994
FXUS64 KJAN 160938
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
438 AM CDT WED OCT 16 2013
.DISCUSSION...
TODAY THROUGH THURSDAY NIGHT...
THE PRIMARY CONCERNS WILL BE RAIN CHANCES WITH THE POTENTIAL OF SOME
MORNING LOCALLY HEAVY RAINS WITH THE FRONT IN THE DELTA REGION FOR
TODAY.
LATEST SATELLITE VAPOR IMAGERY SHOWED A TROPICAL MOISTURE SOURCE
OVER BAJA...WHICH WAS PUSHING OVER THE SOUTHERN PLAINS WITH
PRECIPITABLE WATER OF AROUND 2 INCHES(00Z SHV SOUNDING 2.24 INCHES).
THE BEST MOISTURE TRANSPORT AND CONVERGENCE WAS OVER THE NORTHWEST
DELTA REGION AS THE COLD FRONT WAS SLOWLY PUSHING THROUGH. A POSITIVE
TILTED TROUGH WAS NOTED FROM SOUTHERN CANADA TO THE WESTERN
CONUS...PUTTING THE REGION UNDER SOUTHWEST FLOW ALOFT. SURFACE AND
UPPER ANALYSIS SHOWED RATHER WEAK FLOW AROUND THE COLD FRONT. AREA
RADARS WERE PICKING UP SHOWERS PUSHING NORTHEAST WITH RATHER RAINFALL
AMOUNTS OF AROUND .50 INCH TO AROUND 1 INCH IN 6 HOURS WEST OF THE
REGION.
MODELS CONTINUE TO SHOW THAT INSTABILITY AND JET DYNAMICS WILL
CONTINUE TO BE ON THE WEAK SIDE WITH SHOWERS MOVING ACROSS THE
REGION. THERE MAY BE SOME ISOLATED CONVECTION ACROSS THE REGION WITH
THE FRONT MOVING THROUGH. ISOLATED HEAVIER SHOWERS IS EXPECTED
ACROSS THE NORTHWEST DELTA REGION WITH RAINFALL AMOUNTS OF ONE TO
TWO INCHES. EXPECT THE LOCALLY HEAVIER AMOUNTS TO BE POSSIBLE
FOR THIS MORNING AND WILL CONTINUE TO MENTION IN THE HWO. THE FRONT
WILL BE SLOW TO MOVE THROUGH AND WILL EXIT THE REGION BY EARLY
THURSDAY. EXPECT ONLY LIGHT POSTFRONTAL RAIN FOR TONIGHT AND ON
THURSDAY. EXPECT THE RAINS TO END FROM THE WEST ON THURSDAY.
AS FAR AS GUIDANCE IS CONCERNED...FOR TEMPERATURES WENT CLOSE TO A
BLEND OF MAV AND GMOS. HIGHS TODAY WILL BE FROM THE MIDDLE 60S
NORTHWEST TO THE MIDDLE 80S SOUTHEAST AS WELL AS 70S FOR THURSDAY.
LOWS TONIGHT WILL BE FROM THE LOWER 50S NORTHWEST TO THE LOWER 60S
SOUTHEAST. FOR THURSDAY NIGHT LOWS WILL BE FROM THE UPPER 40S TO THE
MIDDLE 50S. FOR POPS WENT CLOSE TO BLEND OF MET AND MAV GUIDANCE FOR
TODAY THEN CLOSE TO GMOS GUIDANCE FOR TONIGHT AND THURSDAY./17/
FRIDAY THROUGH TUESDAY...
MUCH DIFFICULTY EXISTS TODAY IN CREATING A LONG TERM FORECAST AS
GLOBAL MODELS ARE REALLY STRUGGLING TO HANDLE IMPORTANT SHORTWAVE
DETAILS IN THE CHANGING UPPER LEVEL PATTERN. HAVE TRIED TO STAY THE
COURSE AS MUCH AS POSSIBLE IN AN EFFORT TO IRON OUT MODEL RUN-TO-RUN
INCONSISTENCIES BY PLACING HEAVIER WEIGHT ON THE GFS ENSEMBLE MEAN
GUIDANCE WHILE MAINTAINING SOME CONTINUITY WITH THE PREVIOUS
FORECAST.
SO THE THINKING IS STILL GENERALLY THE SAME TO THE PREVIOUS FORECAST ---
THE COLD FRONT NOTED IN THE SHORT TERM WILL STALL TO OUR SOUTH LATE
THIS WEEK...THEN RETREAT NORTHWARD IN RESPONSE TO AN APPROACHING
SHORTWAVE TROUGH RESULTING IN THE POTENTIAL FOR WIDESPREAD RAINFALL
FRIDAY NIGHT-SATURDAY. WHILE RECENT OPERATIONAL GFS RUNS HAVE
COMPLETELY FLIPPED-FLOPPED WITH THIS SCENARIO...GOING FROM DRY TO
WET BACK TO DRY...THE OPERATIONAL ECMWF IS AT LEAST MAINTAINING SOME
CONSISTENCY AND CONTINUES TO BE SLIGHTLY MORE AMPLIFIED WITH THE
SHORTWAVE TROUGH RESULTING IN GREATER MOISTURE TRANSPORT/LIFT AND
MORE RAINFALL FOR THE ARKLAMISS. NOT SURPRISINGLY...THE GEFS OFFERS
COMPROMISE BETWEEN THE EXTREMES AND HAVE WEIGHTED MEX MOS GUIDANCE
POPS TOWARD HIGHER GEFS MOS VALUES WITH SOME MANUAL ADJUSTMENTS AS
WELL.
IT SHOULD BE NOTED THAT VERY SLIGHT DIFFERENCES IN HEIGHT FIELDS ARE
HAVING BIG IMPACTS IN MODEL SENSIBLE WEATHER OUTPUT. AT ONE EXTREME...
GOING EXPLICITLY WITH THE 00Z ECMWF WOULD SUGGEST A POTENTIAL HEAVY
RAINFALL EVENT FOR FRI NIGHT/SAT FOR MUCH OF THE FORECAST AREA AS IT
SHOWS STRONG UPPER JET ENTRANCE REGION DYNAMICS COMBINING WITH A
VERY MOIST AIRMASS AND STRONG LOW LEVEL THETA-E ADVECTION. A MARGINAL
RISK FOR SEVERE WEATHER WOULD ALSO EXIST FOR THE HIGHWAY 84 CORRIDOR
IN THE ECMWF SOLUTION. THIS OF COURSE IS IN STARK CONTRAST TO THE DRY
GFS WHICH SHOWS LITTLE RAINFALL...MUCH LESS ANY RISK FOR HEAVY RAIN.
SO AS INDICATED PREVIOUSLY...WILL FOLLOW A COMPROMISE AT THIS POINT.
IN FURTHER SUPPORT...SLU CIPS ANALOGS IMPLY A WETTER FORECAST THAN
THE GFS...GIVEN THE 96 HOUR GFS 10/20/ 00Z TOP ANALOGS SHOWING
SIGNIFICANT PROBS FOR UP TO ONE INCH OF RAIN ACROSS SOUTHERN PORTIONS
OF THE ARKLAMISS. WILL KEEP ANY MENTION OF HEAVY RAIN OUT OF THE HWO
FOR NOW GIVEN THE LOW FORECAST CONFIDENCE.
AS ONE CAN IMAGINE...CONFIDENCE DROPS EVEN MORE AS WE GO INTO EARLY
NEXT WEEK. THE GFS INDICATES STRONGER SHORTWAVE EMPHASIS AND RETURN
FLOW FROM MONDAY INTO TUESDAY WHILE THE ECMWF DRIES OUT BEHIND THE
WEEKEND SYSTEM. ONCE AGAIN HAVE WEIGHTED POPS TOWARD GEFS MOS IN
FOLLOWING A COMPROMISE BETWEEN THE WET/DRY EXTREMES. /EC/
&&
.AVIATION...THE LEADING EDGE OF AN AREA OF MOSTLY LIGHT RAIN WAS
NEAR KGWO AND WILL SLOWLY SPREAD EAST OVERNIGHT AHEAD OF AN
APPROACHING COLD FRONT. MAIN AVIATION IMPACT NEXT 24 HOURS WILL BE
THE RAIN BAND AND WIND SHIFT ASSOCIATED WITH THE SLOW MOVING COLD
FRONT. FLIGHT CATEGORIES WILL FALL TO MVFR AND THEN IFR WITH RA
CONTINUING THROUGH THE MORNING. SITES FARTHER EAST AND SOUTH WILL
FALL TO AT LEAST MVFR THIS MORNING WITH LOWER STRATUS DEVELOPMENT.
KHBG WILL LIKELY FALL MVFR/IFR DUE TO FOG IMPAIRED VISIBILITIES
08Z-14Z. SITES WILL BE SLOW TO RECOVER TO VFR THROUGH THIS AFTN AS
THE COLD FRONT AND ASSOCIATED RAIN/LOWER CEILINGS MOVE THROUGH THE
REGION. 4-9 KT SOUTH WINDS WILL TURN NORTH FOR NWRN TAF SITES BY 15Z
WED WITH OTHERS SITES FOLLOWING SUIT THIS AFTERNOON INTO TONIGHT. /17/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 78 57 75 51 / 82 45 35 11
MERIDIAN 83 59 75 49 / 63 44 54 13
VICKSBURG 74 55 74 52 / 85 45 23 10
HATTIESBURG 87 63 79 55 / 33 31 42 13
NATCHEZ 78 56 72 52 / 74 46 29 11
GREENVILLE 66 53 71 50 / 96 35 13 10
GREENWOOD 69 53 74 49 / 97 40 19 10
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
/17/EC/