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000
FXUS64 KHUN 061137 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
537 AM CST FRI DEC 6 2013

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 225 AM CST FRI DEC 6 2013/
AT 1 AM, A 31 DEGREE TEMPERATURE RANGE WAS FOUND ACROSS OUR FORECAST
AREA (39 AT THA TO 70 AT 4A9). THE FRONT WAS NEARING THE I-59
CORRIDOR BUT WILL BE SLOW TO BUDGE TODAY MAKING FOR VERY TRICKY
TEMPERATURES ALONG AND NEAR THIS BOUNDARY. THE NAM SUGGESTS THE
BOUNDARY STALLING OR EVEN PUSHING BACK NW BRIEFLY A BIT LATER TODAY.
HAVE ATTEMPTED TO ACCOUNT FOR THIS GIVEN THAT PRESSURES ARE NOW
FALLING SLIGHTLY AGAIN. RIGHT ALONG THE FRONT, A CLUSTER OF SHOWERS
AND THUNDERSTORMS WAS RACING NE THRU MARSHALL/JACKSON/DEKALB
COUNTIES. FURTHER WEST, THE 850 MB BOUNDARY WAS SITUATED FROM NEAR
NASHVILLE THRU NRN MS AND WAS SERVING AS ANOTHER FOCI FOR ELEVATED
THUNDERSTORMS WITH HEAVY RAINFALL. ECHO TRAINING MAY BECOME A PROBLEM
THIS MORNING WITH THESE STORMS IN NW AL SO WILL HAVE TO WATCH RAIN
RATES CLOSELY. MOISTURE TRANSPORT VECTORS MAXIMIZE AROUND 18Z TODAY
IN A CORRIDOR FROM NRN AL THRU EASTERN TN. MY CONCERN FOR FLASH
FLOODING IS HIGHER THAN PREVIOUS DAYS AS THE CONVECTIVE NATURE OF THE
PRECIP TODAY MAY PRODUCE RAINFALL RATES THAT COULD APPROACH 1-3HR FFG
VALUES THAT ARE FROM 1.8-2.5 INCHES IF THE ECHO TRAINING CAN OCCUR.

THE 850 MB COLD FRONT LOOKS TO RENEW DEVELOPMENT OF SHRA/TSRA THIS
AFTN WHICH WILL TRACK EASTWARD EARLY THIS EVENING. ONCE AGAIN, THE
MODELS CONTINUE TO SHOW RAPID DRYING OF THE MID LEVELS BEHIND THE 850
MB COLD FRONTAL PASSAGE THIS EVENING. THE NAM AND LOCAL WRF BOTH
SUGGEST RAINFALL EXITING NW AL BEFORE 06Z AND MORE IMPORTANTLY BEFORE
THE FREEZING LINE DROPS INTO THE AREA. WILL HOLD ONTO A SMALL CHC OF
-FZRA IN THE FAR NW TIP OF AL FROM 03-06Z, BUT WARM GROUND TEMPS
SHOULD PREVENT ICING PROBLEMS FOR TRAVEL AT THIS POINT. QPF FOR THIS
FIRST ROUND OF RAINFALL IS MORE COMPLEX NOW WITH THE CONVECTIVE
NATURE OF TODAY`S ACTIVITY. A GOOD 1-3 INCHES STILL LOOKS IN THE BALL
PARK, BUT SOME AREAS COULD SEE MORE OR LESS.

SATURDAY NOW APPEARS TO BE A DRY BUT CLOUDY DAY BEFORE THE NEXT WET
EPISODE. MID LEVELS CERTAINLY MOISTEN RAPIDLY SATURDAY EVENING, BUT
LOW LEVEL MOISTENING DOES NOT OCCUR IN EARNEST UNTIL LATER SATURDAY
NIGHT INTO SUNDAY MORNING. FORTUNATELY, TEMPS AT THE SFC SHOULD
REMAIN ABOVE FREEZING, ALTHOUGH THERE IS SOME CONCERN FOR BRIEF IP AT
ONSET OF THE PRECIP. CONFIDENCE IS NOT HIGH TO ENOUGH TO INCLUDE THIS
IN THE FORECAST, BUT WILL NEED TO BE ASSESSED IN FUTURE MODEL RUNS
TODAY. STRONG WARM ADVECTION AND MOISTURE TRANSPORT OCCUR ON SUNDAY
WITH A GOOD POTENTIAL FOR MORE HEAVY RAINFALL, ESPECIALLY FOR NC/NE
AL INTO SRN TN. FEW CHANGES NEEDED HERE AS THIS HAS BEEN FORECAST
CONSISTENTLY THE PAST COUPLE OF DAYS. BOTH THE NAM AND GFS ARE
FOCUSING A HEAVY RAIN CORRIDOR ALONG THE COLD FRONT FROM WEST
CENTRAL INTO NERN AL DURING THE EVENING AND OVERNIGHT HOURS SUNDAY.
RAINFALL TOTALS (FIRST AND SECOND EVENTS) WILL REACH 3-5 INCHES IN
THIS AREA, WITH SOME LOCALLY HIGHER AMOUNTS.

THERE ARE STILL BIG QUESTIONS MARKS WITH REGARD TO THE WINTER
WEATHER POTENTIAL 84-108 HOURS OUT (MONDAY NIGHT INTO EARLY TUESDAY).
THE LATEST GFS SOUNDINGS WOULD INDICATE MORE FREEZING RAIN POTENTIAL
AS OPPOSED TO SNOW. WILL KEEP THE "RAIN OR SNOW" FORECAST GOING UNTIL
A BETTER CONSENSUS IN THE MODEL FORECASTS EXISTS.

AK

&&

.AVIATION...
FOR 12Z TAFS...REDUCED/RESTRICTED FLIGHT CONDS ARE GENERALLY XPCTED
TO PREVAIL FOR JUST ABOUT ALL OF THE TAF PERIOD. PERIODS OF -RA/RA
MOVING NEWD ACROSS THE AREA ALONG/BEHIND A COLD FRONT LOCATED FROM
ERN TN LEADING INTO NE AL WILL CONTINUE INTO THE EVENING HRS BEFORE
TAPERING OFF LATER TONIGHT. SCT TSRA ARE POSSIBLE WITHIN BANDS OF
RA/SHRA TODAY AS WELL...ALTHOUGH CONFIDENCE IN PLACEMENT/TIMING IS
FAIRLY LOW ATTM. LOW CIGS PREDOM IN THE MVFR CAT ARE ALSO XPCTED TO
PREVAIL WELL INTO THE OVERNIGHT PERIOD.

09

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

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AT WEATHER.GOV/HUNTSVILLE.