745
FXUS64 KJAN 220929
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
329 AM CST SUN NOV 22 2009
SHORT TERM...TODAY THROUGH MONDAY NIGHT
SURFACE LOW PRESSURE(1009MB)
RESPONSIBLE FOR THE RECENT RAINFALL OVER THE CWA IS NOW CENTERED OVER
SOUTHEAST LOUISIANA. THE ASSOCIATED MID/UPPER-LEVEL SHORTWAVE TROUGH
IS FORECAST TO DECOUPLE FROM THE LOW-LEVEL CIRCULATION TODAY AS THE
SHORTWAVE CONTRACTS AND BECOMES ABSORBED WITHIN THE SOUTHERN JET
STREAM. AS SUCH...THE LOW-LEVEL CIRCULATION WILL LINGER OVER THE CWA
THROUGH AT LEAST MONDAY WHILE IT BECOMES INCREASINGLY ILL-DEFINED.
NEVERTHELESS... MOISTURE EMBEDDED WITHIN THIS CIRCULATION WILL
MAINTAIN RAIN CHANCES OVER THE EASTERN CWA TODAY. RECENT RADAR TRENDS
INDICATE THAT NORTHWARD-MOVING SCATTERED SHOWERS ARE CURRENTLY
CONFINED TO THE NORTHEASTERN HALF OF THE CWA...AS SUFFICIENT MID-
LEVEL DRY AIR HAS WRAPPED INTO THE SOUTHWESTERN SEMI-CIRCLE OF THE
LOW CIRCULATION TO INHIBIT PRECIP ELSEWHERE. NEVERTHELESS...ENOUGH
LOW-LEVEL MOISTURE IS PRESENT FOR CONTINUED PRECIP CHANCES ACROSS THE
EAST THROUGH THE DAY...THOUGH POPS HAVE BEEN DROPPED BELOW MAV
GUIDANCE ACROSS THE ENTIRE REGION. THIS DECREASE IS SUPPORTED BY
DEEP-LAYER SUBSIDENCE WORKING INTO THE AREA BEHIND THE SHORTWAVE
TROUGH AXIS...ALONG WITH LOCAL WRF ENSEMBLE GUIDANCE SUGGESTING THAT
PRECIP WILL MAINLY BE ISOLATED TO SCATTERED ACROSS THE EASTERN CWA.
FORECAST TEMPERATURES FOLLOW MAV GUIDANCE CLOSELY FOR TODAY.
FOR TONIGHT...FLOW ALOFT BECOMES NEARLY ZONAL WITH MID/UPPER-LEVEL
DRY AIR PREVALENT AREAWIDE. HOWEVER...NWP MODEL GUIDANCE IS
CONSISTENTLY GENERATING RH VALUES OVER 80 PERCENT BELOW THE H85 LEVEL
TRAPPED WITHIN THE REMNANT 925-850MB CYCLONIC CIRCULATION. THIS WILL
BE SUPPORTIVE OF LOW-LEVEL CLOUDS PERSISTING THROUGH THE NIGHT...
KEEPING TEMPERATURES FROM FALLING BELOW THE MID TO UPPER 40S. AN
ISOLATED SHOWER WILL BE POSSIBLE OVER THE FAR NORTHEAST PORTION OF
THE CWA THIS EVENING...THOUGH POPS HAVE BEEN KEPT IN THE SLIGHT
CHANCE CATEGORY IN THE ABSENCE OF ADDITIONAL FORCING. FOR THE FAR
SOUTHERN PORTIONS OF THE CWA...SUFFICIENT LOW-LEVEL DRYING IS
EXPECTED TO OCCUR TONIGHT NEAR A WEAK SURFACE HIGH BUILDING OVER
SOUTHEAST LOUISIANA FOR SKIES TO BECOME PARTLY CLOUDY. THIS COULD
ALLOW PATCHY FOG TO FORM LATE TONIGHT...THOUGH THE AREA OF PATCHY FOG
HAS BEEN GENERALLY RESTRICTED TO LOCATIONS ALONG AND SOUTH OF HIGHWAY
84. THIS REDUCTION IN FOG COVERAGE IS SUPPORTED BY LOWER PROBABILITIES
OF VISIBILITY RESTRICTIONS PER SREF GUIDANCE AND GREATER CLOUD
COVERAGE FURTHER NORTH.
FOR MONDAY...LINGERING LOW-LEVEL MOISTURE WILL KEEP SKIES MOSTLY
CLOUDY ACROSS THE NORTHEAST...WITH SKIES BECOMING PARTLY CLOUDY IN
THE SOUTHWEST. TEMPS WERE DECREASED A COUPLE DEGREES BELOW MAV
GUIDANCE ACROSS THE NORTHEAST WHERE THE CLOUDS PERSIST...RESULTING
IN HIGHS FROM THE MID TO UPPER 60S AREAWIDE. ADDITIONAL CLEARING IS
ANTICIPATED MONDAY NIGHT...WHICH COULD INCREASE THE RISK FOR FOG
DEVELOPMENT. HOWEVER...GIVEN POTENTIAL FOR CLOUDS TO INCREASE AHEAD
OF AN APPROACHING DISTURBANCE...CONFIDENCE IN FOG POTENTIAL IS TOO
LOW FOR MENTION IN THE FORECAST AT THIS TIME. /COHEN/
LONG TERM
A LONGWAVE PATTERN ADJUSTMENT STILL APPEARING LIKELY FOR
THE COMING HOLIDAY WEEK AS A DIGGING UPPER TROUGH IN THE PACIFIC NW
MOVES INTO THE GREAT LAKES/OH VALLEY BY TUESDAY AND STARTS THE
PROCESS OF TROUGHING IN THE ERN CONUS WITH RIDGING IN THE W. OUR
MAIN WEATHER FEATURE APPEARS TO BE THE FRONTAL SYSTEM PASSING
THROUGH THE LOWER MS VALLEY TUESDAY AND TUESDAY EVENING WITH 20-30
PERCENT RAINFALL CHANCES. THIS BOUNDARY IS FOLLOWED AT LEAST ONE
STRONGER REINFORCING TROUGH WEDNESDAY NIGHT WITH A SECOND ONE
POSSIBLE NEXT SUNDAY TO KEEP US COOLER THAN CLIMATOLOGY.
THE DETAILS WITH THE FRONTAL PASSAGE TUESDAY HAVE REMAINED RATHER
CONSISTENT IN THE LATEST SUITE OF MODELS. PWATS PROGGED TO RECOVER
TO BETWEEN 0.8-1.0 INCHES WITH MINIMAL INSTABILITY ALONG THE FRONT SO
WILL KEEP MENTION TO MOSTLY A BAND OF LIGHT/MODERATE RAIN. THE ECMWF
AND GFS IN LOCK STEP WITH QPFS LESS THAN ONE TENTH OF AN INCH BEFORE
MIDNIGHT TUESDAY NIGHT FOLLOWED BY DRYING TREND FOR WEDNESDAY. AFTER
THAT...A QUICK REINFORCING DRY TROUGH SWEEPS THROUGH THE AREA
WITH A FEW CLOUDS FOR WEDNESDAY NIGHT. THIS SETS UP A CHILLY CAA
CELEBRATION FOR THANKSGIVING DAY WITH MOST LOWS IN THE U30S AND HIGHS
IN THE M-U50S.
A 1025+MB SURFACE HIGH OVER SERN TX FRIDAY MOVES ALONG THE GULF COAST
FOR FRIDAY NIGHT AND SATURDAY(1021MB) WITH SOME WEAK WAA RETURN FOR
SATURDAY NIGHT/SUNDAY. A FLATTENING UPPER ZONAL FLOW PATTERN RESUMES
NEXT WEEKEND AND THE NEXT FRONT COULD HOLD OFF UNTIL THE LAST DAY OF
THE MONTH. WILL HAVE TO MONITOR THIS TIME FRAME AS THE ECMWF AGAIN A
LITTLE MORE ROBUST WITH SOME SRN BRANCH ENERGY COMING OUT OF MEXICO
AND WETTER MASS FIELDS/HIGHER RAIN CHANCES. NO MAJOR ADJUSTMENTS TO
THE MEX MOS AS OPERATIONAL RUN-TO-RUN CONSISTENCY HOLDING UP WELL./40/
AVIATION
LIGHT RAIN WILL CONTINUE OVER EASTERN MISSISSIPPI TODAY AS
SURFACE LOW PRESSURE PASSES BY TO THE SOUTH OF THE REGION. LOW-LEVEL
MOISTURE WILL LINGER ACROSS THE AREA THROUGH MONDAY...WITH LOW-LEVEL
CLOUDS RESULTING IN MVFR TO OCCASIONALLY IFR CEILINGS THROUGH MONDAY
MORNING AREAWIDE. THE GREATEST CHANCE FOR IFR CEILINGS WILL BE
TONIGHT. ADDITIONALLY...PATCHY FOG RESULTING IN MVFR VISIBILITIES
WILL BE POSSIBLE LATE TONIGHT AND EARLY MONDAY MORNING ACROSS FAR
SOUTHERN MISSISSIPPI...WITH KHBG HAVING THE GREATEST CHANCE OF
EXPERIENCING THESE CONDITIONS. NORTHEAST WINDS AT 4 TO 8 KT TODAY
WILL BECOME LIGHT TONIGHT. CONDITIONS ARE EXPECTED TO TREND TOWARD
VFR FROM SOUTHWEST TO NORTHEAST ON MONDAY. /COHEN/
PRELIMINARY POINT TEMPS/POPS
JACKSON 59 47 64 46 / 13 13 5 9
MERIDIAN 59 48 65 41 / 40 17 5 9
VICKSBURG 61 46 67 45 / 13 11 4 10
HATTIESBURG 62 48 66 43 / 21 8 5 7
NATCHEZ 61 45 68 48 / 12 8 4 9
GREENVILLE 59 48 65 47 / 14 13 6 13
GREENWOOD 57 49 64 46 / 26 14 7 10
JAN WATCHES/WARNINGS/ADVISORIES
MS...NONE.
LA...NONE.
AR...NONE.
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