Flash Flood Warning 27, NWS Birmingham, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
633 PM CDT FRI JUL 5 2013

.UPDATE...
FOR 00Z AVIATION.

&&

.DISCUSSION...

WE'RE SEEING MORE OF THE SAME TODAY IN TERMS OF THE WIDESPREAD
DEVELOPMENT OF SHOWERS AND STORMS ACROSS CENTRAL ALABAMA. THE LARGE
UPPER TROUGH AND ASSOCIATED CLOSED LOW CONTINUES TO DIG TO OUR
NORTHWEST...WHILE THE BERMUDA HIGH TO OUR EAST REMAINS IN PLACE.
SURFACE ANALYSIS EARLY THIS AFTERNOON DEPICTS SURFACE RIDGING TRYING
TO NOSE INTO EASTERN ALABAMA FROM NORTHERN GEORGIA. SOUTHEASTERLY
WINDS IN RESPONSE TO THE RIDGING HAVE CONTINUED TO TRANSPORT A VERY
TROPICAL AIRMASS INTO THE SOUTHEAST WITH PWATS CURRENTLY 2 INCHES OR
ABOVE BASED ON THE LATEST RAP ANALYSIS. THE 12Z KBMX RAOB THIS
MORNING ACTUALLY PRESENTED A LITTLE MORE INSTABILITY THAN WE
OBSERVED YESTERDAY DUE TO A BIT OF DRY AIR WORKING IN ALOFT JUST
ABOVE 600MB. THIS INCREASE IN INSTABILITY HAS HELPED TO DEVELOP SOME
THUNDERSTORMS TODAY...ESPECIALLY ACROSS THE WESTERN TIER OF
COUNTIES. STILL...WE HAVE NOT SEEN SOLID COVERAGE OF RAIN FOR MOST
LOCATIONS TODAY MOST LIKELY DUE TO ALL OF THE CONVECTION THAT HAS
DEVELOPED ALONG THE GULF COAST THAT MAY BE CUTTING US OFF A BIT.
STILL...THE AMPLE AMOUNTS OF SYNOPTIC LIFT WILL CONTINUE TO PRODUCE
NUMEROUS SHOWERS AND STORMS THROUGHOUT THE AFTERNOON AND EVENING.

ALSO OF NOTE...THE SOUTHEASTERLY FLOW AT THE SURFACE HAS HELPED TO
PRODUCE EASTERLY WAVES/OUTFLOW BOUNDARIES THAT ARE MOVING
NORTHWESTERLY ACROSS SOUTHERN GEORGIA. THOSE BOUNDARIES WILL
CONTINUE TO MOVE INTO OUR SOUTHEASTERN COUNTIES OVER THE NEXT FEW
HOURS AND SHOULD HELP TO DEVELOP ADDITIONAL HEAVY SHOWERS AND STORMS
THROUGH THIS EVENING. WE WILL CONTINUE TO HIGHLIGHT THE THREAT FOR
FLASH FLOODING THROUGH SUNDAY MORNING AS ANY BAND THAT SETS UP COULD
PRODUCE RAINFALL RATES OF AT LEAST 1 TO 2 INCHES PER HOUR. ALWAYS
REMEMBER...IF YOU SEE WATER COVERING A ROADWAY TO TURN
AROUND...DON'T DROWN!

56/GDG

FOR THE REST OF THE PERIOD WE WILL CONTINUE TO SEE THE SAME WET
PATTERN THROUGH AT LEAST SUNDAY MORNING AND POTENTIALLY INTO
SUNDAY AFTERNOON AS THE TROUGH REMAINS OVER THE AREA DUE TO THE
OMEGA BLOCK CURRENTLY IN PLACE ACROSS THE CONUS AT THIS TIME.

THIS BLOCKING PATTERN FINALLY BEGINS TO PIVOT OUT AS THE RIDGE
BUILDS IN THE WEST. THIS WILL GET THE UPPER LOW THAT HAS BEEN
PARKED OVER MISSOURI TO FINALLY START MOVING EAST. ONCE THIS LOW
CAN MOVE EAST...OUR RAIN CHANCES WILL REDUCE DRAMATICALLY AND PUT
CENTRAL ALABAMA BACK INTO MORE OF SUMMERTIME PATTERN BY THE FIRST
OF THE WEEK. WARM AFTERNOONS AND SCATTERED THUNDERSTORMS DURING
THE PEAK HEATING OF THE DAY.

HOWEVER...JUST AS WE GET BACK INTO THE GROOVE OF THINGS ANOTHER
WRINKLE COMES ALONG IN THE FORM A TUTT MOVING ACROSS THE GULF OF
MEXICO. AT THE SAME TIME A FRONTAL SYSTEM IS MOVING SOUTH...SO WE
WILL SEE THE LOW BEGIN TO INTERACT THE TROUGH. MODELS DIFFER ON
THE AMOUNT OF MOISTURE THAT MAKES IT INTO THE AREA...BUT CHANCES
WILL BEGIN TO GO BACK UP ABOVE CLIMO BY WEDNESDAY. WITH TIMING AND
UNCERTAINTY THIS FAR OUT...WENT WITH HIGH CHANCE BUT WOULD EXPECT
THESE NUMBERS TO INCREASE OVER THE NEXT FEW DAYS.

16

&&

.AVIATION...
00Z TAF DISCUSSION.

THE PATTERN FROM THE LAST COUPLE OF DAYS WILL CONTINUE THROUGH
SATURDAY. LOOK FOR SCATTERED SHOWERS THRU THE OVERNIGHT PERIOD
WITH CIGS LOWERING TO IFR. THEN AN INCREASE IN RAIN/TSTORM COVERAGE
DURING THE DAY SATURDAY WITH CIGS IMPROVING SLIGHTLY TO MVFR.
THERE WILL ALMOST CERTAINLY BE FLUCTUATIONS IN CIG HEIGHTS THRU
PORTIONS OF THE PERIOD...AND ON AND OFF VFR CONDITIONS ARE LIKELY
SATURDAY. E/SE WINDS BELOW 10 KTS WILL PREVAIL.

19

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR ALL OF CENTRAL ALABAMA.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
638 PM CDT FRI JUL 5 2013

ALZ011>015-017>050-062345-
MARION-LAMAR-FAYETTE-WINSTON-WALKER-BLOUNT-ETOWAH-CALHOUN-CHEROKEE-
CLEBURNE-PICKENS-TUSCALOOSA-JEFFERSON-SHELBY-ST. CLAIR-TALLADEGA-
CLAY-RANDOLPH-SUMTER-GREENE-HALE-PERRY-BIBB-CHILTON-COOSA-TALLAPOOSA-
CHAMBERS-MARENGO-DALLAS-AUTAUGA-LOWNDES-ELMORE-MONTGOMERY-MACON-
BULLOCK-LEE-RUSSELL-PIKE-BARBOUR-
638 PM CDT FRI JUL 5 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE
NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM.

.DAY ONE...TONIGHT.

PERIODS OF HEAVY RAINFALL WILL CONTINUE TONIGHT AS A TROPICAL AIRMASS
REMAINS IN PLACE ACROSS THE AREA. DUE TO THE PREVIOUS HEAVY
RAINFALL...FLASH FLOODING IS POSSIBLE IF ANY PERSISTENT HEAVIER RAIN
BANDS DEVELOP.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

CONTINUED HEAVY RAINFALL ACROSS CENTRAL ALABAMA WILL LEAD TO
ADDITIONAL FLASH FLOODING POTENTIAL SATURDAY AND POSSIBLY SUNDAY.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT IS NOT
EXPECTED AT THIS TIME.