National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KJAN 231549 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE JACKSON MS
1045 AM CDT THU MAY 23 2013

.UPDATE...COLD FRONT THIS MORNING TRYING TO SLOWLY ORIENT MORE WEST
TO EAST AND SAG SOUTH INTO FAR NORTHERN ZONES. SOUTH OF THIS
BOUNDARY PATCHY LOW CLOUDS AND FOG FORMING LAST NIGHT ARE BURNING
OFF...BUT STILL WILL HAVE SOME OBSERVABLE REMNANT FOR ANOTHER HOUR
OR SO ACROSS PORTIONS OF CENTRAL MS STRETCHING BACK WEST TO NE LA
AND EXTREME SE AR. SOMEWHAT PERTURBED NORTHWEST FLOW EXISTS FROM THE
PLAINS SOUTHEAST ACROSS THE LOWER MS VALLEY THIS MORNING...WITH THE
LOW LEVEL JET FEEDING A CLUSTER OF THUNDERSTORMS ACROSS CENTRAL OK
AND MOVING INTO THE RED RIVER VALLEY.

FOR OUR REGION INSTABILITY IS EXPECTED TO BUILD ALONG AND SOUTH OF
SOUTHWARD SAGGING COLD FRONT AS THE DAY GOES ON...PARTICULARLY IN
WESTERN ZONES WHERE STEEP LAPSE RATES AND BOUNDARY LAYER HEAT AND
HUMIDITY WILL YIELD UP TO 2500 J/KG MLCAPE BY LATE AFTERNOON. MOST
AVAILABLE HI RES MODELS DEPICT AT LEAST ONE SMALL THUNDERSTORM
CLUSTER DEVELOPING ALONG THE BOUNDARY IN THE VICINITY OF THE
ARKLAMISS DELTA BETWEEN LATE AFTERNOON AND EARLY EVENING...THEN
DIVING SOUTHEASTWARD. HOWEVER...SOME GLOBAL MODELS (SUCH AS THE
ECMWF) DEVELOP NO AT ALL. DEVELOPMENT IS INDEED QUESTIONABLE DUE
TO CAPPING AND POTENTIALLY LIMITED FORCING. HOWEVER...FOR THIS
UPDATE...AM LEANING IN THE DIRECTION THAT AT LEAST A BIT OF
THUNDERSTORM ACTIVITY WILL GET GOING BECAUSE OF LIKELIHOOD OF LIFT
BEING ENHANCED BY MCV INITIATED BY OK CONVECTION COMING INTO THE
FRAY BY 00 UTC. FOR THAT REASON UPPED POPS TO 30 PERCENT IN MANY
NORTHWEST AND WEST CENTRAL ZONES THIS EVENING.

WE ALREADY HAVE RISK OF STRONG STORMS IN THE HWO FOR LATE THIS
AFTERNOON AND THIS EVENING ALONG AND WEST OF I-55. HIGHEST RISK WILL
LIKELY BE MORE CONFINED TO THE ARKLAMISS DELTA...BUT WILL LEAVE
WORDING AND AREA GOING FOR NOW BECAUSE OF UNCERTAINTIES INVOLVED.
DEFINITELY SOME CHANCE FOR A FEW SEVERE WIND GUSTS IN NORTHWEST
ZONES IF THE WORST CASE SCENARIO OF BEING AFFECTED BY A SOMEWHAT
ORGANIZED THUNDERSTORM COMPLEX COMES TO FRUITION. WE WILL BE
MONITORING FOR THAT POTENTIAL CLOSELY AND WILL UPDATE PRODUCTS
QUICKLY IF NEED BE. /BB/

&&

.PREV DISCUSSION... /ISSUED 415 AM CDT THU MAY 23 2013/

SHORT TERM...TODAY THROUGH FRIDAY NIGHT...
THE PRIMARY CONCERNS WILL BE THE RISK OF A FEW STRONG STORMS FOR
THE LATER HALF OF THIS AFTERNOON INTO THIS EVENING ACROSS THE WEST
HALF OF THE REGION. ALSO THE RISK OF AREAS OF DENSE FOG ACROSS THE
REGION FOR THIS MORNING. THIS FOLLOWED BY POPS AND TEMPS.

LATEST SATELLITE IMAGERY SHOWED THE REGION UNDER NORTHWEST FLOW
ALOFT WITH THE BASE OF AN UPPER TROUGH OVER THE MIDSOUTH REGION.
A FRONT WAS APPROACHING THE REGION FROM NORTHERN ARKANSAS. SURFACE
HIGH PRESSURE WAS NOTED ACROSS THE REGION. LIGHT WINDS AND A LOW
LEVEL MOIST BOUNDARY LAYER WITH MOSTLY CLEAR SKIES HAD HELP AREAS OF
OCCASIONALLY DENSE FOG TO FORM ACROSS THE REGION. VISIBILITIES HAVE
BEEN BOUNCING UP AND DOWN.

FOR TODAY AND TONIGHT...WITH AREAS OF FOG AROUND. WILL PUT AREAS OF
OCCASIONALLY DENSE FOG ACROSS THE ENTIRE FORECAST AREA AS
VISIBILITIES BOUNCE UP AND DOWN. ALSO OF CONCERN THERE WILL BE
ENOUGH INSTABILITY(ML CAPES >3000 J/KG, LAPSE RATE AROUND 7C,
LINGERING FRONTAL BOUNDARY COMING INTO THE REGION, INCREASING
MOISTURE CONVERGENCE FOR A FEW STRONG STORMS TO DEVELOP FOR THIS
AFTERNOON AND EVENING. THE WRF MODELS ESP THE SPC WRF SHOWS A FEW
STRONG STORMS COMING OUT OF SOUTHERN ARKANSAS AND LOUISIANA TOWARD
THE REGION BY MID AFTERNOON. AREA SOUNDINGS LOOK A LITTLE DRY ESP UP
IN THE MID LEVELS WITH A CAP IN PLACE...BUT THE FRONTAL BOUNDARY MAY
BE THE FOCUS MECHANISM TO GET A FEW STORMS GOING. WILL MENTION IN
HWO BOTH FOG POTENTIAL AND STRONG STORMS. THE INTENSITY OF THE FEW
STRONG STORMS SHOULD DECREASE DURING THE EVENING HOURS. THE SPC WRF
KEEPS THE CONVECTION GOING AFTER MIDNIGHT AND PUSHES IT ACROSS THE
EAST HALF OF THE REGION. HIGHS TODAY WILL BE MID TO UPPER 80S. LOWS
WILL BE FROM THE UPPER 50S TO THE MIDDLE 60S...WHICH IS AROUND
NORMAL FOR THIS TIME OF YEAR. WENT CLOSE TO MAV GUIDANCE. AS FOR
POPS PUT IN LOW POPS FOR TODAY WITH THE SPC WRF IN MIND. MODEL POPS
WERE RATHER DRY PROBABLY DUE TO THE SOMEWHAT DRY SOUNDINGS. MADE
SLIGHT ADJUSTMENTS TO MAV POPS FOR TONIGHT.

FOR FRIDAY AND FRIDAY NIGHT...UPPER RIDGE AXIS OVER THE PLAINS WILL
DEVELOP TOWARD THE REGION. COOL SURFACE HIGH PRESSURE MOVING FROM
THE UPPER MISSISSIPPI VALLEY TO THE GREAT LAKES WILL PROVIDE DRY
WEATHER TO THE REGION. HIGHS ON FRIDAY WILL BE FROM THE MIDDLE 70S
NORTH TO THE UPPER 80S SOUTH. LOWS FRIDAY NIGHT WILL RANGE FROM THE
COOL UPPER 40S EAST TO THE MIDDLE TO UPPER 50S WEST...WHICH WILL BE
WELL BELOW NORMAL. WENT CLOSE TO MAV GUIDANCE./17/

LONG TERM...(SATURDAY THROUGH THURSDAY) HIGH PRESSURE WILL BE IN
CONTROL OF REGIONAL WEATHER SATURDAY. RIDGING BEGINS TO GIVE WAY
SATURDAY NIGHT WITH A SHORTWAVE MOVING THROUGH TO FLATTEN FLOW. THE
EURO IS ADVERTISING STRONGER FORCING WITH THIS WAVE AND BRINGS AN
AREA OF MOISTURE/PRECIP ACROSS NRN ZONES FOR SUNDAY. THE HIGHER POPS
CALLED FOR BY THE EURO FOR MONDAY AFTER THE WAVES PASSES LOOK A
LITTLE OUT OF WHACK...WEAK ISENTROPIC FLOW NOTWITHSTANDING...AND THE
MORE CONSISTENT DRY FORECAST PER THE GFS WILL BE FOLLOWED FOR NOW.
MODEL SOLUTIONS CONTINUE TO DIFFER IN THE FARTHER PERIODS OF THE
EXTENDED REGARDING PLACEMENT OF THE UPPER RIDGELINE AND SHORTWAVES
THAT PUSH THROUGH BUT THE GENERAL PATTERN WILL BE LOW LEVEL SLY FLOW
IN A REGION OF WEAK UPPER FORCING POSSIBLE DEPENDING ON WHERE THE
RIDGE/TROUGH POSITIONS SET UP. IN THIS TYPE OF REGIME THE CHANCE OF
AFTERNOON CONVECTION...EVEN WITHOUT SIGNIFICANT FORCING...WILL
GRADUALLY BE ON THE INCREASE DUE TO PERSISTENT SLY FLOW THAT WILL BE
IN PLACE. HOWEVER MODELS ARE ALSO SUGGESTING A POTENTIAL FOR CAPPING
DUE TO THE PROXIMITY OF THE UPPER RIDGE. DUE TO THESE UNCERTAINTIES
THE DRIER GFS WILL BE FOLLOWED FOR NOW.

&&

.AVIATION...MORNING FOG AND STRATUS HAS JUST ABOUT MIXED OUT AND VFR
CONDITIONS ARE EXPECTED TO PREVAIL THIS AFTERNOON THROUGH TONIGHT. A
LINGERING FRONTAL BOUNDARY WILL PROVIDE THE OPPORTUNITY FOR A FEW
STORMS TO DEVELOP LATE THIS AFTERNOON INTO THE EVENING...ESPECIALLY
OVER WESTERN PORTIONS OF THE FORECAST AREA INCLUDING GLH. WILL NOT
INCLUDE A MENTION OF STORMS IN THE TAFS DUE TO LIMITED COVERAGE.
OTHERWISE...FOG DEVELOPMENT FOR LATE TONIGHT AND EARLY FRIDAY
MORNING IS QUESTIONABLE WITH DRY AIR ADVECTION EXPECTED TO TAKE
PLACE IN INCREASING NORTHEAST LOW-LEVEL FLOW. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       89  63  83  52 /   9  22   6   6
MERIDIAN      89  61  85  47 /   5  12   7   5
VICKSBURG     89  63  82  52 /  16  29   5   5
HATTIESBURG   91  65  88  53 /   5  16   2   3
NATCHEZ       88  65  84  56 /  14  24   5   6
GREENVILLE    88  64  78  54 /  21  21   7   5
GREENWOOD     87  61  78  50 /  12  15   9   5

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

$$

BB/EC/17/03