743  
FXUS64 KBMX 221154  
AFDBMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BIRMINGHAM AL  
654 AM CDT TUE MAY 22 2018  
   
UPDATE
 
 
FOR 12Z AVIATION.  
 

 
   
SHORT TERM
 
 
TODAY AND TONIGHT.  
 
WATER VAPOR IMAGERY THIS MORNING INDICATES A PAIR OF WEAK  
SOUTHERN-STREAM UPPER LEVEL TROUGHS, ONE OVER THE WESTERN GULF  
AND ONE OVER THE EASTERN GULF. THE EASTERN ONE IS DRAWING UP A  
PLUME OF TROPICAL MOISTURE. THESE FEATURES WILL BOTH DRIFT  
EASTWARD THROUGH THE SHORT TERM PERIOD. MEANWHILE, AN MCV-LIKE  
FEATURE IS LOCATED OVER ALABAMA AT MID-LEVELS AND LOW-LEVELS.  
FORCING AND SOUTHERLY FLOW ASSOCIATED WITH THIS FEATURE ALONG WITH  
AN APPARENT LOW-LEVEL CONVERGENCE ZONE OFF THE GULF IS FOCUSING A  
BAND OF SHOWERS AND ISOLATED STORMS OVER SOUTHEAST CENTRAL  
ALABAMA AT THIS HOUR. THE MID-LEVEL VORT MAX ASSOCIATED WITH THE  
MCV WILL DRIFT NORTHEASTWARD THIS AFTERNOON, WITH SHORTWAVE  
RIDGING MOVING IN AT MID-LEVELS AHEAD OF THE WESTERN GULF TROUGH  
AND WEAK 500MB HEIGHT RISES. HOWEVER, THE 925-700MB CIRCULATION  
ASSOCIATED WITH THE MCV WILL PERSIST OVER ALABAMA TODAY. THE 00Z  
BMX SOUNDING INDICATED 1.8" PWATS AND GOES-16 DERIVED PWAT DATA  
INDICATES THIS MOIST AIR MASS REMAINS IN PLACE. THESE VALUES ARE  
NEAR THE CLIMATOLOGICAL MAXIMUM VALUES FOR THIS TIME PERIOD.  
THEREFORE EXPECT THE MOIST AIR MASS AND LOW-LEVEL FORCING TO WIN  
OUT OVER THE LESS FAVORABLE MID AND UPPER-LEVELS, WITH HIGH  
COVERAGE OF SHOWERS AND STORMS TODAY. BEST COVERAGE WILL AGAIN BE  
IN EAST ALABAMA WHERE THE BEST MOISTURE TRANSPORT WILL BE AND  
WHERE SHOWER ACTIVITY IS CURRENTLY. LOWER COVERAGE WILL BE OVER  
SOUTHWEST AL AS SOME DRIER AIR WRAPS AROUND THE MCV. WHILE  
CONFIDENCE IN PRECIPITATION COVERAGE SEEMS PRETTY GOOD, CONFIDENCE  
IN TIMING IS LOWER. SOME SHORT TERM MODELS TRY TO WEAKEN THE  
CURRENT ACTIVITY AROUND SUNRISE, WITH ACTIVITY RAMPING UP AGAIN BY  
LATE MORNING.  
 
CLOUDS AND MORNING PRECIPITATION WILL GENERALLY LIMIT INSTABILITY  
VALUES WITH MLCAPE AROUND 1000 J/KG. THIS COMBINED WITH SATURATED  
PROFILES, WEAK WIND FIELDS, AND WEAK LAPSE RATES INDICATES  
UNFAVORABLE CONDITIONS FOR MICROBURSTS, AND THE THREAT OF STRONG  
STORMS/GUSTY WINDS LOOKS TO BE LOW TODAY. LOCALIZED HEAVY RAINFALL  
WILL BE POSSIBLE GIVEN HIGH PWATS AND SLOW CELL MOTIONS WITH  
TRAINING POSSIBLE. HOWEVER, LIMITED INSTABILITY WILL BE A LIMITING  
FACTOR FOR GETTING HIGH RAINFALL RATES. CLOUDS AND SHOWERS WILL  
LIMIT HIGH TEMPERATURES IN THE EASTERN COUNTIES, WITH THE WARMEST  
READINGS EXPECTED IN WEST/SOUTHWEST CENTRAL ALABAMA. SCATTERED  
SHOWERS/STORMS WILL LINGER INTO THE EVENING, WITH SOME SIGNALS OF  
ACTIVITY LINGERING THROUGH THE OVERNIGHT HOURS IN EAST-CENTRAL  
PORTIONS OF THE AREA.  
 
32/DAVIS  
   
LONG TERM
 
 
WEDNESDAY THROUGH MONDAY.  
 
ENHANCED RAIN CHANCES SHOULD CONTINUE FOR WEDNESDAY AND THURSDAY  
ESPECIALLY SOUTH OF INTERSTATE 20 WHERE POPS ARE IN THE 50-60  
PERCENT RANGE. THERE IS WHERE MODELS INDICATE A STALLED 850MB  
TROUGH AND THE REMNANTS OF A DISTURBANCE.  
 
MODELS CONTINUE TO INDICATE THE DEVELOPMENT OF A LARGE TROUGH  
ENCOMPASSING THE SOUTHEAST STATES AND THE GULF OF MEXICO FOR  
FRIDAY THROUGH MONDAY. THIS SYSTEM HAS THE POTENTIAL TO GAIN  
SUBTROPICAL CHARACTERISTICS WITH PERHAPS AN AREA OF SURFACE LOW  
PRESSURE IN THE GULF. THERE IS HIGH CONFIDENCE IN UNUSUALLY WET  
CONDITIONS DURING THIS PERIOD, AND WIDESPREAD 60-70 POPS ARE  
REASONABLE FOR THIS TYPE OF PATTERN.  
 
87/GRANTHAM  
 

 
   
AVIATION
 
 
12Z TAF DISCUSSION.  
 
OVERALL LOOKING AT STATUS QUO WITH SCATTERED SHOWERS AND ISOLATED  
THUNDERSTORMS THROUGH THE NEXT 12 HOURS AT MOST OF THE SITES.  
IFR/MVFR CONDITIONS ARE PRESENT RIGHT NOW AND WILL TRY TO IMPROVE  
BY 16 TO 18Z. MOST OF THE THUNDERSTORMS WILL HOLD OFF UNTIL 18Z  
AND COULD CONTINUE THROUGH 3 TO 5Z. MVFR/IFR CEILINGS RETURN  
AFTER 6Z ONCE AGAIN.  
 
16  
 

 
   
FIRE WEATHER
 
 
 
A MOIST PATTERN IS EXPECTED OVER THE NEXT SEVEN DAYS AND SHOULD  
RESULT IN DAILY RAIN CHANCES. PATCHY FOG/LOW CLOUDS WILL BE  
POSSIBLE EACH MORNING PARTICULARLY WHERE RAINFALL OCCURS DURING  
THE PRIOR AFTERNOON AND EVENING.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GADSDEN 81 66 85 66 86 / 70 40 40 20 50  
ANNISTON 80 66 85 67 86 / 80 50 50 20 50  
BIRMINGHAM 82 69 87 69 88 / 80 30 40 20 50  
TUSCALOOSA 85 69 88 69 88 / 60 30 40 30 50  
CALERA 81 67 85 68 87 / 80 40 50 30 50  
AUBURN 78 67 82 68 83 / 80 50 60 30 60  
MONTGOMERY 83 69 86 70 87 / 80 50 60 30 60  
TROY 81 68 85 69 87 / 80 50 60 30 60  
 

 
   
BMX WATCHES/WARNINGS/ADVISORIES/
 
 
NONE.  
 

 
 

 
 
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