Flash Flood Warning 31, NWS Raleigh, NC

239 
WGUS72 KRAH 052029
FFSRAH

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
429 PM EDT FRI SEP 5 2014

NCC067-081-052130-
/O.CON.KRAH.FF.W.0031.000000T0000Z-140905T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
GUILFORD NC-FORSYTH NC-
429 PM EDT FRI SEP 5 2014

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 530 PM EDT FOR
WESTERN GUILFORD AND EASTERN FORSYTH COUNTIES...

AT 425 PM EDT...DOPPLER RADAR INDICATED SLOW MOVING THUNDERSTORMS
PRODUCING FLOODING OVER THE WARNED AREA. UP TO THREE INCHES OF RAIN
HAVE ALREADY FALLEN. 

SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
KERNERSVILLE...SEDGE GARDEN...WALKERTOWN AND COLFAX.

THE STORMS ARE SHOWING SIGNS OF WEAKENING. ADDITIONAL RAINFALL 
AMOUNTS OF AN INCH ARE POSSIBLE IN THE WARNED AREA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

&&

LAT...LON 3626 8024 3625 7987 3596 7988 3596 8005
      3601 8005 3603 8014 3603 8021 3602 8021
      3600 8022 3600 8024

$$

23

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
326 PM EDT FRI SEP 5 2014

.SYNOPSIS...THE UPPER LEVEL RIDGE CURRENTLY IN PLACE OVER THE
SOUTHEAST CONUS WILL WEAKEN AS AN UPPER LEVEL TROUGH PROGRESSES
ACROSS THE OHIO VALLEY AND MID ATLANTIC ON SATURDAY...PUSHING A COLD
FRONT SOUTHEAST INTO THE CAROLINAS SATURDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1200 PM FRIDAY...

THE UPPER LEVEL RIDGE OVER THE SOUTHEAST CONUS APPEARS TO BE
CENTERED OVER NORTH-CENTRAL SC PER 15Z WV IMAGERY...WITH THE
WESTERLIES ALONG THE NORTHERN PERIPHERY OF THE RIDGE BEGINNING AT A
LATITUDE NEAR THE NC/VA BORDER. THUS...ANY SMALL AMPLITUDE SHORTWAVE
ENERGY WILL GENERALLY REMAIN ALONG AND NORTH OF THE NC/VA BORDER
THROUGH TONIGHT...AND UPPER LEVEL FORCING WILL LARGELY BE ABSENT
ASIDE FROM THE POSSIBILITY OF A SUBTLE DISTURBANCE EMBEDDED WITHIN
THE RIDGE OVER THE CAROLINAS AND/OR THE POSSIBILITY OF A SMALL
AMPLITUDE WAVE GRAZING NORTHWEST PORTIONS OF THE STATE. FORCING FOR
ASCENT WILL BE CONFINED TO SHALLOW CONVERGENCE ALONG THE SEABREEZE
IN SE PORTIONS OF THE STATE...DIFFERENTIAL HEATING ON THE SLOPES OF
THE MOUNTAINS IN WESTERN NC....AND CONVECTIVE OUTFLOW. A
HOMOGENEOUS...SEASONABLY MOIST/UNSTABLE AIRMASS WILL PREVAIL
TODAY...WITH MLCAPE VALUES OF UP TO ~2000 J/KG DURING PEAK HEATING.
WITH THE ABOVE IN MIND...EXPECT CONVECTIVE DEVELOPMENT TO BE TIED TO
THE SEABREEZE IN THE SOUTHEAST...ISOLD MOUNTAIN CONVECTION DRIFTING
EASTWARD INTO THE FAR NW PIEDMONT ALONG THE NORTHERN PERIPHERY OF
THE RIDGE...AND CONVECTIVE OUTFLOW FROM EITHER OF THE AFOREMENTIONED
REGIONS. WILL CONTINUE TO INDICATE A 20-30% CHANCE DURING PEAK
HEATING...HIGHEST NW AND SE AS MENTIONED ABOVE...WITH CHANCES
DIMINISHING WITHIN SEVERAL HRS AFTER SUNSET. HIGHS SLIGHTLY ABOVE
NORMAL IN UPPER 80S TO LOWER 90S...LOWS IN LOWER 70S.

WITH VIRTUALLY NO DEEP LAYER SHEAR UNDERNEATH THE UPPER LEVEL
RIDGE...ANY CONVECTION THAT DEVELOPS WILL BE OF THE UNORGANIZED/
SINGLE CELL VARIETY. STORM MOTION WILL LARGELY BE DICTATED BY
OUTFLOW GIVEN WEAK/VARIABLE STEERING FLOW...WITH MOTION OTHERWISE
NEARLY STATIONARY/MEANDERING. AS SUCH...THE MOST LIKELY CONVECTIVE
HAZARD WILL BE LOCALLY HEAVY RAINFALL (RAINFALL RATES AS MUCH AS 1-
2"/HR) AND AN ISOLD FLASH FLOOD POTENTIAL...PRIMARILY IN URBAN
LOCATIONS AND AREAS RECENTLY AFFECTED BY HEAVY RAINFALL. -VINCENT

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 320 PM FRIDAY...

SHORTWAVE ENERGY DIGGING SOUTHEAST FROM THE UPPER MIDWEST INTO THE
OH VALLEY WILL AMPLIFY A BROAD TROUGH /CYCLONIC FLOW ALOFT/ OVER THE
MID-ATLANTIC SAT/SAT NIGHT...DRIVING A COLD FRONT SOUTHEAST ACROSS
THE APPALACHIANS INTO VA AND THE CAROLINAS SAT AFTERNOON AND
EVENING. GIVEN A FOCUS IN THE FORM OF LOW-LEVEL CONVERGENCE
ATTENDANT A PRE-FRONTAL TROUGH...AN INCREASING POTENTIAL FOR DPVA
ATTENDANT SMALL AMPLITUDE WAVES IN STRENGTHENING FLOW ALOFT...AND
THE CONTINUED PRESENCE OF A VERY MOIST AIRMASS CHARACTERIZED BY PWAT
VALUES OF 1.75-2.00"...WILL INCREASE CHANCES FOR CONVECTION TO 60%
SATURDAY AFTERNOON INTO SATURDAY NIGHT. EXPECT HIGHS IN THE UPPER
80S TO LOWER 90S...COOLEST NW AND WARMEST S/SE. LOWS SAT NIGHT IN
THE LOWER 70S. -VINCENT

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 140 PM FRIDAY...

THERE CONTINUES TO BE RELATIVELY MINOR RUN TO RUN TIMING DIFFERENCES
CONCERNING THE COLD FRONT PASSAGE THIS WEEKEND...WITH THE LATEST
ITERATIONS HAVING SPED UP THE FRONT...AND HAVE IT NOW REACHING THE
COASTAL PLAIN BY SUNDAY MORNING ON BOTH THE GFS AND ECMWF. MOIST
ENVIRONMENT AND IMPROVED LOW LEVEL FORCING WILL COMPENSATE FOR THE
REDUCED INSTABILITY DUE TO MODESTLY LOWER TEMPERATURES...JUSTIFYING
ONGOING LIKELY POPS FROM I95 EAST...AND CHANCE POPS IN THE WEST.
HEAVY RAINERS ARE A STRONG POSSIBILITY WITH PRECIPITABLE WATER OVER
TWO INCHES...AND ALSO THE POTENTIAL FOR TRAINING STORMS IN THE FRONTAL
ZONE...SO FLOODING MAY BECOME A CONCERN. THE SURGE OF COOLER AIR WILL
BE DELAYED TIL SUNDAY NIGHT AS THE SURFACE HIGH MOVES INTO THE MID
ATLANTIC AND RIDGES SOUTH DOWN THE EASTERN SLOPES. AS A RESULT
SUNDAY HIGHS WILL RANGE FROM LOWER 80S NORTHWEST TO MID AND PERHAPS
SOME UPPER 80S SOUTHEAST. LOWS SUNDAY NIGHT WILL BE MOSTLY IN THE
MID 60S.

THE FRONT WILL BE STALLED IN THE EAST IN A DEEPENING COASTAL TROF...
FURTHER ENHANCING CONVERGENCE ALONG THE FRONT AND POSSIBLE SURFACE
WAVES WHICH MIGRATE UP THE FRONTAL ZONE. THIS WILL MAINTAIN THE POP
DISTRIBUTION OF LIKELY EAST...CHANCE WEST...THROUGH MONDAY NIGHT.
HIGHS MONDAY WILL BOTTOM OUT AS THE DAMMING PEAKS...WITH HIGHS IN THE
NORTHWEST TOPPING OUT IN THE MID...PERHAPS SOME LOWER...70S...AND THE
FAR SOUTH APPROACHING 80 DEGREES. MINS MONDAY NIGHT WILL BE MOSTLY IN
THE MID 60S.

TUESDAY THROUGH THURSDAY...LINGERING DAMMING AIRMASS WILL BEGIN
TO UNDERGO MODIFICATION AS THE PARENT HIGH LIFTS NORTHEAST AND THE
SURFACE FRONT EDGES OFFSHORE. IN ADDITION...FLATTENING MID LEVEL
PATTERN WILL BRING IN DRIER AIR IN WESTERLY FLOW...HENCE DECREASED
CLOUDINESS AND MORE TYPICAL DIURNAL POP DISTRIBUTION IN THE EAST
THANKS TO THE SEA BREEZE...AND IN THE WEST DUE TO DIFFERENTIAL
HEATING INDUCED CONVECTION OFF THE MOUNTAINS MOVING INTO THE
WESTERN PIEDMONT. HIGHS WILL SHOW A CATEGORY RISE EACH DAY...
FROM THE UPPER 70S TO LOWER 80S TUESDAY TO THE LOW TO MID 80S BY
THURSDAY. MORNING LOWS WILL BE MAINLY 65 TO 70. LITTLE CONFIDENCE
IN DAY 7 AT THIS POINT...ALTHOUGH WE WILL BE MOISTENING UP AHEAD
OF A SYSTEM APPROACHING LATE WEEK...WHICH WILL PROVIDE US WITH
NON-ZERO CHANCES FOR CONVECTION ON FRIDAY.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AS OF 1200 PM FRIDAY...

VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD ASIDE FROM A
POTENTIAL FOR ISOLD CONVECTION DURING THE AFT/EVE HOURS (PRIMARILY
INT/GSO AND FAY TERMINALS) AND A POTENTIAL FOR FOG OR LOW CEILINGS
DURING THE PRE-DAWN HOURS SAT MORNING...PRIMARILY AT THE FAY/RWI
TERMINALS.

LOOKING AHEAD: EXPECT ABOVE NORMAL CHANCES FOR ADVERSE AVIATION
CONDITIONS SATURDAY THROUGH EARLY NEXT WEEK IN ASSOCIATION WITH A
MORE ACTIVE UPPER LEVEL PATTERN AND A COLD FRONT EXPECTED TO
PROGRESS THROUGH CENTRAL NC LATE SAT/SAT NIGHT BEFORE STALLING OUT
ALONG OR NEAR THE CAROLINA COAST SUN/MON. -VINCENT

&&

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

&&

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...MLM
AVIATION...VINCENT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
453 AM EDT FRI SEP 5 2014

NCZ007>011-021>028-038>043-073>078-083>086-088-089-060900-
PERSON-GRANVILLE-VANCE-WARREN-HALIFAX-FORSYTH-GUILFORD-ALAMANCE-
ORANGE-DURHAM-FRANKLIN-NASH-EDGECOMBE-DAVIDSON-RANDOLPH-CHATHAM-WAKE-
JOHNSTON-WILSON-STANLY-MONTGOMERY-MOORE-LEE-HARNETT-WAYNE-ANSON-
RICHMOND-SCOTLAND-HOKE-CUMBERLAND-SAMPSON-
453 AM EDT FRI SEP 5 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

A FRONT WILL MOVE INTO CENTRAL NC SATURDAY NIGHT AND
SUNDAY...THEN STALL OVER EASTERN NC THROUGH EARLY NEXT WEEK.
PERIODS OF LOCALLY HEAVY RAIN IN SHOWERS AND THUNDERSTORMS WILL
RESULT...WHICH MAY PRODUCE FLOODING IN URBAN AND OTHER FLOOD PRONE
AREAS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.