIND FRONTAL PASSAGE
HAVE SEEN THE BOUNDARY LAYER ABLE TO DECOUPLE LATE DESPITE THE
GRADIENT AND RESULT IN A RAPID TEMP DROP AROUND SUNRISE. TOO EARLY
TO SAY IF THIS WILL OCCUR...BUT FEEL MORE CONFIDENT GOING WITH UPPER
40S INTO EARLY MONDAY MORNING.

&&

.LONG TERM...(MONDAY THROUGH FRIDAY).
HIGH PRESSURE WILL BE IN CONTROL OF THE WEATHER AT THE START OF THE
PERIOD WITH A SURFACE RIDGE EXTENDING FROM THE NE/MID ATLANTIC SWWD
ACROSS THE DEEP S. THIS WILL PROVIDE THE AREA WITH ANOTHER COOL DAY
ON MON, WITH MINS SIMILAR TO SUN...SEVERAL DEGREES BELOW NORMAL...
AND MAX TEMPS JUST A FEW DEGREES WARMER. UPPER LEVEL RIDGING WILL
THEN MOVE EWD FROM THE SRN PLAINS WITH BOTH MAX AND MIN TEMPS
MODERATING TO SLIGHTLY ABOVE NORMAL BY TUE-WED. BY MID WEEK...WE
BEGIN TO SEE SOME SIGNIFICANT DIFFERENCES DEVELOP IN THE MODEL
SOLUTIONS. BOTH THE GFS AND 16/12Z EURO OPERATIONAL RUNS DEEPEN A
TROUGH OVER CENTRAL N AMERICA. HOWEVER...THE GFS DROPS THE OCCLUDED
SYSTEM MUCH FURTHER S AND W THAN THE EURO...INTO THE CENTRAL
PLAINS...WHERE IT SITS AND SPINS FOR DAYS. THE EURO BRINGS THE
STACKED LOW INTO THE UPPER MS VALLEY AND THEN SWINGS IT EWD ACROSS
THE LAKES INTO THE WEEKEND. THESE DIFFERENCES IMPACT DEVELOPMENTS IN
THE TROPICS AS WELL, WHERE BOTH MODELS SHOW LOW PRESSURE DEVELOPING
IN THE NWRN CARIBBEAN SEA. THE EURO`S TROUGH IS FAR ENOUGH N THAT IT
DOES NOT PICK UP THIS FEATURE WHICH SPINS IN PLACE THROUGH MOST OF
NEXT WEEK. THE GFS PICKS UP THE LOW AND LIFTS IT SLOWLY NWD THROUGH
THE YUCATAN CHANNEL INTO THE SERN GULF OF MEXICO FROM WED-FRI. WITH
THE FRONT STALLED UPSTREAM AND MOISTURE INCREASING FROM THE S AND
E...THE GFS PRESENTS A MUCH CLOUDIER AND BREEZIER SCENARIO FOR LATE
IN THE WEEK THAN THE EURO...WHICH SHOWS A CLEAN COLD FROPA ON FRI.
THE GFS ENSEMBLE MEAN IS MUCH CLOSER TO THE EURO SOLUTION WITH
RESPECT OT THE POSITION OF THE 500 MB HIGH ON FRI. CONSIDERING THE
SPREAD OF THE ENSEMBLE MEMBERS THROUGH, WE ARE NOT CONFIDENT ENOUGH
TO GO STRICTLY WITH THE EURO. WE WILL GENERALLY FOLLOW THE GFS/MEX
FOR POP...BUT WILL SCALE BACK THE AMOUNT OF CLOUD COVER AND ELY
WINDS IN THIS MODEL. IN OTHER WORDS...WE WILL BE HOLDING OFF ON ANY
INDICATION OF A TROPICAL ENTITY IN THE GULF UNTIL WE SEE A TREND
TOWARD THIS SOLUTION WHICH...BY THE WAY...DOES FIT THE CLIMATOLOGY
FOR LATE OCT IN THE ATLANTIC BASIN.

&&

.MARINE...
COLD FRONT WILL CROSS THE WESTERN MAINER LEGS TONIGHT AND THEN THE
EASTERN LEGS EARLY SATURDAY. WINDS ARE EXPECTED TO INCREASE TO NEAR
CAUTIONARY LEVEL ACROSS THE WESTERN LEGS FROM THE NORTH AND
NORTHWEST TONIGHT. STRONG HIGH PRESSURE THEN SLOWLY BUILDS OVER THE
WATERS THE REMAINDER OF THE UPCOMING WEEKEND INTO EARLY NEXT WEEK.
EXPECTING NORTHERLY WINDS NEAR CAUTIONARY LEVELS OVER A LARGE
PORTION OF THE AREA DURING THE DAYLIGHT HOURS ON SATURDAY WITH WINDS
AND SEAS INCREASING TO NEAR ADVISORY LEVELS SATURDAY NIGHT INTO
EARLY SUNDAY. THE EASTERLY FLOW AROUND THE SOUTHERN PERIPHERY OF THE
HIGH TO OUR NORTH WILL FAVOR NOCTURNAL SURGES OF WINDS BOTH SUNDAY
AND AGAIN MONDAY NIGHTS.

&&

.AVIATION...
A LARGE AREA OF LIGHT TO MODERATE RAIN OUT AHEAD OF THE COLD FRONT
CONTINUES TO MOVE NE JUST TO THE NW OF THE CWA EARLY THIS
AFTERNOON...WITH THE MAIN FCST CONCERN BEING IF/WHEN WILL SOME OF
THIS RAINFALL AND POTENTIALLY LOW CIGS MAKE IT TO THE TAF SITES THIS
EVENING AND TONIGHT. THE BEST PROBABILITIES FOR RAIN...LOW CIGS...
AND EARLY ONSET OF PRECIPITATION WILL BE AT DHN AND ABY...WITH A
TIME FRAME IN THE 02-07 UTC RANGE...WITH GRADUALLY LOWERING CHANCES
AT PFN BETWEEN 04-08 UTC...TLH 06-10 UTC...AND VLD FROM 08-12 UTC.
DHN COULD EVEN SEE A SHOWER OR SOME LIGHT RAIN BEFORE SUNSET...SO
WILL CONTINUE TO MONITOR THE FRONTAL PROGRESS. DURING SAT MORNING...
THE STRONG SHORTWAVE NOW DIGGING THROUGH THE MID MS VALLEY WILL BE
CHARGING INTO THE CAROLINAS...AND THIS SHOULD HELP ACCELERATE THE
COLD FRONT THROUGH THE CWA...WITH CLEARING SKIES AND GUSTY N-NW
WINDS DEVELOPING FROM NW TO SE ACROSS THE TAF LOCATIONS.

&&

.FIRE WEATHER...
OUR RH GRIDS ARE NOT QUITE AS LOW AS THE PREVIOUS  SHIFTS...
WITH 35 PERCENT OR LESS NOW CONFINED TO INLAND WALTON...
HOLMES...WASHINGTON...NORTHERN BAY...AND CALHOUN COUNTIES. WITH
DISPERSIONS WELL ABOVE 75 IN THESE AREAS AS WELL...UPGRADED THE
ABOVE ZONES TO A RED FLAG WARNING ON SAT AFTN...AND DROPPED THE
WATCH FOR SE AL AND AREAS FURTHER EAST IN N FL. ON SUNDAY AFTERNOON
...ALMOST ALL OF N FL SHOULD HAVE SUB 35% RH COINCIDENT WITH >75
DISPERSIONS SO ISSUED A FIRE WX WATCH FOR ALL FL ZONES.

&&

.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE  60  80  51  78  49 /  40  10   0   0   0
PANAMA CITY  62  81  54  78  54 /  40  10   0   0   0
DOTHAN       56  78  49  75  48 /  60   0   0   0   0
ALBANY       57  78  50  76  47 /  60  10   0   0   0
VALDOSTA     61  79  51  76  49 /  40  10   0   0   0
CROSS CITY   64  81  52  79  49 /  20  20   0   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING
     FOR THE FOLLOWING ZONES: BAY...CALHOUN...DIXIE...FRANKLIN...
     GADSDEN...GULF...HOLMES...INLAND WALTON...JACKSON...
     JEFFERSON...LAFAYETTE...LEON...LIBERTY...MADISON...TAYLOR...
     WAKULLA...WASHINGTON.

     RED FLAG WARNING FROM 1 PM TO 5 PM CDT SATURDAY FOR THE
     FOLLOWING ZONES: BAY...CALHOUN...HOLMES...INLAND WALTON...
     JACKSON...WASHINGTON.

GM...NONE.

&&

$$

AVIATION/FIRE WEATHER...GOULD
SYNOPSIS/SHORT TERM/MARINE...MROCZKA
LONG TERM...WOOL