FXUS64 KHUN 302343 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
543 PM CST MON NOV 30 2009

.UPDATE...
FOR 00Z TAFS...

&&

.AVIATION...
WINDS ARE DIMINISHING...AND WILL TURN TO THE EAST BY THE END OF
THE FORECAST. SKIES ARE CLEARING ACROSS THE AREA...AND SHOULD
FULLY TRANSITION TO SKC CONDITIONS BY DAYBREAK.

&&

.PREV DISCUSSION... /ISSUED 346 PM CST MON NOV 30 2009/ 

DISCUSSION...
A DYNAMIC WEATHER PATTERN AND FAIRLY CHALLENGING FCST FOR THE MIDDLE 
OF THE WEEK...FOLLOWED BY A RELATIVELY QUIET BUT COLD PATTERN FOR 
THE REMAINDER OF THE FCST. WHILE THE EXACT TRACK OF THE POTENT 
SYSTEM FOR MID-WEEK REMAINS A BIT ELUSIVE...MODEL GUIDANCE IS 
NARROWING IN ON A PROJECTED PATH. THIS IS IMPORTANT...AS SPECIFIC 
SENSIBLE WX IMPACTS WILL BE DEPENDENT ON THIS TRACK. AFTERWARDS...A 
RATHER PROLONGED PERIOD OF COLD TEMPS BUT MOSTLY DRY WEATHER IS 
EXPECTED FOR THE REGION.

SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)...
THE COLD FRONT THAT BROUGHT RAINFALL TO THE AREA LAST NIGHT AND THIS 
MORNING NOW LIES GENERALLY ALONG A LINE FROM GSP...THROUGH ATL...TO 
MGM. THE CLEARING LINE BEHIND THE FRONT IS NOW ENTERING NWRN 
AL...AND OUR NWRN COMMUNITIES MAY SEE A LITTLE SUNSHINE BEFORE 
NIGHTFALL. LOW CLOUDS WILL GRADUALLY DECREASE IN COVERAGE FROM NW TO 
SE AS THE EVENING PROGRESSES...WITH SERN AREAS CLEARING OUT BY 
MIDNIGHT. TEMPS AND DEW POINTS WILL CONTINUE TO DECREASE AS COLD/DRY 
AIR ADVECTION CONTINUE...BUT IT WAS NOTED THAT THE DEWPOINT GRADIENT 
DECREASES JUST UPSTREAM. IT LOOKS LIKELY THAT MOST AREAS WILL SEE 
DEW POINT TEMPS IN THE LOW 30S BY DAYBREAK. WINDS WILL BECOME LIGHT 
LATER TONIGHT AS THE SFC RIDGE BUILDS TO OUR NORTH. GIVEN THAT TEMPS 
WILL BE STARTING OUT IN THE MID 40S IN MOST AREAS THIS 
EVENING...THINK THAT LOWS IN THE LOW/MID 30S LOOK REASONABLE FOR THE 
OVERNIGHT. FCST WILL THUS LEAN TOWARDS LOWER VALUES OFFERED BY MET 
MOS. 

AN UPR-LOW SITUATED OVER NWRN MEXICO WILL MOVE SLOWLY TO THE EAST 
TONIGHT THROUGH TUESDAY AS A TROUGH BEGINS TO DIG INTO THE 
INTER-MOUNTAIN WEST. SFC CYCLOGENESIS WILL TAKE PLACE IN THE WRN 
GULF OF MEX ON TUES AS THE UPR LOW SHIFTS EWRD INTO TX. AS THE 
UPR-LOW BECOMES INCREASINGLY AFFECTED BY THE DIGGING N CENTRAL CONUS 
TROUGH...IT WILL BEGIN TO MAKE A JOG TO THE NE...WITH THE SFC LOW 
FOLLOWING SUIT. AS STATED ABOVE...WHILE THE EXACT TRACK REMAINS A 
BIT UNKNOWN...THE LIKELIEST PATH AT THIS POINT TAKES IT PERHAPS 
THROUGH NWRN AL OR JUST TO THE WEST OF THE BORDER. THIS IS SLIGHTLY 
FURTHER WEST FROM PREVIOUS TRACKS...WHICH WILL PLACE OUR AREA IN A 
MORE FAVORABLE LOCATION FOR RAINFALL/WINDS/INSTABILITY. 

RAINFALL SHOULD BEGIN BY MIDNIGHT OR SHORTLY THEREAFTER IN OUR SWRN 
AREAS AND SPREAD NWRD...AS A 50KT SRLY LOW-LVL JET SPREADS MOISTURE 
QUICKLY ACROSS THE REGION. AIDED BY A FAVORABLE 
DYNAMIC/THERMODYNAMIC SITUATION...THE LOW IS EXPECTED TO STRENGTHEN 
QUICKLY AS IT LIFTS NWRD FROM THE GULF AND INTO THE TN VALLEY. 
ISALLOBARIC FORCING WILL ADD TO THE STRENGTHENING PRESSURE GRADIENT 
TO PRODUCE POTENTIALLY STRONG WINDS/WIND GUSTS ACROSS THE AREA. 
SUSTAINED WINDS MAY EXCEED 25 MPH WITH GUSTS OVER 35 
MPH...ESPECIALLY IN OUR HIGHER TERRAIN ON WED MORNING. AS THE LOW 
LIFTS FURTHER NWRD INTO TN...INSTABILITY IN THE DEVELOPING WARM 
SECTOR MAY BE SUFFICIENT TO PRODUCE LTG IN ERN AL/GA. ALTHOUGH
PARCELS WILL LIKELY NOT BE SFC BASED...COULDN'T RULE OUT A TSRA
FROM ELEVATED CONVECTION IN OUR ERN COUNTIES. SO...THIS WAS ADDED
TO THE FCST.

AS FAR AS TEMPS ARE CONCERNED...OVERNIGHT LOWS ARE LIKELY TO BE 
REACHED ON TUES EVENING...WITH TEMPS GRADUALLY RISING DURING THE 
EARLY MORNING WED AS WINDS/CLOUDS INCREASE. GRIDS WERE TAILORED TO 
DEMONSTRATE THIS. TEMPS MAY REACH THE UPR 50S TO NEAR 60F ON WED 
BEFORE THE COLD FRONT CROSSES THE AREA. MOISTURE WRAPPING AROUND 
BEHIND THE MATURE SYSTEM SHOULD CROSS THE AREA AS IT LIFTS 
NEWD...AND GENERATE MORE -RA OR DRIZZLE FROM WED NIGHT INTO THURS 
MORNING. 

LONG TERM (THURSDAY THROUGH SUNDAY)...
MAINLY COLD ADVECTION WILL CONTINUE THROUGH THE LONG TERM PORTION OF 
THE FCST AS AN UPR VORTEX REMAINS CENTERED OVER ONTARIO. A 
REINFORCING SHOT OF COLD AIR WILL MOVE ACROSS THE AREA ON SAT 
MORNING. MORNING LOWS THROUGH THE PERIOD ARE LIKELY TO BE IN THE 20S 
AREA-WIDE ON FRI/SAT MORNING...WITH AFTN HIGHS MAINLY IN THE 
40S...PERHAPS RISING INTO THE 50S ON SUNDAY. THIS WILL BE THE FIRST 
HARD FREEZE EPISODE FOR MANY OF OUR ALABAMA LOCATIONS. 

MUCH FURTHER OUT...LONGER RANGE GUIDANCE DOES INDICATE A
CONDUCIVE PATTERN FOR SIGNIFICANT COLD AIR INTRUSIONS INTO THE
CONUS BY THE END OF NEXT WEEK. A STRONG RIDGE IS PROJECTED TO
BUILD WELL NWRD THROUGH ALASKA...RESULTING IN A HIGH AMPLITUDE REX
BLOCK IN THE PACIFIC...AND A HIGH AMPLITUDE TROUGH WITH ARCTIC AIR
SPILLING INTO CANADA AND THE LOWER 48. I AM MENTIONING THIS
BECAUSE IT HAS BEEN A PERSISTENT PATTERN IN THE LONG RANGE
GUIDANCE AND IS BACKED UP BY TELECONNECTIONS. FOR NOW...JUST
SOMETHING TO KEEP AN EYE ON.

&&

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

$$

AVIATION...99
PREV DISCUSSION...KDW
DISCUSSION...JMC.34