Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 041616 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1016 AM CST WED MAR 4 2015

.UPDATE...
TEMPS ARE WIDELY IN THE UPPER 60S TO LOW 70S CURRENTLY WITH
DEWPOINTS ACROSS THE AREA IN THE MID 60S...VERY SPRINGLIKE INDEED.
THE MUCH ANTICIPATED COLD FRONT IS KNOCKING ON OUR DOORSTEP AND IS
CURRENTLY LINED UP FROM MEMPHIS TO PINE BLUFF TO TEXARKANA. THE
FORECAST LOOKS PRETTY GOOD FOR TODAY ACTUALLY. THE ONLY CHANGE WAS
TO INCREASE HIGH TEMPERATURES IN THE DELTA WHERE IT IS WARMING UP
QUICKLY JUST AHEAD OF THE FRONT. STILL ANTICIPATE SOME WARM
ADVECTION SHOWERS TO POP UP TODAY. THUNDER WILL BE LIMITED IN THE
WARM SECTOR. ALTHOUGH WITH BULK SHEAR AROUND 50 KTS...A STRONG STORM
IS POSSIBLE WITH WIND GUSTS UP TO 40 MPH POSSIBLE. THUNDER IS MORE
LIKELY POSSIBLE ALONG THE FRONTAL BOUNDARY WHERE FORCING IS GREATER.
/10/

&&

.AVIATION...
A MIX OF MVFR/VFR FLIGHT STATUSES ARE CURRENTLY BEING OBSERVED AT
TAF SITES ACROSS THE AREA THIS MORNING...DUE TO VARYING CEILINGS
HEIGHTS. AS THE DAY PROGRESSES AND A STRONG COLD FRONT BEGINS
IMPEDING UPON THE REGION FROM THE NORTHWEST...LOWER CEILINGS...IN
ADDITION TO SHOWERS AND A FEW THUNDERSTORMS...WILL INCREASE ACROSS
THE REGION. THIS WILL RESULT IN A RETURN TO MVFR/IFR CATEGORIES FROM
LATE THIS AFTERNOON THROUGH AT LEAST THURSDAY MORNING.

WINDS AHEAD OF THE FRONT THROUGH MUCH OF TODAY WILL BE SOUTHERLY
BETWEEN 10-15 KNOTS...WITH SOME GUSTS AROUND 20 KNOTS POSSIBLE.
HOWEVER BEHIND THE FRONT...WINDS WILL QUICKLY BECOME NORTHERLY
SUSTAINED BETWEEN 20-30 KNOTS...WITH GUSTS AROUND 40 MPH
POSSIBLE...ESPECIALLY ACROSS THE DELTA.  THIS WILL USHER IN A VERY
COLD AIRMASS.

THROUGH THE NIGHT...THESE STRONG COLD ADVECTING WINDS WILL
RESULT IN A CHANGEOVER OF RAIN...TO FREEZING RAIN AND SLEET
BEGINNING IN THE DELTA AROUND 03Z TONIGHT.  THIS CHANGEOVER IN
PRECIPITATION WILL CONTINUE SOUTH INTO CENTRAL MISSISSIPPI THROUGH
DAY BREAK THURSDAY MORNING.  CURRENTLY...ICE ACCUMULATION LOOKS MORE
PREVALENT...BETWEEN 0.25-0.50 INCHES...AT KGLH AND KGWO WHERE A
WINTER STORM WARNING IS IN EFFECT FROM TONIGHT THROUGH 18Z
THURSDAY.  AN ADDITIONAL ACCUMULATION OF SLEET AND SNOW UP TO 1 INCH
IS ALSO POSSIBLE AT THESE SITES.  AT KGTR...WHERE A WINTER STORM
WATCH IS IN EFFECT FROM TONIGHT THROUGH 00Z THURSDAY...ICE
ACCUMULATION CURRENTLY LOOKS TO BE < 0.25 INCHES.  FINALLY...AT
KHKS...KJAN...AND KMEI...ICE ACCUMULATION IF ANY...CURRENTLY APPEARS
LIGHT AND ONLY COLLECTING ON METAL SURFACES AND PERHAPS SOME
ELEVATED SURFACES. /19/

&&

.PREV DISCUSSION... /ISSUED 553 AM CST WED MAR 4 2015/

DISCUSSION...
SHORT TERM (TODAY THROUGH THURSDAY)...IT IS A TASTE OF SPRING OUTSIDE
RIGHT NOW...WITH TEMPS IN THE 60S AREAWIDE AND A MOIST SOUTHERLY
BREEZE. THIS ONLY MAKES IT HARDER TO ACCEPT THAT WE ARE ABOUT 24
HOURS AWAY FROM A CRUEL RETURN TO WINTER. TAKING A LOOK AT THE
WEATHER MAPS...UPPER TROUGHING EXTENDS FROM THE UPPER PLAINS DOWN
THROUGH BAJA CALIFORNIA. DOWNSTREAM OF THIS TROUGH IS A
STRENGTHENING JET STREAK...WHICH WILL BE A BIG PLAYER IN WEATHER
HERE OVER THE NEXT 36 HOURS...EXTENDING FROM THE CENTRAL PLAINS
THROUGH THE GREAT LAKES. AT THE SURFACE A STRONG COLD FRONT EXTENDS
FROM THE RED RIVER VALLEY ACROSS THE MIDSOUTH.

THROUGH THE DAY...THE SURFACE FRONT WILL SAG SOUTHWARD TOWARD THE
CWA...REACHING OUR NORTHWEST CORNER BY AROUND NOON. SCATTERED
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE SOUTH OF THE FRONT IN THE
WARM SECTOR...BUT MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL
OCCUR BEHIND THE FRONT. THE FARTHER SOUTH AND EAST YOU GO IN THE
CWA...FORECAST SOUNDINGS SHOW AN INCREASINGLY CAPPED ENVIRONMENT.
LAPSE RATES ARE ALSO MARGINAL IN THIS AREA. THIS WILL LIMIT PRECIP TO
MAINLY SHOWERLY WARM ADVECTION ACTIVITY. AS A RESULT POPS WERE SCALED
BACK ACROSS THE SOUTH AND EAST TODAY. IT WILL ALSO BE A QUITE WARM
DAY AHEAD OF THE FRONT...WITH LOWER 80S POSSIBLE IN A FEW SPOTS. AS
THE FRONT CONTINUES SOUTHWARD INTO THE AREA...RAIN WILL INCREASE WITH
SOME POST-FRONTAL ELEVATED THUNDER EVEN POSSIBLE. TEMPERATURE CHANGE
BEHIND THE FRONT WILL BE RATHER ABRUPT AS RATHER STRONG COLD
ADVECTION ENSUES...WITH TEMP FALLS OF 30-40 DEGREES IN JUST A FEW
HOURS EXPECTED IN MANY AREAS.

THINGS GET A BIT MESSIER THIS EVENING AS SURFACE TEMPS BEGIN TO FALL
BELOW FREEZING...FIRST OCCURRING INTO THE DELTA BETWEEN SUNSET AT
MIDNIGHT. AS A STRONG WARM NOSE PERSISTS BETWEEN 700-900 MB...PRECIP
WILL BE IN THE FORM OF FREEZING RAIN AND SLEET. SEVERAL SUCCESSIVE
RUNS OF THE SREF HAVE CONSISTENTLY SHOWN A SIGNIFICANT PROPORTION OF
THIS PRECIP OCCURRING AS SLEET. AND THE NAM WHICH HAS BEEN A
RELATIVELY WARMER SOLUTION LEADING UP TO THIS EVENT DEPICTS NEAR
SURFACE SUBFREEZING LAYERS AS GREAT AS 3-4 KFT OVERNIGHT IN THE
DELTA. WILL CONTINUE TO HIGHLIGHT BOTH FREEZING RAIN AND SLEET ACCUM
POTENTIAL ACROSS THIS AREA...PARTICULARLY FOR THE OVERNIGHT HOURS.

BY SUNRISE THURSDAY...THE FREEZING LINE IS EXPECTED TO GENERALLY BE
NEAR THE NATCHEZ TRACE...WITH THE LOW LEVEL COLD AIRMASS SURGING MORE
READILY IN OUR WEST ACROSS THE FLAT DELTA AND MORE SLOWLY FARTHER
EAST. THE 00Z GUIDANCE SUITE CONTINUED A TREND TOWARD GREATER
PRECIPITATION THURSDAY MORNING AS THE PREVIOUSLY MENTIONED STRONG
UPPER JET REMAINS JUST NORTH OF THE REGION...PROVIDING A FAVORABLE
ENVIRONMENT FOR LARGE SCALE LIFT AND CONTINUED POST-FRONTAL PRECIP.
THIS PORTENDS THE POTENTIAL FOR RESULTING IMPACTS FARTHER SOUTH AND
EAST INTO THE AREA THAN PREVIOUSLY ADVERTISED. THE FREEZING LINE WILL
LIKELY CONTINUE SOUTHWARD THROUGH MID MORNING TO GENERALLY A
BROOKHAVEN TO JUST SOUTH OF MERIDIAN LINE.

ALONG THE MOST SOUTHERN EXTENT OF AREAS THAT WILL FALL TO OR JUST
BELOW FREEZING...IMPACTS ARE LESS LIKELY AS ANTECEDENT CONDITIONS
WILL MAKE FOR WARM GROUND AND IT IS OFTEN DIFFICULT TO GET ICE
ACCRETION WITH MARGINALLY FREEZING TEMPS. HOWEVER FARTHER
NORTH...ROUGHLY NORTH OF A LINE FROM HARRISONBURG TO NEWELLTON TO
NEAR THE JACKSON METRO TO MACON...LINGERING PRECIP WOULD MAKE FOR
GREATER POTENTIAL FOR ICING THURSDAY MORNING. TEMPERATURES WILL STAY
IN THE 30S FOR THE ENTIRE DAY ACROSS MOST OF THE AREA...WITH SOME
AREAS IN THE DELTA POSSIBLY STRUGGLING TO GET ABOVE FREEZING.

AS WE ARE NOW WITHIN 24 HOURS OF THE BEGINNING OF WINTRY PRECIP FOR
MUCH OF THE EXISTING WINTER STORM WATCH AREA...IT HAS NOW BEEN
UPGRADED TO A WINTER STORM WARNING IN ALL AREAS EXCEPT WEBSTER AND
CLAY COUNTIES. TO THE SOUTH AND EAST OF THIS WARNING...A WINTER STORM
WATCH HAS BEEN POSTED FOR AN ADDITIONAL TIER OF COUNTIES WHERE WE
BELIEVE IT IS POSSIBLE A WARNING MAY EVENTUALLY BE NEEDED IF THE
TREND TOWARD MORE PRECIP THURS MORNING CONTINUES. ACROSS THE WARNING
AREA...ICE ACCUMULATIONS COULD BE SIGNIFICANT. THERE IS A GENERAL
CONSENSUS AMONG THE 00Z OPERATIONAL GUIDANCE FOR 1/4 TO 3/4 OF QPF
WITH SUBFREEZING SURFACE TEMPS. WE ARE CURRENTLY HIGHLIGHTING THE
POTENTIAL FOR 1/4 INCH OF ICE ACCRETION AND UP TO AN INCH OF
SLEET/SNOW IN THE WARNING AREA. THESE PROPORTIONS MAY STILL NEED TO
BE ADJUSTED AS NEWER DATA BECOMES AVAILABLE. OBVIOUSLY A GREATER
PROPORTION OF ICE THAN SLEET/SNOW COULD RESULT IN MORE SIGNIFICANT
ISSUES. /DL/

LONG TERM (THURSDAY NIGHT THROUGH TUESDAY)...CLOUDS LOOK TO CLEAR
OUT THURSDAY EVENING WITH SLOWLY MODIFYING ARCTIC HIGH PRESSURE
SINKING SOUTH TOWARD THE LOWER MS VALLEY. NORTH WINDS WILL CONTINUE
TO BE SOMEWHAT GUSTY IN THE EVENING...BUT WILL GRADUALLY DIE DOWN
THROUGH THE NIGHT. GOOD LATE NIGHT RADIATIONAL COOLING CONDITIONS
ATOP EXPECTED SNOW/ICE COVER OVER THE NORTHWEST THIRD OF ZONES COULD
REALLY PLUMMET TEMPS AND SHATTER SOME RECORD LOWS FOR EARLY FRIDAY
MORNING. TEMPS IN THE ARKLAMISS DELTA POTENTIALLY WAY DOWN IN THE
TEENS COULD ALSO PRODUCE SINGLE DIGIT WIND CHILLS LATER THURSDAY
NIGHT THROUGH EARLY FRIDAY WITH HIGHS ON FRIDAY PERHAPS STRUGGLING TO
BREAK THE FREEZING MARK THERE. THIS IS IMPRESSIVE LEVELS OF COLD WE
ARE TALKING ABOUT...ESPECIALLY GIVEN THE CALENDER DATE...AND WE WILL
MENTION IN THE HWO.

AFOREMENTIONED HIGH PRESSURE SITTING OVER THE REGION AND MODIFYING
SLOWLY ON FRIDAY WILL YIELD ONLY A GRADUAL WARMING TREND ALTHOUGH
SKIES WILL BE MOSTLY CLEAR. TEMPERATURES FRIDAY INTO FRIDAY NIGHT
WILL BE SOME 20 DEGREES BELOW NORMAL ALTHOUGH LOWS WILL THANKFULLY
PROBABLY NOT DIP INTO THE TEENS IN ANY AREAS FRIDAY NIGHT.

CLOUDS WILL BE INCREASING ON SATURDAY AS THE ACTIVE SOUTHERN STREAM
JET RELOADS OFF TO OUR SOUTHWEST. THERE IS ONLY A SLIGHT CHANCE
SHOWERS WILL ENTER BACK INTO SOUTHERN ZONES DURING THE DAY SATURDAY
BUT RAIN CHANCES WILL GRADUALLY INCREASE AT LEAST ALONG AND SOUTH OF
I-20 HEADING INTO SUNDAY. FORTUNATELY...TEMPERATURES SHOULD BE
TRENDING WARM ENOUGH BY THIS TIME TO KEEP WINTRY WEATHER POTENTIAL
OUT OF THE PICTURE.

UNFORTUNATELY...A SOMEWHAT INCLEMENT WEATHER PATTERN WILL LIKELY
LOCK INTO PLACE FOR OUR REGION THROUGH EARLY NEXT WEEK WITH A
SOUTHERN STREAM TROUGH ANCHOR OVER TX AND OLD MEXICO CONTINUING TO
SPILL CLOUDS AND UPPER LEVEL MOISTURE OUR WAY. DEEP WARMTH AND
MOISTURE IN THIS PATTERN SHOULD REMAIN SEQUESTERED IN THE GULF OF
MEXICO...ALONG WITH MUCH OF THE THUNDERSTORM ACTIVITY.
HOWEVER...PERSISTENT RAIN CHANCES ARE HARD TO SHAKE FROM THE
FORECAST (ESPECIALLY SOUTHEAST OF THE NATCHEZ TRACE CORRIDOR)
THROUGH THIS WHOLE PERIOD. TEMPERATURES WILL CONTINUE SHOW
MODERATION...BUT DO NOT HAVE MUCH OF A CHANCE OF GETTING ABOVE
NORMAL THROUGH EARLY NEXT WEEK. /BB/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       81  31  34  22 /  40 100  83   8
MERIDIAN      80  35  36  23 /  24  99  84   9
VICKSBURG     79  29  33  19 /  66 100  83   6
HATTIESBURG   81  42  42  26 /  26  91  64  13
NATCHEZ       79  30  34  23 /  33 100  86   9
GREENVILLE    70  25  31  14 /  98 100  69   4
GREENWOOD     74  27  31  16 /  93 100  76   4

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY AFTERNOON
     FOR MSZ029>033-036>039-042>045-047-048.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO NOON CST THURSDAY
     FOR MSZ018-019-025>028-034-035-040-041.

LA...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY AFTERNOON
     FOR LAZ016-023>025.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO NOON CST THURSDAY
     FOR LAZ007>009-015.

AR...WINTER STORM WARNING FROM 6 PM THIS EVENING TO NOON CST THURSDAY
     FOR ARZ074-075.

&&

$$




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