Severe Thunderstorm Warning 283, NWS Raleigh, NC

AREA FORECAST DISCUSSION...CORRECTED FOR LONG TERM TIME
NATIONAL WEATHER SERVICE RALEIGH NC
300 PM EDT WED AUG 5 2009

.SYNOPSIS...
A WEAK TROUGH OF LOW PRESSURE WILL REMAIN IN PLACE OVER WESTERN
NORTH CAROLINA...WHILE AN APPROACHING UPPER LEVEL DISTURBANCE
INCREASES THE CHANCE OF THUNDERSTORMS LATE TODAY AND TONIGHT.
CONDITIONS SHOULD DRY SOME FOR FRIDAY...WITH A SMALL CHANCE FOR
STORMS OVER THE WEEKEND AS TEMPERATURES WARM.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 140 PM WEDNESDAY...

SHOWERS AND THUNDERSTORMS ARE LINING UP ALONG THE PIEDMONT TROF OVER
THE HEART OF THE CWFA THIS AFTERNOON. COVERAGE WILL BE INCREASING IN
THE EAST WHERE INSTABILITY IS THROUGH THE ROOF WITH MU CAPES
EXCEEDING 3K JOULES. AS SUCH...WILL READJUST POPS TO CHANCE FOR THE
AFTERNOON EAST...WITH CONVECTION IN THE WEST STILL EXPECTED TO BEGIN
BLOSSOMING A LITTLE LATER IN THE EVENING AS THE UPPER TROF EDGES
NEARER. EXPECT THE EASTERN DIURNALLY DRIVEN STORMS TO INITIALLY
DIMINISH EARLY TONIGHT WITH LOSS OF INSOLATION...BUT WITH THE UPPER
DYNAMICS MOVING EAST...SHOWERS AND SCATTERED TSRA WILL BE POSSIBLE
ALL NIGHT.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 300 PM WEDNESDAY...

THURSDAY...UPPER TROF WILL BE SLOW TO EXIT THE AREA...AND DRY AIR
AND DIMINISHING POPS WILL BE SLOWLY PROGRESSING WEST TO EAST
THROUGHOUT THE DAY. RAIN AND CLOUD COVER WILL POTENTIALLY HINDER MAX
TEMPS... ESPECIALLY IN THE EAST. IT IS AUGUST...HOWEVER...AND THE
SURFACE FRONT WILL NOT EXIT THE EAST UNTIL LATE...SO EVEN WITHOUT
INSOLATION EXPECT HIGHS TO REACH THE MID AND UPPER 80S IN SOUTHWEST
FLOW. WILL KEEP POPS IN THE CHANCE CATEGORY DUE TO REDUCED
INSTABILITY...TAPERING TO SLIGHT CHANCE IN THE WEST WHICH SHOULD BE
UNDER SOME SUBSIDENCE BEHIND THE UPPER SHORT WAVE.

THURSDAY NIGHT...ALTHOUGH ANOTHER...WEAKER SHORTWAVE MOVES THROUGH
CENTRAL NORTH CAROLINA OVERNIGHT...THE MEAN AIRMASS DRIES WITH
GENERAL SUBSIDENCE DEVELOPING AS A WEAK SURFACE RIDGE BUILDS IN. THE
NAM AND THE GFS ARE SIMILAR WITH BASIC FEATURES FROM THURSDAY NIGHT
THROUGH FRIDAY NIGHT...AND WHILE THERE MAY BE A SHORT PERIOD WITH A
SMALL CHANCE OF SHOWERS AND THUNDERSTORMS IN VICINITY OF INTERSTATE
95...CURRENTLY BELIEVE THE MID-EVENING HOURS ONWARD WILL BE DRY.

WITH SUBSIDENCE IN PLACE FRIDAY...THE CHANCES FOR SHOWERS APPEARS
SMALL. WEAK LIFT IS PRESENT FRIDAY ONLY ON THE NAM...BUT THE MEAN
AIR MASS ON BOTH MODELS REMAIN DRY WITH OVERALL NEGATIVE MID-LEVEL
VORTICITY ADVECTION IN PLACE OVER CENTRAL NORTH CAROLINA. BUFR
SOUNDINGS ARE STABLE TO DEEP CONVECTION AND WILL SHOW A DRY DAY ON
FRIDAY. ON SATURDAY...THE GFS HAS TRENDED DRIER...WHILE THE NAM
BEGINS TO INCREASE INSTABILITY IN WARM-AIR ADVECTION. BOTH THE GFS
AND THE NAM SHOW AN INCREASE IN 850MB THETA-E...BUT THE NAM IS THE
ONLY MODEL AMONG THE TWO TO SUPPORT ANY QPF. BUFR SOUNDINGS ARE ONLY
MODESTLY UNSTABLE...BUT AS A SURFACE TROUGH RETURNS AND BECOMES
SOMEWHAT MORE PRONOUNCED ON THE GFS AND THE NAM...WILL MAINTAIN A
SLIGHT CHANCE OF THUNDERSTORMS FOR THE MID-MORNING INTO THE EARLY
EVENING. TEMPERATURES THROUGHOUT THE PERIOD WILL BE FORECAST CLOSE
TO MOS GUIDANCE...WITH A NOTICEABLE INCREASE SATURDAY AS THE
WARM-AIR ADVECTION TAKES SHAPE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 300 PM WEDNESDAY...

THE ECMWF CONTINUES TO BE VERY CONSISTENT WITH ITS DEPICTION OF THE
UPPER RIDGE AXIS REMAINING JUST WEST OF THE CAROLINAS AS COMPARED TO
THE OTHER OPERATIONAL MODELS...WHICH SUGGEST THE UPPER-LEVEL RIDGE
WILL BUILD IN FAIRLY STRONGLY OVER THE WEEKEND AND INTO EARLY NEXT
WEEK. WHILE AT TIMES IT IS DIFFICULT TO FOLLOW MORE CLOSELY THE
OUTLIER...IN THIS CASE THE PERSISTENCE OF THE ECMWF AND THE MOS
ENSEMBLE GUIDANCE ON AVERAGE SHOWING CHANCES FOR RAIN AT OR ABOVE
CLIMATOLOGY SUGGEST KEEPING AT LEAST A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE FORECAST...MAINLY DIURNALLY. FORCING FOR ANY
PRECIPITATION WOULD BE A MID-LEVEL WAVE IN THE NORTHWEST FLOW
ALOFT...IF THE ECMWF VERIFIES...AND THE PRESENCE OF A WEAK SURFACE
TROUGH IN THE WARM...UNSTABLE AIR.

THE SAME REGIME CONTINUES FOR MONDAY...AND EVEN THE ECMWF APPEARS
DRIER IN THE MEAN THAN IN PREVIOUS RUNS. IT IS INTERESTING HOW MANY
MOS ENSEMBLE MEMBERS ARE ABOVE CLIMATOLOGY WITH REGARD TO POPS ON
MONDAY...BUT OF ALL DAYS IN THIS PERIOD THIS IS THE DAY WHERE THE
CONSENSUS OF MODELS SUGGEST THE LEAST QPF AND THE DRIEST AIR
OVERALL. WHILE IT IS STILL PRUDENT TO MAINTAIN SOME SMALL CHANCES
FOR SHOWERS...JUST INTO THE SLIGHT CHANCE CATEGORY...FOR MONDAY...
WAS TEMPTED TO GO DRY ON THIS DAY GIVEN SOME INDICATION OF SURFACE
RIDGING ESPECIALLY EARLY IN THE DAY ON THE ECMWF.

THE CONSENSUS OF THE GUIDANCE REMAINS CONSISTENT ON THE SUPPRESSION
AND RETREAT OF THE UPPER-LEVEL RIDGE FOR TUESDAY INTO WEDNESDAY...
AS AN UPPER-LEVEL TROUGH DEVELOPS OVER SOUTHEAST CANADA. THE
PROGRESS OF THE SURFACE FRONT IS SOMEWHAT SLOWER THAN WAS THE CASE
ON TUESDAY MODEL RUNS...WITH THE FRONT NOT GETTING CLOSE TO CENTRAL
NORTH CAROLINA UNTIL WEDNESDAY. STILL...AS THE UPPER-LEVEL TROUGH
BEGINS TO SHARPEN...THE SURFACE REFLECTION OF THE TROUGH SHARPENS AS
WELL...WHICH SHOULD LEAD TO INCREASED CONVERGENCE AND A BETTER
CHANCE FOR SHOWERS AND THUNDERSTORMS. CHANCES FOR SHOWERS AND
THUNDERSTORMS SHOULD ALSO BE AIDED BY THE SOUTHWARD PROGRESSION OF
THE UPPER JET CLOSER TO THE MID-ATLANTIC STATES. CHANCE POPS WILL BE
IN PLACE FROM TUESDAY AFTERNOON THROUGH WEDNESDAY NIGHT...AND IT IS
QUITE POSSIBLE DURING AT LEAST ONE OR TWO PERIODS IN THIS TIME FRAME
THE LOW CHANCES CURRENTLY FORECAST ON THE SIXTH AND SEVENTH DAY WILL
INCREASE.

MOS ENSEMBLE HIGHS HAVE TRENDED DOWNWARD...BUT THICKNESSES STILL
SUPPORT READINGS IN THE 90S ACROSS CENTRAL NORTH CAROLINA SUNDAY
THROUGH TUESDAY. ON MONDAY IN PARTICULAR...THICKNESSES WOULD SUPPORT
HIGHS APPROACHING 100 IN SOME AREAS. THIS IS STILL SLIGHTLY BELOW
RECORDS AT BOTH KGSO AND KRDU...WHICH HAVE RECORDS FROM 100 TO 104
SATURDAY THROUGH MONDAY. BASED ON SOME EVIDENCE TO THE
CONTRARY...WILL HOLD OFF ON HIGHS THAT WARM FOR NOW. STILL...THE
COMBINATION OF HIGHS AND HUMIDITY COULD PUSH HEAT INDICES TO NEAR
105 ESPECIALLY CENTRAL AND EAST SUNDAY AND MONDAY. MORNING LOWS
SHOULD BE SOLIDLY IN THE LOWER TO MID 70S BASED ON LOCAL STUDIES OF
LOWS COMPARED TO EXPECTED 1000-850MB THICKNESSES. READINGS WILL
BEGIN TO COOL INTO WEDNESDAY WITH THE APPROACH OF THE FRONT AND
ANTICIPATED HIGHER CLOUD COVER AND LOWER THICKNESSES.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 145 PM WEDNESDAY...

SCATTERED CONVECTION FIRING ALONG THE SURFACE TROF ACROSS CENTRAL NC
THIS AFTERNOON WILL BEAR WATCHING...SHOWERS IN THE VICINTY IS A GOOD
BET...BUT THE CHANCE OF A THUNDERSTORM OVER THE AIRPORTS IS
SMALL...LESS THAN CRITERIA FOR INSERTION INTO THE TAFS. EXPECT THE
CONVECTION AT RDU/FAY/RWI TO DIMINISH WITH LOSS OF INSOLATION BY
00Z..WHILE UPPER TROF MOVING EAST ACROSS THE MOUNTAINS SHOULD
SUPPORT MORE COVERAGE OVER INT/GSO. AS THE UPPER TROF WILL BE MOVING
ONLY SLOWLY EAST ACROSS THE AREA...WIDELY SCATTERED TO ISOLATED
CONVECTION IS EXPECTED ACROSS THE AREA OVERNIGHT. AIRPORTS WHICH
RECEIVE RAIN THIS EVENING/EARLY TONIGHT COULD SEE IFR
VISIBILITY...AND POSSIBLY IFR STRATUS...DEVELOP IN THE 09-13Z TIME
FRAME.

DRIER AIR WILL BE WORKING ITS WAY ACROSS THE AREA TOMORROW AS THE
UPPER TROF AND SURFACE FRONT MOVE INTO EASTERN NORTH CAROLINA
TOMORROW AFTERNOON. MORNING LOW CLOUDINESS WILL BE MORE LIKELY TO
PERSIST IN RDU/FAY/RWI UNTIL THE TROF PASSES. CONVECTION WILL BE
WIDELY SCATTERED IN THE MORNING...MOSTLY SHOWERY TYPE...BUT THUNDER
COULD AFFECT FAY/RWI IN THE AFTERNOON IF THE FRONT AND TROF ARE
STILL LAGGING ALONG INTERSTATE 95 DURING AFTERNOON HEATING.

IN THE LONGER RANGE...A STRONG RIDGE WILL BUILD OVER THE
AREA...SUPPRESSING CONVECTION AND ENSURING MAINLY VFR CONDITIONS
FRIDAY THROUGH MONDAY.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

SYNOPSIS...MLM/DJF
NEAR TERM...MLM
SHORT TERM...MLM/DJF
LONG TERM...DJF
AVIATION...MLM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
355 PM EDT WED AUG 5 2009

NCZ021-022-038-039-073-062000-
FORSYTH-GUILFORD-DAVIDSON-RANDOLPH-STANLY-
355 PM EDT WED AUG 5 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED TO NUMEROUS THUNDERSTORMS WILL MOVE IN FROM THE WEST.
ISOLATED STORMS MAY BECOME SEVERE...WITH DAMAGING WIND GUSTS THE
PRIMARY THREAT. THERE IS ALSO A CHANCE OF STORMS MOVING REPEATEDLY
OVER THE SAME AREA...WHICH COULD PRODUCE MINOR FLOODING ON ROADS
AND IN LOW LYING AREAS. FURTHERMORE...STRONG THUNDERSTORMS WOULD
PRODUCE FREQUENT LIGHTNING...IN SOME CASES ONE STRIKE EVERY 15
SECONDS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE ENCOURAGED TO REPORT ANY SEVERE OR SIGNIFICANT
WEATHER ASSOCIATED WITH ANY THUNDERSTORM.

NCZ007>011-023>028-040>043-074>078-083>086-088-089-062000-
PERSON-GRANVILLE-VANCE-WARREN-HALIFAX-ALAMANCE-ORANGE-DURHAM-
FRANKLIN-NASH-EDGECOMBE-CHATHAM-WAKE-JOHNSTON-WILSON-MONTGOMERY-
MOORE-LEE-HARNETT-WAYNE-ANSON-RICHMOND-SCOTLAND-HOKE-CUMBERLAND-
SAMPSON-
355 PM EDT WED AUG 5 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED THUNDERSTORMS WILL OCCUR...WITH ISOLATED THUNDERSTORMS
BEING SEVERE. THE PRIMARY THREAT IS DAMAGING WIND GUSTS...THOUGH
STRONGER STORMS COULD PRODUCE HAIL TO NICKEL SIZE. THERE IS ALSO
A CHANCE OF STORMS MOVING REPEATEDLY OVER THE SAME AREA...WHICH
COULD PRODUCE MINOR FLOODING ON ROADS AND IN LOW LYING AREAS.
FURTHERMORE...STRONG THUNDERSTORMS WOULD PRODUCE FREQUENT
LIGHTNING...IN SOME CASES ONE STRIKE EVERY 15 SECONDS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THE COMBINATION OF HEAT AND HUMIDITY COULD RESULT IN HEAT INDICES
APPROACHING 105 DEGREES SUNDAY AND MONDAY AFTERNOONS. FACTOR IN
THE HEAT WHEN MAKING OUTDOOR PLANS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE ENCOURAGED TO REPORT ANY SEVERE OR SIGNIFICANT
WEATHER ASSOCIATED WITH ANY STORMS.

DJF

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
739 PM EDT WED AUG 5 2009

NCZ011-060000-
HALIFAX-
739 PM EDT WED AUG 5 2009

...A STRONG THUNDERSTORM WILL MOVE ACROSS FAR NORTHEAST HALIFAX
COUNTY THROUGH 800 PM EDT...

AT 738 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM
NORTHEAST OF SCOTLAND NECK...NEAR THE COMMUNITY OF NORFLEET.
THE STORM WAS MOVING NORTHEAST AT 20 MPH...AND IT SHOULD EXIT
HALIFAX COUNTY BY 8 PM.

HAIL UP TO ONE HALF INCH IN DIAMETER AND DANGEROUS CLOUD-TO-GROUND
LIGHTNING CAN BE EXPECTED WITH THE THUNDERSTORM. STAY INDOORS UNTIL
THE STORM HAS PASSED.

DJF