Tornado and Damaging Winds in Alabama, December 20, 2012

AREA FORECAST DISCUSSION...UPDATE TO AVIATION
NATIONAL WEATHER SERVICE MOBILE AL
1130 PM CST WED DEC 19 2012

.AVIATION (06Z ISSUANCE)...AS A FRONT APPROACHES THE AREA...IFR
LEVEL CIGS WITH INCREASING COVERAGE OF RAINSHOWERS IS EXPECTED
BEFORE SUNRISE. AROUND 12Z...A FRONT IS EXPECTED TO BEGIN TO CROSS
THE AREA...BRINGING LOCAL LIFR CIGS/VISBYS. STRONG NORTHWESTERLY
WINDS WILL FOLLOW THE FROPA AND SKIES ACROSS THE AREA CLEARING
THROUGH THE AFTERNOON INTO THE EVENING.

/16

&&

.SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...LOW PRESSURE CURRENTLY
OVER THE TEXAS PANHANDLE WILL QUICKLY MOVE EAST NORTHEAST THROUGH
TOMORROW AS A POTENT SHORTWAVE MOVES EAST OUT OF THE FOUR CORNERS.
THE ATTENDANT COLD FRONT WILL BE IN THE VICINITY OF THE MS RIVER BY
12Z TOMORROW...NEAR I-65 BY 18Z...AND WELL EAST OF THE FORECAST AREA
BY 00Z. THE EVENING HOURS LOOK DRY ACROSS THE AREA WITH SHOWERS
LIKELY NOT DEVELOPING OVER THE WESTERN HALF OF THE AREA UNTIL AFTER
MIDNIGHT WHEN ISENTROPIC LIFT STRENGTHENS IN RESPONSE TO THE
INTENSIFYING SOUTHWESTERLY LOW LEVEL JET. THIS ACTIVITY WILL BE
LOCATED WELL AHEAD OF THE COLD FRONT WITH LITTLE TO NO INSTABILITY
PRESENT. THE MAIN RISK FOR STRONGER STORMS OCCURS ALONG AND
IMMEDIATELY AHEAD OF THE COLD FRONT WHERE THE STRONGEST DEEP LAYER
FORCING WILL BE PRESENT. THIS LINE WILL BE IN OR JUST TO THE WEST OF
OUR SE MS COUNTIES BY DAYBREAK...WITH THE LINE RAPIDLY MOVING EAST
THROUGH THE MORNING HOURS. WHILE DEEP LAYER SHEAR AND LOW LEVEL
HELICITY REMAIN SUPPORTIVE OF SEVERE WEATHER...MLCAPES STAY BELOW 500
J/KG IN ALL GUIDANCE WITH WARM MID LEVEL TEMPERATURES PRODUCING
MEAGER LAPSE RATES. THIS MEANS THAT THE CHANCES FOR VIGOROUS UPDRAFTS
WILL BE LIMITED AND THE LINE OF CONVECTION THAT COMES THROUGH WILL BE
LOW TOPPED WITH LITTLE LIGHTNING. ANOTHER NEGATIVE FACTOR FOR SEVERE
WEATHER IS THE ZONE OF UPPER LEVEL DIVERGENCE WILL BE LOCATED WELL TO
THE NORTHEAST OF THE FORECAST AREA AND NOT IN PHASE WITH THE LOW
LEVEL CONVERGENCE NOTED FURTHER SOUTH. WHILE WE ARE NOT EXPECTING AN
OUTBREAK OF SEVERE WEATHER...AN ISOLATED SEVERE CELL CANNOT BE RULED
OUT WITH LOCALIZED DAMAGING WIND GUSTS BEING THE PRIMARY THREAT IN
ANY LEWPS OR BOWS THAT DEVELOP ALONG THE LINE. THE BULK OF THE SHOWER
AND ISOLATED TSTM ACTIVITY IS EXPECTED TO PUSH EAST OF THE FORECAST
AREA DURING THE EARLY AFTERNOON HOURS. THE QUICK MOVEMENT OF THE
SYSTEM WILL LIMIT RAINFALL TOTALS TO UNDER AN INCH IN MOST LOCATIONS
WITH AVERAGE TOTALS OF ONE QUARTER TO ONE HALF INCH CURRENTLY
FORECAST.

IT WILL BECOME QUITE WINDY IMMEDIATELY AHEAD AND BEHIND THE COLD
FRONT. WINDS OF 30-40 KT ARE PRESENT IN THE MIXED LAYER THROUGH THE
DAY WITH MIXING BECOMING MAXIMIZED IN THE COLD AIR ADVECTION THAT
DEVELOPS IN THE WAKE OF THE FRONTAL PASSAGE THURSDAY AFTERNOON.
FREQUENT GUSTS OF 30-35 MPH ARE LIKELY WITH A FEW GUSTS TO 40 MPH. A
WIND ADVISORY HAS BEEN ISSUED FROM 9AM TO 7PM TOMORROW.

DEPICTED A NON DIURNAL TEMP CURVE TONIGHT AND TOMORROW WITH LOWS
BEING REACHED THIS EVENING...WARMING UP OVERNIGHT...HIGHS SET IN THE
MORNING/MIDDAY...WITH FALLING TEMPS BEHIND THE FRONT. HIGHS/LOWS
STILL COME CLOSE TO MAV/MET GUIDANCE AND DID NOT DEVIATE MUCH.
THURSDAY NIGHT WILL BE MUCH COLDER WITH LOWS DROPPING INTO THE LOW TO
MID 30S. A CONTINUED BREEZE OVERNIGHT WILL PLACE WIND CHILLS IN THE
20S.

A RETURN TO WINTER LIKE TEMPS WILL OCCUR ON FRIDAY WITH HIGHS ONLY
CLIMBING INTO THE LOW TO MID 50S WITH MOST LOCATIONS DROPPING BELOW
FREEZING FRIDAY NIGHT. 34/JFB

&&

.LONG TERM (SATURDAY THROUGH WEDNESDAY)...WEAK RIDGING TO ZONAL FLOW
ALOFT AND A LARGE SURFACE HIGH PRESSURE ACROSS THE SOUTHEAST STATES
WILL DOMINATE THE WEATHER PICTURE WITH ANOTHER DRY PERIOD THROUGH
THE WEEKEND. THE SURFACE HIGH WILL MOVE EAST INTO THE WESTERN
ATLANTIC EARLY IN THE WORK WEEK...BRINGING A RETURN FLOW AND LOW
LEVEL MOISTURE BACK ACROSS THE REGION. THIS AHEAD OF ANOTHER COLD
FRONT APPROACHING THE REGION FROM THE NORTHWEST. THIS WILL SET UP
SEVERAL ROUNDS OF SHOWERS AND STORMS ON MONDAY THROUGH WEDNESDAY.
THERE ARE STILL SOME DIFFERENCES BETWEEN THE RELIABLE GLOBAL MODELS
IN THE TIMING OF THE EVENTUAL FRONTAL PASSAGE. TEMPERATURES WILL
RETURN TO NEAR NORMAL OR JUST ABOVE NORMAL BY THE WEEKEND. 22/34

&&

.MARINE...SOUTHERLY WINDS AND SEAS WILL BUILD TONIGHT THROUGH
THURSDAY MORNING IN RESPONSE TO A STRONG COLD FRONT APPROACHING FROM
THE WEST. THE COLD FRONT WILL MOVE ACROSS THE MARINE AREA DURING THE
DAY THURSDAY WITH A STRONG OFFSHORE FLOW DEVELOPING IN THE WAKE OF
THE FRONT BY THE AFTERNOON AND CONTINUING THROUGH FRIDAY. NORTHERLY
WINDS WILL GRADUALLY DIMINISH FRIDAY AND SATURDAY AS HIGH PRESSURE
BUILDS IN FROM THE WEST. /13

&&

.FIRE WEATHER...A STRONG COLD FRONT WILL MOVE THROUGH THE REGION ON
THURSDAY. SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE FRONT AND MOST
LOCATIONS SHOULD EXPERIENCE A WETTING RAIN. IT WILL BECOME BREEZY TO
WINDY JUST AHEAD OF AND BEHIND THE FRONT. MUCH DRIER AND COOLER AIR
WILL FILTER INTO THE REGION THROUGH FRIDAY IN THE WAKE THE FRONT.
RELATIVE HUMIDITY VALUES WILL FALL TO CRITICAL LEVELS ACROSS THE
WESTERN FLORIDA PANHANDLE. IN ADDITION...ERC AND 20 FOOT WIND SPEEDS
ALSO NEAR CRITICAL LEVELS. THEREFORE...A FIRE WEATHER WATCH HAS BEEN
ISSUED FOR THAT AREA. HUMIDITY MAY ALSO COME CLOSE TO CRITICAL LEVELS
ACROSS SOUTHWEST AND SOUTH CENTRAL ALABAMA...AND A FIRE WEATHER WATCH
MAY BECOME NECESSARY. 34/JFB

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      61  72  32  55  30 /  70  80  00  00  00
PENSACOLA   65  74  37  55  34 /  40  80  00  00  00
DESTIN      65  72  39  55  37 /  20  80  00  00  00
EVERGREEN   54  70  31  54  26 /  50  80  00  00  00
WAYNESBORO  58  68  30  54  27 /  70  80  00  00  00
CAMDEN      54  70  30  53  27 /  70  80  00  00  00
CRESTVIEW   54  74  33  55  27 /  20  80  00  00  00

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...WIND ADVISORY FROM 9 AM THURSDAY TO 7 PM THURSDAY FOR THE
     FOLLOWING ZONES: BUTLER...CHOCTAW...CLARKE...CONECUH...
     COVINGTON...CRENSHAW...ESCAMBIA...LOWER BALDWIN...LOWER
     MOBILE...MONROE...UPPER BALDWIN...UPPER MOBILE...
     WASHINGTON...WILCOX...

FL...FIRE WEATHER WATCH FROM 10 AM FRIDAY TO 5 PM FRIDAY FOR THE
     FOLLOWING ZONES: COASTAL ESCAMBIA...COASTAL OKALOOSA...
     COASTAL SANTA ROSA...INLAND ESCAMBIA...INLAND OKALOOSA...
     INLAND SANTA ROSA...

     WIND ADVISORY FROM 9 AM THURSDAY TO 7 PM THURSDAY FOR THE
     FOLLOWING ZONES: COASTAL ESCAMBIA...COASTAL OKALOOSA...
     COASTAL SANTA ROSA...INLAND ESCAMBIA...INLAND OKALOOSA...
     INLAND SANTA ROSA...

MS...WIND ADVISORY FROM 9 AM THURSDAY TO 7 PM THURSDAY FOR THE
     FOLLOWING ZONES: GEORGE...GREENE...PERRY...STONE...WAYNE...

GM...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 9 AM FRIDAY FOR THE
     FOLLOWING ZONES: CHOCTAWHATCHEE BAY...MISSISSIPPI SOUND...
     NORTHERN MOBILE BAY...PENSACOLA BAY SYSTEM...PERDIDO BAY...

     GALE WATCH FROM 6 PM THURSDAY TO 9 AM FRIDAY FOR THE FOLLOWING
     ZONES: COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20
     NM...COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT
     20 NM...SOUTHERN MOBILE BAY...WATERS FROM DESTIN TO
     PENSACOLA FL FROM 20 TO 60 NM...WATERS FROM PENSACOLA FL TO
     PASCAGOULA MS FROM 20 TO 60 NM...

     SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 PM THURSDAY FOR THE
     FOLLOWING ZONES: COASTAL WATERS FROM DESTIN TO PENSACOLA FL
     OUT 20 NM...COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA
     MS OUT 20 NM...SOUTHERN MOBILE BAY...WATERS FROM DESTIN TO
     PENSACOLA FL FROM 20 TO 60 NM...WATERS FROM PENSACOLA FL TO
     PASCAGOULA MS FROM 20 TO 60 NM...

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MOBILE AL
417 AM CST THU DEC 20 2012

ALZ051>064-FLZ001>006-MSZ067-075-076-078-079-211230-
CHOCTAW-WASHINGTON-CLARKE-WILCOX-MONROE-CONECUH-BUTLER-CRENSHAW-
ESCAMBIA-COVINGTON-UPPER MOBILE-UPPER BALDWIN-LOWER MOBILE-
LOWER BALDWIN-INLAND ESCAMBIA-COASTAL ESCAMBIA-INLAND SANTA ROSA-
COASTAL SANTA ROSA-INLAND OKALOOSA-COASTAL OKALOOSA-WAYNE-PERRY-
GREENE-STONE-GEORGE-
417 AM CST THU DEC 20 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
ALABAMA...SOUTHWEST ALABAMA...NORTHWEST FLORIDA AND SOUTHEAST
MISSISSIPPI.

.DAY ONE...TODAY AND TONIGHT

A STRONG COLD FRONT WILL APPROACH SOUTHEAST MISSISSIPPI THIS MORNING
AND PROGRESS EASTWARD ACROSS THE FORECAST AREA THROUGH THIS AFTERNOON.
WHILE THE LACK OF INSTABILITY WILL MAKE THE THREAT FOR WIDESPREAD
SEVERE WEATHER LOW...A FEW STRONG TO BRIEFLY SEVERE STORMS ARE
POSSIBLE THIS MORNING. LOCALIZED DAMAGING WIND GUSTS AND ISOLATED
TORNADOES WILL BE POSSIBLE. STAY TUNED FOR FURTHER UPDATES.

WINDS WILL INCREASE TO 25 TO 30 MPH IN THE WAKE OF THE FRONT. WINDS
COULD GUST AS HIGH AS 30 TO 35 MPH. WIND GUSTS THIS HIGH CAN CAUSE
LIGHTWEIGHT OUTDOOR OBJECTS TO BE BLOWN ABOUT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF SKYWARN SEVERE STORM SPOTTER NETWORKS IS NOT
EXPECTED THROUGH WEDNESDAY.

GMZ630>635-650-655-670-675-211230-
NORTHERN MOBILE BAY-SOUTHERN MOBILE BAY-MISSISSIPPI SOUND-
PERDIDO BAY-PENSACOLA BAY SYSTEM-CHOCTAWHATCHEE BAY-
COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT 20 NM-
COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20 NM-
WATERS FROM PENSACOLA FL TO PASCAGOULA MS FROM 20 TO 60 NM-
WATERS FROM DESTIN TO PENSACOLA FL FROM 20 TO 60 NM-
417 AM CST THU DEC 20 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE COASTAL
WATERS OF ALABAMA AND NORTHWEST FLORIDA.

.DAY ONE...TODAY AND TONIGHT

DUE TO A STRONG ONSHORE FLOW THIS MORNING FOLLOWED BY A STRONG WEST
TO NORTHWEST FLOW THIS AFTERNOON AND TONIGHT HAZARDOUS CONDITIONS
FOR SMALL CRAFT CAN BE EXPECTED OVER THE MARINE AREA THROUGH TONIGHT.
WIND GUSTS TO GALE FORCE WILL BE LIKELY IN THE WAKE OF THE FRONT
THIS AFTERNOON AND OVERNIGHT MOSTLY OVER THE OPEN GULF WATERS OUT TO
60 NM AND THE SOUTHERN END OF MOBILE BAY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

HAZARDOUS CONDITIONS FOR SMALL CRAFT WILL CONTINUE OVER THE MARINE
THROUGH SATURDAY MORNING.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF SKYWARN SEVERE STORM SPOTTER NETWORKS IS NOT
EXPECTED THROUGH WEDNESDAY.