FXUS64 KJAN 050959
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
359 AM CST SAT DEC 5 2009
.DISCUSSION...TODAY THROUGH SUNDAY NIGHT...THE SNOW HAS SHIFTED EAST
OF THE ARKLAMISS AND THE SKIES WERE CLEARING FROM THE WEST.
THUS...HAVE CANCELLED THE WINTER STORM WARNING AND THE WINTER WEATHER
ADVISORY. THE SKIES WERE CLEARING A LITTLE SLOWER OVER CENTRAL
MISSISSIPPI THAN IN THE NORTH BUT THIS SHOULD CHANGE AS THE UPPER
TROUGH AXIS SHIFTS FARTHER EAST THIS MORNING. RUC ANALYSIS HAS THE
TROUGH AXIS EAST OF THE MISSISSIPPI RIVER MOVING OVER CENTRAL
MISSISSIPPI. AT THE SURFACE HIGH PRESSURE WAS NOTED CENTERED OVER
EAST TEXAS. THE HIGH IS EXPECTED TO SHIFT EAST TODAY AND BECOME
CENTERED OVER THE ARKLAMISS BY MID AFTERNOON. DESPITE NEARLY FULL
INSOLATION TODAY...LIGHT SNOW MELT AND LIGHT CAA WILL WORK TOGETHER
TO HOLD TEMPERATURES WELL BELOW NORMAL. MOST SITES WILL TOP OUT IN
THE MID 40S. TONIGHT OUR WINDS ALOFT WILL BE BACKING TO THE SOUTHWEST
AHEAD OF A DEEPENING TROUGH OVER THE WESTERN CONUS WHILE THE SFC HIGH
SHIFTS EAST TO THE SOUTHERN APPALACHIANS. WEAK WAA IS EXPECTED BY
SUNDAY MORNING IN THE WEST BUT WL DO LITTLE TO KEEP TEMPERATURES FROM
PLUMMETING TO THE COLDEST READINGS OF THE SEASON AT MOST SITES. CLEAR
SKIES AND LIGHT WINDS SHOULD ALLOW FOR DECENT RADIATIONAL COOLING OF
OUR COOL DRY AIRMASS AND RESULT IN MORNING LOWS FROM THE LOWER 20S
EAST TO THE UPPER 20S SOUTHWEST. AFTER A RATHER CHILLY START SUNDAY
MORNING TEMPERATURES ARE EXPECTED TO REBOUND AS WAA INCREASES AHEAD
OF THE NEXT LOW PRESSURE SYSTEM. A SHORTWAVE WILL MOVE OVER THE
CENTRAL PLAINS AND HELP DEVELOP A SURFACE LOW OVER THE SOUTHERN
PLAINS SUNDAY. THIS SURFACE LOW IS EXPECTED TO MOVE FROM THE SOUTHERN
PLAINS TO THE MID MISSISSIPPI RIVER VALLEY BY MONDAY MORNING WITH A
TRAILING COLD FRONT EDGING INTO OUR NORTHWEST MOST ZONES BY SUNRISE.
OUR AIRMASS WILL BE RATHER DRY AT THE START SUNDAY WITH A PW BELOW A
QUARTER OF AN INCH. ONE INCH PWS ARE PROGGED BACK INTO OUR SOUTHWEST
LATE SUNDAY AFTERNOON AND A LIGHT RAIN MAY BEGIN REACHING THE GROUND
OVER OUR SOUTHWEST ZONES. MODELS DO SHOW BOTH 850MB AND 500MB FLOW
INCREASING TO 40-50KTS SUNDAY NIGHT WITH INCREASING MOISTURE AHEAD OF
THE COLD FRONT BUT INSTABILITY LOOKS TO REMAIN LIMITED AND WL NOT
CARRY MENTION OF THUNDER. GUIDANCE CAME IN AGAIN WITH CATEGORICAL
POPS SUNDAY NIGHT AND WL ACCEPT. GUIDANCE TEMPS WERE CLOSE BUT LEANED
TOWARD SLIGHTLY COOLER MET GUIDANCE THROUGH SUNDAY. /22/
MONDAY THROUGH NEXT SATURDAY...MODELS CONTINUE TO DEPICT A
PROGRESSIVE AND RATHER ACTIVE PATTERN ACROSS THE FORECAST AREA
THROUGH THE PERIOD. A WEAK COLD FRONT WILL PUSH THROUGH THE CWA ON
MONDAY BRINGING GOOD RAIN CHANCES ALONG WITH IT. THE FRONT WILL
EVENTUALLY STALL ACROSS THE NORTHERN GULF OF MEXICO MONDAY
NIGHT...AND LATER BEGIN LIFTING NORTHWARD TUESDAY MORNING AS A WARM
FRONT.
GOOD RAIN CHANCES REMAIN IN PLACE ACROSS THE FORECAST AREA ON
TUESDAY AS A FAST MOVING UPPER LEVEL TROUGH SWINGS EAST ACROSS THE
CENTRAL PLAINS AND INTO THE MID MISSISSIPPI RIVER VALLEY. THIS WILL
CAUSE A SURFACE LOW TO DEVELOP AND LIFT NORTHEAST ACROSS THE
SOUTHERN PLAINS...WHILE DRAGGING A STRONG COLD FRONT TOWARDS THE
LOWER MISSISSIPPI RIVER VALLEY. AS THE BEFORE MENTION WARM FRONT
LIFTS NORTHWARD IN RESPONSE TO THE APPROACHING SYSTEM...MOISTURE IS
EXPECTED TO SURGE NORTHWARD INTO THE FORECAST AREA AHEAD OF THE COLD
FRONT THAT'S EXPECTED TO TRAVERSE THE ARKLAMISS REGION TUESDAY NIGHT
INTO WEDNESDAY MORNING.
THIS REMAINS SOME FOUR DAYS OUT...AND OTHER THAN SOME MINOR
PLACEMENT ISSUES...MODELS REMAIN IN DECENT AGREEMENT WITH THEIR
HANDLING OF THIS SYSTEM. SEVERAL PARAMETERS WITHIN THE MODELS
CONTINUE TO INDICATE THAT THERE IS THE POTENTIAL FOR SOME STRONG TO
SEVERE THUNDERSTORMS OVER PORTIONS OF THE CWA TUESDAY AFTERNOON INTO
TUESDAY NIGHT AS THE SYSTEM APPROACHES AND MOVES THROUGH THE AREA.
THIS WILL OBVIOUSLY CONTINUE TO BE MONITORED OVER THE NEXT SEVERAL
DAYS IN ORDER TO GET A BETTER IDEA OF WHERE THE BEST POTENTIAL FOR
ANY SEVERE WEATHER IS AS WELL AS OTHER SPECIFICS.
AS THE COLD FRONT EXITS THE FORECAST AREA WEDNESDAY MORNING...HIGH
PRESSURE WILL QUICKLY BUILD INTO THE LOWER MISSISSIPPI RIVER FROM
THE WEST THROUGH THE AFTERNOON AND OVERNIGHT HOURS. SKIES WILL
CLEAR THROUGH THE DAY WEDNESDAY AS A MUCH COOLER DRIER AIRMASS
ADVECTS INTO THE FORECAST AREA DURING THIS TIME. THESE CLEAR AND
COOLER CONDITIONS ARE EXPECTED TO REMAIN OVER THE REGION THURSDAY
INTO EARLY FRIDAY.
I DID LOWER LOW TEMPERATURES QUITE A BIT COMPARED TO WHAT GUIDANCE
WAS SUGGESTING FOR THURSDAY MORNING. GUIDANCE SHOWS LOWS IN THE MID
TO UPPER 30S ACROSS MUCH OF THE AREA DURING THIS TIME. HOWEVER...
LOCAL CLIMATOLOGY SUGGESTS COLDER TEMPERATURES THAN THIS WITH THE
ADVERTISED AIRMASS THAT'LL BE OVER THE REGION AT THE TIME. WITH
LIGHT TO CALM WINDS EXPECTED AS HIGH PRESSURE SITS NEAR THE FORECAST
AREA...COUPLED WITH CLEAR SKIES...TEMPERATURES SHOULD HAVE NO
PROBLEM RANGING FROM THE LOWER 30S TO THE MID 30S WEDNESDAY NIGHT
INTO THURSDAY MORNING.
SUBTLE AMOUNTS OF MOISTURE WILL RETURN TO THE REGION FRIDAY
AFTERNOON INTO SATURDAY AS HIGH PRESSURE SHIFTS EAST OF THE LOWER
MISSISSIPPI RIVER VALLEY. RAIN CHANCES WILL YET AGAIN INCREASE
ACROSS THE ARKLAMISS REGION DURING THIS TIME AS ANOTHER UPPER LEVEL
DISTURBANCE SWINGS EAST INTO THE MID MISSISSIPPI RIVER VALLEY...
FORCING A WEAK COLD FRONT INTO AND THROUGH THE CWA FRIDAY NIGHT INTO
SATURDAY. /19/
&&
.AVIATION...THE SNOW HAS ENDED AND CLEARING SKIES WERE BEING OBSERVED
FROM THE WEST. THIS CLEARING WAS OCCURRING A LITTLE SLOWER OVER
CENTRAL MISSISSIPPI BUT THE ONLY MVFR CEILINGS BEING REPORTED WERE IN
THE SOUTHEAST. HIGH PRESSURE AT THE SURFACE WILL MOVE IN FROM THE
WEST WHILE THE UPPER LEVEL TROUGH AXIS SHIFTS EAST. THIS SHOULD HELP
CLEAR THE REMAINING CLOUDS THIS MORNING AND VFR CONDITIONS ARE
EXPECTED TO PREVAIL AT ALL SITES TODAY AND TONIGHT. MID AND HIGH
LEVEL CLOUDS WILL BE ON THE INCREASE FROM THE SOUTHWEST SUNDAY
RESULTING IN LIGHT RAIN IN THE SOUTHWEST BY LATE AFTERNOON. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 45 25 55 44 / 0 0 13 73
MERIDIAN 46 22 53 40 / 0 0 9 58
VICKSBURG 45 25 55 46 / 0 2 22 81
HATTIESBURG 44 24 56 46 / 0 0 9 58
NATCHEZ 44 26 55 48 / 0 4 28 81
GREENVILLE 45 27 51 39 / 0 1 14 81
GREENWOOD 45 26 53 40 / 0 0 11 73
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
22/19
