000 FXUS64 KJAN 091704 AAA AFDJAN AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE JACKSON MS 1045 AM CST MON NOV 9 2009 .UPDATE...THE NATIONAL HURRICANE CENTER DOWNGRADED IDA TO A TROPICAL STORM A SHORT WHILE AGO. STRONG WIND SHEAR PRODUCED BY AN APPROACHING UPPER LEVEL TROUGH HAS REALLY TAKEN ITS TOLL ON THE SYSTEM OVER THE PAST 12 HOURS AND HURT IDA'S TROPICAL ORGANIZATION. IDA IS NOW EXPECTED TO MAKE LANDFALL NEAR MOBILE BAY AROUND 6 AM TOMORROW MORNING AS A WEAKENING TROPICAL STORM. AS DISCUSSED IN THE PREVIOUS DISCUSSION...THE INTERACTION OF IDA WITH AN INCOMING UPPER LEVEL DISTURBANCE SHOULD MAKE FOR A SHARP BACK EDGE TO THE PRECIPITATION SHIELD RESULTING FROM THE COMBINED SYSTEMS. THIS BACK EDGE SHOULD BE LOCATED SOMEWHERE IN EASTERN MS WITH AREAS TO THE WEST OF THE EDGE RECEIVING VERY LITTLE RAINFALL AND AREAS TO THE EAST POSSIBLE RECEIVING UP TO 2 INCHES OF RAIN TONIGHT THROUGH MIDDAY TOMORROW. THERE IS STILL TOO MUCH UNCERTAINTY TO PREDICT THE EXACT LOCATION OF THIS "BACK EDGE" OF PRECIP...BUT IT WILL LIKELY NOT BE EAST OF THE I-59 CORRIDOR. BUT REGARDLESS OF THE EVOLUTION OF PRECIP ACROSS THE EASTERN PORTIONS OF MS TONIGHT THROUGH EARLY TOMORROW...WE STILL ARE NOT ANTICIPATING ENOUGH RAINFALL TO CAUSE FLOODING PROBLEMS. THE LATEST TRACK OF IDA HAS SHIFTED A LITTLE WESTWARD IN COMPARISON TO WHAT IT WAS EARLIER. WITH THE SUBTLE SHIFT OF THE TRACK THE PROSPECT OF WINDS GETTING ABOVE LAKE WIND ADVISORY IS GREATER ALONG AND EAST OF THE I-59 CORRIDOR (AND SOUTH OF MEI). WENT AHEAD AND "UPGRADED" THE LAKE WIND ADVISORY IN THOSE AREAS TO A WIND ADVISORY WITH THE POSSIBILITY OF SUSTAINED WINDS TO 30 MPH AND GUSTS TO 40 MPH TONIGHT. NPW PRODUCTS HAVE BEEN UPDATED AND ARE OUT. WE WILL UPDATE THE HWO SHORTLY TO REFLECT THE THINKING ON THE WINDS. TEMPERATURES TODAY WERE RAISED UPWARDS A BIT DUE TO CLOUDS BEING OCCASIONALLY LESS THICK THAN EXPECTED. MINOR ADJUSTMENTS TO POPS TODAY AND TONIGHT WITH MAIN CHANCES FOR RAIN COMING IN SE MS TONIGHT. /BB/ && .PREV DISCUSSION... /ISSUED 419 AM CST MON NOV 9 2009/ TODAY THROUGH TUESDAY... IT APPEARS THAT THE RISK FOR HEAVY RAIN HAS LESSENED OVER THE FORECAST AREA AS A SHORTWAVE TROUGH WEST OF HURRICANE IDA IS FAILING TO GENERATE MUCH MOISTURE TRANSPORT...HOWEVER THERE IS STILL UNCERTAINTY REGARDING THE INTERACTION BETWEEN THIS TROUGH AND HURRICANE IDA. THIS MAKES FOR A VERY DIFFICULT QPF FORECAST LATER TODAY AND TONIGHT...ESPECIALLY CONSIDERING THAT NATIONAL GUIDANCE FLIPPED FROM FIVE INCHES OF RAIN OVER PORTIONS OF CNTRL MS TO VIRTUALLY NO PRECIP IN THE SAME AREA IN LESS THAN 12 HRS. PER OFFICIAL NHC FORECAST...A WEAKENING HURRICANE IDA WILL CONTINUE A NORTHWARD TREK ACROSS THE NORTHERN GULF...MAKING LANDFALL IN THE WRN FLORIDA PANHANDLE LATE TONIGHT/EARLY TUES. THIS IS WHEN THE CYCLONE WILL MAKE ITS CLOSEST PASSAGE TO EASTERN PORTIONS OF THE FORECAST AREA AND THIS IS WHEN THE HEAVIEST RAINFALL WOULD BE EXPECTED... ASSUMING THAT IDA'S RAIN SHIELD EXPANDS FAR ENOUGH TO THE NW. THE ECMWF...WHICH HAS INSISTED ON A MORE WWD TRACK OF IDA AND INDICATED MORE SHORTWAVE TROUGH INFLUENCE ON THE RAINFALL PATTERN...HAS SHIFTED FARTHER EAST AND NOW LIMITS HEAVIER QPF TO FAR ERN PORTIONS OF THE FORECAST AREA...SIMILAR TO THE GFS ENSEMBLE MEAN. THE GFS HAS BEEN THE DRIEST MODEL ALL ALONG FOR OUR AREA...BUT NOW THE 06Z GFS SEEMS TO SHOW MORE INFLUENCE FROM THE AFOREMENTIONED MID LATITUDE TROUGH AND WANTS TO BRING HEAVIER PCPN WWD INTO MOST OF THE ERN HALF OF MS. THE TYPICAL BEHAVIOR OF LAND-FALLING TROPICAL SYSTEMS ON THE GULF COAST AS THEY ENCOUNTER MID-LATITUDE INFLUENCES WOULD SUGGEST A WWD SHIFT IN THE PRECIP PATTERN IS A GOOD POSSIBILITY...SO WILL MAINTAIN SOME CONSISTENCY AND KEEP THE MENTION OF HEAVY RAINFALL IN THE HWO/GRAPHICS FOR ERN MS. THERE SHOULD BE A SHARP GRADIENT TO THE RAINFALL WITH AREAS WEST OF THE I-55 CORRIDOR LIKELY STAYING DRY FOR THE ENTIRE EVENT...AND RAIN SHOULD END OVER THE ENTIRE AREA BY TUES AFTN. IN TERMS OF WIND...WITH THE OFFICIAL FORECAST CALLING FOR FURTHER WEAKENING OF IDA AND MORE OF AN EWD TRACK COMPARED TO YESTERDAY... WILL DOWNGRADE THE WIND ADVISORY TO A LAKE WIND ADV OVER SE PORTIONS OF THE FORECAST AREA AND HAVE KEPT THE SAME TIME FROM LATE AFTN THROUGH TONIGHT. IT IS POSSIBLE THAT ANOTHER LAKE WIND ADV WILL BE NECESSARY FOR TUESDAY. /EC/ TUESDAY NIGHT THROUGH SUNDAY... BY TUESDAY NIGHT WE WILL BE ENTERING A QUIET PATTERN FOR THE REST OF THE WORK WEEK AS IDA MOVES EAST OF THE REGION. THE CANADIAN...GFS... AND MOST OF THE ENSEMBLE AND EUROPEAN MODELS BRING AN UPPER RIDGE OVER THE ARKLAMISS REGION BY FRIDAY. THIS WILL BRING DRY WEATHER TO THE REGION UNTIL WE GET TO THE LATER PORTION OF THE WEEKEND. DURING THE WEEKEND THE UPPER RIDGE AXIS WILL SHIFT TO THE EAST AS SOUTHWEST FLOW ALOFT COMES OVER THE REGION. ON SUNDAY A SHORT WAVE WILL PUSH INTO THE SOUTHERN PLAINS. THERE WILL BE JUST ENOUGH RETURN MOISTURE AHEAD OF IT TO BRING SOME ISOLATED SHOWERS TO THE REGION FOR SATURDAY NIGHT INTO SUNDAY. INSTABILITY WILL BE QUITE WEAK OVER THE ARKLAMISS AHEAD OF THIS SHORTWAVE TROUGH. AS FAR AS TEMPERATURES ARE CONCERNED...USED A BLEND OF MAV AND MOS GUIDANCE. ENSEMBLE GUIDANCE LOOKED CLOSE TO THESE TEMPS. /17/ && .AVIATION...WEATHER IS BEING DICTATED BY THE FUTURE TRACK OF TROPICAL STORM IDA. THE WORST CONDITIONS IN THE FORECAST AREA SHOULD BE FELT AT HBG/MEI/GTR TONIGHT AND INTO EARLY TUESDAY WHEN THE CYCLONE WILL BE MAKING ITS CLOSEST PASSAGE. CIGS AND VSBYS AT GTR/MEI/HBG WILL BE MOSTLY MVFR CATEGORY DUE TO STRATUS AND RAIN...WITH IFR CATEGORY RESTRICTIONS POSSIBLE DURING THE HEAVIEST RAINFALL. ELSEWHERE...VFR CONDITIONS SHOULD PREVAIL WITH OCCASIONAL MVFR CIGS AS STRATUS ATTEMPTS TO SPREAD WWD. EXPECT MUCH IMPROVED CONDITIONS BY TUES AFTN OVER ERN MS. /EC/BB/ && .PRELIMINARY POINT TEMPS/POPS... JACKSON 72 57 74 53 / 22 35 9 2 MERIDIAN 70 56 70 48 / 34 79 51 3 VICKSBURG 73 56 75 53 / 17 18 4 2 HATTIESBURG 70 56 76 49 / 57 72 37 1 NATCHEZ 72 57 76 52 / 28 16 4 2 GREENVILLE 72 55 74 52 / 8 14 4 1 GREENWOOD 73 55 74 53 / 10 28 5 2 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM CST TUESDAY FOR MSZ058-066-073-074. LAKE WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM CST TUESDAY FOR MSZ046-051-052-055>057-062>065-072. LA...NONE. AR...NONE. && $$ BB/EC/17