015  
FXUS64 KHUN 280036  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
736 PM CDT SUN MAY 27 2018  
   
UPDATE
 
 
FOR 00Z TAFS.  
 

 
   
NEAR TERM
 
(TONIGHT)  
ISSUED AT 256 PM CDT SUN MAY 27 2018  
 
ISOLATED TO WIDELY SCATTERED CONVECTION HAS DEVELOPED THIS AFTERNOON  
(MAINLY ALONG THE TERRAIN AREAS OF THE CUMBERLAND PLATEAU). WITH  
MODEST INSTABILITY PARAMETERS, WEAK STEERING FLOW, AND NO OTHER  
LIFTING MECHANISM OF NOTE, THIS ACTIVITY HAS REMAINED WEAK AND SHORT-  
LIVED. A FEW OUTFLOW BOUNDARIES SHOULD HELP TO KEEP THIS ACTIVITY  
GOING THROUGH EARLY THIS EVENING, BEFORE BEGINS TO WANE AFTER SUNSET.  
WITH THIS MOIST AIR MASS IN PLACE (PWATS UP TO 1.9 INCHES), THE  
THREAT FOR LOCALLY HEAVY DOWNPOURS WILL EXIST WITH ANY OF THIS  
ACTIVITY -- ALONG WITH FREQUENT LIGHTNING. IN LOCATIONS THAT HAVE  
DESTABILIZED MORE, THE POTENTIAL FOR A SUB-SEVERE, STRONG STORM WILL  
EXIST, BRIEFLY FROM 21-01Z THIS EVENING -- WITH GUSTY WINDS TO 40-50  
MPH BEING THE MAIN THREAT.  
 
SCATTERED SHOWERS AND STORMS WILL BE POSSIBLE OVERNIGHT -- MAINLY ON  
ANY RESIDUAL OUTFLOW BOUNDARIES. CLOUDS WILL ALSO CONTINUE TO FILTER  
IN OVERNIGHT AS SUBTROPICAL STORM ALBERTO MOVES NORTHWARD TOWARD THE  
FL/AL COASTLINE. THESE DENSER CLOUDS (AND THE BOUNDARY LAYER  
MOISTURE) WILL KEEP THE SKY OVERCAST, HELPING TO KEEP LOWS QUITE MILD  
IN THE UPPER 60S TO AROUND 70 DEGREES. SOME VERY LOCALIZED PATCHY  
FOG WILL BE POSSIBLE TONIGHT, BUT THE CLOUD COVER (AND ANY LINGERING  
SHOWER ACTIVITY) WILL LIKELY LIMIT COVERAGE. AS SUCH, HAVE KEPT A  
MENTION OF THIS OUT OF THE FORECAST FOR NOW.  
   
SHORT TERM
 
(MONDAY THROUGH TUESDAY)  
ISSUED AT 256 PM CDT SUN MAY 27 2018  
 
ATTENTION TURNS TO SUBTROPICAL STORM ALBERTO AS THIS SYSTEM  
CONTINUES TO PUSH NORTH INTO FLORIDA PANHANDLE BY MIDDAY MONDAY.  
AHEAD OF THIS SYSTEM, CLOUDS WILL CONTINUE TO EXPAND AND DEEP  
TROPICAL MOISTURE FROM THE GULF OF MEXICO AND WESTERN CARIBBEAN WILL  
ADVECT INTO THE TENNESSEE VALLEY. PWATS WILL CONTINUE TO RISE AND  
APPROACH 2.1 TO 2.3 INCHES BY MONDAY NIGHT INTO TUESDAY, ESSENTIALLY  
RECORD VALUES FOR LATE MAY FOR THIS AREA. SHOWERS AND STORMS WILL BE  
POSSIBLE AGAIN IN THIS TROPICAL AIR MASS AHEAD OF THIS SYSTEM AGAIN  
ON MONDAY (MEMORIAL DAY), BUT LIMITED INSTABILITY WILL ONCE AGAIN  
KEEP THIS ACTIVITY SUB-SEVERE, WITH ONLY AN ISOLATED STRONG STORM  
POSSIBLE. AS ONE MIGHT EXPECT IN THIS ENVIRONMENT, THE MAIN IMPACT  
WITH THIS ACTIVITY WOULD BE LOCALLY HEAVY RAINFALL/DOWNPOURS.  
 
A BROAD UPPER-TROUGH OVER GREAT BASIN WILL SWING ONTO THE CENTRAL  
PLAINS MONDAY NIGHT INTO TUESDAY. THIS SYSTEM WILL HELP TO PICK UP  
ALBERTO AS IT MOVES INTO CENTRAL ALABAMA MONDAY EVENING AND  
ACCELERATE NORTH INTO THE TENNESSEE VALLEY LATE MONDAY NIGHT INTO  
TUESDAY. GIVEN THE DEEP, TROPICAL MOISTURE IN PLACE, LOCALLY HEAVY  
RAINFALL AND FLASH FLOODING WILL BE POSSIBLE, ESPECIALLY ON TUESDAY  
WHEN THE REMNANT "CORE" OF ALBERTO MOVES ACROSS THE AREA. THERE IS  
STILL UNCERTAINTY IN THE TRACK OF THIS STORM WITH SOME MODELS VEERING  
SLIGHTLY TO THE WEST IN RECENT RUNS. THIS TRACK WILL HAVE A BIG  
IMPACT ON WHICH AREAS WILL EXPERIENCE THE HEAVIEST RAINFALL AND  
POTENTIALLY SOMETHING MORE (IN THE FORM OF AN ISOLATED, WEAK TORNADO  
OR TWO). AT THIS TIME, FEEL COMFORTABLE THAT BETWEEN 2 TO 3.5 INCHES  
OF RAIN OVER THE REGION IS POSSIBLE GIVEN HOW PRIMED WE'LL BE FOR  
RAINFALL IN THIS TROPICAL ENVIRONMENT. SHOULD THE REMNANT CENTER OF  
ALBERTO VEER FURTHER WEST, THE REGION WILL BE IN A MORE FAVORABLE  
POSITION FOR RAINFALL AND A TORNADO OR TWO DUE TO FAVORABLE  
SPEED/DIRECTIONAL SHEAR PROFILES. MOST OF THE THUNDERSTORM ACTIVITY  
WILL BE VERY LOW-TOPPED, SO AM NOT EXPECTING DAMAGING WINDS/HAIL TO  
BE MUCH OF A THREAT. BUT SHEAR PROFILES, AS MENTIONED, WILL HELP KEEP  
SOME OF THIS ACTIVITY LITTLE MORE ORGANIZED AND CAPABLE OF PRODUCING  
A QUICK SPIN-UP.  
 
MOST GUIDANCE QUICKLY LIFTS THE REMNANT CENTER OF ALBERTO AND THE  
HEAVY RAINFALL POTENTIAL UP INTO TN/KY AND THE OHIO VALLEY AFTER  
00-06Z WEDNESDAY. HOWEVER SCATTERED TO NUMEROUS SHOWERS AND STORMS  
ARE POSSIBLE THROUGH THE EVENING, BEFORE TAPERING OFF AFTER MIDNIGHT  
AS THIS BEST FORCING LIFTS TO THE NORTH AND EAST. GIVEN THE FORECAST  
CLOUDS AND RAINFALL, HAVE MAINTAINED A BELOW NORMAL TEMPERATURE  
FORECAST. HIGHS ON MEMORIAL DAY WILL LIKELY ONLY REACH THE LOWER 80S,  
AND STRUGGLE TO CLIMB OUT OF THE MID TO UPPER 70S ON TUESDAY.  
   
LONG TERM
 
(TUESDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 256 PM CDT SUN MAY 27 2018  
 
IN THE WAKE OF ALBERTO, I WILL FAVOR THE ECMWF SOLUTION AS THE GFS  
APPEARS TO BE IN ALLOWING SHORTWAVES TO PENETRATE THE GROWING  
PLAINS RIDGE. THE AREA WILL BE IN A WARM AND MOIST SECTOR ON  
WEDNESDAY AS THE TROUGH AXIS PUSHES EAST. THE BLENDED POP GUIDANCE  
MAY NEED TO BE SUBTRACTED IF THIS MOVES BY EVEN FASTER THAN PROGGED  
AS THE WAVE PASSAGE MAY PRECEDE ANY APPRECIABLE DESTABILIZATION  
WEDNESDAY MIDDAY INTO AFTERNOON. ON THURSDAY, I HAVE DISCOUNTED THE  
BLENDED POP GUIDANCE IN FAVOR OF A MORE REASONABLE ECMWF SOLUTION.  
THE GROWING PLAINS RIDGE WILL AMPLIFY THE FLOW FROM THE GREAT LAKES  
INTO THE SOUTHEAST, BUT THE CAP MAY EDGE MOST OF THE PRECIPITATION  
AND "RING OF FIRE" JUST TO OUR NORTHEAST OVER EASTERN KY/TN/NORTH GA  
ON FRIDAY INTO SATURDAY. HAVE MAPPED THE POP FROM LOW CHANCE EAST TO  
SLIGHT CHANCE WEST WITH THIS IN MIND. THE ECMWF SUGGESTS A BETTER  
SHORTWAVE PENETRATING THE RIDGE AND DIVING SOUTHEAST INTO THE TN  
VALLEY SATURDAY NIGHT INTO SUNDAY (DAY 8). HAVE ALSO INCREASED MAX  
TEMPS A DEGREE OR TWO ABOVE GUIDANCE.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)  
ISSUED AT 736 PM CDT SUN MAY 27 2018  
 
PRIMARY NEAR TERM AVIATION CONCERN IS A SLOW-MOVING BAND OF +TSRA  
INVOF HSV, WHICH HAS DEVELOPED ALONG A SUBTLE LOW-LEVEL CONVERGENCE  
AXIS EMBEDDED IN THE BROADER CIRCULATION AROUND ALBERTO. ALTHOUGH  
CONFIDENCE WAS HIGH ENOUGH TO INCLUDE A 1-HR TEMPO FOR PREVAILING  
TSRA AT HSV, THIS ACTIVITY SHOULD LARGELY DISSIPATE BEFORE REACHING  
MSL. NONETHELESS, WE HAVE MAINTAINED VCTS AT BOTH TERMINALS THRU 04Z.  
CONDITIONS WILL REMAIN VFR OUTSIDE OF TSRA, WITH BKN-OVC AS/CS DECKS  
TO PERSIST THRU THE NIGHT. THIS, ALONG WITH A LGT ENE WIND WILL  
LIMIT THE THREAT FOR SIGNIFICANT VSBY REDUCTIONS, HOWEVER SOME PATCHY  
BR WILL BE PSBL AT TIMES DUE TO THE ABUNDANCE OF LOW-LEVEL MOISTURE.  
SHORT TERM MODELS SUGGEST ANOTHER LOW-LEVEL CONVERGENCE AXIS WILL  
INITIATE TSRA INVOF HSV ONCE AGAIN BY 11Z AND MSL BY 14Z, WITH THIS  
ACTIVITY TO CONTINUE THRU THE EARLY AFTN HOURS TOMORROW. PARTIAL  
CLEARING SHOULD OCCUR BY THE END OF THE TAF PERIOD AS COVERAGE OF  
STORMS DECREASES, WITH LOW-LEVEL ENE FLOW EXPECTED TO SLOWLY INCREASE  
DURING THIS PERIOD AS WELL.  
 

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

 
 

 
 
NEAR TERM...AMP.24  
SHORT TERM...AMP.24  
LONG TERM...17  
AVIATION...70/DD  
 
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