984  
FXUS64 KHUN 242241  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
541 PM CDT WED APR 24 2019  
   
UPDATE
 
 
FOR 00Z TAFS.  
 

 
   
NEAR TERM
 
(TONIGHT)  
ISSUED AT 300 PM CDT WED APR 24 2019  
 
SCATTERED MID AND HIGH-LEVEL CLOUDS CONTINUE TO SPREAD ACROSS THE  
FORECAST AREA THIS AFTERNOON, IN THE WEST-SOUTHWEST FLOW REGIME  
DOWNSTREAM FROM A BROAD LONGWAVE TROUGH ENCOMPASSING MUCH OF THE  
CENTRAL/SOUTHERN PLAINS. HOWEVER, INSOLATION HAS BEEN STRONG ENOUGH  
TO SUPPORT TEMPERATURES IN THE U70S-L80S AS OF 2 PM, AIDED BY LOW-  
LEVEL SOUTH-SOUTHWESTERLY FLOW ALONG THE RIM OF A NARROW RIDGE AXIS  
CENTERED ACROSS THE FL PENINSULA.  
 
WE EXPECT A FAIRLY RAPID INCREASE IN CLOUD COVER TO OCCUR THIS  
EVENING, AS A LEAD MID-LEVEL VORT MAX (CURRENTLY LIFTING  
NORTHEASTWARD ALONG THE TX/LA GULF COAST) BEGINS TO APPROACH THE  
REGION. ALTHOUGH THIS DISTURBANCE AND IT'S ASSOCIATED VERTICAL MOTION  
FIELDS ARE NOT PARTICULARLY STRONG, WE HAVE INCLUDED A LOW CHANCE  
POP FOR SHOWERS AND A FEW THUNDERSTORMS, MAINLY BETWEEN 03-09Z. LOWS  
WILL BE A BIT WARMER TONIGHT DUE TO THE INCREASE IN CLOUDINESS AND A  
LIGHT BUT PERSISTENT SOUTH-SOUTHWEST WIND, WITH TEMPS EXPECTED TO  
ONLY FALL INTO THE LOWER 60S (PERHAPS A DEGREE OR SO COOLER IN  
NORTHEAST AL). ASSUMING THAT PORTIONS OF THE AREA DO RECEIVE  
MEASURABLE RAINFALL OVERNIGHT, PATCHY FOG WILL ALSO BE POSSIBLE IN  
THE HOURS AROUND SUNRISE.  
   
SHORT TERM
 
(THURSDAY THROUGH FRIDAY NIGHT)  
ISSUED AT 300 PM CDT WED APR 24 2019  
 
MODELS STILL SUGGEST THAT A CLOSED LOW WITHIN THE BASE OF THE TROUGH  
TO OUR WEST WILL OPEN INTO A WAVE AS IT SHIFTS EASTWARD INTO EASTERN  
AR/WESTERN MS ON THURSDAY. DEEP-LAYER FLOW WILL BACK FURTHER TO THE  
SOUTHWEST AND STRENGTHEN CONSIDERABLY THROUGHOUT THE DAY AS THIS  
OCCURS, SUPPORTING AN INCREASE IN PWAT VALUES INTO THE 1.2-1.4 INCH  
RANGE. AT THIS POINT, WE EXPECT FAIRLY WIDESPREAD CONVECTION IN THE  
WAA REGIME TO THE EAST OF THE TROUGH TO SHIFT EASTWARD INTO THE TN  
VALLEY THROUGHOUT THE DAY, BEGINNING DURING THE LATE MORNING HOURS  
FOR LOCATIONS WEST OF I-65 AND ADVANCING EASTWARD THROUGHOUT THE  
AFTERNOON. IT STILL APPEARS AS IF A QUICK TRANSITION TO MOIST  
ADIABATIC PROFILES ALOFT WILL LIMIT INSTABILITY IN OUR REGION,  
REDUCING THE POTENTIAL FOR STRONG-SEVERE STORMS. HOWEVER, BULK SHEAR  
WILL INCREASE DURING THE LATE AFTERNOON, AND THIS COULD YIELD SOME  
ORGANIZATION TO THE CONVECTION AND THE THREAT FOR A FEW LOCALLY  
STRONG WIND GUSTS. ALTHOUGH THE SHOWERS/THUNDERSTORMS IN THIS REGIME  
WILL LIKELY BE ENDING ACROSS THE SOUTHEASTERN ZONES AROUND OR SHORTLY  
AFTER SUNSET, A SEPARATE ROUND OF CONVECTION MAY DEVELOP ALONG THE  
COLD FRONT ASSOCIATED WITH A NORTHERN STREAM WAVE DIGGING  
SOUTHEASTWARD INTO THE OH VALLEY. THE AREAL COVERAGE OF THIS ACTIVITY  
IS A BIT MORE UNCERTAIN, AND FOR THIS REASON WE HAVE REDUCED POPS  
FOR ALL AREAS, ESPECIALLY AFTER MIDNIGHT. THE COLD FRONT WILL CROSS  
THE FORECAST AREA DURING THE MID-LATE MORNING HOURS ON FRIDAY, WITH  
ANY LINGERING SHOWERS EXPECTED TO END IN THE EASTERN ZONES SHORTLY  
AFTER SUNRISE. GUSTY NORTH-NORTHWEST FLOW IN THE WAKE OF THE FRONT  
WILL ADVECT A COOLER AND DRIER MODIFIED NORTH PACIFIC AIRMASS INTO  
THE REGION, WITH LOWS SATURDAY MORNING FALLING BACK INTO THE M-U 40S.  
   
LONG TERM
 
(SATURDAY THROUGH TUESDAY)  
ISSUED AT 300 PM CDT WED APR 24 2019  
 
A LARGE AREA OF HIGH PRESSURE AT THE SFC WILL CONTINUE TO MOVE EWD  
OVER THE REGION HEADING INTO THE SECOND HALF OF THE WEEKEND PERIOD.  
THE LATTER HALF OF THE GLOBAL MODEL SUITES ALSO SHOW A LOW PRESSURE  
SYSTEM OUT OF THE NRN/MID PLAINS MOVING ESE INTO THE MIDWEST STATES  
DURING THE DAY SAT. THIS FEATURE SHOULD ALLOW A COLD FRONT TO  
APPROACH THE TN VALLEY SAT EVENING, WITH PERHAPS SOME SHOWERS/TSTMS  
DEVELOPING ALONG/JUST AHEAD OF THE SFC BOUNDARY. HOWEVER, MOISTURE  
RETURN AHEAD OF THE FRONT IS NOT THAT STRONG, COUPLED WITH THE LOW  
LEVEL CONVERGENT FIELD BEING FAIRLY WEAK. THE FRONT ITSELF ALSO LOOKS  
TO WEAKEN AS IT SETTLES MORE INTO THE CNTRL TN VALLEY. AS SUCH, RAIN  
CHANCES ALONG/AHEAD OF THE FRONT WILL BE IN THE ISO CAT AT BEST, AND  
SHOULD TAPER OFF BY SUN MORNING.  
 
ANOTHER AREA OF HIGH PRESSURE THEN BEGINS TO BUILD EWD INTO THE  
MIDWEST/OH VALLEY STATES FOR THE SECOND HALF OF THE WEEKEND IN THE  
WAKE OF THE FRONTAL PASSAGE, WHICH SHOULD TRANSLATE INTO FAIRLY NICE  
WX FOR THE LOCAL AREA. AFTER A SEASONABLY WARM DAY SAT, WITH HIGHS IN  
THE MID/UPPER 70S FOR MOST LOCATIONS, AFTERNOON TEMPS SUN AGAIN LOOK  
TO CLIMB INTO THE MID/UPPER 70S, WITH CLOUDS DIMINISHING. THE START  
OF THE NEW WORK WEEK LOOKS QUIET AS WELL, AS THE BERMUDA HIGH BECOMES  
ESTABLISHED OFF OF THE MID/SRN ATLANTIC COASTS AND WEAK UPPER RIDGING  
BEGINS TO BUILD OVER THE GULF REGION. OVERALL TEMPS ALSO LOOK TO BE  
JUST ABOVE SEASONAL TRENDS, WITH HIGHS IN THE LOWER 80S AND LOWS  
CLIMBING INTO THE UPPER 50S/LOWER 60S NEAR THE END OF THE PERIOD.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)  
ISSUED AT 541 PM CDT WED APR 24 2019  
 
VFR CONDITIONS ARE EXPECTED THROUGH MUCH OF THE TAF PERIOD. SOME  
VERY LIGHT SHOWERS MAY BE POSSIBLE AT EITHER KMSL OR KHSV BETWEEN  
04Z AND 09Z. CONFIDENCE IS VERY LOW (THIS MAY BE JUST VIRGA), SO JUST  
KEPT VCSH IN THE FORECAST DURING THAT PERIOD. THERE IS SOME QUESTION  
IN GUIDANCE JUST HOW MUCH LIGHTER WINDS MAY BECOME OVERNIGHT. HOWEVER,  
FOR NOW WILL LEAVE MVFR VSBYS IN THE FORECAST AT BOTH TERMINALS  
BETWEEN 10Z AND 13Z FOR POSSIBLE LIGHT FOG DEVELOPMENT. HOWEVER, IF  
WINDS REMAIN BETWEEN 5 AND 10 KNOTS AS SOME GUIDANCE SUGGESTS, THIS  
MAY BE REMOVED IN THE 06Z ISSUANCE. FOR NOW LEFT OUT, A MORE PREDOMINANT  
PERIOD OF -TSRA OR -SHRA LATE TOMORROW AFTERNOON, BUT THIS WILL  
LIKELY BE ADDED IN 06Z ISSUANCE.  
 

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

 
 

 
 
NEAR TERM...70/DD  
SHORT TERM...70/DD  
LONG TERM...09  
AVIATION...KTW  
 
FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE  
AT WEATHER.GOV/HUNTSVILLE.  
 
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