Flash Flood Warning 10, NWS Huntsville, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
338 AM CST WED MAR 9 2011

.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND H5 RUC ANALYSIS INDICATE TROUGHING
ACROSS THE CENTRAL PLAINS AND MID SOUTH..NUDGING INTO THE SOUTHEAST
STATES ATTM. SEVERAL SHORTWAVES ARE MOVING THROUGH THE GREATER
SOUTHEAST ASSOCIATED WITH THE LONGWAVE TROUGH...AND THESE HAVE
COMBINED WITH ANOMALOUS ATMOSPHERIC MOISTURE CONTENT TO PRODUCE
SEVERAL ROUNDS OF RAINFALL SINCE TUESDAY AFTERNOON. AT THE
SURFACE...THE CENTER OF THE LOW IS SEVERAL HUNDRED MILES NORTHWEST
OF HERE...AND THE COLD FRONT IS CLEARLY VISIBLE ON SATELLITE AND
LOCAL OBS ACROSS MISSOURI...ARKANSAS...AND INTO EAST TEXAS. CLOSER
TO HOME...THE TIGHT PRESSURE GRADIENT AND AMPLE MOISTURE FLUX HAS
HAS BROUGHT GUSTY WINDS /A RECENT OB FROM MSL CLOCKED IN AT 41MPH/
AND RAINFALL OF 1-2 INCHES FOR LOCATIONS GENERALLY WEST OF THE
INTERSTATE...WITH SLIGHTLY LOWER TOTALS IN NORTHEAST ALABAMA AND
SOUTHERN MIDDLE TENNESSEE.

WET WEATHER WILL CONTINUE FOR MOST LOCATIONS FOR MUCH OF THE MORNING
HOURS. WHILE THE BACK EDGE OF THE PRECIPITATION SHIELD IS ROUGHLY
HALFWAY ACROSS NORTHERN MISSISSIPPI ATTM...THE TRACK OF THE PARENT
UPPER LOW AND SURFACE CYCLONE /NORTH-NORTHEAST/ SHOULD SLOW THIS
BACK EDGE AS IT MOVES INTO NORTH ALABAMA EARLY THIS MORNING. WITH
BUFR SOUNDINGS SUGGESTING 1.3-1.4 INCH PWAT VALUES THROUGH THE
MORNING WITH GOOD MOISTURE TRANSPORT...ANOTHER INCH OR TWO OF
PRECIPITATION WILL BE POSSIBLE /ESPECIALLY FOR THE EASTERN COUNTIES/.
EMBEDDED WITHIN THESE SHOWERS ARE SCATTERED ELEVATED
THUNDERSTORMS...AND THIS MAY LOCALLY ENHANCE RAINFALL RATES AS WELL
AS EXACERBATE ANY SORT OF GUSTY WINDS AS THE H85 JET WILL REMAIN AOA
50KT FOR THE AREAS EXPERIENCING THE HEAVIEST RAINFALL. THE LLJ WILL
GRADUALLY WEAKEN AND MOST OF THE RAINFALL SHOULD PASS EAST OF THE
INTERSTATE BY LATE MORNING...HOWEVER LOCALLY HEAVY RAIN WILL REMAIN
A CONCERN IN NORTHEAST ALABAMA THROUGH EARLY AFTERNOON.

THE NEXT CHALLENGE FOR THE FORECAST CENTERS AROUND POSSIBLE
REDEVELOPMENT OF SHOWERS AND THUNDERSTORMS ALONG THE COLD FRONT AS
IT MOVES THROUGH THE CWFA THIS AFTERNOON. FOR SEVERAL RUNS NOW...THE
NAM AND GFS HAVE ADVERTISED A THIN LINE OF SURFACE INSTABILITY
ASSOCIATED WITH THE FRONT /AROUND 3-700 JOULES/KG/. THIS...COMBINED
WITH THE RESIDUAL SHEAR AND STEEP LOW LEVEL LAPSE RATES SUGGESTS
THAT THERE COULD BE AN ISOLATED INSTANCE OF STRONG OR POSSIBLY
SEVERE STORMS AS THE LINE MOVES THROUGH THIS AFTERNOON.
HOWEVER...THERE IS SOME QUESTION AS TO WHETHER PARCELS CAN REALIZE
THE INSTABILITY GIVEN THE AMOUNT AND DURATION OF PRECIPITATION WE
ARE CURRENTLY EXPERIENCING.

THE FRONT WILL BE SLOW TO EXIT THE EASTERN COUNTIES TONIGHT...AND
FOR THIS REASON...HAVE HUNG ONTO PRECIPITATION CHANCES THROUGH THE
OVERNIGHT HOURS AND THROUGH THURSDAY FOR THE EASTERN COUNTIES UNTIL
THE NEXT UPPER TROUGH AXIS PUSHES EAST OF THE TENNESSEE VALLEY ON
THURSDAY EVENING. WITH THIS SLOWER EXIT TO THE SYSTEM...TEMPERATURES
/ESPECIALLY EAST/ WILL BE SLOW TO WARM ON THURSDAY...AND COOL OFF
QUITE QUICKLY BY EARLY FRIDAY MORNING AS SKIES CLEAR. THERE ARE SOME
INDICATIONS THAT THE HIGHEST ELEVATIONS OF NORTHEAST ALABAMA AND
SOUTHERN MIDDLE TENNESSEE COULD SEE A FEW FLURRIES ON THURSDAY
EVENING...BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THE FORECAST ATTM.

AFTER TEMPERATURES AROUND FREEZING ON FRIDAY MORNING...LOOK FOR A
GRADUAL WARMING TREND THROUGH THE WEEKEND AS A SURFACE HIGH AND
FAIRLY ZONAL FLOW MOVE OVER THE AREA. A DRY COLD FRONT WILL DRIFT
INTO THE AREA ON SUNDAY...AND THEN SEVERAL SHORTWAVES WILL BEGIN TO
IMPACT THE SOUTHEAST BY EARLY NEXT WEEK...WITH SHOWERS AND A FEW
THUNDERSTORMS RETURNING TO THE FORECAST BY MONDAY.

.HYDROLOGY...
RAINFALL OVER THE LAST 12 HOURS...COMBINED WITH THE ANTECEDENT WET
CONDITIONS FROM THE STORM LAST WEEKEND...HAS LEAD TO FLOODING
CONCERNS IN SEVERAL AREAS ACROSS THE AREA. THESE CONCERNS WILL BE
EXACERBATED WITH ANOTHER 1-2 INCHES OF PRECIPITATION THIS MORNING.
IN ADDITION TO THE THREAT OF FLASH FLOODING /ESPECIALLY WHERE
CONVECTION LOCALLY ENHANCES PRECIPITATION RATES/...RIVER FLOODING
WILL CONTINUE TO POSE A CONCERN THROUGH THE DAY...AND POSSIBLY FOR
SEVERAL DAYS...GIVEN THE SLOW RESPONSE TIME OF SOME OF THE LARGER
RIVER SYSTEMS. FOR THIS REASON...WILL CONTINUE THE AREAL FLOOD WATCH
ATTM.

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    69  41  49  32  57 / 100  20  20   0   0
SHOALS        69  40  51  32  59 / 100  20  10   0   0
VINEMONT      66  39  47  32  56 / 100  20  10   0   0
FAYETTEVILLE  65  40  47  32  55 / 100  20  20  10   0
ALBERTVILLE   67  40  46  31  56 / 100  30  10   0   0
FORT PAYNE    65  43  47  31  55 / 100  40  20  10   0

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...FLOOD WATCH THROUGH LATE TONIGHT FOR THE FOLLOWING ZONES: DEKALB...
     JACKSON...MADISON...MARSHALL.

     WIND ADVISORY UNTIL NOON CST TODAY FOR THE FOLLOWING ZONES:
     DEKALB...JACKSON...MADISON...MARSHALL.

     FLOOD WATCH THROUGH LATE TONIGHT FOR THE FOLLOWING ZONES: COLBERT...
     CULLMAN...FRANKLIN AL...LAUDERDALE...LAWRENCE...LIMESTONE...
     MORGAN.

     WIND ADVISORY UNTIL 9 AM CST THIS MORNING FOR THE FOLLOWING ZONES:
     COLBERT...CULLMAN...FRANKLIN AL...LAUDERDALE...LAWRENCE...
     LIMESTONE...MORGAN.

TN...FLOOD WATCH THROUGH LATE TONIGHT FOR THE FOLLOWING ZONES: FRANKLIN
     TN...LINCOLN...MOORE.

     WIND ADVISORY UNTIL NOON CST TODAY FOR THE FOLLOWING ZONES:
     FRANKLIN TN...LINCOLN...MOORE.

&&

JLL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HUNTSVILLE AL
339 AM CST WED MAR 9 2011

ALZ001>010-016-TNZ076-096-097-091900-
LAUDERDALE-COLBERT-FRANKLIN AL-LAWRENCE-LIMESTONE-MADISON-MORGAN-
MARSHALL-JACKSON-DEKALB-CULLMAN-MOORE-LINCOLN-FRANKLIN TN-
339 AM CST WED MAR 9 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH ALABAMA AND PORTIONS
OF SOUTHERN MIDDLE TENNESSEE.

.DAY ONE...TODAY AND TONIGHT...

SHOWERS AND SCATTERED THUNDERSTORMS WILL CONTINUE ACROSS THE AREA
THIS MORNING WITH HEAVY RAIN AND GUSTY WINDS. BY THIS AFTERNOON A
LINE OF STRONG TO SEVERE STORMS WILL MOVE ACROSS THE TENNESSEE VALLEY
WITH HEAVY RAIN...DAMAGING WINDS AND SMALL HAIL POSSIBLE.

TOTAL RAINFALL AMOUNTS WILL BE AROUND TWO TO THREE INCHES WITH
LOCALLY HIGHER AMOUNTS POSSIBLE. GIVEN THE HEAVY RAINFALL EXPECTED
OVER THE PERIOD...MINOR TO MODERATE FLOODING MAY OCCUR IN SOME
STREAMS AND RIVERS. THE THREAT OF HEAVY RAIN AND STORMS WILL END
TONIGHT.

OUTSIDE OF THE THUNDERSTORM ACTIVITY...WINDY CONDITIONS WILL CONTINUE
THIS MORNING WITH SUSTAINED WINDS OF 20 TO 30 MPH AND GUSTS UP TO 40
MPH. THE WINDS WILL BEGIN TO DIMINISH AROUND NOON.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY...

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER CALL TO ACTION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL
MAY BE POSSIBLE THIS AFTERNOON.

SS