Severe Thunderstorm Warning 20, NWS Jacksonville, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
458 AM EST TUE FEB 26 2013

...SQUALL LINE OF STRONG TO SEVERE THUNDERSTORMS WILL CROSS OUR
AREA TODAY...
...WINDY CONDITIONS AFTER SUNRISE AHEAD OF THE SQUALL LINE...

.CURRENTLY...
MORNING SURFACE ANALYSIS DEPICTS A STRONG OCCLUDED SURFACE LOW
PRESSURE CENTER (993 MILLIBARS) OVER THE OZARKS...WITH A TRIPLE
POINT LOW DEVELOPING OVER SOUTHEAST ALABAMA. A STRENGTHENING COLD
FRONT EXTENDS SOUTH OF THIS DEVELOPING SECONDARY LOW INTO THE
CENTRAL GULF OF MEXICO. THE WARM FRONT RESPONSIBLE FOR STRONG AND
SEVERE THUNDERSTORMS IN OUR AREA YESTERDAY IS PUSHING NORTHWARD
INTO SOUTHEAST GEORGIA. NORTH OF THE WARM FRONT...TEMPERATURES
NEAR THE ALTAMAHA RIVER REMAIN IN THE 50S. A SQUALL LINE OF STRONG
TO SEVERE THUNDERSTORMS IS DEVELOPING AHEAD OF THE COLD
FRONT...AND CURRENTLY EXTENDS FROM WESTERN SECTIONS OF THE FLORIDA
BIG BEND SOUTHWARD INTO THE EASTERN GULF OF MEXICO. A LARGE RAIN
SHIELD PRECEDES THE SQUALL LINE AND IS POISED TO MOVE OVER
SATURATED GROUNDS IN INTERIOR SOUTHEAST GEORGIA DURING THE PREDAWN
HOURS. NORTHEAST FLORIDA NOW RESIDES IN THE WARM SECTOR...WITH
DEWPOINTS CLIMBING INTO THE MID AND UPPER 60S. ALOFT...AN INTENSE
CUTOFF CYCLONE IS SPINNING NORTHEASTWARD FROM THE OZARKS TOWARDS
THE TENNESSEE RIVER VALLEY. THIS LARGE SYSTEM HAS PUSHED RIDGING
EAST OF THE BAHAMAS...AND OUR REGION NOW RESIDES WITHIN
STRENGTHENING CYCLONIC FLOW...WHICH IS STRONGLY VEERED IN THE
LOWEST 3000 FEET PER LATEST JACKSONVILLE AND MOODY AFB DOPPLER
RADAR DATA. TORNADO WATCHES OVER THE FLORIDA BIG BEND WILL LIKELY
BE EXTENDED TO COVER MOST OF NORTHEAST FLORIDA AND PORTIONS OF
SOUTHEAST GEORGIA EARLY THIS MORNING.

.SHORT TERM (TODAY THROUGH WEDNESDAY NIGHT)...
A STRONG LOW-LEVEL JET WILL TRAVERSE OUR REGION AHEAD OF THE
SQUALL LINE THIS MORNING THROUGH THE EARLY AFTERNOON HOURS. SOUTH
TO SOUTHWEST WINDS WILL RAPIDLY INCREASE AFTER SUNRISE...WITH
SUSTAINED WINDS OF 15 TO 25 MPH AND GUSTS UP TO 35 MPH EXPECTED
REGION-WIDE. WE HAVE PLACED OUR REGION IN A LAKE WIND ADVISORY
THROUGH SUNSET. A STRONGLY VEERED WIND PROFILE AND IMPRESSIVE
SPEED SHEAR...WITH WINDS OF 40 KTS AT 950 MILLIBARS (1500
FEET)...WILL SUPPORT DAMAGING WIND GUSTS. MODEL SOUNDINGS DEPICT
HELICITY VALUES IN EXCESS OF 300 UNITS TODAY...AND THUS ISOLATED
TORNADOES ARE POSSIBLE WITHIN STRONGER CELLS ALONG THE SQUALL LINE
AND ALSO IN CONVECTION DEVELOPING AHEAD OF THE LINE THIS MORNING.
THE STORM PREDICTION CENTER HAS PLACED OUR ENTIRE AREA WITHIN A
SLIGHT RISK FOR SEVERE THUNDERSTORM DEVELOPMENT TODAY. HIGH
RESOLUTION MODEL GUIDANCE PLACES THE SQUALL LINE OVER THE SUWANNEE
VALLEY TOWARDS THE MID MORNING HOURS...WITH ACTIVITY PROGRESSING
TOWARDS COASTAL LOCATIONS DURING THE EARLY AFTERNOON HOURS. HEAVY
RAINFALL AMOUNTS OF 1 TO 2 INCHES PRECEDING AND ALONG THE SQUALL
LINE ARE EXPECTED OVER SOUTHEAST GA AND NORTHERN SECTIONS OF
NORTHEAST FL...AND THUS THE FLOOD WATCH WILL CONTINUE THROUGH
NOON. SINCE THE WARM SECTOR WILL SURGE INTO SOUTHEAST GA AHEAD OF
THE FRONT THIS MORNING...WE EXPECT HIGHS TO SURGE INTO THE MID AND
UPPER 70S REGION-WIDE TODAY. DRIER WEATHER WILL QUICKLY FILTER
INTO INTERIOR SECTIONS OF SOUTHEAST GA AND THE SUWANNEE VALLEY
THIS AFTERNOON...AS WINDS BECOME WESTERLY BEHIND THE COLD FRONT.

THE INTENSE CYCLONE WILL PROGRESS FROM THE TENNESSEE VALLEY INTO
THE OHIO VALLEY TONIGHT...LEAVING OUR AREA IN FAST ZONAL WESTERLY
FLOW ALOFT. WEAK HIGH PRESSURE WILL BRIEFLY BUILD INTO OUR
REGION...AND MINIMAL COLD AIR ADVECTION ON THE HEELS OF MODERATE
WESTERLY FLOW WILL ALLOW HIGHS ON WED TO CLIMB TO NEAR OR
SLIGHTLY ABOVE CLIMO (UPPER 60S IN SOUTHEAST GA AND 70-75 FOR
NORTHEAST FL) BENEATH THINNING MID AND HIGH ALTITUDE CLOUD COVER.
NEAR CLIMO LOWS ARE EXPECTED WED NIGHT...WITH READINGS DROPPING
INTO THE 40S INLAND AND NEAR 50 AT THE COAST AND ACROSS NORTH
CENTRAL FL.

.LONG TERM (THURSDAY THROUGH MONDAY)...
BREEZY...COOL AND DRY CONDS ARE ON TAP FOR THURSDAY WITH ZONAL
FLOW ALOFT. SUSTAINED WEST WINDS OF 15-20 MPH WILL GUST UP TO
30-35 MPH MAKING A LAKE WIND ADV LIKELY. UNDER MOSTLY SUNNY SKIES
MAX TEMPS WILL BE IN THE 60S. INCREASING CLOUDINESS RETURNS FRI-
SAT AS DEEP TROUGHING DIGS INTO THE SERN U.S. USHERING IN A MUCH
COLDER AIR MASS. WITH THICKNESSES TAKING A NOSE-DIVE...TEMPS WILL
BE NEAR 10 DEG BELOW CLIMO FRI/FRI NIGHT AND ONLY REACH THE MID
50S AREA-WIDE ON SAT/SUN UNDER MOSTLY CLOUDY SKIES. ABUNDANT MID
LEVEL MOISTURE RAISES THE POSSIBILITY OF PRECIP...BUT WILL GO WITH
MAINLY SILENT POPS SAT INTO SUN MORNING SINCE MODEL SOUNDINGS
CONTINUE TO SUGGEST DRY CONDITIONS IN THE LOW LEVELS PRECLUDING
ANY MEASURABLE PRECIP. THICKNESSES BOTTOM OUT SUNDAY MORNING WITH
A FREEZE POSSIBLE ACROSS THE INTERIOR. CAVEAT WILL BE CLOUD COVER
ESPECIALLY OVER SE GA AND A TIGHT PRESSURE GRADIENT WHICH WILL
KEEP WINDS NEAR 10 MPH OVERNIGHT. WIND CHILL READINGS EARLY SUN
MORNING ARE EXPECTED TO BE IN LOWER 20S AND A WIND CHILL ADV IS
POSSIBLE FOR NE FL. A MORE WIDESPREAD FREEZE APPEARS POSSIBLE ON
SUN NIGHT AS WINDS SUBSIDE AND SKIES CLEAR WITH SURFACE RIDGING
APPROACHING FROM THE WEST. MONDAY WILL BE MOSTLY SUNNY WITH HIGHS
IN THE 60S AND LIGHT WINDS RESULTING FROM HIGH PRESSURE.

&&

.AVIATION...
HAVE CONTINUED LLWS OVERNIGHT SINCE VAD WIND PROFILES INDICATED
SPEEDS OF 36 KT AT 2 KFT AND SFC WINDS ARE 5 KT OR LESS. HAVE VCTS
BEGINNING 13Z AND SQUALL LINE IS EXPECTED TO REACH TERMINALS
BTWN 15Z AND 18Z. VFR CONDS EXPECTED AFTER FRONTAL PASSAGE WITH
WEST WINDS 15G30KT.

&&

.MARINE...
HAVE EXPANDED THE SMALL CRAFT ADVISORY TO NEAR SHORE WATERS INTO
THE EVENING HOURS. WINDS ARE EXPECTED TO INCREASE TO 20-25 KT
ACROSS ALL LEGS THIS MORNING. SCA OR SCEC CONDS WILL PERSIST
THROUGH THE END OF THE WEEK. SE TO SOUTH WINDS ARE INCREASING AT
THE BUOYS EARLY THIS MORNING AND SEAS ARE RUNNING 6-9 FT.

RIP CURRENTS: MODERATE RISK.

&&

.FIRE WEATHER...
A COOLER AND MUCH DRIER AIR MASS WILL FILTER INTO OUR REGION
TONIGHT AND WEDNESDAY. RELATIVE HUMIDITY VALUES WILL APPROACH
CRITICAL THRESHOLDS ON WED AFTERNOON IN NORTHEAST FL. ERC AND
DISPERSION VALUES WILL NOT APPROACH CRITICAL VALUES ON
WED...AND FIRE WEATHER HEADLINES ARE NOT ANTICIPATED. A
REINFORCING PUSH OF COOL AND DRY AIR WILL APPROACH OUR AREA ON
THURS. BREEZY WESTERLY WINDS MAY COMBINE WITH LOW HUMIDITY AND
HIGH DISPERSION VALUES TO BRING POTENTIAL RED FLAG CONDITIONS TO
NORTHEAST FL ON THURS AFTERNOON.

&&

.HYDROLOGY...
A FLOOD WATCH REMAINS POSTED THROUGH NOON FOR ALL OF SOUTHEAST GA
AND NORTHERN PORTIONS OF NORTHEAST FL...WHERE ADDITIONAL RAINFALL
AMOUNTS OF 1 TO 3 INCHES ARE POSSIBLE. RIVER FLOOD WARNINGS
CONTINUE FOR THE ALTAMAHA RIVER AT BAXLEY...EVERETT CITY...AND
CHARLOTTE...AND ALONG PORTIONS OF THE ALAPAHA RIVER.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  75  43  69  39 /  90   0   0   0
SSI  73  50  66  46 /  90  10   0   0
JAX  78  49  70  43 /  90  10   0   0
SGJ  78  51  70  47 /  80  20   0   0
GNV  79  46  73  42 /  90  10   0   0
OCF  79  49  74  45 /  90  20   0   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...FLOOD WATCH UNTIL NOON EST TODAY FOR BAKER-COLUMBIA-DUVAL-
     HAMILTON-NASSAU-SUWANNEE.

     LAKE WIND ADVISORY FROM 9 AM THIS MORNING TO 6 PM EST THIS
     EVENING FOR ALACHUA-BAKER-BRADFORD-CLAY-COLUMBIA-DUVAL-
     FLAGLER-GILCHRIST-HAMILTON-MARION-NASSAU-PUTNAM-ST JOHNS-
     SUWANNEE-UNION.

GA...FLOOD WATCH UNTIL NOON EST TODAY FOR APPLING-ATKINSON-BACON-
     BRANTLEY-CHARLTON-CLINCH-COASTAL CAMDEN-COASTAL GLYNN-
     COFFEE-ECHOLS-INLAND CAMDEN-INLAND GLYNN-JEFF DAVIS-PIERCE-
     WARE-WAYNE.

     LAKE WIND ADVISORY FROM 9 AM THIS MORNING TO 6 PM EST THIS
     EVENING FOR APPLING-ATKINSON-BACON-BRANTLEY-CHARLTON-CLINCH-
     COASTAL CAMDEN-COASTAL GLYNN-COFFEE-ECHOLS-INLAND CAMDEN-
     INLAND GLYNN-JEFF DAVIS-PIERCE-WARE-WAYNE.

AM...SMALL CRAFT ADVISORY UNTIL 4 AM EST WEDNESDAY FOR ALTAMAHA SOUND
     GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE-
     FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE-
     ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE.

     SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ALTAMAHA
     SOUND GA TO FERNANDINA BEACH FL OUT 20 NM-FERNANDINA BEACH
     TO ST AUGUSTINE FL OUT 20 NM-ST AUGUSTINE TO FLAGLER BEACH
     FL OUT 20 NM.

&&

NELSON/TRABERT

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSONVILLE FL
420 AM EST TUE FEB 26 2013

FLZ020-022-GAZ150-152-162>164-261000-
BRANTLEY-CHARLTON-CLINCH-COLUMBIA-ECHOLS-HAMILTON-WARE-
420 AM EST TUE FEB 26 2013

...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED FOR CENTRAL WARE...
SOUTHWESTERN BRANTLEY...EASTERN CLINCH...SOUTHEASTERN ECHOLS...
NORTHEASTERN COLUMBIA...EXTREME NORTHEASTERN HAMILTON AND
NORTHWESTERN CHARLTON COUNTIES FOR STRONG WINDS AND FUNNEL CLOUDS
VALID UNTIL 500 AM EST...

AT 420 AM EST NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CENTERED 6 MILES SOUTH OF FARGO...MOVING
NORTHEAST AT 50 MPH. THIS STRONG THUNDERSTORM WILL ALSO AFFECT AREAS
AROUND NEEDMORE...FARGO...STEVEN FOSTER STATE PARK...RACE POND AND
NEEDHAM THROUGH 500 AM EST. GUSTY WINDS OF 40 TO 50 MPH CAN BE
EXPECTED ALONG WITH POSSIBLE MINOR DAMAGE. DOPPLER RADAR HAS
INDICATED WEAK ROTATION WITHIN THIS STORM. TORNADOES MAY DEVELOP WITH
LITTLE OR NO ADVANCE WARNING. HEAVY RAINFALL WILL PRODUCE PONDING OF
WATER ON ROADWAYS AND MINOR FLOODING OF LOW-LYING AREAS.

REPORT DAMAGE TO THE NEAREST LAW ENFORCEMENT AGENCY OR YOUR COUNTY
EMERGENCY MANAGEMENT.

LAT...LON 3121 8261 3110 8201 3053 8253 3056 8272
TIME...MOT...LOC 0920Z 212DEG 44KT 3061 8255

NELSON

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSONVILLE FL
656 AM EST TUE FEB 26 2013

FLZ032-033-037-261245-
CLAY-PUTNAM-ST. JOHNS-
656 AM EST TUE FEB 26 2013

...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED FOR SOUTHEASTERN
CLAY...NORTHWESTERN PUTNAM AND CENTRAL ST. JOHNS COUNTIES FOR STRONG
WINDS VALID UNTIL 745 AM EST...

AT 656 AM EST NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM CENTERED 3 MILES SOUTHWEST OF JOHNSON...MOVING
NORTHEAST AT 60 MPH. THIS STRONG THUNDERSTORM WILL ALSO AFFECT AREAS
AROUND JOHNSON...MANNVILLE...INTERLACHEN...HOLLISTER...PUTNAM HALL...
FLORAHOME...CARRAWAY...BOSTWICK...PICOLATA AND GREEN COVE SPRINGS
THROUGH 745 AM EST. GUSTY WINDS OF 45 TO 55 MPH CAN BE EXPECTED ALONG
WITH POSSIBLE MINOR WIND DAMAGE.

REPORT DAMAGE TO THE NEAREST LAW ENFORCEMENT AGENCY OR YOUR COUNTY
EMERGENCY MANAGEMENT.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 300 PM EST TUESDAY AFTERNOON
FOR NORTHEASTERN FLORIDA AND SOUTHEAST GEORGIA.

LAT...LON 2952 8184 2950 8198 2955 8206 2967 8206
      3013 8165 3013 8160 3012 8154 3010 8154
      3010 8149 3004 8134
TIME...MOT...LOC 1156Z 219DEG 53KT 2961 8197

SHULER

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