000
FXUS64 KHUN 061142
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
542 AM CST TUE JAN 6 2009
.UPDATE...FOR 12Z TAFS
&&
.AVIATION...STATIONARY FRONT WAS JUST SOUTH OF THE CWA WITH UPPER
TROF OVER THE CENTRAL PLAINS. STATIONARY BOUNDARY IS PROGGED TO
MOVE BACK NORTH INTO NERN AL...AS SFC WAVE MOVES OVER THE CWA
THIS AFTN. AS A RESULT THE MOST INSTABILITY WILL BE EAST OF THE
TAFS SITES...HOWEVER HSV MAY BE CLOSE ENOUGH TO HAVE A FEW TSRA
ARND 20Z. ATMOSPHERE OVER MSL SHOULD BE STABLE ENOUGH TO PREVENT
TSRA DEVELOPMENT. OTHERWISE EXPECT IFR CONDITIONS FOR BOTH TAF
SITES THRU THE FCST PERIOD...DUE MAINLY TO LOW CLOUDS.
&&
.PREV DISCUSSION... /ISSUED 300 AM CST TUE JAN 6 2009/
SYNOPSIS...A DEEP SUBTROPICAL JET STRETCHING FROM
CENTRAL MEXICO TO OFF THE NORTHEASTERN SEABOARD CONTINUES TO PUMP
MOISTURE ACROSS THE SOUTHEAST US. THIS MOISTURE FETCH IS A RESULT OF
A DEEPENING TROUGH OVER THE SOUTHWEST STATES. THE AXIS IS ACTUALLY
CENTERED FROM ND SOUTHWARD TO NM. A RIDGE EXTENDS FROM THE CENTRAL
PACIFIC OVER THE WESTERN STATES.
A STALLED/STATIONARY FRONT STRETCHES FROM CENTRAL NC SW TO THE NW
GULF OF MEXICO.
DUE TO LARGE AMOUNT OF RAINFALL EXPECTED OVER THE REGION A FLOOD
WATCH WILL CONTINUE THROUGH MIDNIGHT TONIGHT.
SHORT TERM...TODAY THROUGH THURSDAY NIGHT...
A DEEP MOISTURE COLUMN...A STATIONARY FRONT...IMPRESSIVE ISENTROPIC
LIFT...AND PWATS OVER 1.5 INCHES ONLY MEAN ONE THING...RAIN...RAIN
AND MORE RAIN FOR TODAY. CURRENT ANALYSIS OF MODEL AND OBS DATA
INDICATE THAT RAIN WILL INCREASE IN COVERAGE AND INTENSITY WITH THE
APPROACH OF THE DEEPENING TROUGH. SEVERAL WAVES OF ENERGY EVIDENT IN
WATER VAPOR IMAGERY AND DEPICTED BY THE NAM WILL CROSS THE TN VALLEY
BEGINNING EARLY THIS MORNING. FURTHERMORE...SFC CYCLOGENESIS OVER
WEST TX WILL TRANSLATE A LOW NORTHEAST DIRECTLY OVER THE TN VALLEY
ATOP THE STATIONARY FRONT.
THE SFC STATIONARY FRONT WILL GRADUALLY LIFT NORTH AND PARK OVER THE
CENTRAL PORTIONS OF THE CWA DURING THE DAY AND THEN TRANSITION TO A
COLD FRONT AS THE TROUGH APPROACHES THIS AFTERNOON. AS THIS
OCCURS...EXPECTING SHOWERS TO INTENSIFY WITH ENOUGH ELEVATED
INSTABILITY TO TRIGGER SOME T-STORMS. MOST OF THE INSTABILITY
ACTUALLY EXISTS TO THE SOUTH OF THE AREA. THE GREATEST OPPORTUNITY
FOR T-STORMS LOOKS TO BE 18-22Z... ESPECIALLY OVER THE SE COUNTIES
WHERE INSTABILITY LOOKS TO BE THE GREATEST.
GIVEN ALL OF THESE WAVES OF PRECIP...EXPECTING PRODIGIOUS AMOUNTS OF
RAINFALL WITH TOTAL ACCUMULATIONS OF 2 TO 4 INCHES WITH SOME
LOCATIONS OVER 5 INCHES. THE HIGHER AMOUNTS WILL LIKELY OCCUR WITH
ANY EMBEDDED THUNDERSTORMS. THIS AMOUNT OF RAINFALL COUPLED WITH THE
FACT THAT WE HAD WELL ABOVE NORMAL PRECIP LAST MONTH...WILL ONLY ACT
TO EXACERBATE OR ACCELERATE ANY FLOODING THAT IS POSSIBLE.
TEMPS WILL BE DIFFICULT TO FORECAST TODAY GIVEN THE RAINFALL AND
COLD FRONT. HAVE KEPT DAYTIME HIGHS TODAY IN THE 50S WITH SOMEWHAT
HIGHER TEMPS IN THE SOUTHEAST ZONES.
ONCE THE MAIN TROUGH BEGINS ADVECTING TO THE NE...RAINFALL SHOULD
GRADUALLY TAPER OFF. ALL OF THE MODELS SHOW WRAPAROUND MOISTURE
BEHIND THE FRONT. HOWEVER...DRY AIR ALOFT...LACK OF SUBSTANTIVE
MOISTURE ALOFT...ALONG WITH WARM AIR ALOFT SHOULD KEEP THIS PRECIP
LIGHT AND IN LIQUID FORM. HAVE THUS LEFT CHANCE OF LIGHT RAIN IN
FORECAST FOR NOW ON WEDNESDAY MORNING. TEMPS SHOULD FALL FROM THE
40S THROUGHOUT THE DAY TO LOW TO MID 30S GIVEN THE STRONG CAA BEHIND
THE FRONT AND CLOUDS CLEARING.
A STRONG RIDGE WILL MOVE OVER THE REGION BY LATE WEDNESDAY NIGHT
INTO THURSDAY. A SFC COMPLEMENT HIGH CENTERED OVER THE GULF OF
MEXICO MAY SEND SOME SOMEWHAT WARMER AIR OVER THE TN VALLEY WHICH
MAY CONTRIBUTE TO DAYTIME HIGHS REACHING INTO THE 50S.
LONG TERM...FRIDAY THROUGH MONDAY...
THE RIDGE SHOULD CONTINUE TO DOMINATE THROUGH SATURDAY AHEAD OF AN
ELONGATED TROUGH EXPECTED TO BRING ANOTHER SFC COLD FRONT AND
POSSIBILITIES OF RAIN. MOISTURE RETURN LOOKS RATHER DISMAL.
THUS...NOT EXPECTING MUCH RAINFALL WITH THIS SYSTEM WITH MORE OF A
REINFORCING SHOT OF COLD AIR. DID LEAVE SLIGHT CHANCE TO CHANCE
POPS FOR NOW GIVEN UNCERTAINTIES WITH TIMING. HOWEVER...AT THIS
POINT...ONCE THE FRONT PASSES OVER THE REGION ON SATURDAY...ANY
REMAINING CLOUDS LOOK TO QUICKLY DISSIPATE. TEMPS WILL THEN BE
COOLER IN THE 40S AS HIGHS ON SUNDAY GIVEN THE CAA BEHIND THE FRONT.
THE MOVEMENT OF THE HIGH PRESSURE SYSTEM TO THE NORTHEAST WILL ALLOW
SOUTHERLY FLOW TO RE-DEVELOP RESULTING IN WARMER CONDITIONS ON
MONDAY. THOUGH INTRIGUING TO NOTE AT THIS JUNCTURE...ANOTHER
SUBTROPICAL JET SETUP WITH A STRONG TROUGH SENDING WAVES OF MOISTURE
ACROSS THE SOUTHEAST...LOOKS TO DEVELOP LATE DAY 7/8.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...FLOOD WATCH THROUGH THIS EVENING FOR THE FOLLOWING ZONES:
COLBERT...CULLMAN...DE KALB...FRANKLIN AL...JACKSON...
LAUDERDALE...LAWRENCE...LIMESTONE...MADISON...MARSHALL...
MORGAN.
TN...FLOOD WATCH THROUGH THIS EVENING FOR THE FOLLOWING ZONES:
FRANKLIN TN...LINCOLN...MOORE.
&&
$$
SS
