824  
FXUS64 KHUN 251225  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
725 AM CDT SAT MAR 25 2017  
   
UPDATE
 
 
FOR 12Z TAFS.  
 

 
   
NEAR TERM
 
(TODAY)  
ISSUED AT 553 AM CDT SAT MAR 25 2017  
 
ACTIVE WX STILL XPCTED TO SPREAD EWD INTO THE CNTRL TN VALLEY LATER  
TODAY ALONG/AHEAD OF AN ADVANCING COLD FRONT OUT OF THE MID/SRN  
PLAINS STATES. STRONG SLY FETCH PATTERN IS BECOMING BETTER ENTRENCHED  
ACROSS THE REGION, AS H85 FLOW INCREASES INTO THE 40-50KT RANGE. THE  
FRONTAL BOUNDARY/ASSOCIATED STORM SYSTEM ARE BEING DRIVEN BY A POTENT  
UPPER LOW/TROUGH PATTERN OVER THE MID PLAINS. AS THIS SYSTEM BEGINS  
TO LIFT NEWD INTO THE MIDWEST STATES, THE PARENT SFC LOW WILL ALSO  
TRANSLATE INTO THE MO VALLEY AS THE ATTENDANT COLD FRONT TRACKS EWD  
INTO THE LOWER MS/TN VALLEY REGIONS. DEEP LAYER SHEAR AHEAD OF THE  
SFC BOUNDARY LOOKS TO BE IN THE 40-50KT RANGE, ALTHOUGH HIGHER  
BUOYANCY VALUES WILL BE DISPLACED TO THE SW IN AN AREA OF HIGHER DEW  
PTS/INSTABILITY. NEVERTHELESS, INCREASING MID/UPPER FORCING RESULTING  
FROM THE SHRTWV LIFTING INTO THE MIDWEST REGION MAY ALLOW FOR SOME  
ENHANCED DOWNWARD MOMENTUM TRANSFER IN A FEW OF THE STRONGER/MARGINALLY  
SEVERE TSTMS. LOCATIONS ALONG/W OF THE I-65 CORRIDOR WILL HAVE THE  
BETTER CHC OF ANY STRONG/SVR TSTMS THIS AFTERNOON, MAINLY IN A SQUALL  
LINE/BOWING COMPLEX, WITH THE PRIMARY THREATS BEING DAMAGING WIND GUSTS  
AND LARGE HAIL. A VERY LOW TORNADO THREAT EXISTS PROVIDED INDIVIDUAL  
STORM CELLS FORM AHEAD OF THE MAIN LINE OR BOOKEND VORTICES DEVELOP  
WITHIN BREAKS IN THE SQUALL LINE. OUTSIDE OF THE TSTM THREAT, SFC  
WINDS ARE XPCTED TO BE FAIRLY BREEZY AT TIMES, WITH S WINDS INCREASING  
AROUND 15-17MPH WITH HIGHER GUSTS.  
   
SHORT TERM
 
(TONIGHT THROUGH MONDAY NIGHT)  
ISSUED AT 553 AM CDT SAT MAR 25 2017  
 
THE COLD FRONT ITSELF FINALLY LOOKS TO CROSS INTO NW AL AT THE START  
OF THE EVENING PERIOD. THE INITIAL LINE OF SHOWERS/TSTMS IN ALL PROB  
WILL BE MOVING EWD INTO NE AL AND WEAKENING AS MID/UPPER FORCING  
WANE AS THE CONVECTIVE LINE MOVES FURTHER AWAY FROM THE UPPER SHRTWV.  
GOING INTO SUN, THE FRONT WILL CONTINUE TO GRADUALLY MAKE ITS WAY  
ACROSS THE TN VALLEY WITH SHOWERS/TSTMS AGAIN DEVELOPING ALONG/AHEAD  
OF THE SFC BOUNDARY. WHILE BULK/DEEP LAYER SHEAR ARE XPCTED TO BE  
WEAKER ON SUN, BUOYANT ENERGY/LOW LEVEL INSTABILITY LOOKS TO INCREASE  
OUT OF THE SW, AS THE UPPER TROUGH AXIS OVER THE MIDWEST/OH VALLEY  
STATES CONTINUES TO LIFT NEWD. WITH THE FRONT PROVIDING JUST ENOUGH  
OF A LIFTING SOURCE COUPLED WITH THE INCREASE IN LATENT HEATING,  
ENOUGH PARAMETERS SUGGEST THE POTENTIAL FOR STRONG/MARGINALLY SVR  
TSTM DEVELOPMENT AGAIN ON SUN WITH THE FRONTAL PASSAGE. MAIN WX  
THREATS AGAIN LOOK TO BE BRIEF DAMAGING WIND GUSTS AND SMALL HAIL.  
THE ACTIVE WX DOESN'T END WITH THE START OF THE NEW WORK WEEK, WITH  
THE LATEST MODEL SUITES HINTING AT ANOTHER AMPLIFYING UPPER TROUGH  
AXIS OUT OF THE MID PLAINS TRAVERSING EWD INTO THE SE REGION MON INTO  
TUE. THE SFC REFLECTION HAS A PARENT LOW MOVING EWD OUT OF THE SRN  
PLAINS AND INTO THE MIDWEST/OH VALLEY REGION BY TUE, WITH AN  
ATTENDANT FRONTAL BOUNDARY SETTLING INTO THE TN VALLEY AREA. SCT  
SHOWERS/TSTMS LOOK TO DEVELOP ALONG/AHEAD OF THIS NEXT FRONT, WITH A  
FEW STRONG/MARGINALLY SVR TSTMS POSSIBLE YET AGAIN ON MON AND WILL BE  
CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND HAIL.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 553 AM CDT SAT MAR 25 2017  
 
AN UNSETTLED WEATHER PATTERN WILL SET UP FOR THE EXTENDED FORECAST  
PERIOD. ON THE FLIP SIDE, WARMER THAN NORMAL TEMPS WILL STICK AROUND  
THROUGH THE WEEK!  
 
SHOWERS AND THUNDERSTORMS WILL LINGER INTO TUESDAY AS THE COLD FRONT  
MOVES THROUGH THE AREA. THEY WILL TAPER OFF FROM WEST TO EAST AS THE  
FRONT MOVES OUT AND A WEAK UPPER-LEVEL RIDGE BUILDS IN, KEEPING  
TUESDAY NIGHT DRY. THE GFS IS MORE WILLING TO PUSH THE FRONT INTO  
CENTRAL-SOUTH AL COMPARED TO THE ECMWF AT THIS TIME. WITH THE ECMWF  
NOT PUSHING THE FRONT AS FAR SOUTH AS THE GFS, INSTEAD IT GENERALLY  
STALLS THE FRONT IN THE GENERAL AREA INTO WEDNESDAY. ONLY INCLUDED  
ISOLATED POPS FOR MAINLY NE AL AND SO MID TN AT THIS TIME DURING THE  
AFTERNOON ON WEDNESDAY.  
 
AS THE NEXT STORM SYSTEM SWINGS OUT FROM THE FOUR CORNERS AREA ON  
WEDNESDAY, IT WILL PUSH THE SHORT LIVED RIDGE EASTWARD AND OUT OF THE  
REGION BY THURSDAY. HOW THE SYSTEM PROGRESSES ONCE IT MOVES INTO THE  
SOUTHERN PLAINS AND THEREAFTER WILL DEPEND ON WHICH MODEL YOU  
CHOOSE, AS THEY DIVERGE QUICKLY. MODELS DO AGREE THAT WE COULD START  
OFF WITH SOME SHOWERS/STORMS ON WED NIGHT/EARLY THURS MORNING, THEN  
THURS AFTERNOON/NIGHT IS WHEN THE MAIN LINE WILL MOVE THROUGH WITH  
PRECIP LINGERING INTO FRIDAY MORNING. HOWEVER, THE GFS DOES NOT KEEP  
A CLOSED LOW AND NEARLY SHEARS APART WHILE THE ECMWF KEEPS A CLOSED  
LOW BUT OPENS UP INTO A BROAD TROUGH AS IT LIFTS NE. SO WHEN THE  
SYSTEM DOES MOVE INTO THE REGION, THE GFS HAS IT ORIENTATED NE/SW  
WHERE GULF CONVECTION COULD CUT US OFF, OR THE ECMWF HAS A MORE N/S  
LINEAR SYSTEM MOVING IN. WILL LOOK FOR FURTHER MODEL CONSISTENCY  
WITH UPCOMING RUNS TO DETERMINE STORM STRENGTH.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 725 AM CDT SAT MAR 25 2017  
 
VFR CONDS CONTINUE AT THE TWO MAIN AIRPORTS ALTHOUGH THIS WILL BE  
CHANGING HEADING INTO THE LATE MORNING HRS AS A LINE OF SHRA/TSRA  
APPROACHES FROM THE W. MID/HIGH CLOUDS CONTINUE TO STREAM INTO THE  
AREA FROM THE SW, AS SFC WINDS TURN MORE TOWARD THE S NEAR 10KT WITH  
HIGHER GUSTS. CLOUD BASES ARE XPCTED TO LOWER CLOSER TO MVFR LEVELS  
AS THE CONVECTIVE LINE BEGINS TO MOVE EWD ACROSS THE AREA WHILE S  
WINDS INCREASE INTO THE 12-15KT RANGE WITH HIGHER GUSTS. BRIEF IFR  
CONDS/VIS ARE POSSIBLE IN/NEAR +SHRA/TSRA, MAINLY LATE THIS MORNING  
INTO THE EARLY AFTERNOON HRS. LINGERING VCSH SHOULD THEN PREVAIL INTO  
THE EVENING PERIOD, WITH SFC FLOW REMAINING OUT OF THE S NEAR 10KT  
WITH HIGHER GUSTS.  
 

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

 
 

 
 
NEAR TERM...09  
SHORT TERM...09  
LONG TERM...JMS  
AVIATION...09  
 
FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE  
AT WEATHER.GOV/HUNTSVILLE.  
 
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