An outflow boundary from a decaying mesoscale convective system pushed southward into central Alabama on Saturday, May 5. This boundary helped spark isolated convection during the late afternoon and early evening hours.
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The episode as NWS BMX wrote it up.
An outflow boundary from a decaying mesoscale convective system pushed southward into central Alabama on Saturday, May 5. This boundary helped spark isolated convection during the late afternoon and early evening hours.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Birmingham, AL wrote its last area forecast discussion before the first event at May 5, 5:33 PM CST, 49 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BIRMINGHAM AL 633 PM CDT SAT MAY 5 2012 .UPDATE... FOR 00Z AVIATION. && .DISCUSSION... WATER VAPOR IMAGERY INDICATES A BROAD UPPER LEVEL RIDGE ACROSS THE CENTRAL AND EASTERN CONUS. A COUPLE OF UPPER LEVEL TROUGHS ARE CURRENTLY ROTATING THROUGH THE RIDGE. ONE ACROSS THE MID-ATLANTIC AND THE OTHER ACROSS THE MID-MISSISSIPPI RIVER VALLEY. THE FIRST OF THESE WAVES LEAD TO THE CLUSTER OF SHOWERS AND THUNDERSTORMS OVER KENTUCKY AND TENNESSEE LAST NIGHT. THIS CLUSTER OF STORMS HAS LEFT AN OUTFLOW BOUNDARY ACROSS THE AREA AND CURRENTLY STRETCHES FROM NEAR ANNISTON TO DOUBLE SPRINGS. WITH A VERY UNSTABLE AIRMASS IN PLACE...A FEW SHOWERS HAVE ALREADY DEVELOPED EARLY THIS AFTERNOON. THE AREA ALONG THIS BOUNDARY WILL CONTINUE TO BE THE FOCUS FOR NEW CONVECTION INTO THE AFTERNOON AND EVENING HOURS. INDICATIONS ARE THAT A WEAK CAP REMAINS IN PLACE BUT WITH 2000 TO 3500 J/KG OF SBCAPE ANY ADDITIONAL HEATING OR WEAK LIFT COULD LEAD TO STRONG UPDRAFTS. DEEP LAYER 0-6 KM SHEAR REMAINS WEAK AROUND 15-25 KTS. THEREFORE...DO NOT EXPECT UPDRAFTS AND STORMS TO PERSIST FOR LONG. THE MAIN THREATS FROM ANY THUNDERSTORMS THAT DO FORM WILL BE LARGE HAIL AND DAMAGING WINDS. MODELS ARE SHOWING THAT SOME OF THESE SHOWERS AND THUNDERSTORMS COULD PERSIST INTO THE OVERNIGHT. CONFIDENCE STILL REMAINS LOW DUE TO UNCERTAINTY ABOUT HOW THE CONVECTION WILL EVOLVE TODAY. RESIDENTS ACROSS CENTRAL ALABAMA SHOULD REMAIN WEATHER AWARE WITH MANY OUTDOOR ACTIVITIES SCHEDULED THIS WEEKEND. THE MOON WILL BE 14 PERCENT BIGGER AND 30 PERCENT BRIGHTER TONIGHT THAN OTHER FULL MOONS AS IT PASSES ITS CLOSEST POINT TO EARTH IN ITS ORBIT AT 1034 PM CDT. EXPECTATIONS ARE THAT MOST THUNDERSTORMS THAT DO FORM SHOULD WEAKEN BY THEN WITH ONLY SCATTERED CLOUDS AROUND. TOMORROW CONDITIONS LOOK SIMILAR TO TODAY WITH THE UPPER LEVEL WAVE ACROSS THE MID-MISSISSIPPI RIVER VALLEY MOVING CLOSER TO CENTRAL ALABAMA. TEMPERATURES SHOULD WARM UP INTO THE UPPER 80S TO LOWER 90S. THE ATMOSPHERE WILL BE RATHER UNSTABLE AGAIN WITH 1500-2500 J/KG OF SBCAPE. UPPER LEVEL FLOW AND SHEAR WILL AGAIN BE WEAK. THE MESOSCALE FEATURES WILL BE THE MAIN FOCUS FOR CONVECTION ALONG BOUNDARIES. DUE TO THE AMOUNT OF INSTABILITY PRESENT THUNDERSTORMS THAT DUE FORM WILL HAVE THE POTENTIAL TO BE STRONG TO SEVERE WITH LARGE HAIL AND DAMAGING WINDS BEING THE MAIN THREATS. INTO EARLY NEXT WEEK MOISTURE BEGINS TO INCREASE THROUGHOUT THE LOW LEVELS AS BOUNDARY LAYER SOUTHERLY FLOW INCREASE IN RESPONSE TO A LOW ACROSS THE MIDWEST. A COLD FRONT WILL STRETCH DOWN FROM THE LOW INTO THE SOUTHERN PLAINS. SHOWERS AND THUNDERSTORM WILL AGAIN BE POSSIBLE WITH SHORTWAVE TROUGHS EJECTING OUT AHEAD OF THE MAIN UPPER LEVEL TROUGH. MOISTURE AND INSTABILITY WILL BE IN PLACE AGAIN FOR THUNDERSTORMS TO DEVELOP. THE COLD FRONT WILL BEGIN TO NUDGE INTO THE FORECAST AREA ON TUESDAY AND WILL BE THE FOCUS FOR CONVECTION WITH SHOWERS AND THUNDERSTORMS POSSIBLE AGAIN ON TUESDAY. PRECIPITATION CHANCES WILL CONTINUE INTO MID-WEEK AS THE COLD FRONT MOVES THROUGH THE AREA ON WEDNESDAY. BEST PRECIPITATION CHANCES WILL BE ACROSS SOUTHEASTERN PORTIONS OF THE CWA. THURSDAY SHOULD BE A NICE DAY WITH COOLER TEMPERATURES AND SUNNY SKIES. HOWEVER...RAIN CHANCES RETURN QUICKLY TO THE FORECAST NEXT WEEKEND AS A CLOSED LOW SLOWLY APPROACHES THE SOUTHEAST. MA && .AVIATION... 00Z TAF DISCUSSION. VFR CONDITIONS EXPECTED AT LEAST THROUGH 06Z. NOT EXPECTING MUCH IF ANY IN THE WAY OF SHOWER ACTIVITY THROUGH THE OVERNIGHT. NOT SURE IF THE HIGH CIRRUS WILL PERSIST OVERNIGHT. IF THESE HIGH CLOUDS DISSIPATE AND ALLOW FOR BETTER RADIATIONAL COOLING...THERE COULD BE FOG AND/OR LOW STRATUS ESPECIALLY ACROSS THE SOUTH AT KMGM AND KTOI. LESS CONFIDENT IN THIS DEVELOPMENT FOR KANB AND KTCL. SHOULD HAVE A BETTER HANDLE ON THE HIGH CLOUDS AND SUBSEQUENT POTENTIAL FOR LOW CLOUDS AND FOG WITH THE NEXT TAF CYCLE. LEFT OUT MENTION OF SHOWERS OR THUNDERSTORMS FOR SUNDAY AFTERNOON DUE TO THE ANTICIPATED ISOLATED NATURE OF ANYTHING THAT DEVELOPS. 87 NOTE***THE NATIONAL WEATHER SERVICE IS ISSUING SEASONAL TERMINAL FORECASTS FOR THE TALLADEGA MUNICIPAL AIRPORT (KASN) IN TALLADEGA...ALABAMA. THE FORECASTS WILL LAST THROUGH AT LEAST THE 9TH OF MAY. DUE TO THE LIMITED AVAILABILITY OF OBSERVATIONS...KASN TAF WILL HAVE AMD NOT SKED APPENDED TO THE END OF THE FORECAST. && .PRELIMINARY POINT TEMPS/POPS... GADSDEN 64 89 64 83 64 / 20 40 40 40 50 ANNISTON 66 88 65 83 65 / 20 40 40 40 50 BIRMINGHAM 67 89 67 85 66 / 20 30 40 40 50 TUSCALOOSA 68 91 67 88 66 / 20 30 30 40 50 CALERA 68 88 66 85 66 / 20 30 40 40 50 AUBURN 68 89 66 83 65 / 20 40 40 40 40 MONTGOMERY 68 89 67 85 66 / 20 30 40 40 40 TROY 68 89 66 84 66 / 20 30 30 40 40 && .BMX WATCHES/WARNINGS/ADVISORIES... NONE. && 05/87
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BIRMINGHAM AL 1228 PM CDT SAT MAY 5 2012 ALZ011>015-017>050-061730- AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE- CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE- JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY- PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA- TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON- 1228 PM CDT SAT MAY 5 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM. .DAY ONE...THIS AFTERNOON AND TONIGHT. ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS CENTRAL ALABAMA THIS AFTERNOON. THE GREATEST THREAT AREA IS NORTH AND EAST OF A LINE FROM AUBURN TO PRATTVILLE TO ALICEVILLE. THE HAZARDOUS THREATS INCLUDE DAMAGING STRAIGHT LINE WINDS AND LARGE HAIL. AT THIS TIME...THE STORMS APPEAR POSSIBLE THROUGH 8 PM. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY. THERE IS A SMALL THREAT OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON AND AGAIN MONDAY AFTERNOON AND MONDAY NIGHT. THESE STORMS WILL AFFECT MUCH OF CENTRAL ALABAMA. THE THREATS ASSOCIATED WITH ANY SEVERE STORMS THAT DO DEVELOP WOULD BE DAMAGING WINDS AND LARGE HAIL. .SPOTTER INFORMATION STATEMENT... LOCAL ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT MAY BE NEEDED THIS AFTERNOON...SUNDAY...AND AGAIN MONDAY DUE TO THE SEVERE THUNDERSTORM THREAT. 75
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BIRMINGHAM AL 700 PM CDT SAT MAY 5 2012 ALZ019-060045- CALHOUN AL- 700 PM CDT SAT MAY 5 2012 ...SIGNIFICANT WEATHER ADVISORY FOR WESTERN CALHOUN COUNTY UNTIL 745 PM CDT... AT 654 PM CDT...THE NATIONAL WEATHER SERVICE WAS TRACKING A STRONG THUNDERSTORM NEAR OHATCHEE...OR 11 MILES SOUTH OF RAINBOW CITY... MOVING EAST AT 10 MPH. PEA SIZE HAIL AND WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THIS STORM. LOCATIONS IN OR NEAR THE PATH OF THIS STORM INCLUDE... ALEXANDRIA... WELLINGTON... && LAT...LON 3383 8585 3369 8592 3376 8604 3383 8603 TIME...MOT...LOC 0000Z 287DEG 7KT 3379 8602 GRANTHAM
The Birmingham radar (KBMX), 97 km away, was scanning. The volume nearest the first event began at 00:19 UTC.
1 hail. Local standard time, as filed.
Quarter size hail (measured) began falling at 7:22 PM CDT and continued through 7:26 PM CDT.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alabama in 2012Every state in 2012This day in weather historyWarnings in Alabama, May 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 386199.