Area Forecast Discussion
Issued by NWS Jackson, MS

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000
FXUS64 KJAN 301529
AFDJAN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
1029 AM CDT SAT APRIL 30 2016

.UPDATE...LATEST SATELLITE AND UPPER AIR ANALYSIS...SHOWED AN UPPER
TROUGH OVER THE WESTERN CONUS...WHICH WAS ASSOCIATED WITH A LOW TO
MIDLEVEL CLOSED LOW OVER WESTERN KS.  IT WAS SENDING SHORTWAVES IN
THE SOUTHERN STREAM INTO THE LOWER MS VALLEY IN SOUTHWEST FLOW. THE
ACTIVE SUBTROPICAL JET WAS NOTED IN THE SOUTHERN STREAM WHICH WAS
PROVIDING UPPER DIVERGENCE FROM THE WEST. AREA SNDINGS SHOW SOME
LAPSE RATES IN THE MIDLEVELS...WHICH WERE NOT AS IMPRESSIVE AS
YESTERDAY. THERE WAS ALSO DESCENT LOW LEVEL INFLOW OF AROUND 35-40
KNOTS. AREA RADARS WERE PICKING UP A LARGE AREA OF RAIN WITH SOME
THUNDERSTORMS FROM SOUTHWEST LOUISIANA THROUGH PORTIONS OF THE DELTA
REGION. HRRR AND AREA OBS SHOWS THAT A "WAKE LOW" MAY BE DEVELOPING
BEHIND THE RAIN OVER SOUTHERN ARKANSAS. SITE ELD AND LLQ HAD OF
AROUND 35 KNOTS OF WIND. THE HRRR BRINGS THE WAKE LOW INTO THE
REGION FOR THIS AFTERNOON BEHIND THE LINE. SO WILL HAVE TO WATCH FOR
THAT. THERE HAVE BEEN WIND REPORTS FROM AR. OTHERWISE DESPITE THE
LULL IN THE CONVECTION EXPECT THE AIRMASS INSTABILITY TO DESTABILIZE
FOR THIS AFTERNOON. THE LATEST HRRR STILL BRINGS AN ORGANIZED LINE
THROUGH THE REGION FOR THIS AFTERNOON. SO WITH THIS IN MIND WILL
MAKE NO SIGNIFICANT CHANGES TO FORECAST AND WILL CONTINUE THE FLASH
FLOOD WATCH. SO WILL KEEP OUR PRIMARY SEVERE WEATHER RISKS FOR
TODAY./17/

&&

.AVIATION...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO IMPACT
GLH...WITH ACTIVITY LIKELY TO MOVE INTO GWO BEFORE NOON.
THUNDERSTORMS WILL IMPACT THE REMAINING SITES THIS AFTERNOON AND
EVENING. HEAVY RAIN WILL BRIEFLY REDUCE VISIBILITIES TO A MILE OR
LESS. LOW CLOUDS WILL CONTINUE TO IMPACT THE AREA ALSO...MVFR TO
LIFR CONDITIONS LIKELY FOR MUCH OF THE AREA THROUGH THE DAY.

IN ADDITION...RAPID ONSET GUSTY WINDS WILL LIKELY DEVELOP FOR GLH
BETWEEN NOW AND EARLY AFTERNOON...GUSTS TO 40KTS OR HIGHER WILL BE
POSSIBLE.

&&
./PREVIOUS DISCUSSION...452 AM CDT SAT APR 30 2016

.DISCUSSION...
SHORT TERM (THIS WEEKEND)...A RATHER WET AND STORMY WEEKEND IS ON
TAP AS A SOMEWHAT COMPLICATED WEATHER SITUATION UNFOLDS. EARLY THIS
MORNING, A COMPLEX OF SHOWERS AND THUNDERSTORMS EXTENDS FROM THE
OHIO VALLEY/PURCHASE REGION SOUTHWESTWARD THROUGH THE ARKLATEX INTO
SE TEXAS. THIS WAS OCCURRING AHEAD OF A COLD FRONT AND IN
ASSOCIATION WITH A SHORTWAVE SWINGING INTO THE MIDSOUTH. THE MOST
VIGOROUS CONVECTION ALONG THE LINE IS ONGOING OVER EAST TX AND WEST
LA, AND THIS IS WHAT IS EXPECTED TO BE THE MAIN PLAYER ACROSS OUR
AREA LATER ON TODAY AS IT CONTINUES EASTWARD.

CURRENT TRENDS/CONSENSUS AMONG HIGH RES MODEL GUIDANCE SUGGEST STORMS
WILL BEGIN TO REACH OUR NE LA PARISHES AROUND MID-MORNING. WITH THIS
TIME FRAME STILL BEING ON THE DOWNSIDE OF THE DIURNAL INSTABILITY
CURVE, THE STORMS ARE GENERALLY NOT EXPECTED TO BE QUITE AS ACTIVE AT
THAT POINT. HOWEVER, THROUGH THE DAY AS INSTABILITY INCREASES AHEAD
OF THE LINE, STRENGTHENING/REDEVELOPMENT IS EXPECTED TO OCCUR AS
CONVECTION CONTINUES EASTWARD. HIGH RES GUIDANCE SUGGESTS THE
GREATEST POTENTIAL FOR STRONG TO SEVERE STORMS TO BE GENERALLY ALONG
AND SOUTH OF I-20, BUT THERE WILL BE SOME POTENTIAL FOR STRONGER
STORMS TO SPREAD FARTHER NORTH ESPECIALLY WITH EASTWARD EXTENT AS
THERE IS MORE OPPORTUNITY FOR DAYTIME HEATING. THE LOWEST CONFIDENCE
IN STRONG/SEVERE STORMS IS ACROSS THE DELTA, WHERE RAIN WILL LIKELY
BEGIN EARLY IN THE DAY WITH LESS OPPORTUNITY FOR DESTABILIZATION.
WITH THIS IN MIND, FOR GRAPHICS/HWO THE ELEVATED WILL BE REMOVED IN
THE WEST AND THE LIMITED WILL BE EXPANDED ACROSS THE REMAINDER OF THE
AREA. IF IT CONTINUES TO APPEAR THAT THE LINE WILL BE MORE ACTIVE
ACROSS THE SOUTHERN HALF OF THE AREA, AN ELEVATED THREAT MAY NEED TO
BE INTRODUCED LATER TODAY. TIMING WILL ALSO BE BUMPED UP, AS THE
LINE MAY BE THROUGH MUCH OF THE AREA BY LATE AFTERNOON.

HEADING INTO TONIGHT, THERE SHOULD BE A LULL IN THE WAKE OF THE
STORMS THAT PUSH THROUGH TODAY. SOME REDEVELOPMENT WILL BE POSSIBLE
ALONG THE FRONT, BUT RIGHT NOW IT APPEARS MOST OF THAT WILL REMAIN
NORTHWEST OF THE CWA IN ARKANSAS. THE FRONT WILL SINK SOUTHEASTWARD
INTO THE CWA ON SUNDAY, WITH REDEVELOPMENT EXPECTED MAINLY ACROSS THE
SOUTHEAST HALF OF THE AREA IN THE WARM SECTOR. IF THERE IS SUFFICIENT
INSOLATION, INSTABILITY MAY BECOME SUFFICIENT FOR ADDITIONAL STRONG/
SEVERE CONVECTION TOMORROW, BUT FORCING AND LOW LEVEL SHEAR WILL BE
MUCH WEAKER, MAKING THIS THREAT MORE UNCERTAIN. WITH THAT IN MIND, NO
THREAT WILL BE INTRODUCED IN THE HWO AT THIS TIME.

WITH THE SHIFT IN EXPECTATIONS FROM THE AXIS OF MORE ACTIVE STORMS
AND HEAVY RAIN BEING OVER THE DELTA FARTHER SOUTH TO ACROSS CENTRAL
LA AND SOUTH MS, THAT ALSO SHIFTS EXPECTATIONS FOR THE FLOODING
THREAT. THOUGH MUCH OF THE DELTA MAY MISS OUT ON THE HEAVIEST RAIN,
PRECIP IS JUST BEGINNING TO ARRIVE IN THAT AREA, AND WITH THE SLOW
MOVEMENT OF THE LINE THERE IS SOME POTENTIAL FOR FLOODING. THUS, THE
FLOOD WATCH WILL BE MAINTAINED FOR THAT AREA, BUT WE WILL LOWER
EXPECTED AMOUNTS. PERHAPS OF GREATER CONCERN IS AREAS FARTHER SOUTH
FROM CENTRAL LA ACROSS SOUTH MS. IN THESE AREAS, THERE WILL ALSO BE
GREATER RAIN CHANCES CONTINUING INTO SUNDAY. IF MODEL GUIDANCE
CONTINUED TO TREND IN THIS DIRECTION, LATER SHIFTS MAY NEED TO MAKE
AN EASTWARD EXTENSION TO THE WATCH INTO THE PINE BELT. FOR NOW, WE
WILL EXTEND A MENTION OF HEAVY RAIN/FLOODING CONCERNS IN THE HWO
INTO SUNDAY, MAINLY OVER THE SOUTHEAST HALF OF THE AREA. /DL/

LONG TERM (MONDAY THROUGH NEXT WEEKEND)...THE PERIOD OF ACTIVE
WEATHER WE ARE CURRENTLY IN WILL CONTINUE INTO EARLY NEXT WEEK. BY
MONDAY MORNING...ONE WAVE OF SHOWERS AND THUNDERSTORMS WILL DEPART
WITH ANOTHER ON OUR DOORSTEP TO THE WEST. RAIN AND STORMS WILL
AFFECT THE ARKLAMISS REGION THROUGH TUESDAY AS THIS SHOULD BE THE
FINAL ROUND. THIS ACTIVITY WILL COME AHEAD OF THE MAIN COLD FRONT
ACTUALLY MOVING INTO THE REGION SLOWLY THROUGH TUESDAY...FOLLOWED BY
THE MAIN UPPER LEVEL TROUGH SWINGING THROUGH AS WELL BY WEDNESDAY.
HEAVY RAIN/FLOODING WILL CONTINUE TO BE A CONCERN GIVEN HOWEVER MUCH
RAIN MAY FALL PRECEDING THIS PERIOD. TEMPERATURES WILL ALSO BE
TRICKY DURING THIS TIME PERIOD AS CLOUDS AND RAIN WILL HAMPER MUCH
WARMING AND THE PLACEMENT OF THE FRONT WILL ALSO MAKE FOR A
VARIATION IN TEMPERATURE ACROSS THE AREA.

ONCE THE FRONT PASSES AND THE UPPER TROUGH ALSO SWINGS THROUGH...
MUCH DRIER CONDITIONS SHOULD PREVAIL THROUGH THE REMAINDER OF THE
PERIOD. WITH A LARGE UPPER LOW SPINNING ACROSS THE EASTERN HALF OF
THE COUNTRY...THIS WILL LEAVE OUR REGION UNDER NORTHWEST FLOW ALOFT.
THIS WOULD SUGGEST COOLER TEMPERATURES AND WE SHOULD SEE READINGS
BACK CLOSER TO SEASONAL NORMALS. BRIEF SHORTWAVE RIDGING WILL MOVE
OVER THE AREA FOR THE LATTER PART OF THE WEEKEND. OVERALL...SHOULD BE
SOME NICE WEATHER FOR THE LATTER PORTIONS OF THE WEEK AND INTO THE
WEEKEND ONCE WE GET THROUGH SOME OF THE WET WEATHER IN THE SHORTER
TERM. /28/

&&

.AVIATION...MVFR CIGS HAVE DEVELOPED OVER THE SOUTHERN HALF OF THE
AREA THIS MORNING, WITH IMPROVEMENT TO VFR EXPECTED BY LATE MORNING.
CONDITIONS WILL DETERIORATE FROM WEST TO EAST TODAY AS A LINE OF
SHRA/TSRA PUSH EASTWARD ACROSS THE REGION DURING THE LATE MORNING/
AFTERNOON HOURS. BRIEF VISBY CATEGORICAL REDUCTIONS ARE EXPECTED IN
+RA, AND 50 KT WIND GUSTS WILL BE POSSIBLE ALONG THE LINE ALONG WITH
SMALL HAIL. LOW CIGS ARE EXPECTED TO BUILD BACK IN OVER THE AREA
LATER TONIGHT, WITH MVFR/IFR CATEGORIES POSSIBLE. WINDS WILL BEGIN TO
SHIFT TO NW AT SITES IN THE DELTA SUNDAY MORNING AS A COLD FRONT
PUSHES INTO THE AREA. /DL/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       79  67  82  65 /  94  59  53  49
MERIDIAN      82  66  81  64 /  86  43  68  27
VICKSBURG     79  69  83  66 /  94  49  43  58
HATTIESBURG   82  66  82  66 /  95  55  70  29
NATCHEZ       80  67  81  66 /  95  59  62  54
GREENVILLE    79  66  82  63 /  60  30  23  50
GREENWOOD     78  66  82  63 /  57  40  29  49

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR MSZ018-019-025-034-
     035-040-041.

     FLASH FLOOD WATCH FROM 10 AM CDT THIS MORNING THROUGH SUNDAY
     MORNING FOR MSZ026>029-032-036-037-042>044-047>050-053>055-
     059>063.

LA...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR LAZ007>009-015-016-
     023.

     FLASH FLOOD WATCH FROM 10 AM CDT THIS MORNING THROUGH SUNDAY
     MORNING FOR LAZ024>026.

AR...FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR ARZ074-075.

&&

$$

17/DL/28


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