000
FXUS64 KJAN 032118
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
318 PM CST WED DEC 3 2008
.DISCUSSION...SHORT TERM(TONIGHT THROUGH FRIDAY) SURFACE PRESSURE
GRADIENT REMAINS NEARLY 7MB FM W-E ACROSS THE CWFA. WILL KEEP THE
LAKE WIND ADVISORY UNTIL ABOUT AN HOUR AFTER SUNSET WHEN MIXING
SHOULD SUBSIDE AND GRADIENT RELAXES A BIT WITH ONLY OCCASIONAL GUSTS
REACHING CRITERIA AFTER 6PM OR SO. CLOUDS FINALLY SURGING TOWARD THE
CWFA FROM THE W AND SE AHEAD OF COLD FRONT COMING OFF THE OZARKS AT
MID AFTERNOON. LOOK FOR RAPIDLY INCREASING BAND OF SHRA/ISOLD TSRA TO
FORM ALONG AND BEHIND FRONT IN THE ARKLATEX REGION AND THEN MARCH E
WITH THE FRONT. PWATS OF 1.3 INCHES SHOULD SUPPORT A QUICK ONE HALF
TO ONE INCH OF RAIN AS THE PCPN PASSES THROUGH THE CWFA BEFORE 18Z
THURSDAY. GFS SUPPORTS UP TO 1.5 INCHES IN PORTIONS OF NERN LA.
AS FAR AS STORM INTENSITIES...MODELS PERSIST WITH K INDICES OF 30-35
THE SHOWALTERS MINUS 1...MLCAPES LESS THAN 100J/KG...AND 700-500MB
LAPSE RATES OF 6.5-7C ON THE COLD SIDE OF THE FRONT LEADING TO MAINLY
ELEVATED CONVECTION. THERE COULD BE AN ISOLATED STRONG STORM OVER THE
DELTA REGION BEFORE MIDNIGHT AS PEAK ASCENT AXIS ROTATES THROUGH BUT
FILLING LOW LEVEL PRESSURES NOT TOO SUPPORTIVE. WE EXPECT THE FRONT TO
CROSS THE DELTA BETWEEN 02-06Z AND THEN ROUGHLY LIE ALONG THE NATCHEZ
TRACE PARKWAY BY AROUND 10Z THURSDAY MORNING...THEN MOVE THROUGH I-59
REGION BY AROUND 15Z.
COLD WINDS BEHIND THE FRONT ARE A BIT OF CONCERN AND MAY GUST ABOVE
LAKE WIND ADVY CRITERIA FOR A COUPLE OF HOURS BUT WILL HANKDLE THESE
IN SHORT TERM NOWCASTS. A QUICK DRYING TREND WILL FOLLOW BY THURSDAY
AFTERNOON WITH CAA AND INCREASING LOW LEVEL DIFFLUENCE AHEAD OF A
1030MB+ HIGH DROPPING INTO THE CENTRAL PLAINS. HIGH TEMPS WILL HOLD
IN THE U40S AND 50S FOR THE AFTERNOON. MEANWHILE...THE SURFACE HIGH
SHOULD TRACK THROUGH THE TN VALLEY AND KEEP MORE NELY WINDS GOING
THROUGH THURSDAY NIGHT WHEN A LIGHT FREEZE SHOULD RETURN TO MOST OF
THE CWFA EXCEPT POSSIBLY THE FAR S. WINDS GRADUALLY DIE OFF ON FRIDAY
WITH SUNSHINE AND COOL AIR DOMINATING WITH TEMPS HOLDING IN THE 50S.
BEST RADIATIONAL COOLING COMES IN FOR FRIDAY NIGHT WHEN DRY AIR ALLOWS
FROSTY 25-30F READINGS TO SHOW UP FOR SATURDAY MORNING. MAIN QUESTION
HERE WILL BE THE EXTENT OF ANY HIGH LEVEL MOISTURE TRYING TO LINGER
ACROSS THE REGION. WILL DEFER TO MOSTLY TO PREVIOUS DISCUSSION
PORTIONS BEYOND SATURDAY TIME FRAME./40/
LONGER TERM(SATURDAY THROUGH TUESDAY NIGHT)...NORTHWEST FLOW ALOFT
SHOULD BRING A REINFORCING SHOT OF COOL AIR INTO THE REGION FOR
SUNDAY AND SUNDAY NIGHT. THIS AIRMASS HAS POTENTIAL TO BE COLDER THAN
MEX GUIDANCE SUGGESTS (HIGHS IN THE 50S, LOWS IN THE 30S)...BUT
ENERGY GETTING READY TO HEAD INTO THE PLAINS BY THAT TIME MAKES ME
THINK THIS COOL SHOT COULD BE MORE A GLANCING BLOW THAN THE FIRST.
PREVIOUSLY MENTIONED ENERGY COMING TOWARD THE CENTER OF THE NATION
AT THE FIRST OF THE WEEK SHOULD AMPLIFY JUST TO OUR WEST AND INDUCE
RANGE CHANCES FOR THE ARKLAMISS STARTING LATE MONDAY AS INCREASING
SOUTHERLY FLOW PRODUCES ISENTROPIC LIFT. MAIN EUROPEAN AND GFS
MODELS DISAGREE QUITE A BIT WITH THE STRENGTH AND CHARACTERISTICS OF
THIS SYSTEM AS IT MOVES THROUGH OUR REGION TUESDAY AND PERHAPS
WEDNESDAY. REGARDLESS OF STRENGTH...IT SHOULD PRODUCE RAIN AND
ANOTHER COOL/COLD SHOT AS A COLD FRONT MOVES THROUGH. CONSENSUS IS
THAT RAIN CHANCES ARE HIGHEST DURING THE DAY TUESDAY...AND MEX POPS
UPPED FOR THAT PERIOD AND TUESDAY NIGHT SINCE THE RELATED
OPERATIONAL GFS HAS PROBABLY THE QUICKEST ADVERTISED EVOLUTION. THAT
MODEL IS ALSO LEAST BULLISH WITH PRECIP WHILE THE EUROPEAN MODEL
DEPICTS A MUCH MORE POTENT SCENARIO (MAINLY BECAUSE IT PICKS UP
ENERGY CUTOFF FROM THE FLOW OFF THE COAST OF CALIFORNIA). ODDS ARE
THAT THE EUROPEAN SOLUTION HAS MORE TRUTH TO IT AND WE WILL HAVE TO
KEEP OUR EYES ON THE PERIODS AROUND NEXT TUESDAY FOR POTENTIAL ACTIVE
WEATHER. (GOOD AGREEMENT IN ECMWF/GFS RUNS TODAY AND PAST SEVERAL
DAYS ALONG WITH SPC MARS DATA YIELDS ENOUGH CONFIDENCE TO MENTION
STRONG STORMS IN THE HWO...MAINLY S./40/)
OVERALL...I REMAINED VERY CLOSE TO LATEST MEX GUIDANCE THROUGH THE
LONG TERM (ASIDE FROM DEVIATIONS MENTIONED ABOVE). TEMPERATURES ARE
LIKELY TO AVERAGE BELOW NORMAL...ALTHOUGH IT IS PROBABLE THAT
NUMBERS RIGHT NOW ARE NOT COLD ENOUGH ON THE COLD DAYS AND MAYBE NOT
QUITE WARM ENOUGH IN ADVANCE OF THE SYSTEM FOR TUESDAY. HOWEVER...I
CHOSE TO MOSTLY REMAIN WITH THIS GUIDANCE BECAUSE THE ACTIVE NATURE
OF THE PATTERN RIGHT NOW ARGUES AGAINST BEING TOO SPECIFIC ON TIMING
OF FRONTS IN THE LONG TERM. /BB/
&&
.AVIATION...SO FAR SO GOOD BUT THINGS SHOULD CHANGE THIS EVENING AND
OVERNIGHT. A COLD FRONT IS ON THE WAY AND CEILINGS WILL DEVELOP AND
LOWER TONIGHT FROM THE NW TO THE SE. FIRST OFF THE FRONT WILL BRING
LOW CLOUDS AND THEN RAIN WITH SOME ISLTD TSRA. CEILINGS SHOULD
GENERALLY LOWER TO MVFR STATUS AROUND GLH CLOSE TO 00Z WITH GWO
FOLLOWING SUIT SHORTLY AFTER. CEILINGS WILL FALL INTO MVFR STATUS
AROUND JAN CLOSER TO 6Z AND THEN COULD END UP HOLDING OFF TO CLOSER
TO SUNRISE AROUND MEI AND HBG. EACH SITE WILL SEE CEILINGS CONTINUE
TO LOWER POSSIBLY BOTTOMING OFF AROUND 700-900 FT. RAIN WILL ALSO
BEGIN AROUND OR SHORTLY AFTER THOSE TIMES. RAIN SHOULD NOT BE TOO
HARD AND ONLY DROP TAF SITES INTO MVFR STATUS AT TIMES. THE OTHER
CONCERN IS WIND. WINDS WILL CONTINUE TO BE BREEZY ALL NIGHT BUT THEY
WILL QUICKLY VEER FROM 180 TO 340 WITH THE PASSAGE OF THE FRONT. THE
FRONT SHOULD REACH GLH AROUND 7/8Z...JAN BY 11/12Z AND HBG SOMETIME
TOMORROW MORNING. AFTER THE FRONT WINDS WILL PICK BACK UP FOR A
SHORT WHILE AND CEILINGS SHOULD SLOWLY IMPROVE. /CAB/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 46 52 31 54 / 76 60 5 5
MERIDIAN 46 54 31 52 / 47 75 6 5
VICKSBURG 43 52 31 52 / 88 42 5 5
HATTIESBURG 49 59 33 57 / 41 75 6 4
NATCHEZ 46 52 32 52 / 74 46 5 4
GREENVILLE 38 50 31 48 / 100 26 5 5
GREENWOOD 39 48 30 49 / 93 39 6 6
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR MSZ018-019-
025>028-034>037-040>043-047>049-053-054-059>062.
LA...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR LAZ007>009-
015-016-023>026.
AR...LAKE WIND ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR ARZ074-075.
&&
$$
