338  
FXUS64 KHUN 170247  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
847 PM CST SAT DEC 16 2017  
   
NEAR TERM
 
(TONIGHT)  
ISSUED AT 847 PM CST SAT DEC 16 2017  
 
LOW PRESSURE SYSTEM AND ATTENDANT WARM FRONT ARE SLOWLY MAKING THEIR  
WAY NWD ACROSS THE WRN GULF TOWARD S LA THIS SAT EVENING. DEVELOPING  
RAIN/SHOWERS HAVE BEEN CONFINED N OF THE SFC LOW INTO EXTREME SE TX/W  
LA. IT'S CERTAINLY GOING TO BE A LITTLE BIT LONGER BEFORE THIS PRECIP  
SPREADS MORE INTO THE LOWER MS VALLEY AND CLOSE TO NW AL. IN FACT,  
INTERMEDIATE MODEL GUIDANCE REALLY DOESN'T SHOW THE RAINFALL GETTING  
INTO EXTREME NW AL UNTIL CLOSER TO DAYBREAK SUN. GIVEN THIS TREND  
COUPLED WITH SOME FAIRLY DRY AIR REMAINING IN PLACE ACROSS THE CNTRL  
TN VALLEY, AS EVIDENCED BY DEW PTS STILL IN THE UPPER 20S/LOWER 30S,  
HAVE BACKED OFF ON RAIN CHANCES OVERNIGHT TO JUST A SLIGHT CHC MAINLY  
FOR NW AL. EVEN WITH MID/HIGH CLOUDS STREAMING INTO THE AREA AHEAD OF  
THE WRN GULF SYSTEM, TEMPS HAVE ALREADY MANAGED TO DROP INTO THE  
MID/LOWER 30S IN SOME LOCATIONS, WITH LOWER 40S IN PLACE AT OTHER  
SPOTS. AS SUCH, HAVE ALSO ADJUSTED THE OVERNIGHT LOWS A FEW DEGREES  
IN SOME AREAS BASED ON THESE LATEST TRENDS, WHERE EARLY MORNING TEMPS  
SUN NOW MAINLY LOOK TO BE IN THE LOWER/MID 30S.  
   
SHORT TERM
 
(SUNDAY THROUGH MONDAY)  
ISSUED AT 245 PM CST SAT DEC 16 2017  
 
WARM AIR ADVECTION WILL CONTINUE TO TAKE PLACE RAPIDLY AS A WARM  
FRONT ADVANCES NE WITH THE AFOREMENTIONED UPPER-TROUGH. A 40-50 KT  
LLJ WILL ROTATE NE WITH THESE FEATURES AROUND 12-15Z ON SUNDAY  
MORNING, PLACING MUCH OF NORTHERN ALABAMA AND SOUTHERN MIDDLE  
TENNESSEE IN THE RIGHT FRONT ENTRANCE REGION. THIS ENHANCED LIFT WITH  
THE JET AND FRONT SHOULD HELP TO GENERATE A LARGE SHIELD OF MODERATE  
RAIN ACROSS THE ENTIRE REGION SUNDAY MORNING INTO EARLY/MID SUNDAY  
AFTERNOON. AS THIS FEATURE LIFTS NE INTO THE PLATEAU REGION OF  
TENNESSEE AND KENTUCKY, RAIN CHANCES WILL FAVOR AREAS ACROSS FAR  
NORTHEAST ALABAMA INTO EAST TENNESSEE, AND GRADUALLY TAPER OFF FROM  
WEST TO EAST BY LATE AFTERNOON TO EARLY EVENING.  
 
MAY SEE A FEW LIGHT SHOWERS AFTER SUNSET, ESPECIALLY AREAS EAST OF  
I-65 AND SOUTH OF THE TENNESSEE RIVER. HOWEVER, POPS SHOULD REALLY  
TAPER OFF, ESPECIALLY AFTER MIDNIGHT. THIS WILL RESULT IN SIMPLY AN  
OVERCAST SKY AND A MUCH MILDER AIR MASS (WITH HIGHER RH VALUES AND  
DEWPOINTS). AS A RESULT, TEMPERATURES SUNDAY NIGHT WILL STRUGGLE TO  
DROP MUCH AT ALL, BOTTOMING OUT IN THE UPPER 40S. WILL MAINTAIN A  
SIMILAR FLOW PATTERN FOR MONDAY, BUT A SECONDARY JET IMPULSE WILL  
REMAIN SOUTH OF THE THE AREA. THUS, ONLY AN ISOLATED SHOWER EXPECTED  
AND MAINLY SOUTH OF THE TENNESSEE RIVER. TEMPERATURES, HOWEVER, WILL  
BE MILD, WITH HIGHS PEAKING IN THE LOWER 60S.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 245 PM CST SAT DEC 16 2017  
 
A SUBTROPICAL RIDGE TO THE SOUTH WILL MAINTAIN THE MOIST FETCH OFF  
THE GULF OF MEXICO AND GENERALLY AT/ABOVE NORMAL TEMPERATURES THROUGH  
MOST OF THE WORK WEEK AHEAD. HOWEVER, IT APPEARS THERE WILL BE BETTER  
OPPORTUNITIES FOR SHOWERS (AND PERHAPS SOME SCATTERED  
THUNDERSTORMS), ESPECIALLY LATER IN THE WEEK. POPS WILL INCREASE  
TUESDAY AFTERNOON INTO TUESDAY AHEAD OF A MID-LEVEL SHORTWAVE  
TRACKING FROM THE SOUTHERN PLAINS OF TEXAS INTO THE RED RIVER VALLEY.  
WE MAY SEE ENOUGH BREAKS IN THE CLOUDS TO ALLOW FOR ENOUGH HEATING,  
AND THUS INSTABILITY TO DEVELOP ON TUESDAY AFTERNOON. THEREFORE,  
HAVE ADDED SOME ISOLATED TO SCATTERED THUNDER IN THE FORECAST. THE  
BEST CHANCES FOR WIDESPREAD RAINFALL WILL BE TUESDAY NIGHT THROUGH  
WEDNESDAY EVENING AS THE SHORTWAVE PASSES THROUGH THE TENNESSEE  
VALLEY AND EXITS INTO THE SOUTHERN APPALACHIANS. AROUND 1 INCH TO  
PERHAPS 1.5 INCHES OF QPF IS POSSIBLE FROM TUESDAY THROUGH EARLY  
THURSDAY FROM THIS SYSTEM, GIVING US SOME MUCH NEEDED RAINFALL AFTER  
THE PAST COUPLE OF DRY MONTHS WE'VE EXPERIENCED.  
 
BEHIND THIS SHORTWAVE, A BRIEF BOUT OF DRIER AIR SHOULD MOVE IN FOR  
THURSDAY AS THE UPPER RIDGE AXIS OVER THE GULF BUILDS NORTHWARD INTO  
ALABAMA AND TENNESSEE. THURSDAY MAY BE OUR BEST BET FOR SOME DECENT  
SUNSHINE AND HEATING, WITH HIGHS RETURNING TO THE LOW TO MID 60S.  
MODELS ARE, HOWEVER, HINTING AT THE POTENTIAL FOR ANOTHER LONGWAVE  
TROUGH TO DEVELOP OVER THE GREAT PLAINS LATE IN THE PERIOD. THE  
MAGNITUDE OF THIS SYSTEM AND ITS EXACT TRACK ARE FAIRLY UNCERTAIN.  
THIS STORM SYSTEM WILL DRAG A STRONGER COLD FRONT SOUTH FROM THE  
NORTHERN PLAINS AND POTENTIALLY INTO THE OZARKS AND PORTIONS OF THE  
LOWER MISSISSIPPI VALLEY. ADDED LIFT AND MOISTURE FETCH OFF THE GULF  
SHOULD GIVE US A DECENT SHOT FOR SHOWERS (AND SOME THUNDER) AGAIN ON  
FRIDAY. HOWEVER, THE COLDER AIR WILL BE DISPLACED WELL TO THE NW  
THROUGH AT LEAST FRIDAY NIGHT. MODELS DIVERGE A BIT MORE BEHIND THIS  
ON HOW FAR SOUTH THE AFOREMENTIONED COLD FRONT WILL MAKE IT, BUT  
THAT IS BEYOND THE OFFICIAL FORECAST PERIOD FOR NOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)  
ISSUED AT 530 PM CST SAT DEC 16 2017  
 
MID/HIGH CLOUDS CONTINUE TO STREAM NEWD ACROSS THE AREA, AS AN AREA  
OF LOW PRESSURE DEVELOPS IN THE WRN GULF. CIGS WILL BEGIN TO LOWER  
CLOSER TO THE 4-5K FT RANGE OVERNIGHT, AS THE SFC LOW AND ATTENDANT  
WARM FRONT BEGIN TO LIFT NWD INTO THE LOWER MS VALLEY. RA/SHRA ARE  
THEN XPCTED TO SPREAD W TO E ACROSS THE AREA STARTING SUN MORNING,  
WITH MVFR CONDS DEVELOPING AS CIGS LOWER FURTHER INTO THE 2-3K FT  
RANGE AND VIS FALL INTO THE 4-5SM RANGE. VIS MAY BRIEFLY LOWER INTO  
THE 2-3SM RANGE AROUND 15-20Z, WITH CIGS FALLING BELOW 2K FT AT  
TIMES, AS THE BULK OF THE PRECIP MOVES INTO THE AREA. RA/SHRA SHOULD  
BEGIN TO TAPER OFF FROM THE W LATE SUN AFTERNOON, ALTHOUGH MVFR CIGS  
LOOK TO REMAIN IN PLACE THRU THE END OF THE TAF PERIOD. SFC WINDS  
WILL INCREASE INTO THE 10-12KT RANGE WITH HIGHER GUSTS ALONG/JUST  
AHEAD OF THE ADVANCING PRECIP.  
 

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

 
 

 
 
NEAR TERM...09  
SHORT TERM...AMP.24  
LONG TERM...AMP.24  
AVIATION...09  
 
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