FXUS64 KJAN 151647
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
1047 AM CST TUE DEC 15 2009
.DISCUSSION...FLASH FLOOD WATCH CONTINUES AS PRECIP CONTINUES IN
THOSE AREAS. THE GOOD NEWS IS THAT THE EFFECTS OF DRIER AIR
FILTERING SWD HAVE RESULTED IN DRIER CONDITIONS DEVELOPING FROM THE
NORTHWEST AND WEAKENING CONVECTION OVER SRN ZONES. THE LATEST RUC
INDICATES ANOTHER WAVE LIFTING INTO SERN ZONES BEFORE THE DRIER AIR
MASS OVERRUNS SRN ZONES. WITH MANY LOCATIONS IN THE FLASH FLOOD
WATCH AREA RIGHT AT FLOODING CONDITIONS...THE WATCH WILL BE ALLOWED
TO CONTINUE. ADJUSTED HOURLY TEMPS SLIGHTLY TO REFLECT LATEST OBS.
HIGHS FOR THE DAY HAVE ALREADY BEEN REACHED AT MANY LOCATIONS AS
COLDER AIR STREAMS SWD INTO THE REGION TO PRODUCE FALLING TEMPS
THROUGH MUCH OF THE DAY. GUSTY NW WINDS CAN BE EXPECTED THROUGH THE
DAY AND THE LAKE WIND ADVISORY FOR AREA LAKES WILL CONTINUE FOR THIS
AFTERNOON.
&&
.PREV DISCUSSION...TODAY THROUGH WEDNESDAY...COLD FRONT EXTENDS
ACROSS THE CENTRAL PORTIONS OF THE AREA THIS MORNING AND WILL WORKS
ITS WAY TO THE COAST BY LUNCHTIME. ABUNDANT MOISTURE STILL EXISTS
ALONG AND BEHIND THE BOUNDARY WITH PWATS ABOVE 1.6 INCHES FOR AREAS
ALONG AND SOUTH OF I-20. THIS COMBINED WITH A STRONG SHORT WAVE THAT
WILL MOVE THROUGH THE AREA THIS MORNING WILL KICK OFF ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS. THE SHOWERS ARE ALREADY DEVELOPING TO
OUR WEST AND WILL MOVE ACROSS THE CENTRAL AND SOUTHERN PORTIONS OF
THE STATE DURING THE MORNING HOURS BEFORE SHIFTING SOUTH EARLY THIS
AFTERNOON. DRIER AIR WILL BEGIN TO FILTER SOUTH THIS AFTERNOON WITH
MOST OF THE SHOWERS SHIFTING SOUTH OF THE AREA BY THIS EVENING.
HEAVY RAINFALL IS ONCE AGAIN LIKELY FOR AREAS SOUTH OF I-20 WITH
ANOTHER 1 TO 3 INCHES POSSIBLE OVER THE SAME AREAS THAT RECEIVED
RAINFALL YESTERDAY...THUS A FLASH FLOOD WATCH CONTINUES IN AFFECT
FOR AREAS ALONG THE HIGHWAY 84 CORRIDOR.
HIGH PRESSURE RIDGING WILL BUILD IN AT THE SURFACE TONIGHT NOT ONLY
DRYING THINGS OUT...BUT WILL USHER IN MUCH COOLER AIR WITH LOWS IN
THE UPPER 20S TO LOW 30S. HIGH PRESSURE AND CLEAR SKIES WILL PREVAIL
ACROSS THE ARKLAMISS ON WEDNESDAY ALONG WITH COOL TEMPERATURES.
WENT WELL ABOVE GUIDANCE POPS FOR AREAS ALONG AND SOUTH OF I-20 ONCE
AGAIN TODAY AS ALL OF THE MODELS ALONG WITH RADAR TRENDS INDICATE
PRECIPITATION OVER THESE AREAS THIS MORNING. STUCK PRETTY CLOSE FOR
AFTERNOON HIGHS TODAY AND OVERNIGHT LOWS TONIGHT...BUT DID CUT
SLIGHTLY BELOW GUIDANCE HIGHS WEDNESDAY...ALTHOUGH GUIDANCE HAS COME
IN A LITTLE COOLER THAN PREVIOUS RUNS. AFTER LOOKING AT H925/H850
TEMPS AND GFS BUFR SOUNDINGS HAVE DECIDED TO CUT JUST A COUPLE OF
DEGREES BELOW OF GUIDANCE HIGHS./15/
.LONG TERM...WEDNESDAY NIGHT THROUGH FRIDAY...THE MODELS HAVE COME
INTO BETTER AGREEMENT ON THE DEVELOPMENT OF A NORTHWEST GULF LOW
PRESSURE SYSTEM THIS FORECAST PERIOD. GIVEN THAT BETTER LOW LEVEL
MOISTURE TRANSPORT/CONVECTIVE POTENTIAL REMAIN CONFINED TO COASTAL
AREAS...THE WEATHER IMPACTS IN THE ARKLAMISS WILL BE MINIMAL WITH
LIGHT TO MODERATE RAIN (RAINFALL < .50 IN) FOR LOCATIONS MAINLY
SOUTH OF INTERSTATE 20. THIS QPF SCENARIO IS DEPICTED BY THE 03Z
SREF/06Z NAM/00Z GFS...WITH THE ECMWF SLIGHTLY HEAVIER AND FARTHER
NORTH. HAVE CONTINUED THE TREND OF CUTTING GFS MOS HIGHS FOR
THURSDAY GIVEN THE SHALLOW NATURE OF THE AIRMASS AND EXPECTATION FOR
ABUNDANT CLOUD COVER.
FRI NIGHT THROUGH MONDAY...A MOSTLY DRY AND COLDER WEATHER REGIME IS
FORECAST FOR THE WEEKEND INTO EARLY CHRISTMAS WEEK AS STRONG UPPER
LEVEL TROUGH DEVELOPS OVER THE EASTERN CONUS. CONFIDENCE HAS
INCREASED IN THE FORECAST FOR THE LONGER RANGE PERIODS WITH THE 00Z
GFS AND 00Z GFS ENSEMBLE MEAN NOW IN GREAT AGREEMENT. AND THE 00Z
ECMWF SHOWS ENOUGH AGREEMENT SO THAT WE HAVE GENERALLY FOLLOWED THE
GFS FOR FORECAST DETAILS.
AMPLIFICATION OF THE WESTERN RIDGE/EASTERN TROUGH PATTERN WILL
RESULT IN FAIRLY STRONG COLD ADVECTION SATURDAY AND SATURDAY NIGHT.
MODELS HAVE HINTED THAT A WEAK MID LEVEL TROUGH IN THE NORTHWEST
FLOW PATTERN COULD INDUCE VERY LIGHT PRECIPITATION OVER THE LOWER MS
VALLEY REGION AT SOME POINT FROM SATURDAY INTO SUNDAY. WITH THE
COLDER AIR MOVING IN AND LOW LEVEL INSTABILITY...BLUSTERY CONDITIONS
ALONG WITH A MIX OF SPRINKLES AND LIGHT SNOW SHOWERS/FLURRIES WILL
BE POSSIBLE...MOST LIKELY SATURDAY NIGHT. THIS WILL BE FOLLOWED BY
CHILLY AND DRY WEATHER FOR THE SUNDAY-MONDAY PERIOD WITH TEMPERATURES
10 DEGREES BELOW CLIMATIC AVERAGE. THE FORECASTED PATTERN SUGGESTS
THERE COULD BE A DAY OR NIGHT WHICH HAVE COLDER TEMPERATURES...BUT
THE FORECAST DETAILS ARE TOO DIFFICULT TO PIN DOWN AT THIS RANGE.
/EC/
&&
.AVIATION...WIDESPREAD IFR/MVFR CONDITIONS WILL CONTINUE OVER MUCH
OF THE AREA THIS MORNING AND INTO THE EARLY AFTERNOON HOURS. DRYER
AIR WILL BEGIN FILTERING SOUTH BEHIND THE COLD FRONT THIS AFTERNOON
WITH MVFR CEILINGS IMPROVING TO VFR STATUS AT KGLH AND KGWO BY MID
AFTERNOON...AND FOR THE REMAINING TAF SITES DURING THE LATE
AFTERNOON/EARLY EVENING HOURS. THE WINDS WILL REMAIN GUSTY OUT OF
THE NORTH AT KGLH AND KGWO INTO THE AFTERNOON WITH GUSTS TO NEAR 20
KNOTS LIKELY. THESE WINDS WILL REMAIN NORTHERLY THROUGH THE
OVERNIGHT HOURS...BUT DIMINISH TO AROUND 10 KNOTS WITH VFR
CONDITIONS EXPECTED TO PREVAIL AT ALL SITES BY LATE TONIGHT AND
CONTINUING INTO WEDNESDAY AFTERNOON. /19/
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR
MSZ052-054>066- 072>074.
LAKE WIND ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR MSZ026-030-
031-043-049-052.
LA...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR LAZ024-026.
LAKE WIND ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR LAZ009.
AR...LAKE WIND ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR ARZ075.
&&
$$
15/EC
03/19
