Severe Thunderstorm Warning 117, NWS Birmingham, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
921 AM CDT TUE JUL 23 2013

.UPDATE...
MESOSCALE UPDATE.

&&

.DISCUSSION...

FEATURE ONE WAS AN OUTFLOW BOUNDARY LOCATED GENERALLY FROM AUBURN
TO MONTGOMERY TO EUTAW. SHOWERS AND THUNDERSTORMS CONTINUE ALONG
THIS BOUNDARY FROM WETUMPKA TO ROANOKE. THIS ACTIVITY WILL CONTINUE
EAST SOUTHEAST TOWARD TUSKEGEE AUBURN AND PHENIX CITY THIS
MORNING. A SECONDARY OUTFLOW BOUNDARY WAS LOCATED FROM THE
BIRMINGHAM METRO TOWARD HEFLIN. THUNDERSTORMS WERE ALSO DEVELOPING
ALONG THIS AXIS. AN UPPER LEVEL DISTURBANCE WAS MOVING ACROSS
NORTHERN ALABAMA THIS MORNING AND THIS WAS THE INITIATOR OF THE
CONVECTION. ADDITIONAL STORMS WILL AFFECT AREAS FROM ONEONTA TO
CENTRE ASSOCIATED WITH THIS FEATURE ALOFT.

FEATURE TWO WAS AN AREA OF CLEARING SKIES AND INSOLATION NORTH AND
WEST OF I-65/I-20. THUNDERSTORMS ARE INITIATING IN THIS AREA TOO
AS INSTABILITIES ARE INCREASING.

ANOTHER UPPER LEVEL DISTURBANCE IN THE NORTHWEST FLOW ALOFT WAS
LOCATED OVER THE LOWER MISSISSIPPI VALLEY AND WAS PRODUCING STORMS
ACROSS NORTHERN MISSISSIPPI AND INTO ARKANSAS AND TENNESSEE. THIS
FEATURE WILL SWING INTO WESTERN ALABAMA AROUND NOON.
THEREFORE...EXPECT A FEW ROUNDS OF THUNDERSTORMS THROUGH THE EARLY
EVENING HOURS ACROSS MUCH OF CENTRAL ALABAMA.

THE 12Z AREA RAOBS AND THE SATELLITE DEPICTION INDICATE HIGH
PRECIP WATER OVER MUCH OF THE AREA AGAIN TODAY...IN SOME
INSTANCES...OVER 2 INCHES. BULK SHEAR IS NOT IMPRESSIVE BUT A
DEVELOPING COLD POOL IN NORTHERN MISSISSIPPI SHOULD ALLOW SOME
STORM ORGANIZATION AND REGENERATION ALONG WITH THE UPPER SUPPORT.
MID LEVEL LAPSE RATES ARE A BIT BETTER THAN YESTERDAY WITH
INSTABILITY VALUES NEARLY THE SAME. THEREFORE...WENT AHEAD AND
ADDED THE LOCALIZED CHANCE OF FLASH FLOODING AND WIND GUSTS 35 TO
60 MPH IN THE HWO THROUGH 10 PM AREA WIDE.

STAY TUNED FOR FURTHER UPDATES AND BE PREPARED FOR THE ISSUANCE OF
A FEW WARNINGS TODAY.

75

&&

.AVIATION...
12Z TAF DISCUSSION.

ANOTHER MORNING OF VARIABLE CIGS ACROSS CENTRAL ALABAMA...BUT
CURRENTLY CIGS ARE GENERALLY IFR WITH SOME PATCHY FOG OUT THERE
AS WELL. A COMPLEX OF STORMS DEVELOPED OVERNIGHT AND CONTINUES TO
PUSH SE ACROSS THE NORTHERN HALF OF THE FORECAST AREA. HAVE
INCLUDED A TEMPO FOR TSRA AT THE NORTHERN TERMINALS WITH SOME
HIGHER CIGS. STORMS WILL BRING HEAVY RAIN...GUSTY WINDS...AND
LIGHTNING. THESE NORTHERN AREAS COULD SEE A BREAK ONCE THESE
STORMS MOVE THRU BEFORE YET ANOTHER WAVE MOVES IN FROM THE NW
LATER THIS MORNING/AFTERNOON. FOR THE SOUTHERN SITES...IT SHOULD
BE SEVERAL HOURS BEFORE WHAT'S LEFT OF THE ONGOING COMPLEX PUSHES
THAT FAR SOUTH. WILL CARRY VCTS FOR ALL TERMINALS THRU THE
REMAINDER OF THE DAYLIGHT HOURS. DUE TO UNCERTAINTY IN WHETHER ANY
ADDITIONAL WAVES WILL PUSH THRU OVERNIGHT DID NOT INCLUDE ANY
MENTION OF TS AT THIS TIME. WINDS WILL GENERALLY BE OUT OF THE SW
AROUND 10 KTS TODAY.

19

&&

.PREV DISCUSSION...
/ISSUED 335 AM CDT TUE JUL 23 2013/

AN ACTIVE WEATHER PATTERN WILL CONTINUE TODAY AS UPSTREAM
DISTURBANCES EMBEDDED WITHIN NORTHWEST FLOW MOVE TOWARD CENTRAL
ALABAMA. SHOWERS AND STORMS ARE ALREADY DEVELOPING ACROSS NORTHERN
MISSISSIPPI AND WESTERN TENNESSEE AND THIS MAY BE AN EARLY
INDICATION OF A RATHER ACTIVE AFTERNOON FOR US. THERE IS VERY
LITTLE SKILL IN TRYING TO PIN DOWN TIMING AND LOCATION OF THESE
SHOWERS AND STORMS BUT FEELING PRETTY CONFIDENT THAT MUCH OF THE
AREA WILL SEE MEASURABLE RAINFALL THIS AFTERNOON. RAISED INTO THE
LIKELY CATEGORY (60 PERCENT) ACROSS THE ENTIRE CWA. A SIMILAR
STORY IS EXPECTED FOR WEDNESDAY WITH LIKELY POPS ONCE AGAIN.

THE GFS AND ECMWF ARE IN BETTER AGREEMENT THAT DRIER AIR WILL MOVE
INTO THE REGION ON THURSDAY AND FRIDAY IN ASSOCIATION WITH A
SHORTWAVE UPPER-LEVEL RIDGE. EXPECTING MAINLY DRY CONDITIONS BOTH
DAYS WITH A SLIGHT INCREASE IN AFTERNOON HIGHS.

MODEL SPREAD BEGINS TO DEVELOP FOR THE WEEKEND REGARDING THE
TIMING OF THE NEXT DISTURBANCE BUT THE GFS AND ECMWF AGREE THAT A
FAIRLY STRONG SYSTEM BY JULY STANDARDS WILL APPROACH THE REGION.
SUCH A SITUATION SHOULD LEAD TO A DECENT SHOT AT SHOWERS AND
STORMS WITH A POSSIBLE FRONTAL PASSAGE BY SUNDAY IF THE GFS
SOLUTION VERIFIES.

87/GRANTHAM

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     87  70  87  69  87 / 100  40  60  10  10
ANNISTON    86  71  86  68  87 / 100  40  60  10  10
BIRMINGHAM  88  72  88  69  88 / 100  40  60  10  10
TUSCALOOSA  89  72  89  71  91 / 100  40  60  10  10
CALERA      87  71  87  70  88 / 100  40  60  20  10
AUBURN      87  69  87  70  89 / 100  40  60  20  20
MONTGOMERY  89  72  89  72  90 /  70  40  60  20  20
TROY        88  71  88  71  89 /  70  40  60  30  20

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
834 AM CDT TUE JUL 23 2013

ALZ011>015-017>050-241345-
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-
834 AM CDT TUE JUL 23 2013

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

.DAY ONE...TODAY AND TONIGHT.

A FEW ROUNDS OF THUNDERSTORMS ARE EXPECTED TODAY AREA WIDE. LOCALIZED
AREAS MAY EXPERIENCE HEAVY RAINFALL LEADING TO SOME FLOODING.
ADDITIONALLY...ISOLATED STORMS WILL BE CAPABLE OF PRODUCING WIND
GUSTS OF 35 TO 60 MPH. THE ACTIVITY SHOULD LOSE SOME INTENSITY BY
10 PM.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT MAY BECOME
NECESSARY THROUGH THIS EVENING FOR ISOLATED STRONG TO SEVERE
STORMS.

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