Special Weather Statement, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
1101 AM CDT SAT JUN 28 2014

.UPDATE...

WILL MAKE SOME MINOR UPDATES TO RAISE THE POPS AND ADJUST
TEMPERATURES AND OTHER FIELDS FOR TODAY...OTHERWISE THE FORECAST IS
ON TRACK WITH THE THREAT FOR SEVERE STORMS CONTINUING THIS AFTERNOON
AND PERHAPS INTO THE EARLY OVER MAINLY WESTERN PORTIONS OF THE
ARKLAMISS.

AS PREVIOUSLY INDICATED...THE SUBTROPICAL RIDGE IS BEGINNING TO BUILD
OVER THE LOWER MS VALLEY...BUT THERE IS STILL A SIGNIFICANT AMOUNT OF
TROUGHING OVER THE ARKLATEX THIS MORNING THAT IS ENHANCING THE
SOUTHERLY LOW LEVEL FLOW (H850 ~25KTS, 0-1KM SHEAR/SRH OF 15-20KTS
AND 100-150 M2/S2 RESPECTIVELY). IN ADDITION...MORNING RAOBS INDICATE
SUBSTANTIAL MID LEVEL LAPSE RATES WITH VERTICAL TOTALS ~28 AND EXPECT
MIXED LAYER CAPE TO EXCEED 3000 J/KG THIS AFTERNOON IN MUCH OF THE
SEVERE RISK AREA ALONG/WEST OF I-55.

IN TERMS OF STORM EVOLUTION...SHOWERS/THUNDERSTORMS ARE CURRENTLY
DEVELOPING IN BETTER MOISTURE CONVERGENCE AXIS OVER COASTAL REGIONS
OF SE TX INTO SW LA. LATEST NEAR TERM HIGH-RES GUIDANCE SHOWS THIS
ACTIVITY WILL EVENTUALLY ORGANIZE AND SPREAD NORTHEASTWARD TOWARD OUR
AREA BY LATE AFTERNOON AND EARLY EVENING. AHEAD OF THIS
ACTIVITY...SCATTERED-ISOLATED SHOWERS/STORMS SHOULD DEVELOP DIRECTLY
OVER THE FORECAST AREA WITH CONTINUED HEATING...PERHAPS FOCUSING NEAR
MOISTURE/INSTABILITY GRADIENT THAT CURRENTLY EXISTS FROM THE HBG TO
JAN TO GWO AREA. GIVEN THE AMOUNT OF INSTABILITY AND THE POTENTIAL
FOR ORGANIZED CONVECTION...WILL KEEP THE THREAT FOR DAMAGING WINDS
MENTIONED. EXPECT THE INTENSITY OF STORMS TO DIMINISH CONSIDERABLY
AFTER SUNSET AS PREVIOUSLY INDICATED. /EC/

&&

.AVIATION...A MIX OF VFR AND MVFR CONDITIONS ARE OCCURRING THIS
MORNING AS MORNING LOW CLOUDS ARE SLOW TO LIFT. MID AND HIGH CLOUDS
ARE STREAMING NORTH INTO THE REGION AND WILL CONTINUE TO DO SO
THROUGH THE DAY BUT VFR CEILINGS WILL LIKELY PREVAIL. AFTERNOON
STORMS ARE AGAIN POSSIBLE TO LIKELY AND THIS WILL BRING BRIEF MVFR
TO IFR CONDITIONS AT AFFECTED TAF SITES. THE STRONGEST STORMS RIGHT
NOW ARE FORECAST TO AFFECT WESTERN SITES SUCH AS KGLH/KGWO/KHKS/KJAN
AND THESE COULD BRING SOME GUSTY WINDS. ACTIVITY WILL DISSIPATE THIS
EVENING. SOUTHERLY WINDS WILL PREVAIL 5-10KTS OUTSIDE OF STORMS. /28/

&&

.PREV DISCUSSION... /ISSUED 409 AM CDT SAT JUN 28 2014/

MODELS ARE ALSO IN FAIRLY GOOD AGREEMENT WITH ADVERTISING STEEPER
MID-LEVEL LAPSE RATES (6.25-6.5 C/KM)...27-29C VERTICAL TOTALS...
FAVORABLE LOW AND MID-LEVEL FLOW...AND BOTH MODEST SPEED AND
DIRECTIONAL SHEAR (SOUTHERLY 15-20 KNOTS OF 0-1 KM SHEAR AND WESTERLY
20-25 KNOTS 0-6 KM SHEAR). THIS COULD YIELD SOME SEVERE STORMS TODAY
CAPABLE OF PRODUCING SOME DAMAGING WIND GUSTS ALONG WITH HAIL. I'LL
MAINTAIN A LIMITED POTENTIAL FOR SUCH STORMS IN THE HWO OVER THE
WESTERN HALF OF THE CWA...AS IT'S THERE THAT THE BEST CONGLOMERATION
OF THE ABOVE PARAMETERS EXISTS. AS HAS BEEN THE CASE WITH PREVIOUS
DAYS IN THIS MOIST AIRMASS...LOCALLY HEAVY RAINFALL WILL REMAIN
LIKELY WITH ANY CONVECTION ACROSS THE ARKLAMISS TODAY.

CONVECTION FROM THIS AFTERNOON WILL LINGER INTO THE EVENING
HOURS...BUT MOST SHOULD BEGIN DISSIPATING IN BOTH COVERAGE AND
INTENSITY AFTER SUNSET.  RAIN CHANCES WILL REMAIN IN THE FORECAST
OVER MY NORTHWEST ZONES THROUGH THE OVERNIGHT HOURS INTO SUNDAY
MORNING AS ANOTHER WEAK DISTURBANCE APPROACHES FROM THE WEST.  THIS
WAVE WILL AGAIN BRING CHANCES FOR SHOWERS AND STORMS TO THE FORECAST
AREA SUNDAY MORNING INTO SUNDAY AFTERNOON AS IT SWINGS BY JUST
NORTH OF THE CWA...THUS RESULTING IN THE BETTER RAIN CHANCES BEING
OVER THE NORTHERN THIRD OF THE AREA.  HIGHS SUNDAY AFTERNOON WILL
AGAIN WARM TO AROUND 90.

CONVECTION LOOKS TO COME TO AN END...QUICKER THAN IT HAS IN PREVIOUS
DAYS...LATE SUNDAY AFTERNOON AS UPPER RIDGING REALLY INCREASES OVER
THE FORECAST AREA THROUGH THE DAY.  AS A RESULT...LOOK FOR MOSTLY
CLEAR SKIES AS LOWS FALL INTO THE LOW AND MIDDLE 70S. /19/

MONDAY THROUGH NEXT WORK WEEK...LONG-AWAITED DEEP HIGH
PRESSURE MOVING OVER THE REGION MONDAY FINALLY LOOKS TO SHUT DOWN
SIGNIFICANT PRECIP CHANCES FOR THE START OF NEXT WORK WEEK.
SUPPRESSION FROM ANTICYCLONE ALOFT PROBABLY WILL NOT BE ENOUGH TO
KEEP A VERY ISOLATED SHOWER OR TWO FROM POPPING UP MONDAY AND
TUESDAY...BUT CHANCES OF GETTING WET STILL DEEMED LOW ENOUGH TO KEEP
OUT OF THE OFFICIAL FORECAST. OWING LARGELY TO A MUCH GREATER AMOUNT
OF SUNSHINE TEMPERATURES WILL SHOOT UP WITH HIGHS MAINLY IN THE 93
TO 96 DEGREE RANGE ANTICIPATED MONDAY AND TUESDAY.
EVAPOTRANSPIRATION WILL HELP KEEP MOISTURE FROM MIXING OUT IN THE
AFTERNOON AND WILL ALLOW PEAK HEAT INDEX VALUES TO PEAK AT OR A
LITTLE ABOVE THE CENTURY MARK IN MANY AREAS ON BOTH DAYS. CURRENT
EXPECTATIONS ARE FOR THIS HOT STRETCH TO FALL COMFORTABLY SHORT OF
HEAT ADVISORY CRITERIA SO WILL LEAVE MENTION OUT OF HWO FOR NOW.

PRECIP CHANCES WILL COME BACK FROM THE NORTH ON WEDNESDAY AS THE
HIGH PRESSURE RIDGE COMING OUT OF TX FLATTENS IN RESPONSE TO AN
INCOMING AND NON-TRIVIAL COOL FRONT. THERE IS DEFINITELY SOME
UNCERTAINTY ABOUT HOW QUICKLY THIS RIDGE WILL RELENT TO FRONTAL
INCURSION INTO THE LOWER MS VALLEY...BUT MODEL CONSENSUS SEEMS TO
HAVE SPED UP WITH THIS EVOLUTION ALTHOUGH I MAINLY SIDED WITH LEAST
AGGRESSIVE EURO IN THIS REGARD. IF THE EURO IS CORRECT AND
THUNDERSTORM CHANCES ARE MOSTLY LIMITED TO NORTHERN ZONES LATER IN
THE AFTERNOON WEDNESDAY THEN HUMP DAY COULD PROVE TO BE THE HOTTEST
DAY OF THE HOT STRETCH AND IN ANTICIPATION OF THIS MORE LIKELY
SCENARIO I BUMPED UP MEX HIGHS. OF COURSE IN THE HOT ENVIRONMENT IN
NORTHERN ZONES WEDNESDAY AFTERNOON INSTABILITY SHOULD BE HIGH AND
THE POTENTIAL FOR POTENT CONVECTION WILL HAVE TO BE MONITORED AS WE
GO FORWARD IN THE FORECAST PROCESS.

THURSDAY AND FRIDAY MODEL CONSENSUS SUGGESTS THE INCOMING SAGGING
FRONTAL ZONE TO PROBABLY STALL IN THE MIDST OF OUR REGION AFTER
INFILTRATING IN BACKDOOR FASHION. RIDGING ALOFT WILL BE
WEAKENED...BUT MODELS SUGGESTS NOT ENOUGH TO RELENT TO A PERTURBED
NORTHWEST FLOW PATTERN. THUS...EXPECT IN THE VICINITY OF THE
BOUNDARY FOR ISOLATED TO SCATTERED MAINLY AFTERNOON SHOWERS AND
STORMS WITH OTHERWISE SULTRY CONDITIONS...ALTHOUGH PROBABLY SLIGHTLY
LESSER HEAT THAN THE MID-WEEK PEAK. /BB/

&&

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

&&

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