EF0 tornado, Fair Oaks, Alabama, January 23, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1137 PM CST SUN JAN 22 2012

.UPDATE...
AVIATION DISCUSSION.

&&

.DISCUSSION...

WANTED TO TAKE A COUPLE OF MINUTES AND TALK ABOUT THE MESOSCALE
ANALYSIS OF WHAT SEEMS TO BE GOING ON RIGHT NOW AND WHERE WE MAY BE
HEADED OVER THE NEXT FEW HOURS.

LATEST SURFACE ANALYSIS OVER THE SOUTHERN UNITED STATES PUTS THE
LOWER MISSISSIPPI VALLEY SOLIDLY INTO THE WARM SECTOR OF THIS
SYSTEM.  925 AND 850MB LOW LEVEL JETS OF 50-65 KTS HAVE PUSHED THIS
WARM FRONT ALMOST AS FAR NORTH AS THE BOOTHEEL OF MISSOURI.  THIS
HAS ALLOWED LOW TO MIDDLE 60S DEW POINTS TO ADVECT INTO ARKANSAS AND
WESTERN TENNESSEE.  THIS HAS LED TO SIGNIFICANT ATMOSPHERIC
DESTABILIZATION OVER THIS AREA AND WITH THE AMOUNT OF LOW LEVEL
HELICITY BECAUSE OF THE DEEPENING OF THE SURFACE LOW...THIS AREA HAS
BEEN PUT UNDER A PDS WATCH.

CLOSER TO HOME...THE WARM FRONT HAS REALLY BEEN RETARDED FROM MAKING
A STRONG INLAND PUSH DUE TO THE FACT THAT THOSE LOW LEVEL JETS ARE
ONLY AROUND 25-30 KTS. SURFACE DEW POINTS IN THE MIDDLE TO UPPER 50S
ARE BEING SEEN OVER MUCH OF CENTRAL ALABAMA...NOT TO MENTION A 48
DEGREE DEW POINT IN DEKALB OVER THE LAST HOUR.  THIS SHOULD BEGIN TO
CHANGE THOUGH OVER THE NEXT COUPLE OF HOURS.  AS THE UPPER TROUGH
CONTINUES TO PUSH NORTHEASTWARD AND THE SURFACE LOW DEEPENS...THE
MOISTURE NEEDED TO DEVELOP STRONG STORMS WILL START TO PUSH CLOSER
TO US.  LATEST MODELS TRENDS SHOW THIS 50 KT 850MB JET DEVELOP OVER
US IN THE 9 TO 10 PM TIME FRAME...AND THIS IS WHAT WE REALLY NEED TO
DESTABILIZE ENOUGH FOR THE SEVERE CONVECTION.  THE QUESTION WILL BE
IF THERE IS ENOUGH TIME TO GET THAT LOW LEVEL MOISTURE IN HERE AHEAD
OF THE FRONT TO GIVE US ENOUGH SURFACE BASED INSTABILITY.  ONE THING
THAT MIGHT NEGATE THE LACK OF SURFACE BASED INSTABILITY IS THE
OVERALL FORCING OF THIS SYSTEM.  200-300MB WIND FIELDS SHOW QUITE A
BIT OF UPPER LEVEL DIVERGENCE TO HELP WITH THE NECESSARY LIFT.

TIMING-WISE...WE HAVE UPDATED THE ARRIVAL TIME INTO OUR NORTHWESTERN
COUNTIES.  IT LOOKS LIKE IT MAY BE CLOSER TO MIDNIGHT BEFORE THE
LINE STARTS TO MOVE INTO THE STATE...THOUGH I WOULDN'T BE SURPRISED
TO SEE A WATCH COME OUT BEFORE THAT.  WE ARE WATCHING CONVECTION IN
SOUTHERN MISSISSIPPI THAT IS MOVING NEWD...AND THOUGH IT LOOKED
HEALTHY BECAUSE IT IS COMING OUT OF THE VERY UNSTABLE MARINE
LAYER...IT IS MOVING AN ATMOSPHERE THAT IS NOT PERFECT FOR CONTINUED
DEVELOPMENT...JUST YET.  THE CLOUD COVER FROM EARLIER TODAY HAS
REALLY PUT A CRAMP ON ANY DEVELOPMENT AHEAD OF THE LINE.  THAT
SAID...IT LOOKS LIKE THE LINE OF THUNDERSTORMS ALONG THE FRONT IS
GOING TO BE THE MAIN /AND MAYBE ONLY/ EVENT FOR TONIGHT.  WITH LOW
LEVEL HELICITIES OF 200-350 M^2/S^2...THAT SHOULD BE ENOUGH TO ALLOW
FOR SOME EMBEDDED SUPERCELL GROWTH WITH THE LINE AS IT MOVES TO THE
STATE...BUT AGAIN STRENGTH OF THESE STORMS IS REALLY GOING TO DEPEND
ON THE AMOUNT OF SURFACE BASED INSTABLITY WE CAN REALIZE SO THAT
STORMS CAN BE ROOTED FROM THE SURFACE.

AS FOR TIMING FOR THE REST OF THE STATE...BIRMINGHAM IS LOOKING LIKE
2-4 AM...MONTGOMERY 3-5 AM...AND I WOULD LIKE TO SEE THE LINE
PUSHING OUT OF THE STATE...OR WEAKENING BY 6 TO 8 AM.

27

&&

.AVIATION...
06Z TAF DISCUSSION.

SHOWERS AND THUNDERSTORMS ARE BEGINNING TO MOVE INTO WESTERN
ALABAMA...AHEAD OF A STRONG COLD FRONT. THIS ACTIVITY WILL SLOWLY
SPREAD ACROSS THE NORTHERN HALF OF THE STATE DURING THE EARLY
MORNING HOURS. THUNDERSTORMS WILL BE CAPABLE OF PRODUCING DAMAGING
WINDS...LARGE HAIL...HEAVY RAINFALL...AND TORNADOES. HAVE TIMED OUT
CONVECTION FOR EACH TERMINAL BASED ON CURRENT MOTIONS...AND WILL
ADJUST AS NEEDED. CONVECTION WILL BE SLOWER TO MOVE INTO MGM AND
TOI...AND DO NOT EXPECT ACTIVITY THERE UNTIL AFTER 13Z.

BEHIND THE FRONT...WINDS WILL TURN TO THE NORTHWEST AND SKIES WILL
CLEAR THROUGH THE AFTERNOON.

14

&&

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

&&

27/14

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
722 PM CST SUN JAN 22 2012

ALZ011>015-017>050-240100-
AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE-
CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE-
JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY-
PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA-
TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON-
722 PM CST SUN JAN 22 2012

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

.DAY ONE...TONIGHT.

A SIGNIFICANT SEVERE WEATHER THREAT EXISTS OVERNIGHT. DAMAGING
STRAIGHT LINE WINDS...TORNADOES...AND LARGE HAIL ARE ALL POSSIBLE.
THESE THREATS ASSOCIATED WITH A LINE OF THUNDERSTORMS ALONG THE COLD
FRONT COULD BEGIN AS EARLY AS 10 PM IN THE WEST...AND LAST THROUGH
THE OVERNIGHT HOURS ACROSS THE REMAINDER OF THE AREA. SCATTERED
THUNDERSTORMS ARE POSSIBLE AHEAD OF THE MAIN LINE BEFORE 10 PM...AND
THESE COULD CARRY THE SAME SEVERE WEATHER THREATS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE IS A CHANCE THAT ANY SEVERE THUNDERSTORMS THAT DEVELOP
TONIGHT COULD CONTINUE INTO THE MORNING HOURS ON MONDAY IN THE
EASTERN PORTIONS OF CENTRAL ALABAMA. THIS SEVERE WEATHER THREAT
SHOULD END BY 10 AM.

ANOTHER ROUND OF SEVERE WEATHER IS POSSIBLE DURING THE DAY ON
THURSDAY...POTENTIALLY LASTING UNTIL FRIDAY. DIFFERENCES IN TIMING
AND OTHER DETAILS AMONG THE COMPUTER MODEL SOLUTIONS LEADS TO A LOWER
CONFIDENCE AT THIS TIME...SO STAY TUNED OVER THE NEXT FEW DAYS FOR
MORE INFORMATION.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT WILL LIKELY BE
NEEDED IN ALL AREAS TONIGHT THROUGH EARLY MONDAY MORNING. ACTIVATION
MAY ALSO BE NEEDED THURSDAY AND/OR FRIDAY.