FXUS64 KJAN 251604 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1002 AM CST WED NOV 25 2009
.UPDATE...LATEST SATELLITE IMAGERY SHOWS A COOL UPPER TROUGH OVER
THE REGION ON THIS THANKSGIVING EVE. SURFACE HIGH PRESSURE CENTERED
OVER THE SOUTHERN PLAINS WAS PROVIDING CLEAR SKIES TO THE REGION.
TEMPERATURES LATE THIS MORNING WERE IN THE 50S. MORNING 12Z SOUNDING
SHOWS THAT TEMPS WILL NOT RISE MUCH ABOVE 60 DEGREES FOR TODAY. SO
CURRENT HIGHS FROM NEAR 60 NORTH TO THE MIDDLE 60S SOUTHEAST LOOKS
TO BE ON TRACK. WINDS WILL AVERAGE FROM THE NORTHWEST AT 5 TO 10
MPH. SO WILL MAKE NO CHANGES TO GRIDS OR ZONES./17/
&&
.PREV DISCUSSION... /ISSUED 431 AM CST WED NOV 25 2009/
SHORT TERM...TODAY THROUGH THURSDAY NIGHT...UPPER VORT TROUGH
CROSSING ERN IL HEADING INTO THE GREAT LAKES AS A SECONDARY AXIS
DRAGS EWD ACROSS THE CENTRAL GULF OF MEXICO. MEANWHILE...THE
ASSOCIATED DRY SURFACE FRONT WITH THESE SYSTEMS ALONG I-59 PUSHES
SEWD THROUGH THE GULF STATES AS HIGH PRESSURE(1026MB) IN CENTRAL TX
DRIFTS SWD. A THIRD PIECE OF UPPER LEVEL VORTICITY DIVING THROUGH ND
ENDS UP IN ERN IA BY TONIGHT BEFORE IT SWEEPS THROUGH THE OH VALLEY
ON THANKSGIVING DAY. THIS TROUGH BRINGS REINFORCING SURFACE HIGH
PRESSURE FROM THE CENTRAL ROCKIES SEWD INTO THE SRN PLAINS TO
INCREASE OUR GRADIENT NWLY WINDS FOR THE HOLIDAY.
CURRENTLY...PATCHY CLOUD LAYERS 2-4K FEET AND HIGHER WILL GRADUALLY
CLEAR FROM WEST TO EAST AT ABOUT 25KTS THIS MORNING WHILE COOLER
DRIER AIR BEGINS TO WORK IT'S WAY SOUTHEAST INTO THE CWFA. THERE WAS
SOME SHALLOW PATCHY FOG NOTED IN NERN LA MAINLY NEAR RIVERS/LAKES.
OTHERWISE...MOST OF THE CLOUDS SHOULD BE E OF OUR REGION BY 15Z.
TEMPERATURES HAVE SETTLED INTO THE U30S IN SERN AR TO L50S SERN MS.
HIGH TEMPS THIS AFTERNOON IN POST-FRONTAL NWLY FLOW WILL AVERAGE
ABOUT 5-8F COOLER THAN THAN TUESDAY WITH FULL SUNSHINE. MODERATE CAA
TODAY WILL RELAX TONIGHT FOR PARTIAL RADIATIONAL COOLING AND LOWS
34-39F. STRONGER COOLING ARRIVES EARLY THURSDAY AND HOLDS READINGS
DOWN TO BETWEEN 55-60F AS THE REINFORCING TROUGH RIDES SEWD THROUGH
THE TN/OH VALLEYS. BY THURSDAY NIGHT...THE TX SURFACE HIGH WILL
BUILD EWD ALONG THE GULF COAST AND WE SHOULD END UP WITH GOOD
RADIATIONAL COOLING CONDITIONS. SREF SURFACE DEWPOINTS DROP TO
BETWEEN 29-32F THURSDAY EVENING AND THIS DRY AIR WILL EASILY SUPPORT
TEMPS DIPPING TO THE 32-36F RANGE WITH CONSIDERABLE FROST OVER AT
LEAST CENTRAL AND ERN MS. SOME FREEZE WARNINGS COULD BE EMPLOYED BUT
A WIDESPREAD FREEZE REMAINS DOUBTFUL./40/
LONG TERM...FRIDAY THROUGH WEDNESDAY...GFS/ECMWF/GEFS IN GOOD
AGREEMENT TO START OUT THIS PERIOD SHOWING A S/WV TRANSITING THE
GREAT LAKES REGION AND RIDGING OVER THE WESTERN PLAINS. THIS WILL
PLACE THE ARKLAMISS IN DRY NORTHWESTERLY FLOW ALOFT ALLOWING CLEAR
SKIES AND SEASONABLE HIGH TEMPS THROUGH SATURDAY. COOL TEMPS CAN BE
EXPECTED SAT MORNING DUE TO EFFICIENT RADIATIONAL COOLING ASSOCIATED
WITH CLEAR SKIES AND LIGHT WINDS EXPECTED...COUPLED WITH THE COLD
AIRMASS THAT WILL BE IN PLACE. LOW TO MID 30S EAST OF I-55 LOOK VERY
POSSIBLE. USUALLY THIS TIME OF YEAR A FREEZE WILL HAVE OCCURRED
MAKING MENTION OF FROST IN THE FORECAST UNNECESSARY HOWEVER
CONSIDERING WE HAVEN'T SEEN ONE YET THIS YEAR WILL GO AHEAD AND
INCLUDE FROST EAST OF I-55 SAT MORNING.
A LOW CONFIDENCE FORECAST ENSUES SUNDAY THROUGH WEDNESDAY AS LONG
RANGE MODEL GUIDANCE CONTINUES TO SHOW CONSIDERABLE SOLUTION SPREAD.
A S/WV CROSSING THE DESERT SOUTHWEST EARLY SUNDAY WILL MOVE INTO THE
SOUTHERN PLAINS BY MONDAY WITH AN ATTENDANT SURFACE LOW/COLD FRONT
INTENSIFYING OVER EASTERN TX MONDAY AFTERNOON. MODELS DIVERGE FROM
THERE AS TO THE PROGRESSION OF THIS SYSTEM WITH THE GFS DEVELOPING A
DEEP, CLOSED UPPER LEVEL CIRCULATION BY LATE MONDAY WHILE THE ECMWF
MAINTAINS AN OPEN WAVE THROUGH THIS TIME. THE ECMWF DOES EVENTUALLY
CLOSE OFF A CIRCULATION BY TUESDAY AFTERNOON ALTHOUGH NOT NEARLY AS
DEEP AS THE GFS. IMPLICATIONS TO THE FORECAST ARE SIMILAR THROUGH
MONDAY WITH RAIN CHANCES INCREASING FROM WEST TO EAST SUNDAY AS THE
COLD FRONT APPROACHES THE REGION. THE FRONT WILL PASS OVER THE
ARKLAMISS MONDAY MOVING INTO AL SOMETIME IN THE LATE
AFTERNOON/EVENING. SOUTHERLY FLOW AHEAD OF THE FRONT WILL GRADUALLY
INCREASE GULF MOISTURE ACROSS THE REGION BEFORE THE FRONT
PASSES...WITH GFS SHOWING AN AREA OF 100-300J/KG MUCAPE DEVELOPING
ALONG AREAS SOUTH OF I-20. A 100KT+ JET OVER THE CWA WILL PROVIDE
ADDITIONAL LIFT SUPPORT AND WILL KEEP THE SLIGHT CHANCE OF THUNDER
GOING ACROSS SOUTHERN AREAS AS THE FRONT PASSES. FROM HERE GUIDANCE
VARIATIONS SPELL GREAT UNCERTAINTY IN THE FORECAST. THE SLOWER GFS
HANGS ITS DEEP, CLOSED CIRCULATION IN THE TN VALLEY THROUGH WED
MORNING...AND IF THIS PANS OUT...WOULD MEAN A GREATER CHANCE OF
PRECIP ACROSS AREAS NORTH OF I-20 AS LOW LEVEL MOISTURE WRAPS AROUND
THE LOW. THE ECMWF ON THE OTHER HAND SLIDES A MUCH WEAKER, MORE
PROGRESSIVE S/WV INTO THE TN VALLEY BY WED MORNING KEEPING PRECIP
CHANCES LIMITED TO AREAS EAST OF OUR REGION. TRIED TO GO WITH A
BLEND IN TERMS OF THE FORECAST AT THIS TIME WITH MEN POPS LOOKING
REASONABLE AS THEY KEEP A SLIGHT CHANCE OF PRECIP ACROSS NORTHERN
ZONES WITH DRY CONDITIONS ELSEWHERE.
MEX TEMPS GENERALLY ACCEPTED ALTHOUGH SOME LOWERING TOWARD MEN
GUIDANCE WAS NEEDED OVER THE WEEKEND WITH BOTH HIGH AND LOW TEMPS.
/BK/
&&
.AVIATION...VFR CONDITIONS UNDER MAINLY CLEAR SKIES WILL PREVAIL
ACROSS THE ARKLAMISS THROUGH THE PERIOD. THE WINDS WILL REMAIN LIGHT
OUT OF THE NORTHWEST TO NORTH BECOMING LIGHT AND VARIABLE OVERNIGHT.
ANOTHER COLD FRONT WILL SWEEP ACROSS THE AREA ON THURSDAY BRINGING
MAINLY ANOTHER REINFORCING SHOT OF COOL AIR./15/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 62 37 58 34 / 1 1 0 0
MERIDIAN 64 35 58 33 / 3 1 0 0
VICKSBURG 61 37 59 35 / 0 1 0 0
HATTIESBURG 66 38 61 32 / 1 1 0 0
NATCHEZ 61 36 60 34 / 0 1 0 0
GREENVILLE 60 38 56 35 / 0 1 0 0
GREENWOOD 62 36 57 34 / 2 1 0 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
17/15
