FXUS64 KJAN 300047 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
650 PM CST SUN NOV 29 2009
.UPDATE...
SURFACE COLD FRONT AT 30/0000 UTC EXTENDS FROM CENTRAL ARKANSAS
SOUTHWESTWARD ACROSS THE ARKLATEX REGION INTO NORTHEAST TEXAS. KSHV
RADAR INDICATES THAT STRONG TO SEVERE THUNDERSTORMS HAVE DEVELOPED
ALONG AND JUST BEHIND THE BOUNDARY. ALL OF THIS CONVECTION IS
EXPECTED TO BECOME ELEVATED AS IT TRANSLATES SOUTHEASTWARD WITH THE
BOUNDARY OVERNIGHT WHILE SBCAPES DROP TO NEAR ZERO. HOWEVER...
RESERVOIR OF MUCAPES OVER 250 J/KG WILL BE FOUND ALONG AND BEHIND
THE SURFACE FRONT...SPECIFICALLY FOR A PARCEL OF AIR LIFTED FROM 900
MB. GIVEN THAT THE FRONTAL CIRCULATION WILL EXTEND ABOVE 900 MB...
ELEVATED CONVECTION WILL LIKELY IMPACT SOUTHERN PORTIONS OF THE CWA
LATE IN THE NIGHT AND EARLY MONDAY MORNING. HOWEVER...THE THREAT FOR
STRONG TO SEVERE STORMS WILL LIKELY DIMINISH AS STORMS BECOME
INCREASINGLY ELEVATED. THE FORECAST HAS BEEN UPDATED TO INCLUDE
ISOLATED THUNDERSTORMS SOUTH OF INTERSTATE 20...WHERE GFS IS
INDICATING UP TO 450 J/KG OF MUCAPE FOLLOWING THE SURFACE FRONT
THROUGH MONDAY MORNING...AND SREF IS REPORTING AT LEAST 50 PERCENT
OF ITS MEMBERS GENERATING AT LEAST 250 J/KG OF MUCAPE. SEE PREVIOUS
DISCUSSION BELOW FOR UPDATES TO THE EXTENDED FORECAST. /COHEN/
&&
.PREV DISCUSSION... /ISSUED 311 PM CST SUN NOV 29 2009/
PREVIOUSLY...TONIGHT THROUGH MONDAY NIGHT...RAIN CHANCES WILL
INCREASE ACROSS THE ENTIRE FORECAST AREA FROM WEST TO EAST THROUGH
THE OVERNIGHT HOURS AS A COLD FRONT...WHICH CURRENTLY STRETCHES
SOUTHWEST FROM THE GREAT LAKES REGION THROUGH NORTHWEST ARKANSAS AND
SOUTHEAST OKLAHOMA...INTO NORTH CENTRAL AND CENTRAL TEXAS...MOVES
INTO WESTERN PORTIONS OF THE ARKLAMISS REGION LATE TONIGHT. AHEAD
OF THE FRONT...DECENT ISENTROPIC UPGLIDE WILL CONTINUE TO PRODUCE
PATCHES OF LIGHT...TO OCCASIONALLY MODERATE...RAIN ACROSS LOCATIONS
NORTH OF THE INTERSTATE 20 CORRIDOR...WHILE CLOUDS CONTINUE TO
INCREASE FROM WEST TO EAST ACROSS THE REGION. A COMBINATION OF ALL
THE ABOVE WILL ONCE AGAIN RESULT IN A MILD NIGHT AS OVERNIGHT LOWS
WILL RANGE FROM THE AROUND 50 ACROSS THE DELTA TO THE MID 50S ACROSS
SOUTHEAST MISSISSIPPI.
THE FRONT WILL BEGIN PUSHING SOUTHEAST INTO THE NORTHWEST HALF OF
THE FORECAST AREA AFTER MIDNIGHT TONIGHT...AND SHOULD EXIT SOUTHEAST
MISSISSIPPI DURING THE LATE MORNING/EARLY AFTERNOON HOURS MONDAY.
RAIN WILL GRADUALLY TAPPER OFF FROM NORTHWEST TO SOUTHEAST THROUGH
THE DAY...AND FINALLY COME TO AN END ACROSS SOUTHEAST MISSISSIPPI BY
MONDAY EVENING. BEHIND THE FRONT...SKIES WILL GRADUALLY CLEAR AS
COOLER DRIER AIR QUICKLY BEGINS FILTERING INTO THE CWA FROM THE
NORTHWEST...RESULTING IN A COOLER FEEL TO THE AIR OVER MUCH OF THE
FORECAST AREA MONDAY NIGHT./19/
TUESDAY THROUGH SUNDAY...THIS SHOULD LEAVE MOST OF THE REGION FAIRLY
DRY ON TUESDAY. THERE COULD BE SOME LIGHT RAIN BEGINNING ON TUESDAY
AFTERNOON DUE TO ISENTROPIC LIFT ACROSS THE SOUTH AND HAVE INCLUDED
SOME POPS IN DURING THIS TIME PERIOD BUT LEFT NORTHERN SECTIONS DRY.
TIMING AND PLACEMENT DIFFERENCES BETWEEN MODELS LEAVE MUCH
UNCERTAINTY WITH MOST OF THE EXTENDED BUT IT LOOKS LIKE MOST OF THE
ARKLAMISS WILL SEE SOME RAIN WITH WED LOOKING TO BE THE WETTEST DAY.
MODELS INDICATE THAT THE HEAVIER/BULK OF THE RAIN WILL OCCUR
GENERALLY ALONG AND SOUTHEAST OF THE NATCHEZ TRACE WITH LESSER
AMOUNTS ACROSS THE MS DELTA. BY WED. MORNING...THE ECMWF AND OTHER
MODELS CONTINUE TO SHOW THE SFC LOW JUST TO OUR SOUTHWEST WITH THE
GFS FASTER WITH THE LOW ACROSS NW FL/S AL WITH THE MID LEVEL LOW
STILL ACROSS EAST CENTRAL TEXAS.
BY WEDNESDAY NIGHT....THE BULK OF THE RAIN SHOULD MOVE OFF TO
LOCATIONS MUCH FARTHER EAST OF THE CWA AS THE MID LEVEL LOW ENTERS
OUR REGION. LINGERING LIGHT RAIN COULD AFFECT THE CWA THROUGH THURS.
MORNING AND HAVE TAPERED THIS FOR THE EAST/NORTHEAST WITH ONLY
SLIGHT CHANCES IN THE WEST PRIOR TO MIDNIGHT AND LEAVING ONLY SLIGHT
CHANCES IN THE EAST/NORTHEAST THROUGH DAYBREAK. CONDITIONS SHOULD
REMAIN FAIRLY DRY BEGINNING DURING THE DAY THURSDAY THROUGH MOST OF
THE REST OF THE PERIOD.
FOR THU-FRI. THE LARGER SCALE TROUGH SWINGS ON THROUGH AND COLD
HIGH PRESSURE RESUMES AT THE SURFACE. MODELS DIFFER ONCE AGAIN PAST
THIS POINT. THE GFS QUICKLY MOVES THE SFC HIGH OFF TO THE EAST WITH
SOUTHERLY FLOW RETURNING LATE FRIDAY INTO SATURDAY AND THE ECMWF
DOES NOT MOVE THE UPPER TROUGH THROUGH AS FAST AND LINGERS NORTHERLY
FLOW. WITH THE ECMWF THE RETURN FLOW AND EASTWARD PUSH OF THE HIGH
DOES NOT OCCUR UNTIL LATE SUNDAY. GFS WANTED TO BRING RAIN CHANCES
BACK WITH THE NEXT SYSTEM BY SATURDAY BUT HAVE OPTED TO KEEP THESE
OUT OF THE FORECAST UNTIL THERE IS A LITTLE BETTER AGREEMENT.
OVERALL...TRIED TO STAY CLOSE TO MAV/MEX NUMBERS GIVEN UNCERTAINTIES
IN THE EXTENDED. HOWEVER...DID INCREASE POPS FOR TUES-WED IN THE
SOUTH WHERE THE BETTER POTENTIAL FOR RAIN EXISTS AND CUT NORTHERN
POPS DOWN SOME. TRIED TO FOLLOW THE SLIGHTLY SLOWER TIMING OF THE
ECMWF/SREF WHICH WAS ALSO A LITTLE WETTER. UPDATED TEMPS HAVE BEEN
TRENDED TOWARD THE ENSEMBLE MEANS WITH SUBFREEZING OVERNIGHT
READINGS THURSDAY NIGHT AND FRIDAY NIGHT. THE 12Z RUNS OF BOTH
GFS/ECMWF SHOW A NEARLY 1030MB SURFACE HIGH CROSSING THE LOWER MS
VALLEY WITH PLENTY OF DRY AIR FOR THE RADIATIONAL COOLING LOWS TO BE
ACHIEVED. /28/40/
&&
.AVIATION...
SCATTERED SHOWERS WILL LIFT NORTHEASTWARD ACROSS NORTHERN PORTIONS
OF CENTRAL MISSISSIPPI THROUGH THE EARLY EVENING HOURS...POTENTIALLY
IMPACTING KGTR. MVFR CEILINGS AND VISIBILITIES COULD ACCOMPANY THIS
ACTIVITY. OTHERWISE...WIDESPREAD VFR CONDITIONS THIS EVENING WILL BE
FOLLOWED BY MVFR CEILINGS BY LATE EVENING AS LOW CLOUDS THICKEN.
WINDS WILL BE SOUTH AT 3 TO 8 KT THROUGH THE EVENING. THEN BY
30/0600 UTC...A COLD FRONT WILL BEGIN MOVING SOUTHEASTWARD ACROSS
THE REGION...WITH ONE OR MORE BANDS OF MODERATE RAIN ALONG AND JUST
BEHIND THE FRONT. CEILINGS WILL LOWER TO IFR NEAR THIS ACTIVITY...
WITH MVFR TO LOCALLY IFR VISIBILITIES AS WELL. ADDITIONALLY...WINDS
WILL ABRUPTLY SHIFT TO NORTHWEST TO NORTH AND INCREASE TO 10 TO 15
KT WITH GUSTS TO 20 KT IN THE WAKE OF THE FRONT. THE FRONT IS
EXPECTED TO REACH KGLH AND KGWO BETWEEN 08 AND 10 UTC...KGTR AND
KJAN BETWEEN 12 AND 14 UTC...AND KMEI AND KHBG BETWEEN 13 AND 16
UTC. ISOLATED THUNDERSTORMS WILL ALSO BE POSSIBLE ALONG AND SOUTH OF
INTERSTATE 20...BUT THE RISK FOR THUNDERSTORMS IMPACTING ANY TAF
SITE IS TOO LOW FOR MENTION IN THE TAFS AT THIS TIME. AFTER THE
MODERATE RAIN MOVES THROUGH...TWO TO THREE HOURS OF LIGHT RAIN WILL
OCCUR. LOW CLOUDS WITH MVFR CEILINGS WILL CONTINUE THROUGH MONDAY
AFTERNOON...WITH CLEARING EXPECTED TO BEGIN FROM NORTHWEST TO
SOUTHEAST LATE MONDAY AFTERNOON. /COHEN/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 53 58 39 57 / 75 65 3 47
MERIDIAN 52 61 35 57 / 57 75 3 44
VICKSBURG 52 58 40 56 / 89 50 3 47
HATTIESBURG 55 65 40 57 / 24 82 11 64
NATCHEZ 53 57 41 55 / 76 64 8 65
GREENVILLE 50 53 38 56 / 100 30 2 23
GREENWOOD 50 54 37 59 / 100 41 2 23
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
COHEN/19/28/40
