Special Weather Statement, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
150 PM EDT WED AUG 8 2012

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS THE AREA LATE THIS
AFTERNOON AND THIS EVENING. WEAK SFC HIGH PRESSURE WILL BUILD OVER
THE AREA ON THURSDAY BEFORE A STRONG SFC COLD FRONT PUSHES ACROSS
THE AREA FROM THE WEST LATE FRIDAY AND INTO SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 AM WEDNESDAY...

THE TROPICAL...MOISTURE LADEN AIRMASS(PWATS 2 SD ABOVE NORMAL)THAT
HAS BEEN IN PLACE ACROSS CENTRAL NC THE PAST COUPLE OF DAYS WILL
BEGIN TO DRY OUT THIS MORNING AS DRIER AIR ALOFT NOTED OVER THE
CENTRAL AND SOUTHERN APPALACHIANS CONTINUES TO SPREAD EAST IN THE
WAKE OF THE EXITING SHORTWAVE TROUGH. THE HIGH PWATS WILL DECREASE
FROM 2 TO 2.25"...TO MORE SEASONABLE MOISTURE VALUES OF 1.3 TO 1.7".

SO FAR THIS MORNING...WE CONTINUE TO SEE SHOWER AND THUNDERSTORM
RE-DEVELOPMENT ALONG AND EAST OF US1...ALONG AND EAST OF THE DIFFUSE
SFC TROUGH AND WITHIN THE ZONE OF DPVA ASSOCIATED WITH THE EXITING
SHORTWAVE TROUGH. THIS ACTIVITY SHOULD GRADUALLY SHIFT EAST OF THE
AREA THIS MORNING...WITH AFOREMENTIONED DRYING ALOFT GIVING WAY TO
PARTLY TO MOSTLY SUNNY SKIES TO ALL OF CENTRAL NC BY THE
AFTERNOON...WITH RESULTANT STRONG AND UNIFORM DAYTIME HEATING
SPELLING THE DEMISE OF THE LINGERING SFC TROUGH.

FOR THE AFTERNOON AND EVENING...WELL DEFINED UPPER PV ANOMALY OVER
KENTUCKY THIS MORNING WILL PROGRESS SLOWLY EASTWARD ACROSS NC
VIRGINIA BETWEEN 18Z TO 06 TONIGHT. WHILE THE DRIER AIR WILL LIMIT
COVERAGE...ISOLATED TO WIDELY SCATTERED STORMS ARE POSSIBLE WITH
THIS FEATURE AS IT MOVES INTO THE AREA DURING PRIME DAYTIME HEATING
WITH ACCOMPANYING MODEST MID-LEVEL LAPSE RATES OF 6.8-7.0C/KM
OVERSPREADING WESTERN AND NORTHERN PORTIONS OF THE FORECAST AREA.
WITH THE DRIER AND SLIGHTLY COOLER AIR ALOFT...DCAPE VALUES ARE
UP(1000 TO 1500 J/KG)...ESPECIALLY ACROSS THE WESTERN PIEDMONT. SO
CANNOT RULE OUT THE POSSIBILITY OF AN ISOLATED STRONG TO SEVERE
THUNDERSTORM WIND GUSTS WITH ONE OR TWO STORMS. AFTER 18Z...WILL
HAVE CHANCE POPS IN THE WEST...WITH SLIGHT CHANCE EVERYWHERE ELSE.
STORM INTENSITY AND COVERAGE SHOULD DIMINISH WITH LOSS OF
HEATING...BUT WILL MAINTAIN A SLIGHT CHANCE THROUGH 06Z UNTIL THE
UPPER WAVE PASSES EAST OF THE AREA.

RETURN OF SUNSHINE SHOULD BOOST DAYTIME HEATING BACK
THE UPPER 80S TO AROUND 90. LOWS TONIGHT 69-73.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 252 AM WEDNESDAY...

MINOR S/W EXITS THE REGION LATE TONIGHT-EARLY THU. WEAK SUBSIDENCE
IN WAKE OF THE SYSTEM AND LACK OF SUFFICIENT CONVERGENCE SUGGEST
THAT MOST LOCALES ACROSS CENTRAL NC WILL BE DRY THU...WITH JUST
ISOLATED CONVECTION EXPECTED DURING THE MID-LATE AFTERNOON HOURS.
CONVECTION THAT DEVELOPS THOUGH WILL HAVE DECENT POTENTIAL TO
PRODUCE STRONG GUSTY WINDS. THICKNESSES IN THE 1425-1430M RANGE
SUPPORT MAX TEMPS NEAR 90-LOWER 90S.

A WEAK VORTICITY MAX LIFTS NEWD OUT OF THE DEEP SOUTH AND LIFTS INTO
OUR REGION THU NIGHT. AIR MASS ALSO BEGINS TO MOISTEN WITH PRECIP
WATER VALUES AROUND 1.75 INCHES. THIS FEATURE...THOUGH APPROACHING
REGION WHEN LOW LEVEL ATMOSPHERE WILL ATTAIN ITS MOST STABLE
CONDITION...MAY HAVE ENOUGH LIFT WITH IT TO INITIATE/SUSTAIN A FEW
SHOWERS. MIN TEMPS 69-74. -WSS

FRIDAY AND FRIDAY NIGHT:
MODELS CONTINUE TO REMAIN IN OVERALL GOOD AGREEMENT ON THE MID/UPPER
LEVEL PATTERN FOR LATE THIS WEEK... WITH A DEVELOPING DEEP TROUGH
ACROSS THE EASTERN U.S. AND A RIDGING GENERALLY CONTINUING TO HOLD
ACROSS THE WESTERN U.S. S/W ENERGY IS EXECUTED TO DIVE
SOUTH/SOUTHEASTWARD ON THURSDAY INTO THURSDAY NIGHT DEVELOPING A
DEEP TROUGH ALOFT ACROSS THE EASTERN U.S. AND CLOSED LOW ALOFT
CENTERED OVER THE GREAT LAKES AND OHIO VALLEY REGION. THIS WILL SET
THE STAGE FOR A GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS ON FRIDAY
AFTERNOON INTO FRIDAY NIGHT AS LARGE SCALE LIFT OVERSPREADS THE AREA
LATE FRIDAY FROM THE POSITIVE TO NEUTRAL TILTED TROUGH ALOFT...
ALONG WITH AN ASSOCIATED STRONG COLD FRONT FOR THIS TIME OF YEAR
MOVING INTO THE AREA. DETAILS IN HOW THIS POTENTIAL SEVERE WEATHER
EVENT WILL UNFOLD THOUGH REMAIN SOME WHAT UNCLEAR AT THIS TIME...
DESPITE RATHER STRONG FORCING AND GOOD DEEP LAYER SHEAR FOR THIS
TIME OF YEAR. ONE FEATURE THAT MAY AFFECT HOW MUCH WE WILL BE ABLE
TO DESTABILIZE AT THE SURFACE IN ADVANCE OF THE GOOD LARGE SCALE
LIFT AND DEEP LAYER SHEAR IS AN UPPER LEVEL DISTURBANCE CURRENTLY
TRACKING ACROSS THE PLAINS NOW... WHICH MODELS BRING THE SHEAR
AXIS/TROUGH ASSOCIATED WITH THIS ACTIVITY INTO OUR AREA ON FRIDAY
MORNING. THIS FEATURE MAY BE MORE OF THE FOCUS FOR SHOWERS AND
STORMS ON FRIDAY MORNING INTO THE AFTERNOON... ESPECIALLY ACROSS
EASTERN PORTIONS OF THE AREA. WITH THAT SAID... MODELS STILL SHOW
1000 TO 2000 J/KG OF MLCAPE FOR FRIDAY AFTERNOON... LINGERING INTO
THE EVENING. THUS... GIVEN THIS ALONG WITH THE GOOD LARGE SCALE LIFT
AND DEEP LAYER SHEAR FRIDAY AFTERNOON INTO THE OVERNIGHT....
IMPROVING TO 25 TO 35 KTS... WILL CONTINUE TO MENTION THE POTENTIAL
FOR DAMAGING WINDS IN THE HWO... WHICH SOME ORGANIZATION POSSIBLE
LEADING TO AN ENHANCED DAMAGING WIND THREAT. SPC HAD INCLUDED MOST
OF THE AREA FOR AN ENHANCED RISK FOR SEVERE STORMS FOR FRIDAY AND
FRIDAY NIGHT IN YESTERDAYS DAY 4-8 OUTLOOK. HOWEVER... AS OF THIS
WRITING...THE DAY 3 OUTLOOK HAS NOT YET BEEN ISSUED. BESIDES SEVERE
POTENTIAL...WITH PRECIP WATER VALUES HOVERING AROUND TWO INCHES AND
POSSIBILITY OF TRAINING CELLS...MAY SEE AN ENHANCED FLASH FLOODING
EPISODE...MAINLY LATE FRIDAY INTO FRIDAY EVENING.

WITH REGARD TO TIMING OF THE FRONT AN BEST CHANCE OF PRECIP...HAVE
SLOWED THE TIMING DOWN A BIT AND FOLLOWED CLOSEST TO THE 12Z
ECMWF... WHICH IS PREFERRED BY HPC ALONG WITH THE 00Z UKMET/00Z
CANADIAN. THE NAM IS THOUGHT TO BE A SLOW OUTLIER... WHILE THE 00Z
GFS IS CONSIDERED TO FAR NORTH WITH THE CLOSED LOW ALOFT CENTER. WRT
THE TIMING... WILL CONTINUE TO GO WITH LIKELY POPS... GENERALLY LATE
FRIDAY INTO FRIDAY NIGHT/SATURDAY MORNING. THE ACTUAL FRONT IS
EXPECTED TO BE DRAPED ACROSS THE AREA FROM NE TO SW BY AROUND 12Z
SATURDAY.

HIGH TEMPS ON FRIDAY WILL BE TRICKY AND TIED TO HOW MUCH HEATING WE
ARE ABLE TO REALIZE. FOR NOW... WILL GO WITH HIGHS GENERALLY IN THE
MID TO UPPER 80S. LOWS SATURDAY MORNING ARE EXPECTED TO RANGE FROM
THE UPPER 60S TO LOWER 70S. -BSD

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 250 AM WEDNESDAY...

THE COLD FRONT MENTIONED IN THE SHORT TERM DISCUSSION ABOVE IS
EXPECTED TO SLOWLY SHIFT EASTWARD ACROSS THE REMAINDER OF THE AREA
ON SATURDAY... BEFORE STALLING A AND DISSIPATING NEAR THE COAST ON
SUNDAY INTO MONDAY AS THE CLOSED MID/UPPER LEVEL LOW LIFTS
NORTH/NORTHEASTWARD FROM THE GREAT LAKES REGION. THIS WILL RESULT IN
A GOOD CHANCE FOR SHOWERS AND STORMS ON SATURDAY GENERALLY EAST OF
RALEIGH (WITH POSSIBLY SOME SEVERE STORMS AND/OR LOCALIZED FLASH
FLOODING)... WITH ONLY SLIGHT CHANCE TO NO POPS FOR SUNDAY THROUGH
TUESDAY AS MID/UPPER FLOW BECOMES MUCH LESS AMPLIFIED. TEMPS DURING
THE PERIOD ARE EXPECTED TO BE IN THE MID TO UPPER 80S... WITH
PERHAPS A RETURN TO SOME LOCATIONS REACHING 90 DEGREES AGAIN BY
EARLY NEXT WEEK.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 150 PM WEDNESDAY...

SLOW WEST TO EAST EROSION OF LOW CLOUDS STILL HAS KRWI AND KFAY
HANGING ON TO SOME MVFR CEILINGS FOR THE MOMENT...BUT EXPECT
CEILINGS TO IMPROVE TO VFR VERY SOON.

THROUGH THE REMAINDER OF THE AFTERNOON AND INTO THE EARLY
EVENING...AN UPPER LEVEL DISTURBANCE WILL PROGRESS EAST THROUGH
CENTRAL NC THROUGH 06Z TONIGHT...PROVIDING AMPLE LIFT TO SUPPORT
SCATTERED SHOWERS AND STORMS. IN FACT...SOME OF THE NEWER MODEL
GUIDANCE FILTERING IN SUGGESTS CONVECTION COULD BE MORE WIDESPREAD
AND COULD POSSIBLY IMPACT ALL TAF SITES BETWEEN 18Z IN THE WEST...TO
AROUND 03Z ACROSS THE EAST/SOUTHEAST. FOR NOW WILL INCLUDE THUNDER
AT KINT AND KGSO ONLY...AND WILL MONITOR LATEST RADAR TRENDS BEFORE
ADDING THE MENTION OF THUNDER AND ASSOCIATED SUB-VFR CONDITIONS TO
ANY OTHER TAF SITES.

DEBRIS CLOUDINESS SHOULD CLEAR/SCATTER OUT BY MIDNIGHT...GIVING WAY
TO MOSTLY CLEAR SKIES. WITH LIGHT SOUTHERLY WINDS AND CONTINUED
HIGH DEWPOINTS IN THE LOWER 70S...THERE IS THE POTENTIAL FOR SOME
FOG/STRATUS...ESPECIALLY IN THE EAST WHERE NEAR SURFACE MOISTURE
IS HIGHER.

ANY STRATUS/FOG SHOULD LIFT VERY QUICKLY THURSDAY MORNING(BY 13-14Z)
WITH PREDOMINATELY VFR CONDITIONS AND ONLY ISOLATED SHOWER/STORMS
POSSIBLE. A STRONGER MID LEVEL TROUGH AND ASSOCIATED SURFACE
BOUNDARY WILL BRING INCREASING CHANCES FOR SHOWERS AND T-STORMS
LATE THURSDAY NIGHT/FRIDAY MORNING...CONTINUING  FRIDAY AFTERNOON
INTO FRIDAY NIGHT AND POSSIBLY LINGER INTO THE COASTAL PLAIN THROUGH
SATURDAY MORNING. A TRANSITION TO A MORE TRANQUIL WEATHER PATTERN
ANTICIPATED FOR SUNDAY.

&&

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

&&

SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...WSS/BSD
LONG TERM...BSD
AVIATION...CBL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
1204 PM EDT WED AUG 8 2012

NCZ007-008-021>025-038>041-074>076-083-084-091615-
PERSON-GRANVILLE-FORSYTH-GUILFORD-ALAMANCE-ORANGE-DURHAM-DAVIDSON-
RANDOLPH-CHATHAM-WAKE-MONTGOMERY-MOORE-LEE-ANSON-RICHMOND-
1204 PM EDT WED AUG 8 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS ARE POSSIBLE THIS
AFTERNOON. ONE OR TWO STORMS COULD PRODUCE STRONG TO SEVERE
THUNDERSTORM WIND GUSTS.

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

STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON AND
FRIDAY NIGHT. THE PRIMARY SEVERE WEATHER THREAT WILL BE DAMAGING
WIND GUSTS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE ENCOURAGED TO REPORT ANY SEVERE OR
SIGNIFICANT WEATHER IMMEDIATELY TO THE NATIONAL
WEATHER SERVICE.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
1248 PM EDT WED AUG 8 2012

NCZ021-081730-
FORSYTH-
1248 PM EDT WED AUG 8 2012

...A STRONG THUNDERSTORM WILL MOVE ACROSS PARTS OF FORSYTH COUNTY
THROUGH 130 PM EDT...

AT 1247 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR
DONNAHA AND EAST BEND...MOVING SOUTHEAST AT 15 MPH.

SOME LOCATIONS AFFECTED BY THIS STORM INCLUDE...RURAL
HALL...PFAFFTOWN...AND...STANLEYVILLE.

THE STORM COULD APPROACH WINSTON-SALEM AFTER 115 PM.

HAZARDS INCLUDE...
GUSTY WINDS OF 30 TO 40 MPH.
BRIEFLY HEAVY RAINFALL...A QUICK INCH IN LOCAL AREAS IN 15 MINUTES
OR LESS...RESULTING IN PONDING OF WATER ON ROADS.

THIS INCLUDES INTERSTATE 40 BETWEEN EXITS 182 AND 192.

DON'T WAIT UNTIL YOU SEE THE FIRST LIGHTNING FLASH BEFORE HEADING TO
SAFETY. MOVE INDOORS AT THE FIRST SIGN OF THREATENING SKIES OR THE
FIRST SOUND OF THUNDER. MAKE SURE THAT LIGHTNING IS WELL AWAY FROM
YOUR LOCATION BEFORE RESUMING OUTDOOR ACTIVITY. WHEN DRIVING IN
HEAVY RAIN...SLOW DOWN TO AVOID HYDROPLANING.

&&

LAT...LON 3610 8052 3612 8050 3612 8046 3614 8044
      3621 8045 3622 8044 3624 8046 3626 8045
      3627 8029 3619 8004 3598 8039
TIME...MOT...LOC 1647Z 296DEG 15KT 3621 8044

DJF

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
117 PM EDT WED AUG 8 2012

NCZ021-081815-
FORSYTH-
117 PM EDT WED AUG 8 2012

...A STRONG THUNDERSTORM WILL MOVE ACROSS FORSYTH COUNTY THROUGH 215
PM EDT...

AT 116 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER
RURAL HALL...OR ABOUT OVER KING...MOVING SOUTHEAST AT 15 MPH.

SOME LOCATIONS AFFECTED BY THIS STORM INCLUDE...STANLEYVILLE...AND...
PFAFFTOWN...WINSTON-SALEM...WALKERTOWN...SEDGE GARDEN...KERNERSVILLE.

HAZARDS INCLUDE...
PEA SIZE HAIL.
GUSTY WINDS AROUND 50 MPH.

THIS INCLUDES HIGHWAY 52 NORTHWEST OF WINSTON-SALEM.

AS THUNDERSTORMS APPROACH...SEEK SHELTER IN A NEARBY BUILDING OR
VEHICLE. STRONG WINDS ARE CAPABLE OF KNOCKING DOWN TREE LIMBS AND
BLOWING AROUND LIGHT OUTDOOR OBJECTS. WHEN DRIVING...BE PREPARED FOR
POOR VISIBILITY IN HEAVY RAIN. A QUICK INCH OF RAIN COULD FALL IN
LESS THAN 15 MINUTES FROM A SLOW MOVING THUNDERSTORM. DRIVE SLOWLY
TO AVOID HYDROPLANING.

&&

LAT...LON 3614 8044 3621 8045 3622 8044 3624 8045
      3627 8044 3626 8011 3624 8003 3601 8005
      3603 8021 3601 8022 3611 8050 3611 8051
TIME...MOT...LOC 1716Z 296DEG 15KT 3622 8032

DJF

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
159 PM EDT WED AUG 8 2012

NCZ021-081900-
FORSYTH-
159 PM EDT WED AUG 8 2012

...A STRONG THUNDERSTORM WILL MOVE ACROSS PARTS OF WESTERN FORSYTH
COUNTY THROUGH 300 PM EDT...

AT 157 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 6 MILES
NORTHWEST OF DONNAHA...OR ABOUT OVER EAST BEND...MOVING SOUTH AT 20
MPH.

SOME LOCATIONS AFFECTED BY THIS STORM INCLUDE...
DONNAHA...HUNTSVILLE...LEWISVILLE...AND CLEMMONS.

HAZARDS INCLUDE...
PEA SIZE HAIL.
GUSTY WINDS AROUND 50 MPH.

THIS INCLUDES INTERSTATE 40 BETWEEN EXITS 182 AND 188.

IF THUNDERSTORMS MOVE NEARBY OR OVERHEAD...MOVE INDOORS AND STAY
AWAY FROM WINDOWS. STRONG WINDS ARE CAPABLE OF KNOCKING DOWN SMALL
TREE LIMBS AND BLOWING AROUND LIGHT OUTDOOR OBJECTS. STAY TUNED TO
THIS STATION FOR THE LATEST WEATHER INFORMATION.

&&

LAT...LON 3612 8050 3612 8046 3614 8044 3621 8045
      3622 8044 3626 8046 3627 8035 3600 8031
      3597 8040 3599 8043 3601 8042 3606 8047
      3604 8048 3605 8051 3609 8052
TIME...MOT...LOC 1757Z 352DEG 17KT 3626 8052

DJF