520 
FXUS64 KHUN 121449 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
949 AM CDT TUE MAR 12 2013

.UPDATE...
MORNING UPDATE.

&&

.DISCUSSION...
TEMPERATURES ACROSS THE TENNESSEE VALLEY THIS MORNING ARE CURRENTLY
IN THE UPPER 30S TO AROUND 40, AND ARE ON TRACK TO TOP OUT IN THE
MIDDLE TO UPPER 50S THIS AFTERNOON. HIGH PRESSURE IS BUILDING INTO
THE REGION FROM THE SOUTHWEST, WITH A DEPARTING SFC LOW OVER THE
CAROLINAS. IN THE UPPER LEVELS THIS MORNING, TROUGHING ENCOMPASSES
MUCH OF THE NORTHERN CONUS WITH AN UPPER LOW SLIDING SOUTHEASTWARD
FROM THE HIGH PLAINS. A DISTURBANCE IN U/L FLOW HAS DEVELOPED
MID/HIGH CLOUDS OVER THE TX/OK PANHANDLES, BUT THIS ACTIVITY WILL
LIKELY NOT MAKE IT INTO THE FORECAST AREA UNTIL AFTER SUNSET. 

AS SUCH, HAVE ONLY MADE MINOR TWEAKS TO THE CURRENT SKY COVER GRID
TO ACCOUNT FOR CLEAR TRENDS IN NW AL AND DISSIPATING CLOUD COVER OVER
NE AL. ALL OTHER WX ELEMENTS OF THE FORECAST ARE IN GREAT SHAPE AND
NO OTHER ADJUSTMENTS ARE NECESSARY.

WILL FRESHEN WORDING IN ZONES AND RESEND THEM SHORTLY.

12

&&

.AVIATION...
/ISSUED 629 AM CDT TUE MAR 12 2013/
FOR 12Z TAFS... 
MVFR CLOUDS ACROSS MIDDLE/EASTERN TENNESSEE AND NE ALABAMA SHOULD
DISSIPATE SHORTLY AFTER DAYBREAK. OTHERWISE AND ELSEWHERE...VFR
CONDITIONS SHOULD PREVAIL THROUGH THE PERIOD. NW WINDS AROUND 10KT
FOR MUCH OF THE DAY SHOULD BECOME LIGHT FROM THE NW TUE EVENING.

RSB

&&

.PREVIOUS DISCUSSION...
/ISSUED 230 AM CDT TUE MAR 12 2013/
A FAR DIFFERENT WX PATTERN IN PLACE ACROSS THE REGION THIS EARLY TUE 
MORNING COMPARED TO YESTERDAY...WITH QUIET AND MORE SEASONAL LIKE 
CONDITIONS ONGOING. TRAILING LOW CLOUDS CONTINUE TO PUSH EWD ACROSS 
MID TN LEADING INTO NE AL...AS A BROAD UPPER TROUGH PATTERN ACROSS 
THE ERN CONUS GRADUALLY SHIFTS EWD. THIS CLEARING TREND SHOULD 
CONTINUE PAST DAYBREAK...AS A STRONG DOME OF POLAR HIGH PRESSURE OUT 
OF THE NRN PLAINS GRADUALLY BUILDS SWD INTO THE SE REGION. WITH THE 
SFC HIGH SETTLING INTO THE REGION HEADING INTO MID WEEK...QUIET AND 
SLIGHTLY BELOW NORMAL TEMPS LOOK TO PREVAIL ACROSS THE TN VALLEY. 
WITH THE UPPER TROUGH AXIS EXITING TO THE E...DEVELOPING NW FLOW 
PATTERN SHOULD AID IN THE TRANSPORT OF MOD POLAR AIR INTO THE AREA.

THE LATEST MODEL SUITES ARE HINTING AT SOME KIND OF WEAK DISTURBANCE 
EMBEDDED WITHIN THE NWLY FLOW ALOFT TRAVERSING ACROSS THE MIDWEST/OH 
VALLEY REGIONS THU/THU NIGHT...WITH PERHAPS SOME OF THIS ENERGY AND 
MOISTURE SKIRTING THE ERN HALF OF THE AREA. PROBABLY A LITTLE TOO 
EARLY TO BUY INTO THIS SCENARIO YET PENDING FURTHER MODEL RUNS. THIS 
MAY AT LEAST RESULT IN AN INCREASE IN CLOUD COVER THOUGH GOING INTO 
THU NIGHT. IF THE GLOBAL MODELS CONTINUE THIS TREND OVER THE NEXT 
DAY OR SO...THEN SOME LIGHT RAIN OR PERHAPS EVEN A LIGHT WINTRY MIX 
MAY BE WARRANTED THU NIGHT.

HEADING TOWARD THE END OF THE WORK WEEK...THE SFC HIGH ACROSS THE SE 
STATES SHOULD BEGIN TO WEAKEN AND TRANSLATE EWD AS A WEAK AMPLIFYING 
TROUGH PATTERN RETURNS TO THE MID/SRN PLAINS. THIS WOULD ALLOW FOR 
THE ONSET OF A GRADUAL WARMING TREND...AS RETURN FLOW DEVELOPS OVER 
THE CNTRL GULF REGION. AS THIS NEXT UPPER TROUGH AXIS DIGS SWD...THE 
LATTER HALF OF THE MODELS ARE SUGGESTING THE FIRST OF TWO FRONTAL 
BOUNDARIES PUSHING INTO THE REGION SAT/SUN. THIS FIRST SFC BOUNDARY 
LOOKS TO STALL ACROSS TN...WITH LIGHT RAIN/SHOWERS DEVELOPING ALONG 
THE FRONTAL PROGRESSION. THE SECOND AND STRONGER OF THE TWO FRONTS 
THEN LOOKS TO SWEEP THROUGH THE AREA MON...WITH SCT SHOWERS/TSTMS 
DEVELOPING ALONG/AHEAD OF THIS NEXT BOUNDARY AND POSSIBLE SFC WAVE. 
THERE IS OF COURSE SOME DISCREPANCY WITH THE OVERALL STRENGTH AND 
TIMING OF THIS NEXT SYSTEM BETWEEN THE GLOBAL MODELS HEADING INTO 
THE WEEKEND PERIOD...ALTHOUGH HOPEFULLY THE GENERAL CONSENSUS WILL 
IMPROVE OVER THE NEXT COUPLE OF DAYS.

09

&&

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

$$ 

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