FXUS64 KJAN 142208
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
408 PM CST MON DEC 14 2009
.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...LOCAL RADARS ARE
SHOWING NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE
SOUTHERN SECTIONS OF MY CWA. A LINE OF THUNDERSTORMS HAS BEEN MOVING
THROUGH THE PINE BELT REGION WHILE ANOTHER HAS BEEN MOVING THROUGH
SOUTHERN LOUISIANA AND INTO AROUND THE NATCHEZ AREA. LOCATIONS IN
BETWEEN HAVE NOT SEEN AS MUCH RAIN BUT THIS SHOULD CHANGE AS RAIN
LOOKS TO BE FILLING IN. LOCATIONS FURTHER NORTH OF THE HIGHWAY 84
CORRIDOR HAVE NOT SEEN AS MUCH CONTINUOUS RAIN AND
THUNDERSTORMS...THOUGH HEAVY DOWNPOURS HAVE OCCURRED IN AND AROUND
THUNDERSTORMS ALONG THE I-20 CORRIDOR. FURTHER NORTH OF THE I-20
CORRIDOR HAS BEEN PRETTY MUCH DRY AND THIS IS LIKELY DUE TO THE
RELATIVELY DRIER AIR IN PLACE OVER THAT REGION. RADAR ESTIMATED
RAINFALL AMOUNTS HAVE BEEN IN EXCESS OF 2 INCHES AROUND THE
HATTIESBURG AREA. THIS IS NOT GOOD NEWS AS THIS IS THE AREA THAT HAS
BEEN THE MOST SATURATED FROM RAINFALL OVER THE WEEKEND.
A WARM FRONT IS SITUATED ROUGHLY AROUND THE HIGHWAY 98 CORRIDOR AND
SHORTWAVES MOVING THROUGH THE WARM SECTOR HAVE BEEN CONTRIBUTING TO
CONVECTION. ALL OF THIS COMES AHEAD OF A COLD FRONT THAT LOOKS TO BE
DRAPED ACROSS CENTRAL ARKANSAS THIS AFTERNOON. PWAT VALUES WERE
PROGGED TO INCREASE THIS AFTERNOON IN THE SOUTH UP TO AROUND 1.8
INCHES. THIS IS THE AREA THAT HAS SHOWN THE BEST MOISTURE TRANSPORT
AND CONVERGENCE.
NOT MUCH HAS CHANGED IN HOW THE REST OF TONIGHT INTO TUESDAY WILL
EVOLVE. MODELS STILL DEPICT RAIN AND THUNDERSTORMS TO CONTINUE THIS
AFTERNOON AND EVENING FOR MAINLY SOUTH OF I-20. AS THE FRONT MOVES
THROUGH THE REGION TONIGHT...RAIN CHANCES WILL COME TO AN END FROM
NORTH TO SOUTH. HOWEVER...MODELS CONTINUE TO HANG THE FRONT UP IN
THE SOUTH AND ALLOW FOR A FEW MORE WAVES/DISTURBANCES TO RIDE ALONG
THE FRONT THROUGH TUESDAY AFTERNOON. THIS WILL BRING ADDITIONAL
RAINFALL TO ALREADY SATURATED GROUNDS IN THE SOUTHEAST. THE FRONT
FINALLY PUSHES THROUGH TUESDAY AFTERNOON AS THE SHORTWAVE MID LEVEL
TROUGH SWINGS THROUGH THE REGION. HIGH PRESSURE WILL FILTER INTO THE
ARKLAMISS AND BRING COOLER AND DRIER CONDITIONS TO THE ARKLAMISS
THROUGH THE MIDDLE OF THE WEEK. BEHIND THE FRONT...THERE WILL BE GUSTY
WINDS ON TUESDAY DUE TO A TIGHTENING PRESSURE GRADIENT. A LAKE WIND
ADV WILL LIKELY BE NEEDED DURING THIS TIME. CONDITIONS LOOK MARGINAL
RIGHT NOW FOR AREAS OTHER THAN THE MAJOR LAKES AND WILL LET FUTURE
SHIFTS EVALUATE THE NEED FOR AN ADV FOR TUESDAY.
AS HAS BEEN THE CASE...THE MAIN CONCERNS WILL BE FROM FLOODING
ACROSS THE AREAS GENERALLY ALONG THE HIGHWAY 84 CORRIDOR. A STRONG
TO SVR STORM CANNOT BE COMPLETELY RULED OUT BUT IS A LESSER RISK
WITH THIS SYSTEM. CAPE VALUES ARE NOT VERY MUCH AND DEEP LAYER SHEAR
IS NOT IMPRESSIVE AS WELL. UNIDIRECTIONAL WIND PROFILES WILL ALLOW
FOR THE THREAT OF TRAINING TO REMAIN UNTIL THE FRONT MOVES THROUGH
TUESDAY AFTERNOON/EVENING. THAT BEING SAID...PREVIOUSLY ISSUED FLASH
FLOOD WATCH LOOKS TO REMAIN IN GOOD SHAPE AND WILL CONTINUE IT
THROUGH 00Z WED. MODELS STILL DIFFER ON QPF AMOUNTS THROUGH THE TIME
PERIOD WITH THE GFS AGAIN SHOWING THE HIGHEST AMOUNTS. THIS COULD BE
BROUGHT ABOUT BY SOME FEEDBACK ISSUES BUT LOCATIONS IN THE SOUTH
COULD STILL SEE ABOUT 2-3 INCHES OVERALL BEFORE EVERYTHING IS SAID
AND DONE WITH SOME LOCALLY HIGHER AMOUNTS.
ADJUSTMENTS TO GUI WERE MAINLY MADE TO POPS IN THE SOUTH TO INCREASE
THEM FOR TONIGHT INTO TUESDAY. COULD SEE SOME LIGHT RAIN THE NORTH
AS THE FRONT MOVES THROUGH SO LEFT SMALL CHANCE POPS. /28/
.LONG TERM...WEDNESDAY THROUGH THURSDAY...
THE SRN EXTENT OF A CHILLY POLAR AIRMASS WILL SURGE SOUTHWARD INTO
THE FORECAST AREA TUES NIGHT/WEDNESDAY. GFS MOS IS LIKELY NOT
HANDLING THE SHALLOW NATURE OF THE AIRMASS AND LOOKS TOO WARM WHEN
COMPARED TO EXPLICIT OUTPUT...PARTICULARLY FOR WED/THURS HIGHS AND
LOWERED THEM A BIT. THE POSITION OF THE SFC HIGH CENTER...WHICH WILL
SHIFT EWD ACROSS THE MIDWEST AND OH VALLEY...WILL NOT BE IDEAL FOR
FOR SFC RADIATIONAL COOLING AND PERIODS OF HIGH CIRRUS MAY INTERRUPT
COOLING AS WELL SO WILL NOT CUT GFS MOS LOWS.
THURSDAY NIGHT THROUGH SUNDAY...
THE FORECAST FOR THE LONGER RANGE PERIODS IS OF LOWER THAN AVERAGE
CONFIDENCE GIVEN INCONSISTENCIES BETWEEN THE GFS AND ECMWF MODELS.
THE OPERATIONAL GFS IS KEEPING THE THE FORECAST AREA UNDER DRY
NORTHWEST FLOW AS WE GO FROM LATE WEEK INTO THE WEEKEND...AND IT
DE-EMPHASIZES SRN STREAM SHORTWAVE ENERGY THEREBY KEEP ANY GULF LOW
DEVELOPMENT SUPPRESSED WELL TO OUR SOUTH. THE 00Z ECMWF ON THE OTHER
HAND CONTINUES TO SUGGEST THAT SRN STREAM SHORTWAVE ENERGY WILL DIG
SWD OVER NRN MEXICO AND HELP INDUCE A NW GULF LOW THAT WOULD BRING
LIGHT-MDT RAINFALL TO THE SRN HALF OF THE FORECAST AREA FROM THURS
NIGHT AND FRIDAY. THE ECMWF IS ALSO MORE AGGRESSIVE IN DIGGING NRN
STREAM SHORTWAVE ENERGY SWD THROUGH THE PLAINS THUS BRINGING COLDER
AIR AND THE POTENTIAL FOR A FEW SNOW SHOWERS AS WE GO INTO SUNDAY.
WHILE THE THE ECMWF LOOKS A BIT EXTREME...IT HAS SUPPORT FROM
SEVERAL GFS ENSEMBLE MEMBERS AND THE UKMET IN AN EL NINO YEAR. SO
WE HAVE RAISED GFS MOS GUIDANCE POPS A LITTLE FOR THE FRI TO SAT
NIGHT PERIOD AND HAVE INDICATED A SMALLER HIGH/LOW TEMPERATURE RANGE
THAN GFS MOS BASED ON GREATER CLOUD COVERAGE EXPECTED. ANY
PRECIPITATION IS EXPECTED TO LIGHT IF IT OCCURS...AND TEMPERATURES
COULD GET VERY CHILLY AS WE GO THROUGH THE WEEKEND IF THE 00Z ECMWF
VERIFIES. /EC/
&&
.AVIATION...NUMEROUS TSTMS WILL MOVE ACROSS THE REGION THIS
AFTERNOON AND EVENING...MAINLY S OF THE NATCHEZ TRACE CORRIDOR. ONE
OR TWO STORMS MAY BECOME SEVERE WITH LARGE HAIL AND GUSTY WIND BUT
THE MAIN RISK WILL BE HEAVY RAINFALL AND FREQUENT LIGHTNING.
OCCASIONAL IFR CIGS WILL OCCUR WITH WIDESPREAD MVFR BKN-OVC DECKS
FROM 1500-3000 FEET. OCNL IFR VSBYS WILL ALSO DEVELOP...ESPECIALLY
IN AREAS OF HEAVIER RAINFALL. RAIN AND TSTMS WILL DIMINISH FROM THE
NW OVERNIGHT AS A COLD FRONT DROPS ACROSS THE AREA...SHIFTING WINDS
FROM SLY TO NWLY ACROSS ALL AREAS BY SUNRISE TUESDAY. AREAS OF FOG
WILL REDEVELOP OVERNIGHT. MOST AREAS WILL REMAIN FROM 1-3 MILES BUT
LOCALLY DENSE FOG WILL ALSO BE POSSIBLE. IFR/MVFR CIGS CAN BE
EXPECTED OVERNIGHT ACROSS THE REGION. CONDITIONS WILL IMPROVE EARLY
TUESDAY AS FOG ERODES AND CIGS LIFT DURING THE MORNING. OCNL IFR
CIGS WILL PERSIST LONGEST OVER SRN ZONES WHERE RAINFALL CHANCES WILL
BE HIGHEST. /03/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 49 52 36 57 / 83 40 0 0
MERIDIAN 53 56 33 56 / 90 54 0 0
VICKSBURG 47 51 36 54 / 77 35 0 0
HATTIESBURG 58 59 37 60 / 99 97 9 0
NATCHEZ 50 51 37 54 / 97 84 10 0
GREENVILLE 42 49 32 51 / 22 13 0 0
GREENWOOD 43 51 32 54 / 32 15 0 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...FLASH FLOOD WATCH THROUGH TUESDAY AFTERNOON FOR MSZ052-054>066-
072>074.
LA...FLASH FLOOD WATCH THROUGH TUESDAY AFTERNOON FOR LAZ024-026.
AR...NONE.
&&
$$
28/EC/03
