FXUS64 KJAN 301652 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE JACKSON MS
1045 AM CST MON NOV 30 2009
.DISCUSSION...DECENT COLD FRONT SWEEPING SOUTHEAST OF THE NATCHEZ
TRACE CORRIDOR THIS MORNING WITH THE BAND OF MODERATE DOWNPOURS OUT
AHEAD OF IT JUST SHIFTING EAST OF THE I-59 CORRIDOR. STILL
EXPERIENCING SOME LIGHT RAIN AND DRIZZLE BEHIND THE SIGNIFICANT
PRECIP...AND THIS MAY TAKE UNTIL LATER THIS AFTERNOON TO ENTIRELY
EXIT THE EASTERN PORTIONS OF THE FORECAST AREA. LOW CLOUDS ON THE
BACKSIDE OF THE COLD FRONT WILL TRY TO CLEAR OUT FROM THE NORTH THIS
AFTERNOON...BUT MAY NOT MAKE A WHOLE LOT OF PROGRESS AS HIGH CLOUDS
IN ADVANCE OF THE NEXT SYSTEM CONTINUE TO STREAM IN FROM THE
SOUTHWEST. THE END RESULT WILL BE A COOL DAY WITH TEMPERATURES IN
THE 50S AFTER THE FRONT GOES THROUGH WITH A BIT OF NORTH WIND TO
INCREASE THE CHILL A BIT.
SPEAKING OF WIND...I HAVE HOISTED A LAKE WIND ADVISORY THROUGH 6 PM
FOR THE LARGE AREA LAKES. ALTHOUGH CRITERIA OF SUSTAINED 20 MPH
SHOULD NOT BE MET OVER MOST LAND AREAS...THE INCREASE OF WIND SPEED
DUE TO LACK OF FRICTION OVER THE BIG LAKES SHOULD GET VALUES TO THIS
MARK. WINDS OVER LAKES WILL ALSO BOOSTED BY THE COLD ADVECTION
SCENARIO WHICH HELPS TO EFFICIENTLY MIX WINDS A COLD THOUSAND FEET
OFF THE GROUND DOWN TO THE LAKE SURFACE.
UPDATES OUT IN GRIDS AND ZONES. /BB/
&&
.PREV DISCUSSION... /ISSUED 443 AM CST MON NOV 30 2009/
SHORT TERM...TODAY THROUGH TUESDAY NIGHT...IT IS A LITTLE BUSY IN
THE SHORT TERM WITH ONE SYSTEM MOVING THROUGH THIS MORNING/EARLY
AFTERNOON FOLLOWED BY ANOTHER AT THE END OF THE PERIOD. RESIDENTS
COULD SEE MORE RAIN THIS WEEK THAN THEY HAVE DURING THE WHOLE MONTH
OF NOVEMBER.
AS OF ABOUT 10Z...SURFACE FRONT IS LOCATED GENERALLY FROM SOUTH OF
MONROE LOUISIANA...TO NORTH OF JACKSON...TO SOUTH OF TUPELO. LARGE
AREA OF LIGHT TO MODERATE RAIN BEHIND THE FRONT LOCATED JUST ALONG
OR SLIGHTLY TO THE NORTH OF THE NATCHEZ TRACE. THERE HAVE BEEN SOME
EMBEDDED THUNDERSTORMS WITHIN SOME OF THE HEAVIER CONVECTIVE AREAS.
FOR TODAY...FRONT WILL CONTINUE TO TREK THROUGH THE CWA THROUGH THE
REMAINDER OF THE MORNING. ALL MODELS AND LOCAL WRF RUNS ARE IN VERY
GOOD AGREEMENT THAT ALL OR MOST OF THE RAIN SHOULD BE THROUGH THE
CWA BY AROUND 18Z. BEHIND THE FRONT...CONDITIONS COULD BE RAW WITH
TEMPS COOLING INTO THE UPPER 40S TO LOWER 50S WITH GUSTY NORTHERLY
WINDS. AT THIS TIME...LAKE WIND ADV CRITERIA DOES NOT LOOK TO BE MET
THOUGH IF VENTURING OUT ONTO LAKES...CONDITIONS COULD BE GUSTY AT
TIMES. CLOUDS WILL LINGER FOR A LITTLE BIT BEFORE GRADUALLY CLEARING
OUT A BIT LATE THIS EVENING INTO TONIGHT.
SHORTWAVE RIDGING AND HIGH PRESSURE AT THE SURFACE WILL TAKE PLACE
TONIGHT AND ALLOW FOR A QUIET NIGHT AND MUCH OF THE DAY ON TUESDAY.
HOWEVER...THE NEXT SYSTEM MOVES IN LATE TUESDAY. ON TUESDAY...MID
LEVEL LOW OVER THE RIO GRANDE VALLEY AREA WILL MAKE ITS WAY EAST
WHILE CYCLOGENESIS AT THE SFC WILL FORM A LOW ALONG THE PREVIOUS
FRONTAL BOUNDARY JUST SOUTH OF THE CENTRAL TEXAS COAST.
MODELS ARE NOT IN MUCH BETTER AGREEMENT THAN LAST NIGHT. THE
ECMWF/SREF/NAM ALL CONTINUE TO INDICATE THE SFC LOW TRACK ACROSS THE
CWA WHILE THE GFS CONTINUES TO BE THE OUTLIER AND BRING THE LOW MUCH
FURTHER TO THE SOUTH AND EAST. HOWEVER...ALL MODELS HAVE SPED THE
TIMING UP FROM WEDNESDAY TO THIS EVENT OCCURRING MORE ON TUESDAY
NIGHT. I WILL CONTINUE TO FOLLOW A LITTLE CLOSER TO THE
ECMWF/SREF/NAM. THIS WOULD BEGIN TO INTRODUCE RAIN BACK INTO THE
SOUTHWEST CWA BY TUESDAY LATE AFTERNOON WITH SLIGHT
CHANCES...GRADUALLY BECOMING MORE LIKELY THE LATER INTO THE
AFTERNOON AND EVENING WE GO. THE MAIN TIMEFRAME FOR RAIN WILL
DEFINITELY BE OVERNIGHT TUESDAY NIGHT/WED. MORNING. WITH THIS
TRACK...THERE IS THE POSSIBILITY FOR SOME ISOLATED THUNDER IN SOME
OF THE HEAVIER CONVECTIVE BANDS SO HAVE MAINTAINED THE THUNDER
WORDING MAINLY FOR SOUTHEAST MS FROM THE NATCHEZ TRACE TO I-59
CORRIDOR AREA. THIS WILL BE THE SAME REGION THAT SHOULD RECEIVE THE
HEAVIEST RAIN AND IS WHERE THE BETTER MOISTURE TRANSPORT/CONVERGENCE
OCCURS. MODELS INDICATE THAT ANYWHERE FROM 1 TO 3 INCHES COULD OCCUR
IN THIS REGION. WILL CONTINUE TO MENTION HEAVY RAIN THREAT IN THE
HWO. IN ADDITION...SPC HAS GONE AHEAD AND PUT PORTIONS OF MS SOUTH
OF OUR CWA UNDER A 5% SVR DAY 2 SVR OUTLOOK. HOWEVER...DEPENDING ON
THE TRACK OF THE LOW...THIS COULD BE EXPANDED FURTHER INTO OUR CWA
OR PUSHED FURTHER SOUTH OF OUR CWA. GIVEN FORCING/PROXIMITY TO THE
LOW...BEING IN THE WARM SECTOR OF THE LOW(WITH THE POSSIBILITY FOR
SOME HIGHER DEWPOINTS ACROSS THE SOUTHEAST)AND HIGH SHEAR
VALUES(DESPITE LIMITED INSTABILITY)...THERE COULD BE A SMALL TORNADO
THREAT WITH THIS AND IS DEFINITELY SOMETHING TO KEEP IN MIND WITH
FUTURE FORECASTS AS THE LOW TRACK BECOMES CLEARER.
OVERALL....MADE SOME ADJ TO THE FORECAST. RAISED POPS FOR TODAY FOR
LOCATIONS SOUTH AND EAST AND MOST LIKELY TO GET RAIN. DID CUT SOME
ACROSS THE DELTA WHERE RAIN SHOULD END QUICKER. ALSO FOR TUES...I
CUT POPS NORTH AS DRIER AIR SHOULD PRECLUDE ANY APPRECIABLE RAIN.
LOCATIONS ALONG I-20 WERE CUT SOME AND LOCATIONS TO THE SOUTH WILL
HAVE THE BEST CHANCE FOR ANY RAIN AND WAS LEFT IN TACT. TUES NIGHT
POPS WERE LEFT AS THEY WERE ALREADY HIGH TO BEGIN WITH. DID BUMP UP
POPS IN THE SOUTH A LITTLE AS TRACK IS STILL A LITTLE UNCERTAIN.
OVERALL...TEMPS WERE GOOD...DID USE A BLEND OF THE MET/MAV FOR TUES
NIGHT. /28/
LONG TERM...A MORE EARLY WINTERISH TYPE WX PATTERN WILL BE TAKING
SHAPE IN THE MED RANGE/LONG TERM PART OF THE FORECAST. THE REGION
WILL SEE A MID LATITUDE CYCLONE EVOLVE ON WED AND LIFT NE THROUGH
THE MID ATLANTIC STATES. AS THAT OCCURS...COOL/WET CONDITIONS WILL
BE AROUND WED THEN DEPART TO THE NE. THEN...COLDER AIR WILL FILTER
INTO THE REGION BEHIND THE FRONT WED NIGHT INTO THU AND LIKELY
LINGER INTO THE WEEKEND. A FEW MORNINGS WILL LIKELY SEE FREEZING
TEMPS (FRI-SUN) WITH READINGS RUNNING SOME 10-15 DEGREES BELOW
NORMAL VALUES.
FOR WED...OUR CYCLONE WILL BE DEEPENING NICELY WITH THE HEAVY RAIN
E/SE OF THE FORECAST AREA. HOWEVER...STRONG ASCENT WILL REMAIN OVER
THE REGION FOR AT LEAST THE FIRST PART OF THE WED PERIOD AS THE COLD
CORE ALOFT MOVES OVER THE REGION. AS THAT OCCURS...THETA SURFACES
THROUGH A DEEP LAYER WILL QUICKLY RISE AND "SQUEEZE" OUT LEFT OVER
MOISTURE AND ALLOW FOR SOLID PRECIP CHANCES ON WED. OVERALL...THE
PRECIP WILL BE LIGHT AND TAPER TO MORE OF A MIX OF DRIZZLE/LIGHT
RAIN. TEMPS WED WILL BE TRICKY AS THERE ARE MODEL DIFFERENCES ON THE
TRACK OF THE SFC LOW AND TIMING. DUE TO THESE...I WILL JUST FOLLOW
THE GFS GUID FOR HIGH TEMPS WED.
BY WED NIGHT...ALL GUID AGREES THAT THE MAIN ASCENT AREA WILL BE
PUSHING OUT OF THE CWA AND THEY ALL STILL HOLD ONTO A FEW HUNDRETHS
OF LIGHT PRECIP. I WOULD LIKE TO REMOVE ALL POPS/WX. HOWEVER...THIS
IS THE PERFECT RECIPE FOR A FEW SITES GETTING .01-.02 AS STRONG CAA
DEVELOPS AND LOW LEVEL MOISTURE REMAINS RATHER DEEP WITH DECENT RH
VALUES STILL UP TO 700MB. DUE TO THIS...I WILL KEEP THE GUID POPS OF
30-40% AND MENTION DRIZZLE/LIGHT RAIN FOR WED EVENING. AS FOR
TEMPS...GUID HAS TRENDED COOLER AND I MADE SOME MINOR ADJ AND
LOWERED SOME AREAS AS RAW GUID AND BUFR SOUNDINGS WERE A GOOD BIT
COOLER THU MORNING.
FOR THU-FRI NIGHT...MODELS ARE SHOWING A COLDER SOLUTION AND THINGS
LOOK TO GET QUITE CHILLY FOR THE END OF THE WEEK INTO THE WEEKEND.
THIS WILL BE A RESULT OF THE DEEP CYCLONE WHICH WILL CARVE OUT A
SUBSTANTIAL TROUGH OVER THE MID SECTION OF THE CONUS. TO PUT THIS
TROUGH INTO PERSPECTIVE...MID LEVEL HEIGHT ANOMALIES WILL RUN SOME 3
TO 4 STANDARD DEV BELOW CLIMO VALUES. ADDITIONALLY...850MB TEMPS
WILL ALSO BE SOME 3 TO 4 NEG STANDARD DEV WITH ACTUAL 850MB TEMPS
RANGING FROM (-2C TO -8C). ALL THAT SHOULD RESULT IN TEMPS SOME
10-15 DEGREES BELOW NORMAL VALUES FOR EARLY DEC...IF NOT A BIT
COLDER. THIS IS ALL SUPPORTED BY THE EURO AS WELL AS THE GFS
ENSEMBLE. AS A RESULT...I HAVE GONE QUITE A BIT COLDER THAN THE PREV
FORECAST AND SOMEWHAT COLDER THAN THE LATEST GFS GUID WHICH ITSELF
WAS COLDER.
LASTLY...THE GFS WAS WANTING TO RETURN MOISTURE BACK LATE SAT NIGHT
INTO SUN. I AM NOT READY TO JUMP ON THAT AS THE EURO IS DRY AS IT
KEEPS THE SFC HIGH OVER THE REGION ANOTHER 24-36 HRS. THE GFS
ENSEMBLE IS MORE IN LINE WITH THE EURO AND AS A RESULT...I HAVE CUT
POPS AND LOWERED TEMPS FOR THAT TIME FRAME. /CME/
&&
.AVIATION...THE COLD FRONT WILL CONTINUE TO MAKE ITS WAY ACROSS SERN
ZONES THROUGH THE LATE MORNING...EXITING THE REGION BY EARLY
AFTERNOON. A FEW RUMBLES OF THUNDER WILL BE POSSIBLE OVER EXTREME
SERN ZONES THROUGH NOON WHEN THE HEAVIER BAND OF RAINFALL WILL EXIT
MOST AREAS. POCKETS OF LIGHT RAIN WILL CONTINUE BEHIND THE FRONT
OVER CENTRAL AND SRN AREAS...LOWERING CIGS BELOW 1K FEET AND
OCCASIONALLY LOWERING VSBYS 1-3 MILES IN RAIN AND FOG. RAINFALL WILL
GRADUALLY END FROM THE NW BEFORE EXITING SE MS IN THE EARLY
AFTERNOON WITH THE FRONT. GUSTY NW WIND CAN BE EXPECTED BEHIND THE
COLD FRONT GENERALLY FROM 10 TO 15 KTS WITH POSSIBLE GUSTS TO 20
KTS. CIGS WILL GRADUALLY IMPROVE FROM THE NW THIS AFTERNOON WITH
SCT-BKN DECKS FROM 2-4K FEET AND OVC DECKS ABOVE 5K FEET. WINDS WILL
SUBSIDE LATE IN THE DAY AS WELL. GENERALLY VFR CONDITIONS SHOULD
RETURN FOR OVERNIGHT MONDAY NIGHT. AREAS OF FOG WILL DEVELOP
TONIGHT. PATCHES OF DENSE FOG CAN NOT BE RULED OUT BUT VSBYS SHOULD
REMAIN ABOVE 3 MILES OVERNIGHT. /28/03/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 59 38 57 47 / 30 3 30 86
MERIDIAN 59 35 58 49 / 54 5 32 90
VICKSBURG 55 40 56 46 / 17 3 30 84
HATTIESBURG 65 40 57 52 / 90 11 62 88
NATCHEZ 60 41 56 47 / 29 8 62 90
GREENVILLE 52 38 55 44 / 4 3 13 79
GREENWOOD 52 35 58 44 / 11 3 13 80
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR MSZ026-030-
031-043-049-052.
LA...LAKE WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR LAZ009.
AR...LAKE WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR ARZ075.
&&
$$
50/03
