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000
FXUS64 KBMX 181756
AFDBMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1250 PM CDT SAT MAY 18 2013

.UPDATE...
FOR 18Z AVIATION DISCUSSION.

&&

.DISCUSSION...

ROUND ONE JUST ABOUT DONE ACROSS EASTERN SECTIONS OF CENTRAL
ALABAMA...BUT WHAT A FIRST ROUND. RADAR ESTIMATES OF 8 TO 9 INCHES
ACROSS NORTHERN CLAY COUNTY WITH REPORTS OF SERIOUS FLOODING
ACROSS PORTIONS OF CLAY...TALLADEGA...AND CALHOUN COUNTIES. RIVER
FLOODING ALONG THE TALLAPOOSA RIVER NEAR WADLEY IS ALSO ONGOING
AND EXPECTED TO REACH MODERATE STAGE LATER THIS AFTERNOON. PLEASE
REFER TO LOCAL FLOOD STATEMENTS FOR THE LATEST ON THE RIVER
FLOODING.

SO FOR THE AFTERNOON...WATCHING THE MAIN BOUNDARY THAT IS
CURRENTLY STRETCHED ACROSS NORTHWEST ALABAMA AND ARCHES SOUTH AND
EAST TO MONTGOMERY. SCATTERED SHOWERS HAVE DEVELOPED ALONG THIS
BOUNDARY AND WILL CONTINUE TO DEVELOP THROUGH THE PERIOD.
QUESTIONS HERE WILL BE HOW WIDESPREAD WILL ANY MODERATE TO HEAVY
RAINFALL BE THIS AFTERNOON AND TONIGHT ALONG AND JUST SOUTH OF THE
BOUNDARY. YES THE EAST HAS BEEN WORKED OVER QUITE A BIT THIS
MORNING AND WILL LIKELY NOT REBOUND TO MUCH THIS AFTERNOON...THE
WEST IS A DIFFERENT STORY. CLOUDS ARE BEGINNING TO CLEAR OUT AS
THE AIRMASS BEGINS TO MIX OUT SOUTH OF THE BOUNDARY. THIS WILL
LEAD TO WARMER TEMPERATURES AND LIKELY REDEVELOPMENT IN THE
NORTHWEST LATE AFTERNOON AND EVENING. PLENTY OF JUICY AIR STILL IN
PLACE SO STORMS THAT CAN GET ORGANIZED WILL LIKELY HOLD TOGETHER
AND MOVE ACROSS THE STATE. OTHER SMALLER SCALE BOUNDARIES ARE ALSO
MOVING NORTHWARD WITH ONE PARTICULAR ONE MOVING IN SW TUSCALOOSA
COUNTY AS OF 11AM.

LOOKING AT A FEW DEWPOINTS AND INCREASING CAPE NORTH AND WEST OF
THE AREA...FELT CONFIDENT ENOUGH TO GO AHEAD AND ISSUE A FLASH
FLOOD WATCH...PARTICULARLY FOR THE ALREADY IMPACTED AREAS. PWS
ACROSS THE AREA ARE 1.7. THIS PLACES IT IN THE 99TH PERCENTILE FOR
NORMAL PW FOR THIS DATE.

OVERALL LOOK FOR CONVECTION TO BE SLOW TO DEVELOP IN THE NORTH
THIS AFTERNOON...BUT ONCE IT DOES...LOOK FOR THE ANOTHER SLOW
MOVING COLD POOL MCS...ESPECIALLY WITH THE 850 JET KICKING IN WITH
NORTHWEST FLOW ON THE BACKSIDE OF THE UPPER TROUGH. UPDATES OUT
ALREADY.

16

&&

.AVIATION...
18Z TAF DISCUSSION.

ALTHOUGH THE ENTIRE REGION IS VERY UNSTABLE WITH CAPES NEAR OR ABOVE
2000 J/KG AND PW VALUES OF OVER 1.5 INCHES.  THIS WILL RESULT IN
NUMEROUS SHOWERS AND THUNDERSTORMS.  HOWEVER OF EVEN MORE CONCERN IS
SFC BOUNDARY FROM KJFX-KBHM-KMGM...UPPER LEVEL TROUGH JUST TO THE
NORTHEAST OF STATE...AND RIDGE TO THE WEST. AS A RESULT...EXPECT
WIDESPREAD MVFR CIGS THROUGH SUNSET DUE TO CUMULUS
INITIATION/PRECIP. IN ADDITION...BOUNDARY AND ONE MORE SHORT WAVE
OVERNIGHT WILL AID IN ANOTHER ROUND OF CONVECTION ESPECIALLY FOR THE
NORTHEAST SECTIONS OF STATE.  REGARDLESS OF CONVECTION...EXPECT
WIDESPREAD IFR CIGS/VSBYS DUE TO VERY MOIST CONDITIONS AND STRATUS
FORMATION...WHICH WILL LIKELY PERSIST THROUGH 15Z. AFTER 18Z...UPPER
RIDGE WILL MOVE OVER THE STATE WHICH WILL DIMINISH PRECIP CHANCES
DURING SUNDAY AFTERNOON.  STEFKOVICH

&&

.PREV DISCUSSION...
/ISSUED 347 AM CDT SAT MAY 18 2013/

MID LEVEL SHORT WAVE STRETCHING SOUTHEASTWARD ACROSS THE TENNESSEE
RIVER VALLEY CONTINUES TO SLOWLY MOVE EASTWARD THIS MORNING. THE
FORCING ASSOCIATED WITH THIS FEATURE COMBINED WITH CONTINUED
MOISTURE TRANSPORT FROM THE SOUTHWEST AND A LOW LEVEL CONVERGENT
ZONE HAS RESULTED IN CONTINUED REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ACROSS NORTHERN PORTIONS OF THE AREA. TRAINING OF
HEAVIER CELLS AS THEY MOVE WEST TO EAST COULD LEAD TO LOCALIZED
FLOODING THROUGH THE REMAINDER OF THE OVERNIGHT PERIOD. ACTIVITY
WILL GRADUALLY SHIFT EASTWARD THROUGH THE MORNING...WITH THE EAST
BECOMING THE FOCUS FOR CONVECTION SATURDAY AFTERNOON. WITH PWS
OVER 1.5 INCHES...HEAVY RAINFALL OVER ALREADY SOAKED AREAS COULD
LEAD TO LOCALIZED FLASH FLOODING THROUGH THE DAY. WITH TEMPS
REACHING INTO THE LOW TO MID 80S AND DEWPOINTS IN THE 60S...CAPE
VALUES WILL REACH 2000+ J/KG. WIND SHEAR VALUES ARE NOT EXPECTED
TO BE AS HIGH AS FRIDAY...LIMITING STORMS SEVERE POTENTIAL.
HOWEVER...ACTIVITY WILL LIKELY REMAIN ORGANIZED ALONG THE LOW
LEVEL CONVERGENT ZONE AS IT SHIFTS EAST AND SOUTH TODAY. SMALL HAIL
AND GUSTY WINDS WILL BE POSSIBLE WITH STRONGER STORMS. WILL CARRY
LIKELY POPS ACROSS A SIGNIFICANT PORTION OF THE AREA TODAY...BUT
WILL MAKE ADJUSTMENTS BEFORE SUNRISE BASED ON UPSTREAM TRENDS.
EXPECT POPS TO INCREASE FOR SOME PORTION OF CENTRAL ALABAMA WITH
THAT UPDATE.

MID LEVEL RIDGE AXIS MOVES ACROSS THE LOWER MISSISSIPPI RIVER VALLEY
SATURDAY NIGHT...PUSHING THE SHORT WAVE SLIGHTLY FURTHER EASTWARD. A
STRONG IMPULSE WILL ROTATE THROUGH THE MID LEVEL TROUGH AXIS JUST
TO OUR EAST ON SUNDAY. MODELS ARE SHOWING AN MCS DEVELOPING ACROSS
SOUTHEASTERN TN AND DIVING SOUTHEASTWARD ACROSS GEORGIA DURING THE
AFTERNOON AND EVENING. WILL MAINTAIN LIKELY POPS ACROSS THE EAST
ON SUNDAY AS HEIGHTS CONTINUE TO INCREASE ACROSS THE WEST. WILL
HAVE TO WATCH FUTURE MODEL RUNS FOR ANY CHANGES IN THE POTENTIAL
MCS TRACK...A SHIFT FURTHER WEST WOULD RESULT IN HIGHER POPS AND
SEVERE WORDING IN THE HWO.

THE RIDGE AXIS CONTINUES TO BUILD ACROSS THE SOUTHEAST MONDAY AND
TUESDAY...LIMITING CONVECTION DESPITE CONTINUED LOW LEVEL MOIST FLOW
FROM THE SOUTHWEST. THE NEXT SYSTEM WILL AFFECT CENTRAL ALABAMA BY
MIDWEEK AS A TROUGH MOVES OUT OF THE PLAINS AND DRAGS A WEAK FRONT
THROUGH THE AREA WEDNESDAY AND THURSDAY. MODELS CURRENTLY SHOW
CONSERVATIVE INSTABILITIES AND WIND SHEAR VALUES AS THE PARENT
SURFACE LOW IS WELL TO OUR NORTH. WILL CONTINUE TO EVALUATE
THAT SYSTEM OVER THE NEXT COUPLE DAYS. THROUGH NEXT WEEK...HIGHS
WILL BE IN THE 80S AND LOWS IN THE 60S.

14

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     78  65  84  66  90 /  60  70  70  20  10
ANNISTON    78  65  84  65  89 / 100  70  70  30  10
BIRMINGHAM  81  66  86  66  89 /  60  40  40  10  10
TUSCALOOSA  81  67  88  66  89 /  30  20  10  10  10
CALERA      81  66  86  66  89 /  60  30  20  10  10
AUBURN      78  64  85  65  88 / 100  30  50  30  10
MONTGOMERY  82  66  88  66  91 / 100  20  20  10  10
TROY        83  65  88  66  91 / 100  20  20  10  10

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR THE FOLLOWING
COUNTIES: BLOUNT...BULLOCK...CALHOUN...CHAMBERS...CHEROKEE...
CLAY...CLEBURNE...COOSA...ELMORE...ETOWAH...JEFFERSON...LEE...
MACON...MONTGOMERY...RANDOLPH...RUSSELL...SHELBY...ST. CLAIR...
TALLADEGA...TALLAPOOSA.

&&

$$