FXUS64 KJAN 011649
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
1030 AM CST TUE DEC 1 2009
.UPDATE...LATEST SURFACE ANALYSIS SHOWS A LOW IN THE WESTERN GULF
EAST OF BROWNSVILLE WITH HIGH PRESSURE CENTERED OVER THE
APPALACHIANS. THE HIGH IS STILL EXPECTED TO SHIFT EAST WHILE THE LOW
TRACKS NORTHEAST TOWARD THE LOUISIANA MISSISSIPPI GULF COAST BY THIS
EVENING. ALOFT THE CLOSED LOW WAS NOTED MOVING OVER THE TEXAS BIG
BEND. THIS UPPER LOW IS STILL EXPECTED TO TRACK SLOWLY EAST TODAY.
CIRCULATION AROUND THIS UPPER LOW WAS HELPING TO DRAW UP MOISTURE
ACROSS OUR REGION. THE MORNING JAN SOUNDING WAS DRY 500-950MB WITH
ONLY A PW OF A QUARTER OF AN INCH. THE MORNING SLIDELL SOUNDING
SHOWED A PW AROUND ONE INCH. IT WILL LIKELY TAKE UNTIL MID AFTERNOON
TO GET SIGNIFICANT PRECIPITATION FALLING TO OUR HIGHWAY 84 CORRIDOR
BUT LOCAL RADARS SUGGEST SOME LIGHT RAIN ACROSS OUR SOUTHEAST MOST
COUNTIES BY NOON. STILL LOOKS LIKE WITH A SOUTHERN TRACK OF THE LOW
THAT INSTABILITY AND DEEP MOISTURE WILL BE CONFINED THIS AFTERNOON
TO JUST SOUTHEAST OF OUR CWA BUT WL MAINTAIN MENTION OF LOCALLY
HEAVY RAIN AMOUNTS OF ONE TO THREE INCHES IN THE HWO OVER OUR SE.
CLOUDS HAVE BEEN ON THE INCREASE THIS MORNING FASTER THAN EXPECTED
AND TEMPERATURES WERE RUNNING COOLER IN OUR NORTH BY SEVERAL
DEGREES. CURRENT HIGHS STILL LOOK ACHIEVABLE BUT HAVE UPDATED FOR
CLOUD COVER AND TWEAKED TEMPERATURE CURVES THIS MORNING. UPDATES
HAVE BEEN POSTED.
&&
.AVIATION...INTENSIFYING LOW PRESSURE WILL TRACK NORTHEASTWARD
ACROSS THE SOUTHEASTERN UNITED STATES THROUGH WEDNESDAY. BANDS OF
MODERATE TO HEAVY RAIN WILL PIVOT AROUND THE LOW THROUGH WEDNESDAY
MORNING INTO EAST CENTRAL AND SOUTHEAST MISSISSIPPI...RESULTING IN
IFR CEILINGS AND VISIBILITIES. THE WORST CONDITIONS ARE EXPECTED AT
KHBG...KMEI...AND KGTR...WITH KHBG LIKELY RECEIVING THE LONGEST
DURATION OF IFR...AND POTENTIALLY LIFR...CEILINGS/VISIBILITIES FOR
TONIGHT. LIGHT RAIN IS EXPECTED TO WORK NORTHWARD ACROSS SOUTHEAST
AND EAST CENTRAL MISSISSIPPI THROUGH THIS EVENING...WITH MODERATE TO
HEAVY RAIN EXPECTED BY EVENING CONTINUING INTO WEDNESDAY MORNING.
ISOLATED THUNDERSTORMS WILL BE POSSIBLE IN THIS AREA TONIGHT...
THOUGH THE CHANCE FOR THUNDERSTORMS IMPACTING ANY TAF SITE IS TOO
LOW FOR MENTION IN THE TAFS. FARTHER TO WEST...INCLUDING
KGWO...KGLH...AND KJAN...LIGHT TO MODERATE RAIN...ALONG WITH
MVFR/IFR CEILINGS/VISIBILITIES...IS EXPECTED TO SPREAD NORTHWARD
THIS AFTERNOON THROUGH WEDNESDAY MORNING. RAIN WILL BEGIN TO TAPER
OF FROM SOUTH TO NORTH ACROSS THE AREA DURING THE DAY WEDNESDAY...
THOUGH MVFR/IFR CEILINGS/VISIBILITIES WILL CONTINUE AS LOW CLOUDS
AND DRIZZLE PERSIST. FOR TODAY...NORTHEAST TO EAST WINDS AT 5 TO 10
KT ARE EXPECTED TO SHIFT TO THE NORTH 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 WESTERLY AT 8 TO 12 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/
&&
.PREV DISCUSSION... /ISSUED 556 AM CST TUE DEC 1 2009/
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...TONIGHTS FORECAST IS
EVEN MORE OF A HEADACHE THAN LAST NIGHTS AND NOTHING IS MUCH CLEARER
YET.
WATER VAPOR IMAGERY AND RUC ANALYSIS INDICATES THE HIGHLY
ANTICIPATED MID LEVEL LOW SPINNING OVER THE NEW MEXICO/WEST
TEXAS/OLD MEXICO AREA. SFC LOW DOES NOT LOOK TO HAVE DEVELOPED YET
ALONG THE TEXAS GULF COAST BUT PLENTY OF MOISTURE EXISTS AND THIS IS
BRINGING SOME LIGHT RAIN TO SOUTH LOUISIANA AND COASTAL AREAS. OVER
THE ARKLAMISS...SFC HIGH PRESSURE REMAINS IN TACT ACROSS MOSTLY
NORTHERN AREAS AND THIS IS EXPECTED TO MOVE OFF TO THE EAST ACROSS
PORTIONS OF TENNESSEE LATER TODAY.
TODAY SHOULD REMAIN FAIRLY QUIET FOR MOST OF THE ARKLAMISS AND FOR
MOST OF THE DAY WITH HIGH PRESSURE AND DRIER AIR IN TACT(THIS WILL
ESPECIALLY BE THE CASE FOR AREAS JUST ALONG AND NORTH OF I-20). ALL
MODELS CONTINUE TO SHOW THAT AS THE MID LEVEL LOW BEGINS TO PROGRESS
TO THE EAST...CYCLOGENESIS ALONG RESIDUAL FRONTAL BOUNDARY ALONG THE
GULF COAST WILL OCCUR AND DEVELOP A SFC LOW JUST TO THE SOUTH OF THE
CENTRAL TEXAS COAST. THIS LOW WILL MOVE IN OUR DIRECTION DURING THE
DAY TODAY. ALL MODELS/LOCAL WRF SHOW SOME LIGHT RAIN BEGINNING TO
AFFECT MY SOUTHERN ZONES LATER THIS AFTERNOON BUT THIS SHOULD BE
CONFINED TO AREAS SOUTH OF I-20 WITH THE BETTER CHANCES ALONG AND
SOUTH OF THE HIGHWAY 84 CORRIDOR.
STARTING TONIGHT IS WHERE THE QUESTION MARKS BEGIN. THE GFS HAS BEEN
RATHER CONSISTENT RUN TO RUN(ALBEIT AN OUTLIER FROM THE OTHER
MODELS) AND DEPICTS THE SFC LOW REMAINING MOSTLY OFFSHORE/ALONG THE
COAST AND MAKING LANDFALL AROUND THE FLA/AL BORDER. IT LOOKS LIKE IT
MIGHT BE A TAD FURTHER SOUTH THIS RUN BUT HAS REMAINED FAIRLY
CONSISTENT. WITH THIS SOLUTION...MOST OF THE RAIN WILL BE SOUTH AND
EAST OF THE CWA. THE GFS ENSEMBLE IS ALSO SIMILAR WITH THE LOW A
LITTLE SLOWER AND TO THE WEST MOVING OVER THE PINE BELT REGION OF
MS/I-59 CORRIDOR. STILL SHOWS THE HEAVIEST RAINS OCCURRING EAST OF
THE CWA. THE 21Z SREF RUN WAS A LITTLE OUT TO LUNCH BRINGING THE LOW
UP THE MISSISSIPPI RIVER BUT WITH THE 03Z RUN...IT HAS COME BACK A
LITTLE MORE IN LINE WITH THE OTHERS AND PREVIOUS RUNS AND BRINGS THE
LOW UP THROUGH THE NATCHEZ TRACE. THE ECMWF ALSO BRINGS THE LOW
ACROSS THE I-59 CORRIDOR. THE 00Z NAM...WHICH HAS PROBABLY BEEN THE
MOST INCONSISTENT MODEL...IS IN LINE DECENTLY WITH THE EURO WHILE
THE 06Z RUN IS MORE IN LINE WITH THE GFS. THE UKMET AND CANADIAN ALL
ARE IN SOME AGREEMENT WITH THE ECMWF WITH THE TRACK LOCATION.
SO WHAT DOES THIS MEAN? WELL, THE BEST POPS AND HIGHEST RAIN AMOUNTS
WILL REMAIN HOW THEY WERE PREVIOUSLY....AND BASICALLY IN THE SOUTH
AND EAST FOR TUESDAY NIGHT...FOLLOWING THE SOUTHERN TRACK. THE LOWER
CHANCES WILL REMAIN ACROSS THE DELTA AND ARKANSAS. BY WEDNESDAY
MORNING THE SFC LOW MOVES OFF INTO ALABAMA/GEORGIA/FLORIDA AND THE
UPPER LOW WILL PIVOT ACROSS THE REGION. AS THIS OCCURS...THE BETTER
RAIN CHANCES WILL OCCUR FOR THE NORTHERN SECTION OF THE CWA AS ANY
MOISTURE THAT IS LEFT WILL BE SQUEEZED OUT ACROSS THIS AREA. MOST OF
THE RAIN WILL BE LIGHT IN NATURE. THE UPPER LOW WILL PIVOT THROUGH
AND MOST OF THE RAIN WILL TAPER OFF OVERNIGHT WEDNESDAY NIGHT AND
SHOULD BE OVER BY DAYBREAK THURSDAY. RAIN SHOULD END EARLY FOR THE
SOUTH AS A PUNCH OF DRIER AIR MOVES IN AND SHOULD MOVE MOST OF THE
RAIN OUT. HOWEVER...FOR NOW...WILL LEAVE SLIGHT CHANCES OF LIGHT
RAIN/DRIZZLE IN UNTIL WEDNESDAY EVENING.
AS FOR THE SEVERE POTENTIAL....SPC HAS PUT THE SOUTHERN PART OF THE
I-59 CORRIDOR/PINE BELT REGION UNDER A SLIGHT RISK FOR TONIGHT WITH
15% WIND AND 5% TOR THREAT. I AM NOT COMPLETELY BUYING OFF ON IT
YET(BUT NOT DISCREDITING THE POSSIBILITY EITHER). THIS WILL HIGHLY
DEPEND ON THE TRACK OF THE LOW AND ASSOCIATED CONVECTION. IF
CONVECTION ALONG THE COAST GETS GOING AND GOING EARLY....I CAN SEE
US GETTING SHUT OFF FROM ALL OF THE GOOD THETA-E AIR/MOISTURE/HIGHER
DEWPOINTS. THIS SCENARIO IS SHOWN ON SOME OF THE HI-RES SPC WRF RUNS
WITH THE BETTER CONVECTION ALONG THE COAST OR OFFSHORE. IF THIS
HAPPENS...WE MAY NOT EVEN GET THUNDER IN OUR ZONES AND IT WOULD BE
MORE IN THE FORM OF STRATIFORM RAIN. HOWEVER IF THIS DOES NOT
HAPPEN...THEN SOME OF THE MODELS DO INDICATE THAT THE HIGHER 60-65
DEWPOINTS COULD MAKE IT INTO THE I-59 CORRIDOR. WITH HIGH SHEAR
VALUES AND FORCING FROM THE LOW...THERE IS A SMALL SHOT FOR SOME
WIND AND/OR TORNADO THREAT. I WILL INCLUDE SOME LOW NUMBERS IN THE
PROB HAZARD GRIDS BUT WILL NOT MENTION THIS IN THE HWO DUE TO HIGH
UNCERTAINTY. SPC ALSO DEPICTS ABOUT 2% TOR UP ACROSS CENTRAL MS. I
REALLY DONT THINK THIS IS GOING TO HAPPEN UNLESS THE TRACK OF THE
LOW GOES MUCH FARTHER NORTH THAN MOST MODELS ARE INDICATING AND WE
GET THE DEWPOINTS. I THINK OF ALL OF THE THREATS WITH THIS
SYSTEM...THE HEAVY RAIN IS THE HIGHER THREAT. HPC QPF AMOUNTS SHOW
ABOUT 2-3 INCHES ACROSS THE SE. WHILE THE MUCH HIGHER AMOUNTS WILL
FALL TO THE SOUTH AND EAST OF THE CWA...WILL CONTINUE TO MENTION THE
THREAT FOR HEAVY RAINFALL IN THE HWO.
OVERALL...GUI NUMBERS CAME IN FINE. DID UP POPS FOR THE SOUTH FOR
TODAY AND TONIGHT BUT OTHERWISE VALUES CAME IN HIGH AND WERE
ACCEPTED. TEMPS SEEM REASONABLE. /28/
LONG TERM...THURSDAY 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 THU-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 THU THROUGH THE WEEKEND.
BOTH THE EURO/GFS ARE NOT AS BULLISH WITH SURGING COLD AIR THROUGH
THE AREA ON THU...BUT THE AIR IS STILL ON THE COLD SIDE AND BRINGS
925-850MB TEMPS IN THE (-4C TO 2C) RANGE WITH THE COOLEST READINGS
IN THE NW/N PART OF THE CWA. THERE IS ALSO INDICATIONS THAT SOME LOW
STRATO CU WILL EXIST ON THU. I CAN SEE A MIX OF MO CLOUDY TO
BECOMING PARTLY CLOUDY. THOSE CLOUDS...COMBINED WITH AT LEAST SOME
WEAK CAA...SHOULD PROVIDE COOLISH CONDITIONS AND I WENT WITH THE
COOLER NAM GUID OR LOWERED THE GFS A TAD TO STAY NEAR THE COOLER
ENSEMBLE MEAN.
THE PRIMARY DIFFERENCES IN THIS NEW FORECAST WILL BE NOT GOING WITH
THOSE COLD LOWS FOR FRI-SAT MORNINGS. 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
FRI 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/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 55 45 52 38 / 16 91 73 18
MERIDIAN 56 46 56 38 / 20 97 67 20
VICKSBURG 54 43 50 36 / 14 87 75 18
HATTIESBURG 53 50 57 39 / 70 98 45 14
NATCHEZ 52 43 53 35 / 65 97 58 15
GREENVILLE 51 42 47 34 / 2 76 88 22
GREENWOOD 55 43 51 37 / 3 80 91 24
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
22/COHEN/28/CME
