Severe Thunderstorm Warning 107, NWS Birmingham, AL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BIRMINGHAM AL
644 PM CDT FRI JUN 28 2013

.UPDATE...
FOR 00Z AVIATION AND MESOSCALE UPDATE.

&&

.DISCUSSION...

ISSUED THE WATCH FOR THE ACTIVITY ONGOING IN THE SOUTHWEST. THE
OVERALL CORES ON THE LATEST TRENDS ARE NOT QUITE HIGH...BUT THE
LIGHTNING IS EXTREME RIGHT NOW. THE ACTIVITY IS MOVING INTO AN
AREA THAT HAS NOT REALLY BEEN WORKED OVER YET TODAY...WITH MLCAPE
AT 3500. THIS GRADIENT IS FAIRLY TIGHT AND ONLY 1500 AS YOU WORK
INTO CENTRAL TUSCALOOSA AND CENTRAL BIBB. THIS IS THE MAIN FACTOR
OF NOT INCLUDING TUSCALOOSA AND BIBB IN THE WATCH. LOOKS LIKE THE
ACTIVITY IN JACKSON IS BEGINNING TO COLD POOL AND ACCELERATE
SOUTHWARD...SO THE SEVERE THREAT MAY NOT GO AS LONG AS THE CURRENT
WATCH. ACTIVITY ALONG AND EAST OF I-65 FORMED ALONG THE
DIFFERENTIAL HEATING BOUNDARY. HOWEVER...THIS BOUNDARY IS FAIRLY
SMALL AS MOST OF THE ACTIVITY FORMED ALONG I-20 AND MOVED SOUTH
THIS AFTERNOON. NOT EXPECTING SEVERE STORMS WITH THE NORTHERN
ACTIVITY.

16

&&

.AVIATION...
00Z TAF DISCUSSION.

MADE ADJUSTMENTS FOR THE TIMING OF THUNDERSTORMS FOR THE TAF
SITES. HIGHEST CONFIDENCE IN TCL FOR TSRA THROUGH 01 TO 02Z. VCTS
FOR BHM AND EET WILL END FAIRLY QUICKLY AFTER 01Z. ANB MAY SEE A
THUNDERSTORM THROUGH 02Z. IF THIS ACTIVITY CAN HOLD TOGETHER THEN
IT WILL WORK INTO MGM AND TOI AFTER 3Z...SO WENT AHEAD AND
INCLUDED VCTS. HOWEVER GIVEN THE FACT THAT THESE AREAS ALREADY
GOT WORKED OVER...THINKING THAT THE OVERALL COVERAGE WILL
DECREASE...SO DID NOT INCLUDE ANY TEMPO HERE AT ALL.

PATCHY FOG POSSIBLE ONCE THE ACTIVITY DISSIPATES. THE MAIN TROUGH
THAT THIS ACTIVITY IS ASSOCIATED WITH WILL BE CLOSER TO MGM AND
TOI ON SATURDAY...SO WENT WITH VCTS ONLY FOR THESE SITES AFTER
18Z. AMENDMENTS WILL BE SENT AS NEEDED.

16

&&

.PREV DISCUSSION...
/ISSUED 317 PM CDT FRI JUN 28 2013/

THUNDERSTORMS DEVELOPED EARLIER TODAY ALONG AN OUTFLOW BOUNDARY
WHICH PUSHED INTO NORTHWESTERN AREAS THIS MORNING. LINE IS CURRENTLY
NEAR INTERSTATE 85 AND QUICKLY PUSHING SOUTHEASTWARD. THERE REMAINS
QUITE A BIT OF UNCERTAINTY AS TO WHETHER ADDITIONAL DEVELOPMENT IS
POSSIBLE THIS EVENING. A COUPLE BRIEF SHOWERS HAVE DEVELOPED ACROSS
NORTHERN LOCATIONS THIS AFTERNOON...BUT HAVE HAD PROBLEMS
MAINTAINING ANY SIGNIFICANT UPDRAFTS. AIRMASS ACROSS THE NORTH HAD A
DIFFICULT TIME RECOVERING TODAY...WITH TEMPS ONLY MAKING IT INTO THE
MID TO UPPER 80S AND DEWPOINTS IN THE UPPER 60S AND LOWER 70S.
ACROSS THE SOUTH...DEWPOINTS JUMPED INTO THE MID TO UPPER 70S AS
TEMPS REACHED THE LOWER 90S PRIOR TO RAINFALL.

LOOKING FURTHER TO OUR NORTHWEST...A BOUNDARY CAN BE SEEN ON VISIBLE
EXTENDING FROM NORTH OF NASHVILLE TO NEAR MEMPHIS...AND A SECOND
BOUNDARY ACROSS SOUTHERN ILLINOIS AND MISSOURI. BELIEVE THE MOST
SOUTHERN BOUNDARY IS ANOTHER PREFRONTAL TROUGH WHERE DEWPOINTS ON
THE BACK SIDE FALL INTO THE 60S WITH A SHIFT TO NORTHWESTERLY WINDS.
THE SECOND BOUNDARY IS THE ACTUAL COLD FRONT WE HAVE BEEN
ADVERTISING FOR SEVERAL DAYS...WITH DEWPOINTS DROPPING INTO THE 50S
WITH GUSTY NORTHERLY WINDS. THESE BOUNDARIES WILL CONTINUE
SOUTHWARD...AND BRING THE POSSIBILITY OF SCATTERED THUNDERSTORM
DEVELOPMENT LATE THIS EVENING. DO NOT EXPECT THE COVERAGE OR
INTENSITY WE SAW THIS AFTERNOON...BUT WILL CARRY CHANCE POPS INTO
THE OVERNIGHT PERIOD. WITH THE UNPREDICTABILITY OF NORTHWESTERLY
FLOW...THERE IS A CHANCE A MORE ORGANIZED CLUSTER OF STORMS COULD
DEVELOP IN ARKANSAS...BUT STORM MOTION SHOULD KEEP IT TO OUR WEST.
SATURDAY...THE FRONT CURRENTLY STILL TO OUR NORTH SETS UP OVER THE
AREA AND VERY SLOWLY DRIFTS SOUTHWARD. WIND PARAMETERS AND PWS
DECREASE SIGNIFICANTLY BY TOMORROW. EXPECT SCATTERED THUNDERSTORMS
MAINLY DURING THE AFTERNOON WITH MOST OF THE ACTIVITY ACROSS THE
SOUTHEASTERN HALF OF THE AREA. SEVERE THUNDERSTORMS ARE UNLIKELY.

UPPER LEVEL LONGWAVE TROUGH BEGINS TO DIG SOUTHWARD ACROSS THE
EASTERN CONUS SUNDAY...GRADUALLY RETROGRADING WESTWARD THROUGH MUCH
OF NEXT WEEK AS ADDITIONAL SHORTWAVES ROTATE SOUTHWARD FROM CENTRAL
CANADA. THIS WILL KEEP THE POSSIBILITY OF SCATTERED ACTIVITY IN THE
FORECAST FOR MOST PERIODS NEXT WEEK. LOWER THICKNESSES AND CLOUD
COVER WILL ALSO KEEP TEMPS IN CHECK...WITH HIGHS IN THE 80S MID TO
UPPER 80S AND OVERNIGHT LOWS IN THE 60S.

14

&&

.PRELIMINARY POINT TEMPS/POPS...
GADSDEN     69  89  64  85  64 /  50  20  10  30  20
ANNISTON    72  88  66  84  65 /  30  20  10  30  20
BIRMINGHAM  72  89  66  85  65 /  40  20  10  30  20
TUSCALOOSA  71  91  67  87  66 /  40  20  10  20  20
CALERA      73  88  67  85  65 /  30  20  10  20  20
AUBURN      74  88  66  87  66 /  30  50  20  30  20
MONTGOMERY  76  91  69  90  67 /  50  50  20  20  20
TROY        75  89  68  89  67 /  50  50  30  20  20

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
528 PM CDT FRI JUN 28 2013

ALZ011>015-017>050-292230-
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-
528 PM CDT FRI JUN 28 2013

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

.DAY ONE...TONIGHT.

SEVERE THUNDERSTORMS ARE POSSIBLE THROUGH 9 PM ACROSS A SMALL
PORTION OF SOUTHWEST CENTRAL ALABAMA. THESE STORMS COULD PRODUCE
DAMAGING WINDS....LOCALLY HEAVY RAINFALL...AND FREQUENT CLOUD TO
GROUND LIGHTNING.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT WILL BE
NEEDED UNTIL AROUND 9 PM THIS EVENING ACROSS SOUTHWEST CENTRAL
ALABAMA.

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