FXUS64 KJAN 012052
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
245 PM CST TUE DEC 1 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT...WET WEATHER RETURNS
FOR TONIGHT AND WEDNESDAY WITH DRY WEATHER INDICATED THURSDAY AND
THURSDAY NIGHT.
WATER VAPOR IMAGERY AND RUC ANALYSIS INDICATES A CLOSED MID/UPPER
LEVEL LOW SPINNING OVER THE TEXAS BIG BEND REGION. MODELS ARE IN
AGREEMENT THAT THIS CLOSED LOW WILL TRACK SLOWLY TO THE EAST TONIGHT
AND THEN NORTHEAST WEDNESDAY WHILE HELPING TO DEEPEN THE SFC LOW
OVER THE WESTERN GULF OF MEXICO THAT WILL TRACK NORTHEAST THROUGH
THURSDAY. THE 12Z GFS IS AGAIN THE FARTHEST EAST WITH THE TRACK OF
THE SURFACE LOW. UKMET/ECMWF/SREF WERE LEANED TOWARD WHICH BRING THE
SFC LOW TO THE LOUISIANA COAST BY MIDNIGHT AND INTO CENTRAL
MISSISSIPPI BY SUNRISE. THIS LOW PRESSURE SYSTEM WILL BRING
WIDESPREAD RAIN TO OUR CWA TONIGHT AND WEDNESDAY WITH THE HEAVIEST
RAINFALL STILL EXPECTED ACROSS OUR INTERSTATE 59 CORRIDOR WHERE ONE
TO THREE INCHES OF RAIN ARE POSSIBLE THROUGH THE NEXT 24 HOURS. MUCH
LIGHTER AMOUNTS ARE EXPECTED ELSEWHERE OVER OUR AREA. LOCAL RADARS
ALREADY SHOW THE LEADING EDGE OF A LARGE AREA OF LIGHT TO MODERATE
RAIN TO THE HIGHWAY 84 CORRIDOR. THIS AREA WILL CONTINUE TO ADVANCE
NORTHWARD TONIGHT. THE THICK CLOUD COVER AND A COOL EAST WIND HAVE
HELD TEMPERATURES DOWN THIS AFTERNOON. INSTABILITY LOOKS TO REMAIN
LIMITED TONIGHT AREAWIDE DESPITE THE INCREASE IN DEEP
MOISTURE...SHEAR AND FORCING OVER THE SOUTHEAST. AS THE SFC LOW
LIFTS UP INTO TENNESSEE BY NOON WEDNESDAY...THE MID/UPPER LEVEL LOW
WILL MOVE OVER OUR DELTA REGION. ALTHOUGH THE ASSOCIATED 500MB TEMP
OF -22C IS EXPECTED WITH THE LOW...SHOWALTERS REMAIN POSITIVE AND
LIGHT RAIN AND LIGHT DRIZZLE WILL MOVE INTO OUR CWA. THE CLOSED LOW
WILL WEAKEN INTO AN OPEN TROUGH AS IT MOVES NORTHEAST OF OUR CWA
WEDNESDAY AFTERNOON. THE COOLER AND DRIER AIR WILL BRING AND END TO
THE PRECIPITATION AND A DECREASE IN CLOUD COVER WEDNESDAY NIGHT.
ALTHOUGH THE WINDS MAY NOT DECOUPLE AND THE CLOUDS CLEAR BY
MORNING...MOST SITES WILL BOTTOM OUT IN THE MID 30S THURSDAY
MORNING. DRY WEATHER WILL RETURN TO THE ARKLAMISS THURSDAY WHILE
COOLER THAN NORMAL TEMPERATURES CONTINUE. A COLD CANADIAN CENTER OF
HIGH PRESSURE WILL BE DROPPING INTO THE NORTHERN PLAINS WHILE A
POTENT NORTHERN STREAM SHORTWAVE WILL BEGIN AMPLIFYING A LARGE UPPER
LEVEL TROUGH OVER THE CENTRAL CONUS. THIS WILL SEND COLDER AIR OUR
WAY AND THE EXPECTED 850MB ZERO DEGREE ISOTHERM IS EXPECTED TO BE
JUST SOUTH OF INTERSTATE 20 WITH THE 925MB ZERO DEGREE ISOTHERM
ACROSS SOUTHEAST MISSISSIPPI FRIDAY MORNING. ALTHOUGH THE LARGE
CENTER OF HIGH PRESSURE WILL BE TO OUR NORTHWEST THURSDAY NIGHT THE
RESULTING NORTHERLY FLOW WILL HELP SEND TEMPERATURES DOWN TO NEAR
FREEZING OVER THE NORTHERN HALF OF THE AREA. /22/
.LONG TERM...FRIDAY THROUGH TUESDAY...A LOT MORE QUESTION MARKS
EXIST IN THE MED RANGE PORTION OF THE FORECAST THIS GO ROUND THAN
COMPARED TO LAST NIGHT. DUE TO THIS...THE POTENTIAL FOR COLD
CONDITIONS FRI-SAT IS SOMEWHAT LESS...BUT STILL POSSIBLE AS A WIDE
RANGE OF SOLUTIONS STILL EXIST. EVEN WITH THAT...A PERIOD OF BELOW
NORMAL CONDITIONS WILL EXIST FOR FRI THROUGH THE WEEKEND.
THE PRIMARY DIFFERENCES IN THIS NEW FORECAST WILL BE NOT GOING WITH
THOSE COLD LOWS SAT MORNING. THE REASON FOR THAT IS NOW THE
MODELS ARE NOT HAVING A SFC HIGH SETTLE OVER THE REGION...THE CENTER
OF THE HIGH LOOKS TO BE FURTHER TO THE NW OF THE CWA. THAT WILL KEEP
SOME WEAK PRESSURE GRADIENT GOING AND KEEP WINDS UP A TAD.
ALSO...THE LATEST MODELS ARE MORE AGGRESSIVE WITH MID LEVEL CLOUD
COVER AS A SOLID S/W ROUNDS THE BASE OF THE LONG WAVE TROUGH FRI/FRI
NIGHT. ACTUALLY...THE GFS BREAKS OUT SOME LIGHT PRECIP AS IT
GENERATES A GULF LOW WILL DEEPENS AND TRACKS E ACROSS THE NORTHERN
GULF. THE OPS GFS IS AN OUTLIER WITH THAT SOLUTION BUT BEARS
WATCHING AS SUCH PRECIP WOULD HAVE SOME POTENTIAL TO BE OF THE
FROZEN NATURE. HOWEVER...I WILL STAY WITH THE MODEL CONSENSUS AND
KEEP THINGS DRY.
AS FOR TEMPS...I STAYED EITHER WITH GUID OR LOWERED A FEW DEGREES
SAT MORNING THROUGH SUN MORNING. THE GFS ENSEMBLE MOS STRONGLY
SUGGESTS THAT COLDER CONDITIONS WILL BE QUITE POSSIBLE FOR THIS TIME
FRAME WITH VALUES MORE IN LINE WITH THE PREV FORECAST. THOSE MEMBERS
ARE STRONGER WITH THE SFC HIGH AND KEEP LESS CLOUD AROUND.
HOWEVER...THERE JUST EXISTS TOO MUCH UNCERTAINTY WITH THE LATEST
DATA TO GET TOO AGGRESSIVE AND GO REALLY COLD. I STAYED PRETTY MUCH
WITH GUID TEMPS SUN-TUE WITH ONLY SOME MINOR ADJ TO HIGHS ON TUE.
THE PATTERN LOOKS TO SUPPORT SOME WARMER CONDITIONS BY AT LEAST
TUE...IF NOT SOONER. LARGE TEMP SPREADS EXIST IN THE ENSEMBLE GUID
FOR SUN-TUE SO IT MAY BE A WILD RIDE DURING THAT TIME AS WE
TRANSITION THE PATTERN.
AS FOR POPS/WX...I STAYED WITH THE DRY SOLUTION FOR FRI-SUN. THIS
RESULTED IN SOME LARGE DEVIATIONS FROM GFS POPS FRI/FRI NIGHT. ASIDE
FROM THAT...GUID POPS WERE USED FOR THE REST OF THE WEEKEND INTO
EARLY NEXT WEEK. GUID WAS OFFERING SOME 30-50% POPS STARTING SUN
NIGHT INTO TUE AND I SEE NO REASON TO DEVIATE FROM THAT AS
UNCERTAINTY IS RATHER LARGE DURING THAT TIME. /CME/
&&
.AVIATION...STRENGTHENING LOW PRESSURE WILL TRACK NORTHEASTWARD
ACROSS THE SOUTHEASTERN UNITED STATES THROUGH WEDNESDAY. BANDS OF
MODERATE TO HEAVY RAIN WILL PIVOT AROUND THE LOW INTO EAST CENTRAL
AND SOUTHEAST MISSISSIPPI THROUGH WEDNESDAY MORNING...RESULTING IN
IFR AND OCCASIONALLY LIFR CEILINGS AND VISIBILITIES. THE WORST
CONDITIONS ARE EXPECTED AT KHBG...KMEI...AND KGTR. LIGHT RAIN IS
EXPECTED TO PUSH NORTHWARD ACROSS SOUTHEAST AND EAST CENTRAL
MISSISSIPPI THROUGH LATE AFTERNOON...WITH MODERATE TO HEAVY RAIN
EXPECTED BY EVENING AND CONTINUING INTO WEDNESDAY MORNING. FARTHER
TO WEST...INCLUDING KGWO...KGLH...AND KJAN...LIGHT TO MODERATE
RAIN...ALONG WITH IFR CEILINGS/VISIBILITIES...ARE EXPECTED TO SPREAD
NORTHWARD LATE THIS AFTERNOON THROUGH WEDNESDAY MORNING. RAIN WILL
BEGIN TO TAPER OFF FROM SOUTH TO NORTH ACROSS THE AREA DURING THE
DAY WEDNESDAY... THOUGH MVFR/IFR CEILINGS/VISIBILITIES WILL CONTINUE
AS LOW CLOUDS AND DRIZZLE PERSIST. NORTHEAST TO EAST WINDS AT 5 TO
10 KT ARE EXPECTED TO SHIFT TO THE NORTH OVERNIGHT TONIGHT. WIND
GUSTS TO 20 KT WILL BE POSSIBLE ACROSS EAST CENTRAL AND SOUTHEAST
MISSISSIPPI TONIGHT NEAR THE HEAVIER RAIN. AS THE LOW IS PULLED
NORTHEAST OF THE AREA ON WEDNESDAY...WINDS WILL BECOME SOUTHWESTERLY
TO WESTERLY AT 8 TO 12 KT WITH GUSTS OF 15 TO 18 KT WHILE A
DEVELOPING COLD FRONT SWEEPS ACROSS THE AREA. SOME UNCERTAINTY
EXISTS IN THE WIND DIRECTION FORECAST FOR TONIGHT AND
WEDNESDAY...DUE TO CONTINUING UNCERTAINTY IN THE EXACT TRACK OF THE
SURFACE LOW. IF THE LOW TRACKS FURTHER TO THE WEST OVER
MISSISSIPPI...WINDS WILL BECOME MORE SOUTHWESTERLY FOR WEDNESDAY.
/COHEN/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 44 53 37 54 / 89 49 7 5
MERIDIAN 46 57 37 54 / 88 44 10 5
VICKSBURG 44 52 36 52 / 89 51 7 5
HATTIESBURG 48 59 39 56 / 94 32 8 5
NATCHEZ 43 52 35 54 / 94 28 7 5
GREENVILLE 42 48 35 48 / 79 76 10 5
GREENWOOD 42 48 35 51 / 79 76 16 5
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
22/CME/COHEN
