045
FXUS64 KBMX 042337
AFDBMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
637 PM CDT SAT JUL 4 2009
UPDATE
FOR 00Z AVIATION.
DISCUSSION
DISCUSSION
AFTER A FEW DAYS MOSTLY CLEAR SKIES AND LOWER
HUMIDITIES..THE AIR MASS WILL CHANGE QUICKLY OVERNIGHT AS
DEEPENING SOUTHWEST FLOW BRINGS MOISTURE INTO CENTRAL ALABAMA.
SURFACE DEW POINTS IN THE LOWER 70S HAVE ADVECTED INTO EASTERN
ARKANSAS AHEAD OF COLD FRONT. THIS AIR MASS WILL MOVE INTO CENTRAL
ALABAMA BY SUNDAY MORNING AND SET STAGE FOR ACTIVE WEATHER. BOTH
NAM AND GFS MODEL SOUNDINGS SHOW PRECIPITABLE WATER VALUES IN THE
2.00-2.25 INCH RANGE BY 18Z SUNDAY...WHICH ATTESTS TO THE WARM
TEMPERATURE PROFILE. SUCH WARM AND MOIST MID LEVELS WILL TEND TO
LIMIT WIND GUST POTENTIAL FOR THUNDERSTORMS... BUT DAYTIME HEATING
AND MODEST WIND PROFILES INDICATE POTENTIAL FOR SOME ORGANIZED
STORMS AS LOW LEVEL LAPSE RATES INCREASE.
THUNDERSTORMS CURRENTLY DEVELOPING OVER ARKANSAS WILL LIKELY FORM
INTO A ORGANIZED CONVECTIVE SYSTEM TONIGHT AND TRACK SOUTHEAST
INTO NORTH ALABAMA AFTER MIDNIGHT. THE NAM MODEL HAS BEEN VERY
CONSISTENT WITH THIS FEATURE AND RAISED POPS NORTHERN COUNTIES FOR
SUCH A SYSTEM. THE NAM MODEL INDICATES THE SYSTEM WILL WEAKEN BY
SUNRISE AS LOW LEVEL FLOW VEERS AND BECOMES WESTERLY. THE COLD
POOL OUTFLOW FROM THIS MCS WILL LIKELY PUSH A BOUNDARY TO NEAR THE
I-20 CORRIDOR BY LATE MORNING. THIS BOUNDARY WILL BE THE FOCUS FOR
ADDITIONAL THUNDERSTORM DEVELOPMENT IN THE AFTERNOON. THE STORM
PREDICTION CENTER HAS THE NORTHERN HALF OF ALABAMA UNDER A
SLIGHT RISK OF SEVERE STORMS FOR SUNDAY.
MODELS BEGIN TO DIVERGE AFTER SUNDAY AS GFS MODEL SHOWS A MORE
PROGRESSIVE SYSTEM AND CLEARS RAIN OUT FASTER THAN NAM. THE ECMFW
MODEL TAKES A SOLUTION BETWEEN THE OTHER TWO MODELS. A COMPROMISE
IS IN ORDER AND WILL INCREASE RAIN CHANCES ON MONDAY...BUT NOT AS
WET AS INDICATED BY NAM MODEL. ANOTHER SHORT WAVE TROF WILL PUSH
ACROSS THE AREA MONDAY NIGHT AND PUSH THE DEEPER MOISTURE DOWN
TOWARDS THE GULF COAST. THE SURFACE BOUNDARY WILL LIKELY HANG
AROUND SOUTH ALABAMA TUESDAY THRU THURSDAY AND MAY EVEN RETREAT
NORTHWARD DURING THIS TIME FRAME AS A WEAK INVERTED TROF DEVELOPS
NEAR THE COAST. BEST CHANCE OF RAIN TUESDAY THRU THURSDAY WILL BE
SOUTH OF I-85. STRONG UPPER RIDGE OVER THE SOUTHWEST UNITED STATES
WILL BUILD EASTWARD BY THE END OF THE WEEK RESULTING IN SMALLER
RAIN CHANCES AND WARMER TEMPERATURES.
AVIATION
00Z TAF DISCUSSION.
NO AVIATION CONCERNS THROUGH 12Z. SOME SHOWERS AND ISOLATED
THUNDERSTORMS WILL BE POSSIBLE ACROSS THE NORTHERN TAF LOCATIONS
BEGINNING BETWEEN 13Z AND 17Z...BECOMING MORE WIDESPREAD BY
AFTERNOON. CEILINGS OF 5KFT ARE EXPECTED BY MID MORNING. NOT AS
MUCH CONFIDENCE MGM AND TOI WILL SEE ANY WEATHER THROUGH THE TAF
PERIOD BUT CERTAINLY POSSIBLE A FEW SHOWERS OR STORMS COULD
DEVELOP NEARBY DURING THE LATE AFTERNOON.
BMX WATCHES/WARNINGS/ADVISORIES
NONE.
56/88
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