670  
FXUS64 KBMX 152337  
AFDBMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BIRMINGHAM AL  
637 PM CDT SUN SEP 15 2019  
   
UPDATE
 
 
FOR 00Z AVIATION.  
 

 
   
SYNOPSIS
 
 
DEEP-LAYER RIDGING REMAINS ENTRENCHED ACROSS THE DEEP SOUTH  
REGION TODAY. TROPICAL STORM HUMBERTO REMAINS EAST OF THE FLORIDA  
PENINSULA WHILE A DISTURBANCE IS POSITIONED OVER THE WESTERN GULF  
OF MEXICO. TO OUR NORTH, A SHALLOW TROUGH WAS APPROACHING THE  
WESTERN OHIO RIVER VALLEY FROM THE WEST.  
 
SURFACE HIGH PRESSURE WAS ANALYZED CENTERED OVER WESTERN  
PENNSYLVANIA WITH AN EXTENSIVE FOOTPRINT EXTENDING FROM SOUTHEAST  
CANADA THROUGH THE MID ATLANTIC STATES WEST TO THE MID MISSISSIPPI  
RIVER VALLEY AND DOWN SOUTH THROUGH THE TENNESSEE VALLEY INTO  
CENTRAL ALABAMA AND GEORGIA.  
 
THE 15/12Z BMX SOUNDING CONTAINED MEAGER INSTABILITY ALOFT THIS  
MORNING WITH SEVERAL SUBSIDENCE INVERSION FROM OFF THE SURFACE  
THROUGH 500 MB. MOISTURE DISTRIBUTION WAS FAIRLY UNIFORM THROUGH  
THE VERTICAL PROFILE WITH AN OVERALL PRECIPITABLE WATER (PW) VALUE  
OF 1.64 INCHES. THE VERTICAL WIND PROFILE WAS EASTERLY FROM THE  
SURFACE TO 500 MB WITH SPEEDS UP TO 20 KT. WINDS BECAME NORTHERLY  
AROUND 400 MB FOLLOWED BY A SHIFT FROM THE WEST AND SOUTHWEST  
ABOVE 300 MB. SPEEDS WERE GENERALLY UP TO 30 KT ABOVE 500 MB.  
 
05  
 

 
   
SHORT TERM
 
 
/UPDATED AT 0134 PM CDT SUN SEP 15 2019/  
 
WITH DEEP-LAYER RIDGING OVER THE AREA AND SURFACE HIGH PRESSURE  
TO THE NORTHEAST, AN EASTERLY FLOW WILL PREVAIL IN THE LOWER TO  
MID LEVELS WHILE A MORE WEST TO SOUTHWEST FLOW IS EXPECTED ALOFT.  
 
LOW-LEVEL INSTABILITY VALUES FROM STRONG SOLAR INSOLATION WILL BE  
SUFFICIENT FOR CUMULUS FORMATION OVER THE AREA THIS AFTERNOON  
INTO EARLY EVENING. ONLY A FEW SHOWERS MAY DEVELOP WITH SOME  
BECOMING THUNDERSTORMS THROUGH THE REMAINDER OF THE AFTERNOON INTO  
EARLY EVENING BUT CONDITIONS DO NOT FAVOR THE WIDESPREAD COVERAGE  
OF PRECIPITATION THAT IS NEEDED ACROSS MUCH OF THE FORECAST AREA.  
 
SKIES WILL BE FAIR TONIGHT INTO MONDAY AS HIGHER-LEVEL CLOUDS  
WILL MOVE OVER THE AREA FROM THE SOUTHWEST FROM THE DISTURBANCE  
OVER THE WESTERN GULF OF MEXICO. THE COMBINATION OF OVERALL  
SUBSIDENCE WITH DRIER THAN NORMAL GROUND CONDITIONS IS CONTINUING  
TO SUPPORT A LARGER THERMAL SPREAD BETWEEN HIGH AND LOW TEMPERATURES  
ALONG WITH LOWER CHANCES FOR SHOWER AND THUNDERSTORM ACTIVITY  
THAN TYPICALLY EXPERIENCED THIS TIME OF YEAR.  
 
05  
   
LONG TERM
 
 
/UPDATED AT 0134 PM CDT SUN SEP 15 2019/  
 
MONDAY THROUGH SATURDAY.  
 
EXAMINING THE UPPER LEVEL PATTERN, A ZONAL FLOW OVER MUCH OF THE  
NORTHERN HALF OF THE COUNTRY IS FORECAST TO AMPLIFY OVER THE NEXT  
FEW DAYS AS A POTENT TROUGH SWINGS INTO THE PACIFIC NORTHWEST  
TONIGHT AND TOMORROW. IN RESPONSE DOWNSTREAM, THE BROAD RIDGING  
OVER OUR PORTION OF THE COUNTRY WILL CONSOLIDATE AND AMPLIFY FROM  
CENTRAL TEXAS THROUGH GEORGIA AND NORTHWARD INTO THE MID  
MISSISSIPPI RIVER VALLEY REGION. THE RESULT WILL BE MUCH OF THE  
SAME WITH MOSTLY DRY CONDITIONS PERSISTING AS HIGHS REACH THE MID  
TO UPPER 90'S THROUGH MIDWEEK WHILE LOWS WILL CONTINUE TO RANGE  
FROM THE 60'S TO THE 70'S ACROSS THE FORECAST AREA THROUGH  
WEDNESDAY.  
 
LATER THIS WEEK, ANOTHER TROUGH WILL DIVE INTO THE PACIFIC  
NORTHWEST AND WILL FURTHER AMPLIFY THE PATTERN ALOFT ACROSS THE  
COUNTRY. RIDGING IS FORECAST TO ELONGATE FURTHER FROM EASTERN  
TEXAS NORTHEAST INTO THE GREAT LAKES REGION. AS THE DEEP-LAYER  
RIDGE BECOMES CENTERED MORE TO OUR WEST ALONG WITH THE SURFACE  
PRESSURE GRADIENT GRADUALLY INCREASES BETWEEN HUMBERTO OVER THE  
SOUTHWEST ATLANTIC BASIN AND SURFACE HIGH PRESSURE OVER THE  
NORTHEAST, SOME HEAT RELIEF IS EXPECTED AS A NORTHEAST FLOW  
DEVELOPS LATE WEDNESDAY INTO THURSDAY AND PERSISTS INTO THE NEXT  
WEEKEND.  
 
SHOWER AND THUNDERSTORM CHANCES WILL REMAIN MINIMAL THROUGH THE  
REST OF THE WORK WEEK WITH A SLIGHTLY HIGHER CHANCE IN THE  
WEDNESDAY THROUGH THURSDAY TIME FRAME AS A WEAK "BACK DOOR" OR  
"WEDGE" FRONT ADVANCES SOUTHWEST THROUGH THE FORECAST AREA WITH  
SOME COOLER/DRIER AIR ARRIVING FROM THE NORTHEAST. THOUGH  
TEMPERATURES WILL GRADUALLY MODERATE WITH TIME OVER THE WEEKEND,  
EXPECT DRY CONDITIONS TO PERSIST AS BROAD EXPANSIVE DEEP-LAYER  
RIDGING REMAINS OVER THE REGION.  
 
05  
 

 
   
AVIATION
 
 
00Z TAF DISCUSSION.  
 
VFR CONDITIONS ARE FORECAST THROUGH THE TAF PERIOD. CALM TO  
OCCASIONAL VERY LIGHT BREEZES ARE EXPECTED TONIGHT, INCREASING TO  
BETWEEN 5-10 KNOTS FROM THE ~NORTHEAST POST SUNRISE MONDAY. A FEW  
SPELLS OF PASSING HIGH-LEVEL CLOUDS ARE POSSIBLE, THE RESULT OF  
BLOWOFF FROM A DISTURBANCE ATOP THE NORTHERN GULF OF MEXICO.  
 
89^GSATTERWHITE  
 

 
   
FIRE WEATHER
 
 
 
OTHER THAN A FEW WIDELY ISOLATED SHOWERS AND SOME OF WHICH MAY  
DEVELOP INTO THUNDERSTORMS, HOT AND DRY CONDITIONS WILL PERSIST  
ACROSS THE FORECAST AREA. RELATIVE HUMIDITY VALUES WILL FALL INTO  
THE LOW 40 PERCENTILE THIS AFTERNOON FOLLOWED BY EVEN LOWER VALUES  
IN THE 30 PERCENTILE RANGE ON MONDAY AND TUESDAY AFTERNOONS AS  
DRIER AIR ARRIVES FROM THE NORTHEAST. WITH VERY LOW RAIN CHANCES  
PERSISTING AND LOW AFTERNOON RH VALUES, EXPECT KBDI VALUES TO  
CONTINUE IN THE ELEVATED RANGE AS DROUGHT CONDITIONS CONTINUE.  
 
05  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GADSDEN 66 95 67 96 67 / 0 10 0 10 0  
ANNISTON 68 95 68 97 69 / 0 10 0 10 0  
BIRMINGHAM 70 97 71 98 71 / 0 10 0 10 0  
TUSCALOOSA 72 97 70 98 71 / 0 10 0 10 0  
CALERA 70 96 70 97 70 / 0 10 0 10 0  
AUBURN 71 93 70 96 70 / 0 10 0 10 0  
MONTGOMERY 72 97 70 99 70 / 0 10 0 10 0  
TROY 70 95 69 97 69 / 0 10 0 10 0  
 

 
   
BMX WATCHES/WARNINGS/ADVISORIES/
 
 
NONE.  
 

 
 

 
 
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