FXUS64 KJAN 061603 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1003 AM CST SUN DEC 6 2009
.UPDATE...HIGHER(20K FEET) CLOUD SHIELD HAS THICKENED UP QUICKER THAN
EXPECTED AND IT NOW APPEARS THAT OUR HIGH TEMPERATURES WILL SUFFER A
SLIGHT SETBACK. A FEW SUN BREAKS WILL CONTINUE UNTIL AROUND 17Z WHEN
EVEN THICKER/LOWER(4-6K FEET) CLOUDS ARRIVE AS THEY STREAM ACROSS
WRN LA AT 42KTS OR BETTER. AS A RESULT...HAVE ADJUSTED SKY COVER
UPWARD AND MOST MAX TEMPS DOWNWARD 2-3F FOR THIS AFTERNOON. MOISTURE
TRANSPORT IN THE LOWER LEVELS STILL LOOKING DECENT AFTER 06Z TONIGHT
FOR SOME ISOLATED TSRA AND HAVE INCLUDED THEM FOR SWRN SECTIONS
BEFORE SPREADING THEM EWD MONDAY. BEST UPGLIDE ON THE 290-300K
SURFACES AS CONDENSTION PRESSURE DEFICITS DROP TO 5 MB OR LESS BY
MIDNIGHT...ESPECIALLY ALONG AND W OF NATCHEZ TRACE PARKWAY.
PWATS REMAIN LESS THAN ONE HALF INCH CURRENTLY BUT A RAPID RISE TO OVER
1 INCH EXPECTED TONIGHT WHEN THE RAINS BREAK OUT. RAINS JUST BEGINNING
IN CENTRAL AND SERN TX AND LOOK FOR THIS INITIAL RAIN SHIELD TO BE
APPROACHING THE MS RIVER BY 6-9PM AND THEN REACH LOCATIONS ALONG I-55
BY MIDNIGHT-2AM PER LATEST SPC/LOCAL WRF MODEL RUNS. NO OTHER
CHANGES TO PACKAGE AND UPDATES SHOULD ALL BE AVAILABLE. /40/
&&
.PREV DISCUSSION... /ISSUED 406 AM CST SUN DEC 6 2009/
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...CLOUDS WILL CONTINUE TO
STREAM INTO THE FORECAST AREA FROM THE WEST AHEAD OF A WEAK COLD
FRONT THAT WILL APPROACH THE CWA FROM THE WEST LATE TONIGHT. RAIN
CHANCES REALLY INCREASE OVERNIGHT ACROSS THE ENTIRE FORECAST AREA AS
THE FRONT MOVES CLOSER AND EVENTUALLY INTO REGION EARLY MONDAY
MORNING. WITH THE CLOUD COVER AND INCREASING MOISTURE OVER THE
AREA...LOWS TONIGHT WILL BE SIGNIFICANTLY WARMER THAN THOSE SEEN THE
PAST COUPLE OF MORNINGS AS THEY RANGE FROM THE UPPER 40S IN MY
SOUTHWEST TO THE MID 30S IN MY NORTHEAST.
AS MENTIONED EARLIER...THE FRONT WILL MOVE INTO WESTERN PORTIONS OF
THE CWA EARLY MONDAY MORNING. IT'LL TRY TO TRAVERSE THE AREA
THROUGH THE DAY...BUT GRADUALLY SLOW IT'S SOUTHWARD PROGRESSION IN
THE PROCESS...BEFORE WEAKENING FURTHER AND BRIEFLY STALLING ALONG TO
JUST SOUTH OF THE HIGHWAY 84 CORRIDOR MONDAY NIGHT. WARM AIR
ADVECTION WILL THEN ENSUE EARLY TUESDAY MORNING...ESPECIALLY ACROSS
THE SOUTHERN HALF OF THE CWA...AS THE FRONT MODIFIES AND BEGINS TO
LIFT NORTHWARDS AS A WARM FRONT...WITH RAIN ALSO SPREADING NORTHWARD
IN THE PROCESS. /19/
LONG TERM...TUESDAY THROUGH SUNDAY...STILL EXPECTING TWO MAIN LOW
PRESSURE SYSTEMS IN THE LONG TERM WITH THE FIRST ONE BEING THE
STRONGEST TUESDAY INTO TUESDAY NIGHT. THE SECOND WEAKER SYSTEM IS
EXPECTED FRIDAY INTO FRIDAY NIGHT. COME TUESDAY WAA WILL INCREASE
SIGNIFICANTLY OVER OUR REGION AHEAD OF A STRONG MID LEVEL SHORTWAVE
TROUGH AND DEEPENING SURFACE LOW THAT IS EXPECTED TO MOVE FROM THE
FOUR CORNERS REGION ACROSS THE CENTRAL PLAINS TUESDAY AND THEN
NORTHEAST ACROSS THE MID MISSISSIPPI RIVER VALLEY TUESDAY NIGHT. THE
ASSOCIATED WARM FRONT WILL LIFT NORTH ACROSS OUR AREA THROUGH THE
DAY. BY TUESDAY EVENING 40-50KT SW 850MB FLOW IS EXPECTED TO HAVE
HELPED INCREASE PWS BACK ABOVE AN INCH AND A HALF WITH LOWER 60 DEW
POINTS BACK NORTH OF THE INTERSTATE 20 CORRIDOR. DESPITE THE
INCREASE IN DEEP LAYER MOISTURE AND DEEP LAYER SHEAR...INSTABILITY
LOOKS TO REMAIN LIMITED WITH WEAK LAPSE RATES AND MLCAPES BELOW
500J/KG. GUIDANCE HAS COME IN WITH CATEGORICAL POPS AND WIDESPREAD
RAIN WITH MAINLY ISOLATED THUNDERSTORMS NORTH AND SCATTERED
THUNDERSTORMS SOUTH IS EXPECTED. SOME OF THE STORMS MAY BECOME STRONG
TO SEVERE AND WL CONTINUE MENTION IN THE HWO. AT THIS POINT DAMAGING
WINDS LOOKS TO BE THE MAIN THREAT BUT WITH FAVORABLE ENOUGH SHEAR
PROFILES TO INCLUDE MENTION OF TORNADOES ESPECIALLY INTERSTATE 20
AND SOUTH. THE STRONG COLD FRONT WITH RACE THROUGH OUR AREA
WEDNESDAY. AT LEAST A 5MB PRESSURE GRADIENT WILL HELP RESULT IN
GUSTY WEST TO NORTHWEST WINDS THAT WILL BE STRONG ENOUGH FOR A LAKE
WIND ADVISORY. THE COLD FRONT IS EXPECTED TO BE SOUTH OF HATTIESBURG
BY NOON WEDNESDAY. HIGH PRESSURE WILL QUICKLY BUILD INTO THE LOWER
MISSISSIPPI RIVER FROM THE NORTHWEST WEDNESDAY NIGHT AND BECOME
CENTERED OVER OUR AREA THURSDAY. WINDS WILL LIKELY NOT DECOUPLE
WEDNESDAY NIGHT BUT CAA WILL LEAD TO MOST SITES BOTTOMING OUT IN THE
30S. FREEZING TEMPERATURES ARE EXPECTED ALONG THE HIGHWAY 82
CORRIDOR. PWS WILL BE BACK DOWN TO AROUND A QUARTER OF AN INCH WITH
SURFACE DEW POINTS IN THE 20S THURSDAY MORNING BUT HIGH PRESSURE
WILL MOVE EAST AND BECOME CENTERED OVER THE MID ATLANTIC COAST BY
NOON FRIDAY. MOISTURE WILL BEGIN TO RETURN AND WAA WILL INCREASE
FRIDAY AHEAD OF ANOTHER SHORTWAVE AND DEVELOPING SURFACE LOW. THE
GFS IS MUCH FASTER THAN THE ECMWF WITH SHIFTING THE SFC HIGH EAST OF
OUR AREA AND BRINGING THE NEXT SFC LOW ACROSS OUR AREA SATURDAY
MORNING. INSTABILITY AND MOISTURE LOOK TO BE MORE LIMITED WITH THIS
SYSTEM BUT THE RIGHT ENTRANCE OF A 150KT JET STREAK WILL HELP AID
CONVECTION. THE LOW AND ASSOCIATED COLD FRONT WILL SHIFT EAST OF OUR
CWA DURING THE DAY SATURDAY. HIGH PRESSURE WILL BRIEFLY BUILD INTO
OUR REGION SATURDAY NIGHT INTO SUNDAY. /22/
&&
.AVIATION...VFR CONDITIONS ARE EXPECTED TO PREVAIL AT ALL TAF SITES
THROUGH THE AFTERNOON AND EVENING HOURS AS HIGH CLOUDS CONTINUE TO
MOVE INTO THE REGION FROM THE WEST TODAY. MID-LEVEL CLOUDS WILL ALSO
INCREASE FROM WEST TO EAST LATER TONIGHT AS A WEAK COLD FRONT SHIFTS
TO THE EAST AND CLOSER TO THE AREA AFTER 06Z TONIGHT. RAIN WILL MOVE
INTO LOCATIONS WEST OF THE MISSISSIPPI RIVER BY 10 PM...THEN CONTINUE
TO SPREAD FARTHER EAST ACROSS THE AREA EARLY MONDAY MORNING. DURING
THIS TIME...MVFR OCCASIONAL IFR CEILINGS AND VISIBILITIES WILL BE
POSSIBLE AT SITES...PARTICULARLY ALONG AND WEST OF THE INTERSTATE 55
CORRIDOR...THAT OBSERVE RAIN. /15/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 51 44 55 51 / 7 47 65 59
MERIDIAN 51 38 56 48 / 4 25 68 49
VICKSBURG 51 45 57 50 / 15 61 53 64
HATTIESBURG 54 43 60 54 / 2 27 61 53
NATCHEZ 53 49 59 53 / 18 58 58 77
GREENVILLE 47 39 53 44 / 13 68 42 40
GREENWOOD 49 39 52 46 / 8 61 53 35
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
