004  
FXUS64 KHUN 192028  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
328 PM CDT FRI JUL 19 2019  
   
NEAR TERM
 
(TONIGHT)  
ISSUED AT 300 PM CDT FRI JUL 19 2019  
 
A REMNANT UPPER LOW IS CONTINUING TO INSTIGATE THE DEVELOPMENT OF  
SHOWERS AND THUNDERSTORMS IN THE REGION TODAY. MOST OF THE ACTIVITY  
HAS BEEN CONCENTRATED TO OUR SOUTH, WHERE A SURFACE BOUNDARY HELPED  
WITH EARLY DEVELOPMENT. SINCE THEN, OUTFLOW FROM CONVECTION HAS  
PUSHED EASTWARDS INTO GEORGIA, IGNITING MORE SHOWERS/STORMS THERE.  
IN OUR AREA, ACTIVITY HAS BEEN ISOLATED TO SCATTERED AT BEST, MOSTLY  
IN THE EAST. DEBRIS CIRRUS FROM THE DEEP CONVECTION HAS FLOWED  
WESTWARD ACROSS THE AREA AND HAS HELPED TO TEMPER TEMPERATURE RISES  
IN EASTERN AND CENTRAL LOCATIONS. IN THE WEST, TEMPERATURES HAVE  
RISEN INTO THE UPPER 80S TO LOWER 90S. WITH DEWPOINT TEMPERATURES IN  
THE MID 70S, HEAT INDICES HAVE BEEN AROUND 100-105 DEGREES. SOME  
LOCATIONS CLOSER TO THE AL/MS BORDER WHERE THERE ARE LITTLE TO NO  
OBS MAY HAVE HEAT INDICES AT OR ABOVE 105F. A HEAT ADVISORY WAS  
ISSUED FOR LAUDERDALE, COLBERT AND FRANKLIN COUNTIES EARLIER, WHICH  
WILL BE IN EFFECT UNTIL 23Z.  
 
OTHERWISE, SHOWERS WILL GRADUALLY DECREASE ACROSS THE AREA AS THE  
UPPER WAVE SHIFTS JUST SOUTH OF THE AREA AND SOLAR HEATING WANES.  
SOME FOG DEVELOPMENT IS POSSIBLE LATER TONIGHT, ESPECIALLY WHERE ANY  
SHOWERS OCCURRED TODAY OVER THE EAST. VALLEYS WILL BE THE MOST  
SUSCEPTIBLE AS USUAL.  
 
LATER TONIGHT, THE UPR WAVE TO OUR SOUTH WILL LIKELY BEGIN TO PIVOT  
TO THE NORTH, WITH SHOWERS INCREASING IN SOUTHERN AREAS MAINLY BEFORE  
DAYBREAK. FORECAST SOUNDINGS AND INSTABILITY PARAMETERS SUGGEST A FEW  
THUNDERSTORMS COULD OCCUR AS WELL.  
 
   
SHORT TERM
 
(SATURDAY THROUGH SUNDAY)  
ISSUED AT 300 PM CDT FRI JUL 19 2019  
 
ON SATURDAY, THE UPPER LOW WILL CONTINUE TO PINWHEEL ACROSS THE  
SOUTH, WITH SUFFICIENT ASSOCIATED VORTICITY/LIFT MOVING ACROSS  
NORTHERN AL. SHOWER AND THUNDERSTORM ACTIVITY WILL BE HEIGHTENED  
COMPERED TO THE TYPICAL DIURNAL PATTERN COMMON ACROSS THE AREA  
DURING THE SUMMER. IN FACT, SHOWERS AND THUNDERSTORMS MAY ALREADY BE  
ONGOING DURING THE MORNING AS INDICATED IN THE DISCUSSION ABOVE.  
ACTIVITY WILL LIKELY INCREASE IN COVERAGE AND INTENSITY WITH THE  
ADVENT OF DAYTIME HEATING. LIKELY POPS HAVE BEEN CARRIED AGAIN FOR  
MUCH OF THE AREA IN THIS FORECAST UPDATE. CENTRAL AND EASTERN AREAS  
MAY BE MORE LIKELY TO EXPERIENCE SHOWERS/STORMS GIVEN THE LOCATION OF  
THE UPPER LEVEL FEATURE. FORECAST VERTICAL THERMO PROFILES INDICATE  
LONG, "SKINNY" CAPE SIMILAR TO TROPICAL ENVIRONMENTS. ADDITIONALLY,  
LAPSE RATES ARE RATHER SMALL, BUT PWS WILL BE HIGH...GENERALLY ABOVE  
2 INCHES. STORM MOVEMENT WILL BE RATHER SLOW IN THE GENERALLY LIGHT  
WIND ENVIRONMENT, AND SHEAR WILL BE VERY WEAK. WITH THE ABOVE SAID,  
SOME LOCALLY HEAVY RAINFALL COULD OCCUR FROM SOME TRAINING CELLS, BUT  
JUST GENERAL THUNDERSTORM ACTIVITY IS EXPECTED. SOME THUNDERSTORMS  
COULD PRODUCE A LOT OF LIGHTNING AND SOME GUSTY WINDS, BUT SEVERE  
WEATHER DOES NOT APPEAR LIKELY. GIVEN THE EXPECTATION FOR ABUNDANT  
CLOUD COVER AND PRECIPITATION, TEMPERATURES WILL BE LOWER THAN TODAY,  
MAINLY IN THE 80S.  
 
THE UPPER RIDGE IN THE OH VALLEY WILL WEAKEN WHILE THE ATLANTIC SUB-  
TROPICAL RIDGE BECOMES DOMINANT ACROSS THE REGION. THE UPPER LOW-WILL  
CONTINUE TO MOVE TO OUR SOUTH, BUT THEN A BIT TO THE NORTH AS IT  
BECOMES INCREASINGLY SHEARED ON SUNDAY. SHOWERS AND THUNDERSTORMS  
WILL STILL CONTINUE ACROSS THE AREA, BUT POSSIBLY LESSER IN COVERAGE  
AND INTENSITY THAN SATURDAY, WITH THE EXCEPTION OF NW LOCATIONS.  
FORECAST SOUNDING PROFILES LOOK MUCH THE SAME AS SATURDAY, WITH  
RELATIVELY LONG THIN CAPE AND HIGH PWS. SO, SIMILAR ACTIVITY WILL BE  
EXPECTED. A FLASH FLOOD THREAT WILL BE HEIGHTENED DURING THE WEEKEND,  
WHICH PROBABLY BE THE MAIN THREAT WITH ALL OF THIS ACTIVITY.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 300 PM CDT FRI JUL 19 2019  
 
THE REMNANT SHEARED UPPER LOW WILL LARGELY BE TO OUR W-NW BY MONDAY,  
BUT EVENTS UPSTREAM WILL SET THE STAGE FOR A RELATIVELY DRIER/COOLER  
WEATHER REGIME FOR THE REGIME LATER NEXT WEEK. A PRONOUNCED HIGH-  
AMPLITUDE PATTERN ESPECIALLY FOR LATE JULY WILL TAKE SHAPE AS A STEEP  
RIDGE BUILDS IN THE WEST CONUS. DOWNSTREAM, A TROUGH WILL DEVELOP IN  
THE EAST, WITH A COLD FRONT PROGGED TO MOVE SOUTHWARD ACROSS THE  
OH/TN VALLEY REGION PERHAPS AS EARLY AS LATE MONDAY, BUT MORE LIKELY  
INTO TUESDAY. HIGH POPS ON MONDAY NIGHT ARE DUE TO THE EXPECTATION  
FOR SHOWERS/THUNDERSTORMS AHEAD OF THE COLD FRONT AS IT MOVES  
SOUTHWARD INTO THE REGION. MOISTURE POOLING AHEAD OF THE FRONT WILL  
LEAD TO HIGH PW VALUES AND POTENTIALLY HEAVY SHOWERS. CAPE MAY BE  
EVEN LESS THAN ON SATURDAY/SUNDAY WITH A CONTINUATION OF LOW LAPSE  
RATES.  
 
EXACTLY WHEN THE FRONT CROSSES THE AREA IS UNCERTAIN, AND THERE  
REMAINS SOME UNCERTAINTY IN WHETHER OR NOT THE FRONT FULLY CROSSES  
THE AREA, WHICH WOULD BE EXPECTED FOR THIS TIME OF YEAR. HOWEVER,  
GIVEN THE AMPLITUDE OF THE LARGE SCALE RIDGE/TROUGH PATTERN, IT DOES  
APPEAR LIKELY THAT THE SURFACE FRONT MAY CROSS THE ENTIRE AREA. DEW  
POINT TEMPERATURES MAY FALL INTO THE UPPER 50S TO LOWER 60S BY  
WEDNESDAY, AND CONTINUING INTO THE LATTER HALF OF THE WEEK, GIVING  
SOME RELIEF FROM THE VERY HOT/HUMID WEATHER.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)  
ISSUED AT 1235 PM CDT FRI JUL 19 2019  
 
AN UPR LEVEL SYSTEM AND RESIDUAL LOW-LVL BOUNDARY ARE INSTIGATING  
SHRA/TSRA DEVELOPMENT TO THE EAST OF KHSV/KMSL TAF SITES CURRENTLY.  
THESE FEATURES ARE EXPECTED TO DRIFT GRADUALLY SOUTHWARD TODAY, SO  
THE MAIN FORCING FOR DEVELOPMENT WILL LIKEWISE MOVE SOUTHWARD.  
NEVERTHELESS, DAYTIME HEATING AND OUTFLOW BOUNDARIES FROM THIS  
ACTIVITY WILL SPARK SOME MORE SHRA/TSRA IN THE AREA. KHSV IS CLOSER  
TO THESE EFFECTS AND A VCSH WAS INCLUDED IN TAFS BETWEEN 20-00Z TO  
ACCOUNT FOR THIS. HOWEVER, TOO UNCERTAIN IN COVERAGE AND PROXIMITY TO  
KHSV SO NO IMPACTS INCLUDED ATTM. OTHERWISE, ACTIVITY WILL TEND TO  
DECREASE ESPECIALLY AFTER 00Z. THE UPR-LOW WILL PIVOT ACROSS THE AREA  
WITH AN ATTENDANT BOUNDARY BY ~15Z, POTENTIALLY AFFECTING TAF SITES  
WITH SHRA ACTIVITY. TSRA ARE LESS LIKELY AND WERE HANDLED THUS WITH  
PROB30 GROUP.  
 

 
   
HUN WATCHES/WARNINGS/ADVISORIES
 
 
AL...HEAT ADVISORY UNTIL 6 PM CDT THIS EVENING FOR ALZ001>003.  
 
TN...NONE.  

 
 

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