000 FXUS64 KJAN 181520 AAA AFDJAN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON MS 920 AM CST TUE NOV 18 2008 .UPDATE...MINOR ADJUSTMENT TO HOURLY TEMPS/DEWPOINTS/WINDS FOR CURRENT TRENDS AS 1038MB CANADIAN HIGH CENTER IN WRN MO SINKS SWD TOWARD THE REGION. STIFF NLY WINDS KEEPING A CHILL IN THE AIR FOR TODAY AHEAD OF A SOLID FREEZE LIKELY FOR TONIGHT. NO CHANGES MADE TO TEXT PRODUCTS FOR NOW AS FORECAST IN GOOD SHAPE./40/ PREVIOUS DISCUSSION FOLLOWS: TODAY THROUGH WEDNESDAY...NORTHWEST FLOW CONTINUES TO PREVAIL OVER THE ARKLAMISS AND THIS WILL CONTINUE THROUGH THE SHORT TERM. STRONG COLD AIR ADVECTION WILL PREVAIL OVER THE ARKLAMISS TODAY WITH COOL TEMPS AND BREEZY NORTHEAST WINDS. THE SURFACE HIGH WILL CONTINUE TO SHIFT TO THE SOUTHEAST FROM THE MIDWEST TODAY AND WILL BE CENTERED OVER THE AREA BY TONIGHT. WITH THE SURFACE HIGH OVER THE AREA TONIGHT EXPECT STRONG RADIATIONAL COOLING AND COLD TEMPS. THE SURFACE HIGH QUICKLY SHIFTS TO THE EAST OF THE AREA ON WEDNESDAY AND THIS WILL ALLOW THE SURFACE FLOW TO SWING AROUND TO THE SOUTHWEST AND THUS WARMER AFTERNOON HIGHS. STUCK CLOSE TO GUIDANCE TEMPERATURES TODAY...BUT DID CUT BELOW GUIDANCE TONIGHT. H925/H850 TEMPERATURES AND STRONG RADIATIONAL COOLING SHOULD SUPPORT TEMPS IN THE UPPER 20S TO NEAR 30 TONIGHT ACROSS THE AREA. THE LATEST GFS GUIDANCE CAME IN WITH SLIGHTLY WARMER TEMPS...BUT THE NAM IS COOLER AND SEEMS TO HANDLE STRONG RADIATIONAL COOLING EVENTS BETTER...SO WILL GO WITH MET GUIDANCE. THE QUICK RETURN TO SOUTHERLY FLOW ON WEDNESDAY WILL ALLOW FOR A BIT OF A WARMUP. H925 TEMPS WARM TO NEAR 10 TO 13C DURING THE AFTERNOON AND THIS WILL SUPPORT SLIGHTLY WARMER TEMPS THAN GUIDANCE SUGGEST...SO WILL BUMP THEM UP A TOUCH. /15/ .LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY...OVERALL MEDIUM RANGE MODELS ARE DRIER A COOLER THROUGH MOST OF THE LONG TERM COMPARED TO LAST NIGHT'S RUN. THE GFS AND ECMWF ARE IN REASONABLE AGREEMENT THROUGH FRIDAY BUT SIGNIFICANT DIFFERENCES BEGIN BY THE WEEKEND AND CARRY OVER INTO NEXT WEEK. WEDNESDAY NIGHT NORTHWEST FLOW ALOFT WILL HELP DROP ANOTHER DRY REINFORCING COLD FRONT OUR WAY WHILE SURFACE HIGH PRESSURE CENTERED OVER THE GULF COAST WEAKENS AND SHIFTS INTO THE NORTHERN GULF. THE LIGHT SOUTHERLY FLOW FROM THIS HIGH TO OUR SOUTH WILL HELP KEEP THURSDAY MORNING LOWS FROM BEING AS COLD COMPARED THE WEDNESDAY MORNING LOWS. HOWEVER...LATEST MAV GUIDANCE TEMPS WERE AMONG THE HIGHEST ENSEMBLE MEMBERS AND A BIT TOO WARM. WL CUT THURSDAY MORNING LOWS SEVERAL DEGREES AT MOST SITES FOR LOWS IN THE 30S ACROSS THE AREA. THE DRY COLD FRONT WILL MOVE ACROSS THE CWFA DURING THE DAY THURSDAY. VERY LITTLE CLOUD COVER IS EXPECTED SO STRONG INSOLATION WILL BATTLE AGAINST DECENT CAA. OUR NORTHERN TIER ZONES MAY STRUGGLE TO REACH 60 DEGREES BUT MOST SITES SHOULD CLIMB INTO THE 60S. IN THE WAKE OF THE COLD FRONT A LARGE >1035MB CENTER OF HIGH PRESSURE WILL DROP SOUTH OUT OF CANADA AND OVER THE MID MISSISSIPPI VALLEY BY FRIDAY MORNING THEN SHIFT EAST OVER THE SOUTHERN APPALACHIANS BY SATURDAY MORNING. THIS WILL PROVIDE DRY WEATHER WITH COOLER THAN NORMAL TEMPERATURES THROUGH SATURDAY. IT IS SATURDAY WHERE THE GFS AND ECMWF DIVERGE. THE GFS IS STILL PROGGING A NORTHERN STREAM SHORTWAVE TROUGH MOVING ACROSS OUR REGION SATURDAY AND TRYING TO SQUEEZE OUT SOME QPF. THE ECMWF HAS NO SUCH FEATURE AND NEARLY ZONAL FLOW ALOFT OVER OUR REGION. CONSIDERING THE COOL DRY AIRMASS EXPECTED OVER OUR CWFA AT THE TIME WL CONTINUE TO CUT POPS SATURDAY. THE GREATEST SPREAD IN ENSEMBLE GUIDANCE TEMPERATURES THROUGH THE PERIOD WAS SEEN WITH SUNDAY MORNING LOWS WHERE STANDARD DEVIATIONS OF SIX WERE AT MOST SITES. LATEST MEX GUIDANCE TEMPS WERE CLOSE TO THE LOWEST MEMBERS AND GENERALLY ACCEPTED. THE ECMWF SUGGESTS WARMER SUNDAY TEMPS AS IT BEGINS INCREASING WAA SATURDAY NIGHT AHEAD OF A LOW PRESSURE SYSTEM IT DEVELOPS OVER THE NORTHERN PLAINS. THE ECMWF HAS SHOWN SOME CONSISTENCY WITH THIS SYSTEM AND BRINGS AN ASSOCIATED COLD FRONT THROUGH OUR CWFA MONDAY AS IT DID LAST NIGHT. THE GFS HAS NO SUCH FEATURE AND BEGINS DIGGING AN UPPER TROUGH DOWN THE WEST COAST WITH RIDGING OVER THE MISSISSIPPI RIVER VALLEY BY TUESDAY. ALTHOUGH WL GO WITH THE COOLER SUNDAY MORNING MEX TEMPS...WL LEAN TOWARD THE MORE CONSISTENT ECMWF AN INCLUDE POPS MONDAY THROUGH TUESDAY WITH THE EXPECTATION THAT A COLD FRONT WILL MOVE ACROSS THE CWFA DURING THAT TIME AND BRING THE NEXT BEST CHANCE FOR WIDESPREAD RAIN. /22/ && .AVIATION...VFR CLEAR WILL DOMINATE WITH 12-18KT NLY WINDS DIMINISHING TO LESS THAN 6KTS BY 23Z OR SO./18/ && .PRELIMINARY POINT TEMPS/POPS... JACKSON 52 28 65 38 / 0 0 0 0 MERIDIAN 51 26 60 35 / 0 0 0 0 VICKSBURG 53 31 66 40 / 0 0 0 0 HATTIESBURG 58 27 62 36 / 0 0 0 0 NATCHEZ 55 32 65 42 / 0 0 0 0 GREENVILLE 53 31 63 39 / 0 0 0 0 GREENWOOD 52 29 62 35 / 0 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...NONE. LA...NONE. AR...NONE. && $$