FXUS64 KJAN 251544 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
944 AM CST FRI DEC 25 2009
.UPDATE...THE CHRISTMAS EVE STORM PULLING FARTHER UP THE MS VALLEY
THIS MORNING AS IT BOTTOMED OVERNIGHT IN SRN IA WITH THE LOW CENTER
REACHING 985MB. LATEST SATELLITE VISIBLE IMAGES SHOWING A RATHER
SHARP CLEARING LINE IN THE CAA STRATOCU NOW ALONG A CROSSETT TO
TALLULAH TO NATCHEZ LINE MOVING ENE AT 28KTS OR SO. THAT RATE OF
EROSION WILL BRING SOME WELCOME SUNSHINE RETURNING TO THE KGLH-KJAN-
BROOKHAVEN AREAS BY NOON...THE KGWO-KLUL-KHBG AREAS BY 2PM...AND THE
REST OF ERN MS BEFORE SUNSET. OUR WLY SURFACE WINDS SLACKING UP
SOMEWHAT AS THE PRESSURE GRADIENT WILL GRADUALLY RELAX FROM S TO N
AND HAVE ENDED THE LAKE WIND ADVY FOR SRN MS AS A 1023MB SURFACE HIGH
IN SRN TX BUILDS INTO SRN MS FOR TONIGHT.
HAVE ADJUSTED SKY COVER GRIDS/WINDS/TEXT PRODUCTS AND POSTED UPDATES
SHOULD BE AVAILABLE./40/
BALANCE OF PREVIOUS DISCUSSION FOLLOWS: SPEAKING OF TONIGHT AND
SATURDAY...HIGH PRESSURE WILL QUICKLY BUILD INTO AND ACROSS THE
LOWER MISSISSIPPI RIVER VALLEY. WITH CLEAR SKIES EXPECTED TONIGHT
AND WINDS EASING UP...THE MERCURY SHOULD FALL INTO THE MID AND UPPER
20S IN MOST LOCATIONS EARLY SATURDAY MORNING. ALTHOUGH MOSTLY CLEAR
SKIES WILL BE OBSERVED ACROSS THE FORECAST AREA SATURDAY...SOME HIGH
CLOUDS WILL BEGIN TO FILTER EAST NORTHEAST INTO MAINLY CENTRAL AND
SOUTHERN PORTIONS OF THE REGION AS YET ANOTHER LOW PRESSURE SYSTEM
BEGINS TO DEVELOP OVER THE WEST CENTRAL GULF OF MEXICO. HIGH
TEMPERATURES WILL ALSO BE A TAD WARMER SATURDAY AFTERNOON AS THE FLOW
OVER THE AREA BECOMES MORE SOUTH TO SOUTHEASTERLY DURING THE DAY./19/
LONG TERM...SATURDAY NIGHT THROUGH FRIDAY...COOLER THAN NORMAL
TEMPERATURES WILL CONTINUE THROUGH TUESDAY WITH NEAR NORMAL
TEMPERATURES EXPECTED FOR THE END OF THE NEXT WEEK. ONLY A SLIGHT
CHANCE OF RAIN IN THE SOUTH IS EXPECTED FOR SATURDAY NIGHT INTO
SUNDAY BEFORE CHANCES FOR A MORE WIDESPREAD RAIN INCREASE FOR THE
MIDDLE OF THE WEEK. FOR SATURDAY NIGHT...THE LARGE UPPER LEVEL VORTEX
WILL BE SPINNING OVER THE GREAT LAKES REGION BUT SENDING US A
SHORTWAVE WHILE AT THE SAME TIME A DISTURBANCE IN THE SOUTHERN BRANCH
OF THE JET STREAM MOVES EAST FROM THE SOUTHERN PLAINS. AS A RESULT A
REINFORCING SHOT OF COOL DRY AIR WILL BE SINKING OVER OUR REGION
WHILE THE SOUTHERN DISTURBANCE HELPS DEVELOP A WEAK SURFACE LOW OVER
THE GULF AND SENDS OVERRUNNING MOISTURE NORTHWARD. THE ECMWF
CONTINUES TO BE RATHER DRY WITH THIS SYSTEM BUT THE NAM AND GFS BRING
LIGHT QPF INTO OUR SOUTHERN ZONES AFTER MIDNIGHT AND THROUGH SUNDAY
MORNING. THE COLDEST TEMPERATURES OF THE NIGHT SHOULD BE WELL NORTH
OF THE MEASURABLE PRECIP...NORTH OF INTERSTATE 20 SO WL MENTION THE
SLIGHT CHANCE OF LIGHT RAIN AND NO WINTRY MIX WITH THIS PACKAGE. THE
LIGHT RAIN WILL SHIFT SOUTH OF OUR AREA DURING THE AFTERNOON AS THE
DISTURBANCE AND SFC LOW SHIFT EAST.
SUNDAY...THE UPPER VORTEX WILL ALSO BE FINALLY LIFTING OUT TO THE
NORTHEAST WHILE ANOTHER LARGE CLOSED LOW DROPS SOUTH DOWN THE WESTERN
CONUS. THIS WILL RESULT IN NEAR ZONAL FLOW ALOFT OVER OUR REGION
MONDAY BUT SHORTWAVE RIDGING SURFACE AND ALOFT IS EXPECTED TO DEVELOP
OVER OUR REGION MONDAY NIGHT INTO TUESDAY. THIS SHOULD BRING US SOME
WARMER TEMPS TUESDAY ALTHOUGH THE SURFACE HIGH WILL BE CENTERED NORTH
OF OUR REGION KEEPING OUR REGION UNDER A DRY NORTHERLY LOW LEVEL
FLOW. MOISTURE AND CLOUDS WILL INCREASE FROM THE WEST TUESDAY AS THE
LARGE UPPER LEVEL LOW BEGINS SWINGING EAST ACROSS THE DESERT SW. BOTH
THE GFS AND ECMWF BRING PRECIPITATION BACK INTO OUR CWA TUESDAY NIGHT
BUT THIS TIME IT'S THE GFS WITH STINGY QPF AMOUNTS. THE ECMWF IS
STRONGER WITH THE SHORTWAVE TROUGH THAN THE GFS AND DEVELOPS A SFC
LOW FARTHER NORTH OVER THE WESTERN GULF. OVERALL...BOTH MODELS ARE
WARMER TUESDAY NIGHT WITH CRITICAL THICKNESSES JUST NORTH OF OUR AREA
AND WELL NORTH OF WHERE THE SIGNIFICANT RAINFALL IS EXPECTED. AGAIN
WL NOT INCLUDE MENTION OF WINTRY MIX PRECIPITATION WITH THIS PACKAGE
BUT FUTURE MODEL RUNS MAY END UP TRENDING COLDER. BY WEDNESDAY NIGHT
BOTH GFS AND ECMWF HAVE SFC LOWS JUST SOUTH OF OUR CWA BUT WITH THE
ECMWF BEING OVER SOUTHERN LOUISIANA AND THE GFS SOUTH OVER THE
NORTHERN GULF WATERS. THE RAIN WILL END FROM THE WEST THURSDAY AS THE
SFC LOW AND SHORTWAVE TROUGH SHIFT EAST. THE ECMWF HAS A
SIGNIFICANTLY LARGER AMPLITUDE UPPER LEVEL TROUGH OVER THE CENTRAL
CONUS FRIDAY AND IS MUCH COLDER OVER OUR REGION THAN THE GFS BUT
FRIDAY LOOKS DRY. /22/
&&
.AVIATION...WIDESPREAD MVFR CEILINGS ARE BEING OBSERVED AT TAF SITES
ACROSS THE REGION THIS CHRISTMAS DAY MORNING. THE CLEARING LINE WAS
NOTED AROUND THE MISSISSIPPI RIVER...ADVANCING EASTWARD. EXPECT
CEILINGS TO LIFT TO VFR CONDITIONS FOR THIS AFTERNOON FROM THE
WEST. VFR CONDITIONS WILL THEN PREVAIL AT ALL SITES FROM THIS
EVENING AND THROUGH THE OVERNIGHT HOURS INTO SATURDAY MORNING.
GUSTY WEST TO SOUTHWEST WINDS WILL ALSO GRADUALLY SUBSIDE THROUGH
THE DAY AND OVERNIGHT HOURS AS THE STRONG LOW PRESSURE SYSTEM LIFTS
NORTHWARDS ALLOWING THIS TIGHT PRESSURE GRADIENT OVER THE REGION TO
FINALLY RELAX. /17/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 44 27 53 31 / 1 0 4 14
MERIDIAN 46 27 54 31 / 1 0 4 14
VICKSBURG 43 29 53 32 / 1 0 4 13
HATTIESBURG 48 28 56 34 / 0 0 8 28
NATCHEZ 44 29 54 33 / 0 0 8 30
GREENVILLE 40 29 49 28 / 1 1 3 9
GREENWOOD 41 28 49 29 / 1 1 3 9
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR MSZ018-019-
025>052.
LA...LAKE WIND ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR LAZ007>009-
015-016.
AR...LAKE WIND ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR ARZ074-075.
&&
$$
