River Flood Warning 12, NWS Huntsville, AL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
532 PM CST THU DEC 24 2015

.UPDATE...
FOR 00Z TAFS

&&

.SHORT TERM (TONIGHT THROUGH SATURDAY NIGHT)...
/ISSUED 402 PM CST THU DEC 24 2015/

...FLOOD WATCH FOR THE AREA FOR FRIDAY AND FRIDAY NIGHT...

ANOTHER DIFFICULT FORECAST SCENARIO IS CURRENTLY UNFOLDING FOR THE
TENNESSEE VALLEY REGION. THE PRIMARY WEATHER CONCERN IN THE SHORT
TERM CENTERS AROUND THE FLOODING POTENTIAL SETTING UP FOR THE AREA
BEGINNING TOMORROW MORNING AND CONTINUING THROUGH TOMORROW NIGHT.
THE UNUSUAL RECORD-BREAKING WARMTH IS SET TO CONTINUE FOR THE REGION
THROUGH THE WEEKEND AND POSSIBLY INTO THE EARLY PART OF NEXT WEEK.
THEN...ANOTHER ROBUST STORM SYSTEM WILL BRING FURTHER WEATHER
CONCERNS TO THE AREA EARLY NEXT WEEK. DETAILS FOLLOW BELOW.

A BAND OF MDT/HVY RAIN WITH EMBEDDED NUMEROUS THUNDERSTORMS IS
CURRENTLY ALIGNED SW-NE TO OUR SOUTH...ESSENTIALLY SLICING ACROSS
SOUTHERN MISS/ALABAMA AND INTO CENTRAL GEORGIA. THIS BAND OF HVY
PRECIP IS CAUSING NUMEROUS INSTANCES OF FLOODING/FLASH FLOODING IN
THOSE AREAS. THIS ACTIVITY IS OCCURRING WELL AHEAD OF THE COLD FRONT
WHICH ESSENTIALLY STALLED IN OUR AREA TODAY. AS A TROUGH GRADUALLY
DIGS IN THE WEST...UPR FLOW WILL VEER MORE FROM THE SOUTH...ALLOWING
A DEVELOPING WARM FRONT TO MOVE NORTHWARD ACROSS OUR AREA BEGINNING
TONIGHT. FORCING/LIFT AND ASSOCIATED CONVECTION MAY INITIALLY BE
NARROW ALONG THE NARROWLY FOCUSED FRONT. HOWEVER...THE MAJORITY OF
REGIONAL/GLOBAL MODELS INDICATE INCREASING ISENTROPIC ASCENT IN THE
WARM SECTOR TO THE SOUTH OF THE STALLED SFC FRONT...ESPECIALLY LATE
TONIGHT. IN ADDITION...THE MAJORITY OF CONVECTION-ALLOWING MODELS
SUGGEST THE STRONGEST FORCING AND HEAVIEST BAND OF PRECIP WILL SETUP
UP ACROSS THE AREA. THERE ARE OF COURSE A RANGE OF DIFFERENCES...WITH
SOME PLACING THE BEST FORCING RIGHT ACROSS OUR AREA WITH SOME FARTHER
NORTH. HOWEVER...A CONSENSUS BLEND APPROACH FROM A SUITE OF 00Z AND
12Z GUIDANCE SUGGESTS THE HEAVIEST AXIS OF PRECIP WOULD LIKELY LAY
ACROSS OUR AREA...WITH PERHAPS NORTHERN COUNTIES FAVORED A BIT MORE.
THE ISENTROPIC ASCENT WILL BE CENTERED WITHIN AN UNSTABLE LAYER
ALOFT...ALLOWING FOR ADDED CONVECTION TO THE PRECIP BAND. FORECAST PW
VALUES ARE AROUND 1.6-1.8 INCHES...WHICH IS WELL INTO RECORD HIGH
TERRITORY FOR THIS TIME OF YEAR. THE POTENTIAL THUS EXISTS FOR
EFFICIENT RAINFALL PRODUCTION AND LOCALLY HEAVY RAINFALL. CURRENT
FORECAST AMOUNTS FOR THE PERIOD ENDING 12Z SATURDAY ARE AROUND 2.3 TO
3.5 INCHES...AGAIN, WITH NORTHERN AREAS FAVORED FOR THE HIGHEST
PRECIP. THESE AMOUNTS COMBINED WITH ELEVATED RELATIVE SOIL MOISTURE
VALUES PER NASA SPORT LIS INDICATE SFC WATER RUNOFF COULD BE A
PROBLEM. WITH ALL OF THIS SAID...WAS STRUGGLING A BIT WITH WHETHER TO
ISSUE A FLASH FLOOD OR FLOOD WATCH...BUT ENDED WITH FLOOD WATCH GIVEN
SOME UNCERTAINTY IN THE EVENTUAL LOCATION OF BEST INSTABILITY IN THE
REGION. NEVERTHELESS...FLOODING OR FLASH FLOODING MAY BE CONCERNS FOR
TOMORROW. THANKS TO AREA OFFICES AND TO THE WPC FOR COORDINATION ON
THIS EVENT.

THE DEEP WARM FRONT AND ASSOCIATED LIFT WILL GRADUALLY PUSH TO THE
NORTH LATE FRIDAY NIGHT AND INTO SATURDAY. RAINFALL AND THUNDERSTORM
ACTIVITY WILL LIKEWISE GRADUALLY TAPER OFF FROM SOUTH TO NORTH.
HOWEVER...SCATTERED SHOWERS/STORMS WERE RETAINED IN THE FORECAST FOR
SATURDAY PARTLY DUE TO SOME CONTINUED WARM ADVECTION/ISENTROPIC
ASCENT IN THE WARM SECTOR ACROSS OUR REGION. A FAIRLY STRONG CAPPING
INVERSION MAY EVENTUALLY DEVELOP ON SAT AND CONTINUE THROUGH SUNDAY
AROUND 850MB AS TEMPS CLIMB TO AROUND 15-16C...QUITE AMAZING FOR
THIS TIME OF YEAR. THUS...THUNDERSTORM POTENTIAL MAY BE
LIMITED...BUT WILL RETAIN SLIGHT CHANCE MENTION FOR TSRA SAT AND SAT
NIGHT.

KDW

.LONG TERM (SUNDAY THROUGH WEDNESDAY)...
ON SUNDAY THE CLOSED LOW ACROSS THE DESERT SOUTHWEST SHIFTS EASTWARD
INTO THE SOUTHERN PLAINS. MODELS ARE ALL IN GOOD AGREEMENT IN THE
SUBTROPICAL RIDGE TO OUR EAST WEAKENING AS THE CLOSED LOW BEGINS TO
MOVE INTO THE SOUTHEASTERN CONUS. THE LOW BECOMES NEGATIVELY TILTED
ON MONDAY AS IT EJECTS NEWRD OUT OF THE ARKLATEX REGION INTO THE OH
VALLEY. AT THIS POINT IT'S HARD TO PIN DOWN ANY SPECIFICS ON THE
SEVERITY OF ANY STORMS BUT THE ENVIRONMENT COULD BE SUPPORTIVE OF
STRONG TO POTENTIALLY SEVERE STORMS BASED ON THE FORCING ASSOCIATED
WITH THE SYSTEM, THE HODOGRAPHS AND SHEAR PROFILES. WILL WATCH THIS
CLOSELY OVER THE NEXT FEW MODEL RUNS AS ANY SHIFT IN THE TRACK OF THE
SYSTEM COULD LIMIT THE STRENGTH OF ANY STORMS NEXT WEEK.

TEMPS BEGIN TO FALL BACK TO MORE SEASONABLE VALUES BY THE MIDDLE OF
NEXT WEEK.

STUMPF

&&

.AVIATION...
FOR 00Z TAFS...

A WARM FRONT LIES JUST NORTH OF THE KMSL AND KHSV TERMINALS...AS OF
00Z...WITH MOISTURE INCREASING SOUTH OF THIS FRONT. ALTHOUGH CIGS
HAVE REMAINED IN THE VFR CATEGORY...CONDITIONS ARE EXPECTED TO
DETERIORATE WITHIN THE NEXT FEW HOURS. BASED ON UPSTREAM OBS...MVFR
CIGS ARE EXPECTED TO PUSH NORTHWARD INTO THE FORECAST TERMINALS BY
03Z. CIGS WILL CONTINUE TO LOWER THROUGH THE REMAINDER OF THE
OVERNIGHT PERIOD...AND BECOME IFR BY 12Z. SOME MODEL GUIDANCE SUGGEST
LIFR CIGS TO MOVE IN AFTER 09Z...HOWEVER CONFIDENCE IS TOO LOW TO ADD
MENTION. SHOWERS...HEAVY AT TIMES...WILL LINGER FROM 07Z...THROUGH
THE REMAINDER OF THE FORECAST PERIOD. THE HEAVIER SHOWERS WILL REDUCE
VISIBILITIES...HOWEVER IT IS DIFFICULT TO PUT A TIMING ON WHEN THIS
MAY OCCUR AND HOW LOW THEY MAY BE...SO HAVE OPTED FOR PREVAILING
MVFR VSBYS TO ACCOMPANY THE IFR CIGS. IN ADDITION TO THE SHOWER
ACTIVITY...WIDESPREAD THUNDER IS POSSIBLE TOMORROW...HOWEVER THERE IS
LOW CONFIDENCE ON THE TIMING...THOUGH FEEL IT WILL BE AFTER 15Z. HAVE
OPTED TO KEEP THE VCTS UNTIL CONFIDENCE INCREASES.

73

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...FLOOD WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT FOR
     ALZ001>010-016.

TN...FLOOD WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT FOR
     TNZ076-096-097.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.

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PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE HUNTSVILLE AL
445 PM CST THU DEC 24 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     TORNADO          3 N WATERLOO            34.95N 88.07W
12/23/2015                   LAUDERDALE         AL   NWS STORM SURVEY

            EF-2 TORNADO SNAPPED AND UPROOTED NUMEROUS
            TREES...DAMAGED SEVERAL SINGLE FAMILY HOMES...AND ONE
            CHURCH ALONG ITS 7.4 MILE PATH. MAX WIND SPEED 115 MPH.
            MAX PATH WIDTH 150 YDS.

0700 PM     TORNADO          3 N WATERLOO            34.96N 88.06W
12/23/2015                   LAUDERDALE         AL   TRAINED SPOTTER

            SMALL TREES DOWN ALONG COUNTY ROAD 54 BETWEEN CR 14 AND
            21. TIME ESTIMATED FROM RADAR.

0705 PM     TORNADO          5 SE WALNUT GROVE       35.00N 87.98W
12/23/2015                   LAUDERDALE         AL   EMERGENCY MNGR

            HOUSES DAMAGED ALONG CR 40 JUST SOUTH OF THE TENNESSEE
            LINE. DAMAGE CORRESPONDS TO TORNADO DEBRIS SIGNATURE FROM
            DUAL POL RADAR. TIME ESTIMATED FROM RADAR.

&&

BCC