FXUS64 KJAN 051641 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1041 AM CST SAT DEC 5 2009
.UPDATE...SURFACE HIGH(1027MB) PRESSURE AXIS FROM THE OH VALLEY TO
THE TX COAST WILL KEEP COLD DRY AIR MASS IN PLACE THROUGH SUNDAY
MORNING. MORNING VISIBLE SATELLITE IMAGES SHOWING THE BEST SNOW COVER
LEFTOVER WAS ROUGHLY ALONG I-55 S OF THE JACKSON AREA...ESPECIALLY IN
ERN COPIAH AND LINCOLN COUNTIES WHERE 2.5-4 INCHES LIKELY OCCURRED. THE
REST OF THE OVERNIGHT SNOWS WERE RAPIDLY MELTING AND WILL SET THE
STAGE FOR A GOOD RADIATIONAL COOLING SETUP TONIGHT. THAT WILL RESULT
IN SOME OF THE COLDEST TEMPS SO FAR THIS AUTUMN(OR IS IT WINTER)...
ACTUALLY THE COLDEST SINCE THE MIDDLE OF LAST FEBRUARY.
MINOR ADJUSTMENTS TO HOURLY DEWPOINTS/WINDS WITH NO OTHER CHANGES
NEEDED FOR NOW. NO ZONE TEXT UPDATE EXPECTED BUT GRAPHICS SHOULD BE
AVAILABLE. /40/
&&
.PREV DISCUSSION... /ISSUED 359 AM CST SAT DEC 5 2009/
DISCUSSION...TONIGHT THROUGH SUNDAY NIGHT...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...
HIGH PRESSURE AT THE SURFACE WILL MOVE SLOWLY EAST WHILE THE UPPER
LEVEL TROUGH AXIS PULLS AWAY FROM OUR REGION. THIS SHOULD MAINTAIN
CLOUD FREE SKIES AND VFR CONDITIONS ARE EXPECTED TO PREVAIL AT ALL
SITES THROUGH TONIGHT. MID AND HIGH LEVEL CLOUDS WILL BE ON THE
INCREASE FROM THE SOUTHWEST EARLY SUNDAY RESULTING IN LIGHT RAIN IN
THE SOUTHWEST PORTIONS OF THE CWFA BY LATE AFTERNOON. /15/
&&
.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.
&&
$$
