128  
FXUS64 KHUN 291505  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
1005 AM CDT MON MAY 29 2017  
   
NEAR TERM
 
(REST OF TODAY)  
ISSUED AT 1005 AM CDT MON MAY 29 2017  
 
SCATTERED SHOWERS ARE QUICKLY MAKING THEIR WAY THROUGH NE AL AND S  
MIDDLE TN AS OF 10AM WITH TEMPERATURES SLOW TO RISE, IN THE UPPER  
60S/LOWER 70S. A COLD/STATIONARY FRONT WAS ANALYZED BACK IN NW MS AS  
OF 12Z AND LOOKING AT OBS, IT DOESN'T LOOK LIKE IT'S MOVED MUCH  
FARTHER EAST SINCE THEN. WITH WINDS ALOFT MOSTLY PARALLEL TO THE  
FRONT, IT IS GOING TO TAKE IT'S TIME MOVING EAST-SOUTHEAST. HIRES  
GUIDANCE HAS BEEN CONSISTENT WITH SHOWING THE BRIEF BREAK IN  
RAINFALL AS THIS BATCH EXITS WITH AN INCREASE IN COVERAGE AGAIN THIS  
AFTERNOON. ALTHOUGH IT IS STILL UP IN THE AIR WITH HOW DENSE THE  
COVERAGE WILL BE.  
 
CURRENT LAPS SOUNDING SHOW A PRETTY SATURATED SOUNDING, MORE THAN  
MODEL SOUNDINGS WERE INDICATING, WITH DEW POINTS IN THE UPPER 60S,  
NEAR 70. THIS IS HELPING TO CONTRIBUTE TO 600-800 J/KG OF SURFACE  
BASED CAPE. TEMPS HAVE BEEN SLOW TO WARM DUE TO CLOUDS/RAIN BUT IT  
LOOKS LIKE THERE ARE A FEW BREAKS IN THE CLOUDS STARTING TO MOVE INTO  
LAWRENCE/FRANKLIN COUNTIES IN AL. THIS, COUPLED WITH THE LESSENING  
RAIN, SHOULD WARM TEMPS A BIT MORE, STEEPEN THE LAPSE RATES AND LEAD  
TO AN INCREASE IN INSTABILITY. EVEN WITH THIS WARMING, I DID DECREASE  
HIGHS BY A DEG OR TWO TO MAKE UP FOR THE HIGHER AMOUNT OF CLOUD  
COVER.  
 
FOR THE AFTERNOON SHOWERS/STORMS, A MID LEVEL WAVE IS FORECAST TO  
MOVE FROM SW TO NE AROUND 18-21Z. AS WELL, CURRENT SATELLITE SHOWS  
NUMEROUS OUTFLOW BOUNDARIES COMING FROM THE CONVECTION ALONG THE  
COAST AS WELL AS FROM S. MS. THE COMBINATION OF THE UPPER WAVE, THE  
OUTFLOW BOUNDARIES, INCREASING INSTABILITY, A MOIST ATMOSPHERE AND A  
FRONT IN THE VICINITY, THINKING COVERAGE WILL INCREASE BY 18-19Z.  
CANNOT RULE OUT A STRONG STORM THIS AFTERNOON BUT THE CHANCES OF  
ANYTHING SEVERE ARE PRETTY LOW.  
   
SHORT TERM
 
(TONIGHT THROUGH WEDNESDAY NIGHT)  
ISSUED AT 318 AM CDT MON MAY 29 2017  
 
SHOWERS AND THUNDERSTORMS WILL DIMINISH IN COVERAGE AND INTENSITY  
TONIGHT AS THE FORCING MOVES OFF TO THE EAST/NORTHEAST AND WE LOSE  
OUR DAYTIME HEATING. THERE MAY BE SOME LINGERING SHOWERS THROUGH THE  
OVERNIGHT PERIOD, AS THE FRONT MOVES SLIGHTLY TO THE SOUTH.  
OVERNIGHT LOWS WILL BE DEPENDENT ON IF WE SEE ANY CLEARING, BUT  
SHOULD REMAIN JUST ABOVE NORMAL FOR THIS TIME OF YEAR.  
 
THE FRONT WILL REMAIN STALLED TO THE NORTH ON TUESDAY BUT MAY DRIFT  
SLIGHTLY SOUTHWARD. GUIDANCE SHOWS SEVERAL SHORTWAVES CONTINUING TO  
MOVE ACROSS THE REGION IN THE QUASI-ZONAL FLOW ALONG. THESE IMPULSES  
WILL ENHANCE ANY CONVECTION ALONG THE STALLED SURFACE BOUNDARY,  
ESPECIALLY DURING THE PEAK HEATING HOURS. AN UPPER LEVEL SHORTWAVE  
WILL MOVE FROM THE NORTHEAST AND INTO THE AREA OVERNIGHT TUESDAY,  
WHICH SHOULD HELP PUSH THE FRONT TO OUR SOUTH BY DAYBREAK ON  
WEDNESDAY. HOWEVER, SCATTERED SHOWERS AND THUNDERSTORMS WILL  
CONTINUE TO BE POSSIBLE ONCE AGAIN ON WEDNESDAY GIVEN THE AMPLE  
MOISTURE AND THE LACK OF SUBSIDENCE. THERE MAY BE A STRONG STORM OR  
TWO ON BOTH TUESDAY AND WEDNESDAY, BUT ORGANIZED CONVECTION DOES NOT  
APPEAR LIKELY GIVEN THE LACK OF WIND SHEAR. ANY ACTIVITY THAT  
DEVELOPS WILL DIMINISH AFTER SUNSET. TEMPERATURES WILL GENERALLY BE  
NEAR NORMAL FOR THIS TIME OF YEAR, BUT MAY BE DEPENDENT ON WHEN AND  
IF RAIN FALLS OVER A GIVEN LOCATION.  
   
LONG TERM
 
(THURSDAY THROUGH SUNDAY)  
ISSUED AT 318 AM CDT MON MAY 29 2017  
 
AN UNSETTLED PATTERN WILL CONTINUE FOR THE LATTER HALF OF THE WORK  
WEEK, CONTINUING INTO THE UPCOMING WEEKEND. BIG PICTURE WISE, MOST  
EFFECTS FROM THE NORTHERN STREAM INFLUENCE ON THE TENNESSEE VALLEY'S  
SENSIBLE WEATHER WILL FOR THE MOST PART REMAIN NORTH OF THE REGION.  
WEAK BUT BROAD UPPER LEVEL RIDGING PARKED OFF OF THE EAST COAST WILL  
BE A CONTROLLING FACTOR IN OUR SENSIBLE WEATHER. A SOUTHWESTERLY  
FLOW AROUND THIS RIDGE WILL CONTINUE INTO THE WEEKEND. SURFACE HIGH  
PRESSURE IN A SIMILAR POSITION WILL ALSO BRING A GOOD SUPPLY OF  
MOISTURE LADEN AIR FROM THE GULF INLAND. THIS MOISTURE, ALONG WITH  
HEATING AND RESULTING INSTABILITY WILL BRING CHANCES OF SHOWERS AND  
THUNDERSTORMS ACROSS THE FORECAST AREA.  
 
BIG QUESTIONS FOR THE EXTENDED INCLUDE HOW HIGH WILL THE RAIN  
CHANCES GO? GIVEN THAT WE ARE GETTING INTO A SUMMER LIKE PATTERN,  
LIMITED RAIN CHANCES TO SCATTERED (LESS THAN 55%). GIVEN THAT THIS  
PRECIPITATION ARE SHOWERS, AKA HIT/MISS, STAYED THAT ROUTE. EVEN SO,  
THE BEST RAIN CHANCES WILL BE DURING THE FRIDAY TO SATURDAY TIME  
FRAME, AS DEEPER MOISTURE (PRECIP WATER PER THE GFS INCREASE INTO THE  
1.5 TO 1.7 INCHES RANGE) DURING THIS PERIOD. THIS WILL PRODUCE CAPE  
VALUES RANGING UP INTO THE 1500 J/KG RANGE DURING FRI/SAT AFTERNOONS.  
WIND SHEAR VALUES FOR THE MOST PART SHOULD REMAIN LOW. THUS MAINLY  
"GENERAL" INTENSITY CONVECTION IS EXPECTED - WITH THE USUAL GUSTY  
WINDS, LOCALLY HEAVY RAINFALL AND OCCASIONAL TO FREQUENT LIGHTNING  
OCCURRENCE. WITH THE MOISTURE AND MORE CLOUDS THAN SUN, HIGHS SHOULD  
ONLY WARM INTO THE LOWER 80S LATE NEXT WEEK. USUAL VALUES IN EARLY  
JUNE ARE IN THE MID 80S.  
 
A FRONTAL BOUNDARY WILL MAKE A MOVE SOUTHWARD ACROSS THE REGION EARLY  
NEXT WEEK IN THE SUNDAY/MONDAY TIME FRAME. THE CANADIAN MODEL WAS THE  
MOST AGGRESSIVE AND COOLEST OF THE GLOBAL MODELS LOOKED AT, WITH THE  
ECMWF THE WARMEST AND THE GFS IN BETWEEN. EVEN WITH THE FRONTAL  
BOUNDARY LURKING ABOUT, RAIN CHANCES SHOULD CONTINUE EARLY NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 615 AM CDT MON MAY 29 2017  
 
VFR CONDITIONS WILL PREVAIL AT THE KMSL AND KHSV TERMINALS THROUGH  
MOST OF THE PERIOD. LOW CLOUDS MAY IMPACT THE TERMINALS THIS MORNING,  
HOWEVER BASED ON CURRENT OBSERVATIONS AND FORECAST TRENDS, DO NOT  
HAVE ENOUGH CONFIDENCE TO KEEP MVFR CEILINGS IN THE FORECAST.  
ALTHOUGH MOST OF THE SHOWER ACTIVITY HAS DISSIPATED, THERE MAY BE AN  
ISOLATED SHOWER AND WILL MAINTAIN THE VCSH THROUGH 18Z. AFTER 18Z,  
WINDS WILL SHIFT TO THE WEST AND ISOLATED TO SCATTERED THUNDERSTORMS  
WILL DEVELOP. CONFIDENCE ON EXACT TIMING AND LOCATION IS STILL  
UNCERTAIN AND THEREFORE HAVE KEPT VCTS IN THE FORECASTS. ANY  
THUNDERSTORMS THAT DEVELOP WILL QUICKLY DISSIPATE AFTER SUNSET,  
LEAVING LIGHT WINDS AND ONLY HIGH CLOUDS THROUGH MUCH OF THE  
OVERNIGHT. GIVEN THE ABUNDANT MOISTURE AND COOLER OVERNIGHT  
TEMPERATURES, PATCHY BR MAY DEVELOP AND HAVE INCLUDED MVFR  
VISIBILITIES AT EACH TERMINAL AFTER 09Z.  
 

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

 
 

 
 
NEAR TERM...LN  
SHORT TERM...73  
LONG TERM...RSB  
AVIATION...73  
 
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