River Flood Warning 57, NWS Jackson, MS

AREA FORECAST DISCUSSION...UPDATED FOR AVIATION
NATIONAL WEATHER SERVICE JACKSON MS
627 AM CST THU DEC 11 2008

...RARE EARLY DECEMBER WINTER STORM ON OUR DOORSTEP...

.DISCUSSION...HAVING TO UPDATE THE FORECAST ALREADY. QUITE A BIT OF
CONVECTION IS DEVELOPING WITH TSRA MOVING ACROSS THE NORTHEAST.
THERE HAS EVEN BEEN TSSN AT BTR THIS MORNING. GOES TO SHOW YOU HOW
DYNAMIC THIS SYSTEM IS. I WILL NEED TO ADD T WORDING AND NEED TO ADD
TSSN ACROSS THE SOUTH WHERE THINGS LOOK LIKE THEY ARE ALREADY
BEGINNING TO SET UP. MCB OB ALREADY REPORTING SN AND WE HAVE REPORTS
OUT OF HBG BIG WET SNOWFLAKES AND STARING TO STICK TO CARS AND THE
GRASS. THIS IS EVOLVING VERY QUICK WITH THE EXPECTED HEAVY BAND OF
SNOW LOOKING LIKE IT WILL DEVELOP ACROSS SRN MS AND SERN LA. ZONES
AND GRIDS WILL BE OUT SHORTLY. /CAB/

&&

.PREV DISCUSSION...SHORT TERM...UNLIKE WITH OTHER WEATHER
SITUATIONS...GETTING RIGHT UP TO THE EVENT HAS BROUGHT ABOUT MORE
QUESTIONS THAN ANSWERS. MDLS TRENDED WARMER BUT THEY ALSO APPEAR TO
BE TOO WARM COMPARED TO ACTUAL CONDITIONS. THIS IS LEADING TO A
SOMEWHAT LOWER CONFIDENCE FCST BUT EVEN WITH THAT SAID WE ARE STILL
CONFIDENT THAT A SIGNIFICANT AND RARE EARLY DEC SNOW STORM WILL
OCCUR TODAY. SNOW AND SLEET HAS BEEN OCCURRING ACROSS SERN TX AND
MUCH OF WRN LA ALL MORNING.

NAM...ECMWF...AND GFS ALL TRENDED A LITTLE FURTHER SOUTH WITH THE
UPPER LOW AND TRENDED WARMER BUT I AM NOT SURE HOW MUCH OF THAT TO
BELIEVE. THERE IS A CONCERN THAT THE MDLS ARE OVERESTIMATING THE WAA
ALOFT ASSOCIATED WITH THE DEVELOPING TROWAL AND THEN UNDERESTIMATING
THE COOLING BY MELTING AND DYNAMIC COOLING. THE NAM ALSO LOOKS A
LITTLE SQUIRRELLY WITH ITS AMOUNT OF WARMING AND UPPER LOW. THE
ECMWF ALSO LOOKS A LITTLE SUSPECT WITH ITS TEMPS...H925 TEMPS ARE
RATHER COLD WITH IT SHOWING NEAR -4C OVER THE AREA THIS MORNING BUT
H85 TEMPS BARELY GET TO FREEZING AND THAT ONLY OCCURS ACROSS THE
SOUTH AND THAT SEEMS A LITTLE EXTREME. THE KEY IN ALL OF THIS WILL
BE WHEN THE UPPER LOW STARTS TO TURN NE AND HOW WARM/THICK THAT WARM
LAYER IS. WILL STICK CLOSER TO THE GFS WHICH IS PROBABLY THE BEST
COMPROMISE RIGHT NOW.

WELL IT LOOKS LIKE THE UPPER LOW WILL TRACK ENE ACROSS SRN LA AND
INTO SERN MS THEN INTO CNTRL AL TONIGHT. THE DEFORMATION AXIS WILL
STILL SET UP ACROSS SRN/CNTRL MS AND INTO NERN MS. THE TROWAL WILL
CONTINUE TO FEED INTO NRN MS KEEPING THINGS WARM IN THE LOWER TO MID
LEVELS FOR A LITTLE WHILE BUT BY MIDDAY DYNAMIC COOLING...COOLING BY
MELTING SHOULD START TO WIN OVER THAT AS PRECIP PICKS UP AGAIN.
PRECIP ACROSS THE SW WILL ALREADY HAVE BEGUN TO MIX IN WITH SLEET
AND SNOW IF NOT COMPLETELY CHANGING TO SLEET/SNOW BY SUNRISE. BY MID
MORNING CNTRL AND SRN MS SHOULD BEGIN TO CHANGE OVER WITH EVERYTHING
PROBABLY SNOW JUST BEFORE MIDDAY. SNOW WILL CONTINUE INTO THE
AFTERNOON TAPERING OFF FROM WEST TO EAST WITH ALL SNOW LIKELY OUT OF
AREA BEFORE THIS EVN. THE HEAVIEST SNOW MAY END UP BEING SLIGHTLY
FURTHER SOUTH THAN EXPECTED BUT IT IS STILL TOO DIFFICULT TO
DETERMINE WHERE THE BAND OF MODERATE TO HEAVY SNOW WILL DEVELOP.
ALSO AS THE UPPER LOW REALLY BEGINS TO WRAP UP THIS AFTN MODERATE
TO HEAVY SNOW COULD EASILY DEVELOP ACROSS ERN MS FOR ABOUT 2HRS
LEADING TO SOME DECENT SNOW FALL TOTALS IN THAT AREA AS WELL. SO
THIS BASICALLY LEAVES PRETTY MUCH MOST OF THE AREA SE OF THE NATCHEZ
TRACE PARKWAY IN QUESTION AS TOO HOW MUCH SNOW WILL
ACCUMULATE...1-3 OR 3-5 WITHIN THAT HEAVIER BAND. WITH THIS WE
WILL CUT BACK ON THE WINTER STORM WARNING SLIGHTLY AND DOWNGRADE TO
AN ADV FOR AREAS WEST OF A LINE FROM VALLEY PARK TO GREENWOOD THAT
WERE IN THE WINTER STORM WARNING. EVERYTHING ELSE WILL REMAIN THE
SAME AT THIS TIME.

TONIGHT AND TOMORROW THINGS WILL FINALLY BE QUIET. TEMPS WILL BE
BELOW NORMAL AND WHERE THERE IS SNOW ON THE GROUND LOWS COULD DROP
INTO THE MID 20S BUT I CANT REALLY SHOW THAT YET. OTHERWISE TEMPS
SHOULD RANGE FROM THE UPPER 20S TO LOWER 30S. TOMORROW H925 TEMPS
ARE ONLY EXPECTED TO BE AROUND 2-3C AND THIS WOULD NORMALLY EQUATE
TO LOWER 50S. THE CONCERN WOULD BE SNOW ON THE GROUND WHICH BY THE
END OF THE DAY WILL HAVE ALL MELTED BUT THIS WILL HAVE AN EFFECT ON
HIGHS. AGAIN NOT KNOWING WHERE THE HEAVIEST SNOW WILL OCCUR MAKES
THIS DIFFICULT TO TELL SO I WILL JUST MAKE A GENERAL ADJUSTMENT DOWN
A DEGREE OR TWO FROM THE MAV ACROSS THE SERN HALF OF THE CWA. /CAB/

.LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY

A BIG PATTERN CHANGE WILL TAKE PLACE OVER THE WEEKEND. THE NORTHWEST
FLOW THAT HAS DOMINATED THE WEATHER OVER THE ARKLAMISS WILL SHIFT TO
A SOUTHWEST FLOW PATTERN AS A MAJOR LONGWAVE TROUGH DEVELOPS OVER
THE WRN CONUS AND A RIDGE DEVELOPS OVER THE GULF. COLD CONTINENTAL
POLAR (CP) AIRMASSES INTRUDING UPON THE NRN CONUS WILL OOZE
SOUTHWARD AND ATTEMPT TO UNDERCUT THE SOUTHWEST FLOW ALOFT. THE
GFS/GFES/ECMWF AND UKMET ALL INDICATE THE CP BOUNDARY WILL AT LEAST
REACH THE ARKLAMISS AND STALL IN THE VICINITY. THE ENERGETIC
SOUTHWEST FLOW ALOFT WILL HELP TRIGGER A FEW ROUNDS OF RAINFALL
ALONG THE BOUNDARY SO WE COULD END UP WITH AN ACTIVE WEATHER WEEK IN
TERMS OF RAINFALL...ALTHOUGH IT APPEARS THE RETURN OF GULF MOISTURE
WILL BE LIMITED SOME BY THE PRESENCE OF THE UPPER RIDGE. HAVE
ACCEPTED MEX GUIDANCE TEMPS/POPS...WITH RAIN CHANCES JUST ABOUT
EVERY PERIOD. WHILE NOT DEPICTED EXPLICITLY BY MOS...THERE COULD BE
QUITE A TEMPERATURE RANGE FROM NW TO SE ACROSS THE AREA DEPENDING ON
WHERE THE FRONTAL BOUNDARY SETS UP...PERHAPS UP TO A 30-35 DEG F
RANGE. /EC/

&&

.AVIATION...TOUGH AVIATION CONDITIONS ARE EXPECTED THE NEXT 24 HOURS
WITH MOSTLY LIFR TO IFR CONDITIONS PREVAILING. A STRONG UPPER LOW
WILL BRING A COLD POCKET OF AIR OVER THE REGION TODAY AS LIGHT TO
MODERATE RAIN MOVES ACROSS THE AREA THIS MORNING.  A DEFORMATION
ZONE OF SNOW WILL DEVELOP FROM THE SOUTHWEST TO NORTHEAST LATER THIS
MORNING AND INTO THE EARLY AFTERNOON FROM SOUTHERN AND CENTRAL
MISSISSIPPI INTO NORTH MISSISSIPPI.  REPORTS OF A RAIN/SLEET TO
RAIN/SNOW MIX HAVE ALREADY BEEN REPORTED THIS MORNING AT SEVERAL
LOCATIONS ALONG AND WEST OF THE MISSISSIPPI RIVER.  THIS WINTERY
PRECIPITATION...AS STATED EARLIER...WILL CONTINUE TO SPREAD FURTHER
TO THE EAST THROUGH THE MID MORNING HOURS.  IN ADDITION...AS THE
RESULT OF A STRONG PRESSURE GRADIENT OVER THE REGION...WEST TO
NORTHWEST WINDS SUSTAINED FROM 15 TO 20 KNOTS WITH HIGHER GUSTS ARE
BEING OBSERVED AT MANY SITES THIS MORNING.  THESE GUSTY WINDS WILL
CONTINUE THROUGH THE DAY TODAY...BUT WILL WEAKEN TO AROUND 10 KNOTS
BY 00Z...AND WEAKEN FURTHER TO BETWEEN 5-10 KNOTS AFTER MIDNIGHT.

CONDITIONS WILL IMPROVE FROM WEST TO EAST DURING THE AFTERNOON AND
EVENING HOURS...WITH VFR CONDITIONS EXPECTED AT ALL SITES BETWEEN
03-06Z TONIGHT AND CONTINUING INTO EARLY FRIDAY MORNING. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       39  29  51  32 / 100   3   0   0
MERIDIAN      39  29  51  27 / 100   6   0   0
VICKSBURG     44  31  54  33 /  79   3   0   0
HATTIESBURG   39  27  57  29 / 100   3   0   0
NATCHEZ       41  30  56  33 /  85   3   0   0
GREENVILLE    44  32  51  32 /  63   3   0   0
GREENWOOD     42  29  53  31 /  71   3   0   0

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR MSZ018-019-
     025>066-072>074.

     WINTER STORM WARNING UNTIL 6 PM CST THIS AFTERNOON FOR
     MSZ028>033-037>039-043>066-072>074.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR MSZ018-
     019-025>027-034>036-040>042.

LA...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR LAZ007>009-
     015-016-023>026.

     WINTER STORM WARNING UNTIL 6 PM CST THIS AFTERNOON FOR LAZ016-
     023>026.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
     LAZ007>009-015.

AR...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR ARZ074-075.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR ARZ074-
     075.

&&

CAB/40/19

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
404 PM CST WED DEC 10 2008

LAZ016-023>026-MSZ025>033-035>066-072>074-112215-
MADISON LA-FRANKLIN LA-CATAHOULA-TENSAS-CONCORDIA-LEFLORE-GRENADA-
CARROLL-MONTGOMERY-WEBSTER-CLAY-LOWNDES-CHOCTAW-OKTIBBEHA-
HUMPHREYS-HOLMES-ATTALA-WINSTON-NOXUBEE-ISSAQUENA-SHARKEY-YAZOO-
MADISON MS-LEAKE-NESHOBA-KEMPER-WARREN-HINDS-RANKIN-SCOTT-NEWTON-
LAUDERDALE-CLAIBORNE-COPIAH-SIMPSON-SMITH-JASPER-CLARKE-JEFFERSON-
ADAMS-FRANKLIN MS-LINCOLN-LAWRENCE-JEFFERSON DAVIS-COVINGTON-
JONES-MARION-LAMAR-FORREST-
404 PM CST WED DEC 10 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MUCH OF CENTRAL AND SOUTHERN
MISSISSIPPI AND EAST CENTRAL LOUISIANA.

.DAY ONE...TONIGHT AND THURSDAY

A WINTER STORM WARNING HAS BEEN ISSUED FOR THE AREA ALONG AND SOUTHEAST
OF A LINE FROM WINNSBORO TO ROLLING FORK TO GREENWOOD FROM MIDNIGHT
THROUGH 6 PM THURSDAY. A LARGE UPPER LEVEL SYSTEM IS EXPECTED TO MOVE
ACROSS THE NORTHERN GULF OF MEXICO AND INTO ALABAMA TONIGHT AND
TOMORROW. THIS WILL INITIALLY BRING WIDESPREAD RAIN TO THE AREA BUT AS
THINGS COOL OFF LATE TONIGHT THE RAIN WILL BEGIN TO MIX WITH SNOW.
RAIN SHOULD START TO CHANGE COMPLETELY OVER TO SNOW EARLY THURSDAY
MORNING AND PERSIST THROUGH MOST OF THE DAY. EVEN WITH THE SURFACE
TEMPERATURES EXPECTED ABOVE FREEZING THE SNOW WILL BE MODERATE AT TIMES
LEADING TO SOME ACCUMULATIONS. SNOW ACCUMULATIONS OF 3 TO 4 INCHES
ARE POSSIBLE AND THERE IS A GOOD CHANCE THAT A LINE OF HEAVIER SNOW
WILL DEVELOP WHICH WOULD LEAD TO GREATER SNOW ACCUMULATIONS.

IN ADDITION...NORTHERLY WINDS WILL INCREASE TO 15 TO 25 MPH WITH
HIGHER GUSTS THURSDAY. THIS WILL KEEP WIND CHILLS BELOW FREEZING
ALONG WITH HAZARDOUS DRIVING CONDITIONS ALONG EAST-WEST ORIENTED
HIGHWAYS.

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

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS...IS NOT EXPECTED THROUGH NEXT TUESDAY.

ARZ074-075-LAZ007>009-015-MSZ018-019-034-112215-
ASHLEY-CHICOT-MOREHOUSE-WEST CARROLL-EAST CARROLL-RICHLAND-
BOLIVAR-SUNFLOWER-WASHINGTON-
404 PM CST WED DEC 10 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EXTREME SOUTHEAST
ARKANSAS...NORTHEAST LOUISIANA AND WEST CENTRAL MISSISSIPPI.

.DAY ONE...TONIGHT AND THURSDAY

A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE AREA ALONG AND
NORTHWEST OF A LINE FROM WINNSBORO TO ROLLING FORK TO GREENWOOD FROM
MIDNIGHT THROUGH 6 PM THURSDAY. A LARGE UPPER LEVEL SYSTEM IS
EXPECTED TO MOVE ACROSS THE NORTHERN GULF OF MEXICO AND INTO ALABAMA
TONIGHT AND TOMORROW. THIS WILL INITIALLY BRING WIDESPREAD RAIN TO
THE AREA BUT AS THINGS COOL OFF LATE TONIGHT THE RAIN WILL BEGIN TO
MIX WITH SNOW. RAIN SHOULD START TO CHANGE OVER TO SNOW EARLY THURSDAY
MORNING AS THE PRECIPITATION ENDS FROM THE WEST. EVEN WITH THE SURFACE
TEMPERATURES EXPECTED ABOVE FREEZING SOME SNOW ACCUMULATIONS OF 1 TO
2 INCHES WILL BE POSSIBLE ON GRASSY SURFACES.

N ADDITION...NORTHERLY WINDS WILL INCREASE TO 15 TO 25 MPH WITH
HIGHER GUSTS THURSDAY. THIS WILL KEEP WIND CHILLS BELOW FREEZING
ALONG WITH HAZARDOUS DRIVING CONDITIONS ALONG EAST-WEST ORIENTED
HIGHWAYS.

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

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS...IS NOT EXPECTED THROUGH NEXT TUESDAY.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.

22

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