961 
FXUS64 KJAN 210229
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
825 PM CST FRI NOV 20 2009

.UPDATE...LATEST SATELLITE IMAGERY SHOWED A SHORT WAVE OVER THE SOUTHERN
PLAINS WITH AN ASSOCIATED SURFACE WAVE OVER THE NORTHWEST GULF OF 
MEXICO. THE ARKLAMISS WAS WELL NORTH IN THE COOLER AND STABLE 
AIRMASS. AREA RADARS WERE PICKING UP SOME PATCHY VERY LIGHT RAIN
TO THE WEST AND SOUTH OF THE REGION. STILL EXPECT SOME VERY LIGHT
RAIN TO IMPACT THE REGION LATER TONIGHT FROM THE SOUTH.  THIS WILL
NOT BE A SHOWERY TYPE SYSTEM FOR THIS REGION IN THIS COOL STABLE 
AIRMASS. SO FOLLOWING RADAR TRENDS OF DEVELOPMENT. HAVE PUSHED BACK THE
FIRST WAVE OF VERY LIGHT RAIN IN THE SOUTH UNTIL NEAR MIDNIGHT...THEN PUT
PULLED BACK RAIN CHANCES FOR THE REST OF THE NIGHT. GOING FROM A SLIGHT
CHANCE ALONG AND NORTH OF INTERSTATE 20 TO CHANCE POPS SOUTH. ALSO DELAYED
HIGH POPS UNTIL THE LATER HALF OF SATURDAY MORNING FOR THE REGION.
CURRENT LOWS IN THE 40S LOOKS TO BE ON TRACK. WILL KEEP THE BEST 
CHANCE POPS ACROSS THE SOUTH HALF WHERE THE LIGHT RAIN WILL 
ORIGINATE FROM./17/ 




.PREV DISCUSSION...352 PM CST FRI NOV 20 2009

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...PRIMARY CONCERN THIS 
PERIOD REVOLVES AROUND WIND SPEEDS AND PRECIP ACCUMULATIONS THROUGH 
SUNDAY AFTERNOON.

THIN UPPER LEVEL CLOUD COVER IS ON THE INCREASE THIS AFTERNOON AHEAD 
OF A S/WV TROUGH CROSSING THE RIO GRANDE VALLEY. THIS S/WV WILL 
DEEPEN AN AREA OF SFC LOW PRESSURE LOCATED OVER THE WESTERN GULF OF 
MEXICO AS IT ADVANCES EAST THROUGH THE NIGHT TONIGHT. AS A 
RESULT...PRECIP CHANCES WILL INCREASE FROM THE SW OVERNIGHT AS THE 
SFC LOW TRANSLATES TOWARD THE LA COAST. SOME DIFFERENCES EMERGE 
AMONG THE NWP GUIDANCE AT THIS POINT CALLING THE EVENTUAL 
PROGRESSION OF THIS SYSTEM INTO QUESTION. THE GFS REMAINS ON THE 
FAST EDGE OF THE ENVELOPE THROUGH THE WEEKEND AND MAINTAINS A WEAKER 
MORE PERSISTENT SFC LOW RIGHT ALONG THE COAST. THE ECMWF DEVELOPS A 
MUCH DEEPER SURFACE LOW WITH SOME UNUSUAL BULLS EYES IN THE PRECIP 
FIELDS LIKELY ASSOCIATED WITH GRID SCALE FEEDBACK PROBLEMS. SREF 
CAME IN MORE WITH THE GFS IN TERMS OF SURFACE LOW TRACK ALTHOUGH WAS 
NOT AS FAST PUSHING THE LOW INTO THE AL COAST. FOR THIS 
PACKAGE...LEANED MORE ON THE SREF IN TERMS OF OVERALL SPEED OF THE 
SYSTEM WITH A GFS/ECMWF/SREF BLEND FOR THE TRACK. THIS DID MEAN SOME 
DIVERGENCE FROM THE 12Z MAV GUIDANCE POPS...PRIMARILY ON SATURDAY 
AFTERNOON/NIGHT WHERE ALL AREAS GOT BUMPED ABOVE GUIDANCE. GFS 
REALLY KEEPS THE RAIN ISOLATED SE OF THE NATCHEZ TRACE. THIS IS NOT 
SUPPORTED BY THE ECMWF OR SREF WHICH BOTH SHOW MEASURABLE RAINFALL 
ACROSS THE AREA DURING THESE TIMES. DO FEEL THE HEAVIEST RAINFALL 
WILL BE SE OF THE TRACE...BUT NOT LIMITED TO THIS AREA.

AT THIS POINT...HEAVY RAINFALL WARRANTING ANY FLOOD PRODUCTS IS NOT 
NEEDED AS PW VALUES STRUGGLE TO CLIMB ABOVE 1.25 IN...EVEN ACROSS 
SOUTHEASTERN AREAS. RAINFALL TOTALS ON THE ORDER OF 0.50 TO 1 INCH 
ARE PROBABLE ACROSS THE CWA WITH THE HIGHEST AMOUNTS SE OF THE 
TRACE. THAT BEING SAID...LOCALIZED AREAS RECEIVING A LITTLE OVER AN 
INCH IS NOT OUT OF THE QUESTION. EASTERLY WINDS ARE STILL EXPECTED 
TO INCREASE TOMORROW AFTERNOON AS THE SFC LOW NEARS. STRONGEST WINDS 
WILL BE LIMITED TO AREAS S AND E...AND WILL GO AHEAD AND ISSUE A 
LAKE WIND ADVISORY FOR THE ROSS BARNETT RES AND LAKE OKATIBBEE 
STARTING LATE TOMORROW MORNING. THIS IS A MARGINAL EVENT CONSIDERING 
THE SYNOPTIC SET-UP AND WILL BE WATCHED CLOSELY FOR POSSIBLE 
TEMPORAL AND AREAL CHANGES AS THIS SYSTEM EVOLVES. IN ADDITION... 
WENT AHEAD AND LEFT A SLIGHT CHANCE OF A THUNDERSTORM OR TWO 
DEVELOPING ACROSS SERN AREAS TOMORROW AFTERNOON INTO THE EARLY
EVENING. GFS HINTS AT 100-200 J/KG OF MUCAPE SLIDING ACROSS THE AREA
AS THE LOW MAKES ITS CLOSEST POINT OF APPROACH AND COUPLED WITH DEEP
LAYER LIFT IN PLACE AHEAD OF THE UPPER LEVEL S/WV...FEEL THE CHANCES
ARE NON-ZERO.

PRECIP WILL CONTINUE INTO THE OVERNIGHT HOURS SAT NIGHT BEFORE 
BEGINNING TO TAPER OFF FROM W TO E LATE SUN MORNING INTO THE 
AFTERNOON AS THE BEST LIFT AND LOW LEVEL MOISTURE FEED MOVE INTO AL. 
S/WV RIDGING AND SFC HIGH PRESSURE MOVE INTO THE ARKLAMISS LATE 
SUNDAY AND SHOULD PROVIDE SOME CLOUD CLEARING AS A RESULT. WINDS 
LOOK TO GO VERY LIGHT OR EVEN CALM MONDAY NIGHT...AND CONSIDERING 
THE LACK OF A COOL/DRY PUSH AND RESIDUAL SFC MOISTURE FROM THE 
RAINS, ADDED SOME PATCHY FOG FOR MONDAY MORNING. 

MAV TEMPS LOOKED GOOD EXCEPT FOR SUN AFTERNOON HIGHS WHERE GFS 
APPEARED TOO WARM CONSIDERING THE LINGERING RAIN AND CLOUD COVER. 
WENT AHEAD AND LOWERED TEMPS A DEGREE OR TWO AREAWIDE AT THAT TIME. 
/BK/

.PREVIOUS LONG TERM...FOR MID- TO LATE-WEEK...A SERIES OF SHORTWAVE
TROUGHS AND ASSOCIATED SURFACE COLD FRONTS WILL DIVE SOUTHEASTWARD
ACROSS THE MIDWEST AND OHIO VALLEY REGIONS...CARVING OUT A MEAN
TROUGH OVER THE EASTERN CONUS. NWP MODEL GUIDANCE HAS COME INTO
BETTER AGREEMENT IN DROPPING ONE OF THESE COLD FRONTS SOUTHWARD
ACROSS THE REGION ON TUESDAY. THE FRONT WILL BECOME MORE SHALLOW AS
IT APPROACHES AND MOVES ACROSS THE ARKLAMISS AS THE ASSOCIATED UPPER
TROUGH AND STRONGER DEEP-LAYER SYNOPTIC-SCALE ASCENT REMAIN WELL
NORTH OF THE AREA. NEVERTHELESS... MOISTURE POOLING ALONG THE
BOUNDARY RESULTING IN PWATS NEAR ONE INCH WILL BE SUFFICIENT FOR
ISOLATED LIGHT SHOWERS ALONG OR JUST BEHIND THE SURFACE FRONT...ALONG
WITH AN INCREASE IN CLOUDS. POPS WERE LOWERED FROM MEX GUIDANCE TO
SLIGHT CHANCE FOR LATE MONDAY NIGHT OVER NORTHWESTERN AREAS...AS THE
OPERATIONAL GFS APPEARS TO MOVE THE FRONT TOO QUICKLY TO THE SOUTH
RELATIVE TO GFS ENSEMBLE MEMBERS AND ECMWF...AND WITH WEAK UPPER
SUPPORT OVER THE ARKLAMISS. BEHIND THE FRONT...WINDS WILL BECOME
NORTHERLY AND ADVECT COOLER AIR ACROSS THE REGION...WITH HIGH
PRESSURE BUILDING IN THE WAKE OF THE FRONT.

FOR WEDNESDAY NIGHT OR THURSDAY...A REINFORCING COLD FRONT WILL 
QUICKLY SURGE SOUTH ACROSS THE REGION...THOUGH DEEP-LAYER DRY AIR 
WILL BE IN PLACE /PWATS OF ONLY 0.3 INCHES/ PRECLUDING PRECIP CHANCES 
WITH THIS FRONT. THE ONLY IMPACTS TO SENSIBLE WEATHER WITH THE FRONT 
WILL BE AN INCREASE IN NORTH WINDS ALONG WITH THE POTENTIAL FOR MUCH 
COOLER CONDITIONS LATE IN THE WEEK. THE CORE OF THE COLD AIRMASS 
WILL REMAIN NORTH OF THE CWA...THOUGH GFS AND ECMWF INDICATE 850-MB 
TEMPS FALLING TO 3C ACROSS NORTHERN AREAS BEHIND THE FRONT... 
POTENTIALLY SUPPORTING TEMPERATURES SEVERAL DEGREES BELOW SEASONAL 
AVERAGES. HOWEVER...SIGNIFICANT DIFFERENCES BETWEEN GFS AND ECMWF IN 
THE CHARACTERISTICS OF THE ASSOCIATED UPPER TROUGH SUGGEST LOW 
CONFIDENCE IN THE TIMING OF THE CORRESPONDING SURFACE FRONT...AS 
WELL AS HOW COLD TEMPERATURES GET. /COHEN/


&&

.AVIATION...A LOW PRESSURE SYSTEM APPROACHING FROM THE WEST KEPT
THE CIRRUS SHIELD OVER THE REGION FOR THIS EVENING. THIS CLOUD DECK 
WILL GRADUALLY LOWER TONIGHT...BUT CEILINGS SHOULD REMAIN ABOVE 8000 
FT THROUGH THE NIGHT GIVEN THE VERY DRY LOW LEVEL AIR IN PLACE. AS 
RAIN DEVELOPS OVER THE AREA NORTH OF A WARM FRONT...CEILINGS AND 
VISIBILITY WILL DETERIORATE...ESPECIALLY AT JAN/HBG/MEI WHERE IFR 
CEILINGS MAY BECOME PREVALENT PRIOR TO NOON SATURDAY. ALL SITES 
COULD EXPERIENCE MVFR/IFR RESTRICTIONS DUE TO LOWER CEILINGS AND 
RAIN AS WE GO INTO SATURDAY AFTN/NIGHT. GREATER INSTABILITY IN THE 
MEI/HBG AREA WILL SUPPORT A FEW TSTMS FROM SATURDAY AFTERNOON INTO 
SATURDAY EVENING. /17/


&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       46  58  45  61 /  22  89  63  13 
MERIDIAN      44  57  45  61 /  22  86  80  24 
VICKSBURG     46  58  45  62 /  22  89  58   9 
HATTIESBURG   48  58  49  63 /  49  90  56  12 
NATCHEZ       47  57  44  63 /  47  90  45   5 
GREENVILLE    46  60  44  63 /  18  80  69  13 
GREENWOOD     45  60  45  62 /  13  83  80  19 

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY FROM 9 AM SATURDAY TO MIDNIGHT CST SATURDAY 
     NIGHT FOR MSZ043-049-052.

LA...NONE.
AR...NONE.
&&

$$

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