Area Forecast Discussion
Issued by NWS Jackson, MS

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000
FXUS64 KJAN 231415 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
915 AM CDT SAT AUG 23 2014

.UPDATE...REDUCED HIGH TEMPERATURES 1-3F AND MIXED OUT DEWPOINTS
1-2F DEGREES MORE FOR THIS AFTERNOON GIVEN RAOB AND SURFACE TRENDS
OVER PAST 24 HOURS. WHILE HEAT INDICES WILL STILL BE ELEVATED IN THE
100-108F RANGE THIS AFTN, THE OVERALL LONGEVITY WILL BE SHORTENED
FROM PREVIOUS FORECAST. UPDATED GRAPHICS HAVE BEEN POSTED.

.DISCUSSION...12Z KJAN RAOB YESTERDAY INDICATED 23C AT H925 AND
WARMING TO NEAR 26C BY 00Z AND THUS ALLOWING FOR AROUND 94-97F
SURFACE TEMPS ACROSS THE REGION. THIS MORNINGS SOUNDING INDICATED
H925 TEMPS NEAR 24C AND WITH MODEL BUFR SOUNDINGS SHOWING A WARMING
TOWARDS 27C, FEEL THAT 95-98F SURFACE TEMPS ARE MORE JUSTIFIABLE
VERSES THE WARMER GUIDANCE OFFERED. IN ADDITION, RAW MODELS TRY TO
MIX OUT DEWPOINTS INTO THE MID 60S BUT GIVEN YESTERDAYS OBSERVATIONS
FEEL THIS MAY BE TOO OVERDONE AND KEPT THEM IN UPPER 60S TO NEAR 70.
THESE VALUES ARE STILL A SLIGHT DROP FROM PREVIOUS FORECAST AND
ALTHOUGH HEAT INDICES WILL REACH INTO THE 100-108F RANGE THIS AFTN,
THEIR LONGEVITY WILL BE A TOUCH SHORTER. DEWPOINTS WERE ALSO LOWERED
SUNDAY AS WELL.

WITH DAILY LOWS STILL FALLING INTO THE LOWER 70S, THE OVERALL
TEMPERATURE/HUMIDITY COMBO FALLS BELOW HEAT ADVISORY CRITERIA AND
FEEL THE HAZARD IS COVERED WELL IN CURRENT GRAPHICS AND HWO.

AN UPDATED AVIATION DISCUSSION CAN BE FOUND BELOW. /ALLEN/

&&

.AVIATION...VFR EXPECTED TO PREVAIL THROUGH PERIOD WITH VCTS LIKELY
FOR KHBG THIS AFTN FROM 19-23Z BEFORE ACTIVITY DIMINISHES BY EARLY
EVENING. SURFACE WINDS WILL BE LIGHT AND VARIABLE FROM WEST AND
NORTH AT LESS THAN 10 KT GOING NEAR CALM OVERNIGHT. /ALLEN/

&&

.PREV DISCUSSION... /ISSUED 451 AM CDT SAT AUG 23 2014/

DISCUSSION...

TODAY THROUGH SUNDAY NIGHT...

THE PRIMARY CONCERN WILL BE THE DANGEROUS HEAT STRESS FOR THIS
WEEKEND WITH HEAT INDICES FROM 105 TO 109 FROM NOON TO 6 PM EACH DAY.
ALSO OF CONCERN WILL BE THE POSSIBILITY OF ISOLATED STRONG TO
POSSIBLY SEVERE STORMS COMING OUT OF ALABAMA IN THE EAST ON SUNDAY
AFTERNOON.

THE LATEST SATELLITE IMAGERY SHOWED THE RIDGE CONTINUING OVER THE
LOWER MISSISSIPPI VALLEY. THIS WAS PROVIDING SOME DECENT SUBSIDENCE
OVER THE REGION...WHICH WAS RESULTING IN MUGGY CONDITIONS EARLY THIS
MORNING. TEMPERATURES PRIOR TO DAWN WERE IN THE LOWER 70S.
HATTIESBURG AIRPORT HAS BEEN GETTING SOME PATCHY FOG
OVERNIGHT...WHILE THE SURROUNDING AREAS WERE REPORTING GOOD
VISIBILITY.

FOR TODAY INTO TONIGHT IT WILL BE ANOTHER HOT DAY AS TEMPS WILL CLIMB
INTO THE MIDDLE TO UPPER 90S...WHICH WILL RESULT IN HEAT INDICES FROM
105 TO 109. WE MAY GET SOME ISOLATED CONVECTION ACROSS THE SOUTH
INDUCED BY THE SEA BREEZE FRONT THIS AFTERNOON PER WRF GUIDANCE.
PRECIPITABLE WATER TODAY WILL ONLY BE AROUND 1.5 INCHES. THE DIURNAL
CONVECTION WILL DIMINISH BY THIS EVENING. EXPECT LOWS THIS MORNING TO
DIP DOWN TO THE LOWER 70S AS HAS BEEN THE CASE FOR THE LAST FEW
DAYS...WHICH WILL KEEP US OUT OF THE HEAT ADVISORY CRITERIA FOR
TODAY. HEAT INDICES FOR THE PAST FEW DAYS HAS BEEN FROM 100 TO 106
WITH THE EXCEPTION OF 108 AT GTR. LOWS TONIGHT WILL ONCE AGAIN DROP
INTO MAINLY THE LOWER 70S.

FOR SUNDAY INTO SUNDAY NIGHT...EXPECT MUGGY CONDITIONS TO CONTINUE
AS THE MEAN RIDGE FLUCTUATES SOME. ON THE SURFACE AN INVERTED TROUGH
WILL PUSH INTO THE REGION FOR SUNDAY AFTERNOON AND EVENING. HIGHS
WILL ONCE AGAIN BE IN THE MIDDLE TO UPPER 90S WITH HEAT INDICES OF
105 TO 109...WITH MOISTURE/CLOUDS INCREASING FROM THE EAST (PW INCREASE
TO THE 1.8 TO 2.4 INCH RANGE). ISOLATED CONVECTIVE CHANCES WILL
DEVELOP OVER THE EASTERN COUNTIES. WITH SOME LIFT AROUND THE SURFACE
TROUGH A FEW OF THE STORMS IN THE EAST MAY BE STRONG TO POSSIBLY
SEVERE WITH GUSTY WINDS POSSIBLE. HOWEVER MID LEVEL LAPSE RATES WILL
NOT BE OVERLY IMPRESSIVE WITH VERTICAL TOTALS IN THE MID 20S. K
INDICES IN THE UPPER 30S SUGGEST LOCALLY HEAVY RAINFALL FROM SLOW
SOUTHWEST-MOVING STORMS IN THE EAST. DEEPER MOISTURE FIELDS WILL
DEVELOP ACROSS THE EAST FOR SUNDAY NIGHT. FOR NOW WILL HOLD OFF ON
MENTIONING THE ISOLATED STRONG TO SEVERE OPTION IN THE HWO...SINCE
THE HIGH-RES GUIDANCE IS STINGY WITH COVERAGE AND DOES NOT SHOW MUCH
FOR NOW FOR SUNDAY AFTERNOON AND EVENING...BUT WILL KEEP THE
DANGEROUS HEAT LEVELS IN THE HWO FOR THIS WEEKEND. LOWS FOR SUNDAY
NIGHT WILL ONCE AGAIN DROP INTO THE LOWER 70S...WHICH WILL KEEP US
OUT OF THE HEAT ADVISORY SECTOR FOR SUNDAY. EXPECT THE CONVECTIVE
ACTIVITY TO SPREAD WEST ACROSS THE REGION ON SUNDAY NIGHT...WHICH WAS
SHOWN BY MAINLY THE GFS.

AS FAR AS TEMPERATURES ARE CONCERNED MADE SLIGHT ADJUSTMENTS TO THE
MAV FOR THIS AFTERNOON. GFS MOS GUIDANCE WAS A LITTLE WARM WITH
HIGHS IN THE LOWER 100S IN THE DELTA REGION. WENT WITH THE CURRENT
FORECAST FOR LOWS TONIGHT AS MODEL GUIDANCE LOOKED A LITTLE COOL IN
SOME SPOTS...WHILE THE NAM LOOKED TOO WARM WITH WITH LOWS IN THE MID
TO UPPER 70S. KEPT THE SAME HIGHS FOR SUNDAY AS MOS GUIDANCE HAD
HIGHS FROM 98 TO 102. FOR SUNDAY NIGHT WENT CLOSE TO MAV GUIDANCE.

FOR POPS...WENT A LITTLE HIGHER THAN GFS MOS CROSS THE SOUTH WITH
THE EXPECTED SEA BREEZE ACTIVITY. FOR TONIGHT KEPT DRY POPS. FOR
SUNDAY WENT CLOSE TO MAV GUIDANCE CROSS THE EAST. FOR SUNDAY NIGHT
KEPT CLOSE TO MAV GUIDANCE AS ACTIVITY SPREADS ACROSS THE REGION FROM
THE EAST. /17/

FOR MONDAY THROUGH NEXT FRIDAY...

NWP MODELS ARE IN AGREEMENT THAT SHORTWAVE ENERGY IN THE WESTERLIES
NORTH OF THE SUBTROPICAL RIDGE WILL BE DRAWN SOUTHWARD AND THEN
WESTWARD TOWARD THE ARKLAMISS FROM THE EAST AS WE GO INTO MONDAY.
EXPECT NUMEROUS SHOWERS/TSTMS TO DEVELOP...WITH SUFFICIENT FLOW AND
OUTFLOW GENERATION TO SUPPORT WESTWARD-MOVING MULTICELL BANDS OF
CONVECTION. TIMING WILL BE CRITICAL IN REGARD TO SEVERE POTENTIAL -
IF DEVELOPMENT CAN BE DELAYED UNTIL THE AFTERNOON WHEN SURFACE
TEMPERATURES HAVE THE POTENTIAL TO REACH AT LEAST THE MID 90S...THEN
THERE WOULD BE MORE POTENTIAL FOR SEVERE MICROBURSTS. FOR NOW...IT
APPEARS THAT DEVELOPMENT MAY BE QUICK ENOUGH OVER CENTRAL/EASTERN MS
TO LIMIT THE INSTABILITY AND RESULTING DOWNDRAFT INTENSITY...WITH
LOCATIONS ALONG AND WEST OF THE MS RIVER BEING MORE LIKELY TO HEAT
UP. FOR NOW WILL KEEP OUT ANY MENTION OF SEVERE STORM POTENTIAL IN
THE HAZARD PRODUCTS UNTIL TIMING CAN BE BETTER ASSESSED.

OTHERWISE...IT APPEARS THAT HEAT STRESS MAY DECREASE A BIT AS WE GO
THOUGH NEXT WEEK. THE CONVECTIVE ACTIVITY MONDAY WOULD LIMIT HEAT
INDICES MORE THAN INDICATED IN THE FORECAST IF THE TROUGH PASSAGE IS
A LITTLE QUICKER THAN EXPECTED...AND THEN THE RIDGE CENTER IS
FORECAST TO SHIFT EAST OF THE AREA MID TO LATE WEEK WITH THE
POTENTIAL FOR A LONG-WAVE TROUGH TO SET UP OVER THE ARKLAMISS AS WE
GO FROM LATE WEEK INTO NEXT WEEKEND. HEAT INDICES ARE STILL EXPECTED TO
AVERAGE ABOVE CLIMATIC NORMAL THIS COMING WEEK...BUT THEY SHOULD FALL
BELOW THE DANGEROUS LEVELS RECENTLY EXPERIENCED. RAIN CHANCES WILL BE
RATHER LOW AFTER PASSAGE OF THE EARLY WEEK TROUGH. /EC/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       97  72  99  74 /   9   5   8  32
MERIDIAN      98  72  99  73 /   8   7  18  35
VICKSBURG     96  71  98  71 /   7   5   8  28
HATTIESBURG   98  73  99  75 /  25  13  17  23
NATCHEZ       94  74  96  73 /  15   9   6  20
GREENVILLE    97  74  99  74 /   3   4   9  24
GREENWOOD     96  72  98  74 /   3   4  14  31

&&

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

$$

ALLEN/17/EC





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