445  
FXUS64 KHUN 190420 AAC  
AFDHUN  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
1120 PM CDT FRI AUG 18 2017  
   
UPDATE
 
 
FOR 06Z TAFS.  
 

 
   
NEAR TERM
 
(REST OF TONIGHT)  
ISSUED AT 938 PM CDT FRI AUG 18 2017  
 
QUIET WEATHER CONDITIONS EXIST ACROSS THE CWFA THIS EVENING, AND  
SHOULD PERSIST OVERNIGHT AS A WEAK SURFACE RIDGE TRANSLATES EASTWARD  
IN THE WAKE OF THE COLD FRONTAL PASSAGE EARLIER TODAY. WELL TO THE  
NORTHWEST OF OUR REGION, A MID-LEVEL SHORTWAVE TROUGH IS FORECAST TO  
DIG SOUTHEASTWARD...REACHING THE SOUTHERN GREAT LAKES AND LOWER OH  
VALLEY BY 19/12Z. SCATTERED MID AND HIGH-LEVEL CLOUDS PRECEDING THE  
TROUGH WILL BEGIN TO SPREAD EASTWARD ACROSS THE TN VALLEY AFTER  
MIDNIGHT, AND MAY INHIBIT RADIATIONAL COOLING JUST ENOUGH TO PREVENT  
THE DEVELOPMENT OF WIDESPREAD FOG...ESPECIALLY GIVEN THE ADVECTION OF  
DRIER AIR INTO THE REGION EARLIER THIS AFTERNOON. NONETHELESS,  
CONDITIONS WILL BE FAVORABLE FOR FOG FORMATION IN RIVER VALLEYS AND  
NEAR LARGE BODIES OF WATER...ESPECIALLY BETWEEN 08-13Z...AND THIS HAS  
BEEN INCLUDED IN THE UPDATED WEATHER GRIDS. OTHER ELEMENTS OF THE  
FORECAST APPEAR TO BE ON TRACK AT THIS POINT, WITH ONLY A MINOR  
INCREASE IN MINIMUM TEMPS MADE TO REFLECT THE INTRODUCTION OF MORE  
CLOUDS AFTER MIDNIGHT.  
   
SHORT TERM
 
(SATURDAY THROUGH SUNDAY NIGHT)  
ISSUED AT 247 PM CDT FRI AUG 18 2017  
 
THE UPPER TROUGH AXIS WILL MOVE EAST OF THE FORECAST AREA BY THE  
AFTERNOON HOURS ON SATURDAY. DESPITE THE SLIGHT INCREASE IN  
MOISTURE, LITTLE IN THE WAY OF FORCING IS EXPECTED AND THEREFORE DO  
NOT ANTICIPATE ANY SHOWERS AND THUNDERSTORMS DEVELOPING DURING THE  
DAY. MEANWHILE, A COLD FRONT TO OUR NORTH WILL SHIFT THROUGH THE  
AREA, BRINGING A REINFORCING SHOT OF DRIER AIR ACROSS THE REGION.  
MODELS ARE HINTING AT AN MCS MOVING ACROSS THE WESTERN SECTION OF  
THE FORECAST AREA LATE SATURDAY AFTERNOON, HOWEVER DUE TO THE DRY  
AIR IN PLACE, DO NOT FEEL CONFIDENT ENOUGH TO ADD SHOWERS AND  
THUNDERSTORMS BACK INTO THE FORECAST. BY SUNDAY, THE AXIS OF AN  
UPPER LEVEL RIDGE WILL BEGIN TO BUILD NORTHWARD ACROSS THE AREA,  
WITH LIGHT FLOW KEEPING MOISTURE ADVECTION LIMITED. THUS, ANOTHER  
DRY DAY IS EXPECTED AGAIN ON SUNDAY. TEMPERATURES THROUGH THE PERIOD  
WILL GENERALLY BE NEAR SEASONAL NORMS. SKIES ARE EXPECTED TO REMAIN  
MOSTLY CLEAR AND WITH SLIGHT HEIGHT RISES, HIGHS WILL WARM INTO THE  
UPPER 80S TO LOWER 90S. MEANWHILE, OVERNIGHT LOWS WILL DROP INTO THE  
UPPER 60S TO LOWER 70S.  
   
LONG TERM
 
(MONDAY THROUGH THURSDAY)  
ISSUED AT 247 PM CDT FRI AUG 18 2017  
 
THE EXTENDED WILL START OFF WITH THE MOST ANTICIPATED FORECAST OF  
THE WEEK...FOR THE ECLIPSE. ECLIPSE VIEWERS ACROSS OUR AREA SHOULD BE  
IN GOOD SHAPE WITH MOSTLY CLEAR SKIES AND ISOLATED COVERAGE OF  
DIURNAL SHOWERS AND THUNDERSTORMS. A RIDGE BUILDING WESTWARD ACROSS  
THE SOUTHEAST ON MONDAY WILL BRING BACK SOUTHERLY FLOW AND KEEP TEMPS  
IN THE LOWER 90S. ON TUESDAY, WITH ADDITIONAL MOISTURE AND TEMPS  
STILL IN THE LOWER 90S, SCATTERED COVERAGE OF DIURNAL SHOWER/STORMS  
ARE EXPECTED WITH A HEAT INDEX AROUND 100 DEGREES.  
 
AS A SFC LOW LIFTS INTO THE GREAT LAKES TUESDAY NIGHT/WEDNESDAY, THE  
TRAILING COLD FRONT WILL MAKE WAY INTO THE TN VALLEY BY WEDNESDAY  
NIGHT/THURSDAY. THIS WILL BRING A GREATER COVERAGE OF SHOWERS AND  
THUNDERSTORMS ACROSS THE AREA WEDNESDAY/WEDNESDAY NIGHT. BEHIND THE  
FRONT, TEMPS WILL BE A FEW DEGREES LOWER IN THE UPPER 80S, BUT  
LOOKING MORE FORWARD TO THE DEWPOINTS DROPPING INTO THE 60S!  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 1100 PM CDT FRI AUG 18 2017  
 
VFR/SKC CONDITIONS WILL PERSIST AT BOTH HSV/MSL INTO THE OVERNIGHT  
PERIOD IN THE WAKE OF A COLD FRONT WHICH PUSHED SWD THRU THE REGION  
EARLIER TODAY. HOWEVER, A HIGH-LEVEL TROUGH CURRENTLY ACROSS THE  
UPPER MS VALLEY IS EXPECTED TO CONTINUE SPREADING ESEWD INTO THE  
CENTRAL APPALACHIANS OVER THE COURSE OF THE TAF PERIOD. SCT-OCNLY BKN  
ALTOSTRATUS ASSOCIATED WITH THIS TROUGH AXIS SHOULD BEGIN TO MOVE  
ACROSS THE REGION AFTER MIDNIGHT. ALTHOUGH CLOUD BASES WILL LIKELY BE  
IN THE 10-15 KFT RANGE, THE PRESENCE OF THESE CLOUDS COUPLED WITH A  
DRIER BOUNDARY LAYER SHOULD REDUCE THE THREAT FOR FOG.  
OCCASIONAL/MINOR VSBY REDUCTIONS IN THE -BR CAT WILL STILL BE PSBL  
BTWN 08-13Z, ALTHOUGH THE PROB REMAINS FAIRLY LOW ATTM. SCT CU SHOULD  
DEVELOP ARND 17Z AS LOW-LEVEL MOISTURE SLOWLY RETURNS TO THE REGION  
AHEAD OF THE UPPER TROUGH PASSING TO OUR NORTH. A FEW SHRA/TSRA WILL  
ALSO BE PSBL TOMORROW AFTN AS THE TROUGH AXIS MAKES ITS CLOSEST  
APPROACH TO OUR REGION, BUT THREAT IS TOO REMOTE TO INCLUDE IN THE  
FORECAST ATTM. SFC WINDS WILL REMAIN LIGHT/VRB THRU THE TAF PERIOD.  
 

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

 
 

 
 
NEAR TERM...70/DD  
SHORT TERM...73  
LONG TERM...JMS  
AVIATION...70/DD  
 
FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE  
AT WEATHER.GOV/HUNTSVILLE.  
 
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