Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 191613 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE JACKSON MS
1110 AM CDT SUN APR 19 2015

...LARGE HAIL AND DAMAGING WINDS A CONCERN NORTHWEST OF THE NATCHEZ
TRACE CORRIDOR THIS EVENING...

.UPDATE... FORECAST IS PRETTY ON MUCH ON TRACK THIS MORNING. THERE
ARE A FAIR AMOUNT OF CLOUDS ACROSS THE REGION CURRENTLY BUT MANY
SUCH LAYERS ARE LOW AND SHOULD MIX OUT IN THE NEXT HOUR OR SO.
SCATTERED SHOWERS NOW PROGRESSING FROM THE ARKLAMISS DELTA INTO
NORTH CENTRAL MS ARE ASSOCIATED WITH A DISTURBANCE/MCV WHICH WILL BE
PULLING AWAY FROM THE REGION THIS AFTERNOON. IT IS NOT OUT OF THE
REALM OF POSSIBILITY THIS DISTURBANCE COULD KICK UP AN ISOLATED
SEVERE STORM IN THE VICINITY OF THE HIGHWAY 82 CORRIDOR EAST OF I-55
THROUGH 3PM...AND THIS WILL BE MONITORED CLOSELY. ELSEWHERE IN THE
REGION THE PROSPECT OF SEVERE WEATHER THROUGH LATE AFTERNOON IS
RATHER LOW AND POPS WERE GENERALLY DROPPED A BIT FOR THE REMAINDER
OF THE DAYLIGHT HOURS IN MOST SPOTS TO BETTER REPRESENT EXPECTATION
OF DRY AND WARM CONDITIONS.

HOWEVER...BY THIS EVENING THE PREVIOUSLY-ANTICIPATED RISK OF SEVERE
WEATHER STILL LOOKS ON THE MARK. MODEL CONSENSUS DEPICTS A PRE-FRONTAL
SURFACE TROUGH TRIGGERING EXPLOSIVE THUNDERSTORM DEVELOP THIS
AFTERNOON IN THE VICINITY OF THE ARKLATEX...WITH THIS ACTIVITY
SLIDING EAST INTO AREAS NORTHWEST OF THE NATCHEZ TRACE CORRIDOR
BEFORE 11 PM (POSSIBLY ENTERING ASHLEY CO AR AND MOREHOUSE PARISH BY
7 PM). THIS ACTIVITY WILL BE FORMING IN AN ENVIRONMENT OF HIGH
ATMOSPHERE LAPSE RATES WITH ASSOCIATION MLCAPE VALUES OVER 2000 J/KG
AND MODERATE DEEP LAYER SHEAR SUGGESTIVE OF A MIXED MODE OF GUSTY
LINE SEGMENTS AND SUPERCELLS. PARTICULARLY WITH SUPERCELLS COMING IN
FROM THE WEST THE POTENTIAL WILL EXIST FOR LARGE HAIL OVER GOLF BALL
SIZE WHILE ANY BOWING LINE SEGMENTS COULD BE CAPABLE OF WINDS TO 70
MPH OR MORE.

AS ACTIVITY PUSHES TOWARD THE NATCHEZ TRACE CORRIDOR IN THE LATE
EVENING TO NEAR MIDNIGHT INSTABILITY WILL BE GRADUALLY WANING AND
SOME HIRES MODEL SOLUTIONS SUGGEST STORMS MAY HAVE A HARD TIME
HOLDING TOGETHER THROUGH THE HEART OF THE CWA. THUS THE ADVERTISED
RISK OF SEVERE WEATHER POTENTIAL DECREASING SUBSTANTIALLY INTO THE
SOUTHEASTERN PORTION OF THE CWA LATE IN THE NIGHT LOOKS VERY
ACCURATE.

FINALLY...IT IS WORTH MENTIONING THAT ALTHOUGH WE ANTICIPATE THE
MAIN SEVERE WEATHER RISKS LATER TODAY WILL COME FROM LARGE HAIL AND
DAMAGING WINDS WE CANNOT RULE OUT A FEW TORNADOES CONSIDERING THERE
WILL BE SUFFICIENT LOW LEVEL SHEAR FOR ROTATING STORMS. LCL HEIGHTS
WITH THE MOST POTENT CONVECTION (NORTHWEST OF THE NATCHEZ TRACE)
WILL LIKELY BE HIGHER THAN OPTIMAL FOR APPRECIABLE TORNADIC
ACTIVITY...BUT STILL NOT ENOUGH OF AN IMPEDIMENT TO RULE IT OUT. /BB/

&&

.AVIATION...A MIX OF VFR/MVFR CONDITIONS PREVAIL ACROSS TAF SITES
THIS MORNING WITH A FEW SHOWERS MOVING ACROSS GLH. EXPECT MOST SITES
TO BECOME VFR BY EARLY AFTERNOON AS DRIER AIR MOVES INTO THE AREA.
SHRA/TSRA WILL BE POSSIBLE ONCE AGAIN BY EARLY EVENING AT GLH/GWO
AND SPREAD EAST ACROSS THE REMAINING SITES LATER IN THE EVENING INTO
THE OVERNIGHT HOURS. ALONG WITH THE SHRA/TSRA MVFR CONDITIONS WILL
RETURN TO MOST SITES AFTER 06-07Z.  WINDS TODAY WILL BE SOUTHERLY
AROUND 10 KNOTS...BUT AS A FRONT PASSES THROUGH LATER TONIGHT...
WINDS WILL BECOME NORTHERLY IN ITS WAKE. /15/

&&

.PREV DISCUSSION... /ISSUED 459 AM CDT SUN APR 19 2015/

DISCUSSION...TODAY THROUGH NEXT SUNDAY...OTHER THAN SOME HIGH- RES
MODELS...OVERALL SUITE OF GLOBAL MODELS HAVEN`T BEEN MUCH HELP WITH
RECOGNIZING WHAT`S GOING ON RIGHT NOW AND WHAT WILL TRANSPIRE THROUGH
AT LEAST THE MORNING AND EARLY AFTERNOON HOURS. THEREFORE... THE
FORECAST FOR A GOOD BIT OF TODAY AT LEAST WILL BASICALLY BE A BLEND
OF CURRENT RADAR TRENDS AND SAID HIGH-RES MODELS.

CURRENT RADAR SHOWS AN AREA OF SHOWERS EXITING THE EASTERN HALF OF
THE CWA.  AS THIS IS HAPPENING...SCATTERED CONVECTION IS DEVELOPING
OUT AHEAD OF ANOTHER LINE OF SHOWERS AND STORMS THAT`S SHIFTING EAST
NORTHEAST AND INTO THE WESTERN HALF OF MY CWA.  BASED ON THIS
ALONE...I`VE INCREASED POPS ACROSS THE BOARD FOR TODAY.  THE
THINKING IS...AND HIGH-RES MODELS AGREE...THERE WILL BE A GRADUAL
DECREASE IN ACTIVITY FROM MID TO LATE MORNING.  HOWEVER...DAYTIME
HEATING COMBINED WITH THE DISTURBANCE STILL TREKING EAST ACROSS THE
CWA...WILL CAUSE CONVECTION TO AGAIN INCREASE IN COVERAGE OVER MY
EAST HEADING INTO THE EARLY AFTERNOON.  SOME OF THE STORMS IN MY
WEST...MAINLY THOSE ALONG THE SQUALL LINE...THIS MORNING COULD BE
STRONG TO SEVERE AND CAPABLE OF PRODUCING GUSTY WINDS.  HEAVY
RAINFALL RESULTING IN LOCALIZED FLASH FLOODING CANNOT BE RULED OUT
EITHER.

ONCE THIS CONVECTION EXITS THE REGION THIS AFTERNOON...THERE WILL BE
FEW HOURS IN WHICH THERE WILL BE A LULL IN ACTIVITY.  LATE IN THE
DAY AND INTO THIS EVENING HOWEVER... ANOTHER...AND MORE POTENT...
PIECE OF ENERGY AND COLD FRONT IS EXPECTED TO BEGIN IMPEDING UPON
THE CWA FROM THE WEST. THIS WILL BE WHEN THE BETTER POTENTIAL FOR
SEVERE WEATHER ENTERS THE FORECAST FOR THE ENTIRE CWA.

THE OVERALL SETUP FOR THIS SEVERE POTENTIAL LATE THIS AFTERNOON...
BUT MORE SO THIS EVENING...HASN`T CHANGED MUCH.  WHILE THIS
MORNING`S ACTIVITY DOES TAKE SOME PUNCH OUT OF THE AIRMASS FOR THE
AFTERNOON...MODELS AGREE THAT THERE WILL BE A GOOD BIT OF RECOVERY
AND INCREASED SEVERE WEATHER PARAMETERS THIS EVENING AS A PRE-
FRONTAL TROUGH AXIS SHIFTS IN FROM THE WEST.  A BROKEN LINE OF
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND
GUSTS...PERHAPS SOME IN EXCESS OF 60 MPH...REMAIN THE PRIMARY
THREATS WITH THESE STORMS.  HOWEVER...A TORNADO OR TWO CANNOT BE
RULED OUT.  THIS ACTIVITY IS EXPECTED TO BEGIN MOVING INTO THE DELTA
AROUND TO JUST AFTER 7 PM THIS EVENING.  I`LL MAINTAIN THE CURRENT
LAYOUT OF THE HWO THIS MORNING AS THE BETTER CONFIDENCE OF SEVERE
WEATHER EXISTS ACROSS THE DELTA WHERE SEVERE PARAMETERS LOOK MOST
FAVORABLE.  WHILE ACTIVITY IS EXPECTED TO GRADUALLY WEAKEN THE
FURTHER EAST IT MOVES...THE RISK FOR SEVERE WEATHER DOES EXIST
ACROSS THE ENTIRE CWA THIS EVENING INTO TONIGHT.

AS THE SYSTEM EXITS EAST INTO ALABAMA EARLY MONDAY MORNING...
NOTICEABLY COOLER DRIER AIR WILL ADVECT INTO THE CWA ON MONDAY AS
HIGH PRESSURE BUILDS IN FROM THE WEST.  THIS LOOKS TO LEAD TO A
BRIEF DRY PERIOD OF WEATHER MONDAY THROUGH AT LEAST WEDNESDAY...
ALTHOUGH SOME SMALL RAIN CHANCES DO EXIST IN THE FORECAST FOR
WEDNESDAY AFTERNOON AS WARM ADVECTION ENSUES ACROSS THE REGION.

THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD...THURSDAY THROUGH
NEXT SUNDAY...WITH SUBTLE DISTURBANCES EMBEDDED IN ZONAL FLOW
TRAVERSING THE REGION...COUPLED WITH DAYTIME HEATING...RAIN CHANCES
REMAIN IN THE FORECAST EACH AFTERNOON.  BETTER RAIN CHANCES COULD
EXIST OVER NEXT WEEKEND AS A TROUGH SWINGING THROUGH THE MID-
MISSISSIPPI RIVER VALLEY TRIES TO PUSH A COLD FRONT INTO AND THROUGH
THE FORECAST AREA. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       82  61  75  49 /  12  49   6   5
MERIDIAN      82  63  76  48 /  17  48  12   5
VICKSBURG     83  58  74  49 /  20  53   5   5
HATTIESBURG   85  65  80  53 /  12  31  10   5
NATCHEZ       84  60  75  50 /  22  38   3   4
GREENVILLE    80  57  72  48 /  23  72   7   5
GREENWOOD     79  58  72  47 /  31  64  13   5

&&

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

$$

BB/15/19



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