438  
FXUS64 KHUN 280802  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
302 AM CDT WED JUN 28 2017  
   
NEAR TERM
 
(TODAY)  
ISSUED AT 302 AM CDT WED JUN 28 2017  
 
BENIGN WEATHER PATTERN CONTINUES EARLY THIS MORNING, WITH HIGH  
PRESSURE BUILT IN AT THE SURFACE AND A BROAD UPPER-TROUGH EXITING THE  
REGION TO THE EAST. THE DRIER AIR THAT FILTERED INTO THE REGION HAS  
MADE FOR A MOSTLY CLEAR SKY EARLY THIS MORNING, SAVE FOR A FEW HIGH  
CLOUDS PASSING OVERHEAD. THERE MAY BE ENOUGH BOUNDARY LAYER MOISTURE  
NEAR RIVERS/LAKES TO GET SOME LIGHT PATCHY FOG THIS MORNING, BUT  
GENERALLY THINK WE'LL STAY FREE OF IT IN MOST LOCATIONS. WITH THE  
RIDGE GENERALLY DOMINATING THINGS TODAY, THINK WE'LL GENERALLY SEE  
MOSTLY SUNNY CONDITIONS THROUGHOUT THE DAY GIVEN THE SUBSIDENCE  
TAKING PLACE. HOWEVER, WINDS WILL VEER TO THE SOUTHEAST AND  
EVENTUALLY TO THE SOUTH BY EARLY EVENING. THIS WILL SET THE STAGE FOR  
A GOOD RETURN FLOW OF GULF MOISTURE HEADING BACK INTO THE AREA IN  
THE COMING DAYS. WITH INCREASED THICKNESS VALUES/TEMPERATURES ALOFT,  
HIGHS WILL RUN ANYWHERE FROM 3-5 DEGREES HIGHER THAN YESTERDAY  
(GENERALLY IN THE MID TO UPPER 80S).  
   
SHORT TERM
 
(TONIGHT THROUGH FRIDAY NIGHT)  
ISSUED AT 302 AM CDT WED JUN 28 2017  
 
A RETURN OF A MUGGY, HUMID AIR MASS IS EXPECTED LATE THIS WEEK --  
ALONG WITH INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS. AS  
MENTIONED ABOVE, A GOOD RETURN FLOW FROM THE GULF OF MEXICO WILL  
SET-UP BY TONIGHT AS WINDS INCREASE FROM THE SOUTHWEST. A WEAK AREA  
OF LOW PRESSURE ALONG THE MS/LA GULF COAST MAY HELP TO GENERATE SOME  
SHOWER ACTIVITY ACROSS LOWER ALABAMA LATER TONIGHT THAT COULD  
POTENTIALLY DRIFT INTO OUR FAR SOUTHERN ZONES BY THURSDAY MORNING.  
THE MAIN GENERATOR OF PRECIPITATION ON THURSDAY, HOWEVER, WILL BE  
DAYTIME HEATING. THIS ACTIVITY WILL FAVOR THE HIGHER TERRAIN OF  
NORTHEAST ALABAMA AND WILL BE OUTFLOW DRIVEN ONCE IT GETS GOING.  
MODEL SOUNDINGS INDICATE SOME MODEST INSTABILITY AND LOW SHEAR VALUES,  
SO JUST THINK GENERAL THUNDER IN THE FORM OF PULSE CELLS IS THE MOST  
LIKELY STORM MODE. FEEL CONFIDENT ENOUGH TO GO LIKELY POPS ACROSS  
AREAS EAST OF I-65 (FAVORING THE TERRAIN OF SAND MOUNTAIN) BETWEEN  
18-00Z, WITH SOLID CHANCE POPS ELSEWHERE.  
 
A DEEPENING UPPER-TROUGH ACROSS THE GREAT LAKES WILL SEND A COLD  
FRONT SE TOWARD THE MISSISSIPPI VALLEY FRIDAY INTO FRIDAY NIGHT.  
THOUGH THIS BOUNDARY WILL REMAIN NW OF THE AREA, IT WILL SERVE AS A  
FOCUS FOR SHOWERS AND STORMS -- SOME OF WHICH MAY APPROACH THE REGION  
FROM THE WEST LATE FRIDAY NIGHT. AS FOR THE DAY ON FRIDAY, THE  
AFOREMENTIONED HIGH WILL SHIFT TO THE EAST, RESULTING IN LOWER  
THICKNESS VALUES AND A WEAKER CAP IN PLACE. THOUGH THERE IS NO TRUE  
FORCING MECHANISM IN PLACE, DIURNALLY DRIVEN CONVECTION WILL  
REDEVELOP ACROSS THE AREA BY EARLY AFTERNOON AND PERSIST WELL INTO  
THE EVENING. INSTABILITY PARAMETERS LOOK AT LITTLE BIT BETTER (WITH  
ML CAPES AROUND 1200 J/KG) WHICH COULD YIELD A STRONG STORM OR TWO  
CAPABLE OF SOME GUSTY WINDS AND LOCALLY HEAVY RAINFALL GIVEN THE VERY  
HIGH PWATS THAT WILL BE CLOSE TO 2 INCHES. MODEL SOLUTIONS DIVERGE A  
BIT FOR FRIDAY NIGHT, WITH THE GFS FAR MORE BULLISH ON HIGHER POPS  
AND QPF LATE INTO THE NIGHT (ESPECIALLY TOWARD THE WEST NEAR THE  
FRONT). FOR NOW, HAVE GONE WITH A BLEND TO HANDLE THIS (SLIGHTLY  
FAVORING THE DRIER NAM).  
 
ONE OTHER NOTE: DO HAVE FAIRLY GOOD CONFIDENCE THAT CLOUD COVER FOR  
THIS PERIOD WILL BE A LITTLE BIT HIGHER THAN PREVIOUSLY THOUGHT  
EARLIER THIS WEEK. THUS, THIS MAY KEEP HIGH TEMPERATURES A DEGREE OR  
TWO COOLER -- CLOSER TO THE MID 80S.  
 
   
LONG TERM
 
(SATURDAY THROUGH TUESDAY)  
ISSUED AT 302 AM CDT WED JUN 28 2017  
 
THIS WEEKEND IT LOOKS LIKE WE WILL BE CAUGHT IN THE MIDDLE OF A  
TROUGH MOVING ACROSS THE GREAT LAKES AND A SUBTROPICAL RIDGE  
CENTERED OVER THE EASTERN GULF OF MEXICO. THE RESULT OF WHICH IS A  
FEW DISTURBANCES MOVING BETWEEN THESE FEATURES AND ACROSS THE TN  
VALLEY. THE PRIMARY FORCING SHOULD REMAIN WELL TO THE NORTH BUT  
THERE WILL BE ENOUGH LIFT WITH THE WEAK DISTURBANCES TO GENERATE  
NUMEROUS THUNDERSTORMS ON SATURDAY. CAPE ON THE ORDER OF 1,000-2,000  
J/KG AND SHEAR ALBEIT WEAK (~20KTS) SHOULD BE MORE THAN ENOUGH FOR A  
FEW STRONG STORMS. THE ONLY QUESTION FOR SATURDAY IS THAT MODELS ARE  
SHOWING WHAT IS LIKELY TO BE A COMPLEX OF STORMS DEVELOPING OVER  
OK/TX LATE FRIDAY NIGHT AND MOVING TOWARDS THE AREA DURING THE  
OVERNIGHT PERIOD. THESE MAY KEEP SKIES CLOUDY AND COULD LIMIT  
AFTERNOON HEATING BUT THOSE KINDS OF DETAILS ARE A BIT HARD TO  
DISCERN THIS FAR OUT.  
 
THE RIDGE NEVER REALLY GOES ANYWHERE AND FOR THE MOST PART THE SAME  
CAN BE SAID FOR THE TROUGH, WHICH SHOULD ALLOW FOR A CONTINUED  
PROGRESSION OF WEAK WAVES ACROSS THE AREA INTO EARLY NEXT WEEK. THE  
WEAK FORCING TIED TO THOSE WAVES AND THE GENERALLY WARM AND HUMID  
SUMMER-TIME AIRMASS SHOULD ALLOW FOR SCATTERED THUNDERSTORMS TO  
DEVELOP EACH AFTERNOON SUNDAY AND MONDAY. THE GFS AND TO SOME EXTENT  
THE ECMWF ARE SHOWING SIGNIFICANT DRYING OF THE LOWER LEVELS SUNDAY  
AND MONDAY AFTERNOON WITH A VERY PRONOUNCED INVERTED-V ON THE LATEST  
GFS SOUNDING BOTH DAYS. THAT SEEMS RATHER OVERDONE AT THIS POINT AND  
WILL WAIT ANOTHER FEW RUNS BEFORE TRYING TO PIN DOWN SOME OF THE  
STORM THREATS. WITH HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES AND  
DEWPOINTS IN THE LOWER 70S, HEAT INDEX VALUES SHOULD BE IN THE MID  
TO UPPER 90S.  
 
BEYOND MONDAY, MODEL AND ENSEMBLE SPREAD INCREASES WITH SOME  
GUIDANCE ATTEMPTING TO BUILD A RIDGE OUT WEST AND TRAPPING A  
LOW/SHORTWAVE OVER THE TN VALLEY AND OTHERS SHOWING THE RIDGE OVER  
THE CENTRAL CONUS. IN EITHER CASE IT COULD BE A STORMY FOURTH OF  
JULY AROUND THE TN VALLEY. DUE TO THE DIFFERENCES AND SPREAD IN THE  
GUIDANCE HAVE GONE WITH A BLEND OF GUIDANCE, WHICH PUTS TEMPS NEAR  
NORMAL FOR THIS TIME OF YEAR (UPPER 80S - LOWER 90S).  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)  
ISSUED AT 1200 AM CDT WED JUN 28 2017  
 
VFR CONDITIONS WILL BE THE PREDOMINANT FLIGHT CATEGORY AT EACH  
TERMINAL THROUGH THE PERIOD. THERE MAY BE ENOUGH BOUNDARY LAYER  
MOISTURE TO YIELD SOME LIGHT MVFR RADIATION FOG EARLY THIS MORNING AT  
KMSL, SO HAVE ADDED A TEMPO FOR THIS BETWEEN 10-13Z. OTHERWISE, A  
MOSTLY CLEAR SKY AND LIGHT WINDS ARE EXPECTED ACROSS THE TENNESSEE  
VALLEY OVER THE NEXT 24 HOURS.  
 

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

 
 

 
 
NEAR TERM...AMP.24  
SHORT TERM...AMP.24  
LONG TERM...STUMPF  
AVIATION...AMP.24  
 
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AT WEATHER.GOV/HUNTSVILLE.  
 
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