FXUS64 KJAN 011156 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
556 AM CST TUE DEC 1 2009
.AVIATION...OVERNIGHT CONDITIONS GENERALLY VFR WITH SCATTERED
MID-HIGH LEVEL CLOUD LAYERS ABOVE 10K FEET. HIGHER CLOUDS WILL
CONTINUE TO STREAM OVER THE AREA AND THICKEN/LOWER OVER THE FORECAST
AREA THIS MORNING WITH CLOUD LAYERS LOWERING TO 3-5K FEET WITH
INCREASING CHANCES OF RAIN THIS AFTERNOON. THESE RAIN CHANCES
WILL BEGIN FOR LOCATION SOUTH OF I-20(AFFECTING POSSIBLY THE KHBG
TAF SITE) BY 16-18Z. TAF SITES ALONG AND NORTH OF I-20 SHOULD BE
FINE FOR MOST OF THE DAY AND VFR CONDITIONS SHOULD PREVAIL AT THESE
PLACES. AS A LOW PRESSURE SYSTEM FORMS AND MOVES CLOSER TO THE
REGION...FLYING CONDITIONS WILL DETERIORATE DURING THE LATE
AFTERNOON AND DEFINITELY OVERNIGHT TUESDAY NIGHT/WEDNESDAY MORNING.
MVFR CONDITIONS WILL RESUME TUESDAY EVENING OVER MOST TAF SITES AS
RAIN WILL SPREAD ACROSS THE AREA. LOCATIONS IN THE NORTH WILL SEE
LESSER RAIN(LIGHTER RAIN) THAN THOSE AT KMEI...KJAN AND ESPECIALLY
KHBG. SITES COULD SEE IFR TO LIFR VIS/CEILINGS WITH THE LOCATIONS
MOST LIKELY TO SEE THIS BEING KHBG(WITH KJAN AND KMEI BEING RANKED
SECOND). KGLH...KGTR AND KGWO WILL LIKELY SEE THE BETTER FLYING
CONDITIONS(THOUGH STILL NOT GREAT). THERE IS THE POSSIBLITY FOR
THUNDERSTORMS AT KHBG BUT ONLY ISOLATED. RAIN WILL BEGIN TO TAPER
OFF FROM SOUTHWEST TO NORTHEAST ON WEDNESDAY(WHEN THE BETTER CHANCES
FOR RAIN WILL EXIST FOR KGLH...KGWO AND KGTR) BUT CLOUD COVER SHOULD
LINGER FOR MOST OF THE DAY ON WEDNESDAY. WINDS COULD BE GUSTY AT
TIMES...ESPECIALLY FOR KHBG AND ESPECIALLY IN ANY TS THAT MAY
OCCUR. /28/
&&
.PREV DISCUSSION... /ISSUED 442 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 OCCURING 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/
&&
.AVIATION...
WILL BE ISSUED SHORTLY.
&&
.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.
&&
$$
28/CME/
