Special Weather Statement, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
735 PM EDT TUE APR 3 2012

.SYNOPSIS...
A WARM FRONT WILL LIFT NORTH ACROSS OUR REGION OVERNIGHT. A COLD
FRONT IS THEN EXPECTED TO PUSH BACK SOUTH ACROSS SOUTHERN VIRGINIA
AND NORTH CAROLINA LATE WEDNESDAY AND WEDNESDAY NIGHT.
&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 325 PM TUESDAY...

WARM FRONT PRESENTLY LIFTING NORTHEAST ACROSS CENTRAL NC THIS
AFTERNOON. DEW POINTS ACROSS SC HAVE REBOUNDED INTO THE LOWER 60S
WITH DEWPOINTS NEAR KCLT AND KEHO NOW NEAR 60. RECENT SPC
MESOANALYSIS SHOWS THAT SBCAPE VALUES ACROSS THE WESTERN PIEDMONT
ARE NEGLIGIBLE WITH CAPE VALUES AROUND 1500 ACROSS THE HIGHER
TERRAIN. CONVECTION ONGOING ACROSS THE MOUNTAINS WILL TEND TO DRIFT
SLOWLY EAST THIS AFTERNOON AND EARLY EVENING INTO THE FOOTHILLS AND
TOWARD THE WESTERN PIEDMONT. IT WILL BE A RACE TO SEE IF THE SURGING
DEWPOINTS AND THE ASSOCIATED INSTABILITY MAKE IT INTO THE WESTERN
PIEDMONT AS THE SCT SHOWERS AND THUNDERSTORMS APPROACH FROM THE
WEST. AT THIS TIME...FEEL THAT THIS CONVECTION WILL TEND TO WEAKEN
AS IT MOVES OFF THE MOUNTAINS AND APPROACHES THE TRIAD REGION BUT
WILL STILL HOLD A SLIGHT CHANCE OF A THUNDERSTORM THIS EVENING IN
THIS AREA. FURTHER SOUTH ACROSS THE SOUTHERN PIEDMONT REGION IN AN
AREA OF GREATER INSTABILITY...THERE IS A GREATER POTENTIAL FOR
CONVECTION TO REMAIN MORE PERSISTENT AND LAST FURTHER INTO THE
EVENING HOURS. BOTH THE NCEP NMM AND ARW HIRES WINDOW WRF
SIMULATIONS SUGGEST THIS TREND AS WELL. EXPECT VERY LITTLE
CONVECTION OVERNIGHT WITH LIMITED FORCING FOR ASCENT. WITH A FAIR
AMOUNT OF CLOUDINESS AND WARM ADVECTION OVERNIGHT...LOW TEMPERATURES
SHOULD RANGE IN THE MID 50S TO NEAR 60.

NWP GUIDANCE IS CONSISTENT IN PLACING THE WARM FRONT ACROSS CENTRAL
VA ON WEDNESDAY MORNING. THE GUIDANCE THEN BRINGS THE FRONT BACK
SOUTH ON WEDNESDAY AFTERNOON AS A COLD FRONT WITH THE MOST RECENT
MODEL RUNS BRINGING THE BOUNDARY IN A LITTLE FASTER. AHEAD OF THE
FRONT...THE AIRMASS DESTABILIZES DURING THE AFTERNOON WITH THE NAM
AND GFS BOTH INDICATING A MARGINALLY UNSTABLE AIRMASS WITH MLCAPE
VALUES REACHING AROUND 1000 J/KG. HI RES MODEL SIMULATIONS SUGGEST
THAT THE CONVECTION WILL INITIALLY DEVELOP AHEAD OF THE SOUTHWARD
SLIPPING COLD FRONT DURING THE MID AFTERNOON. THE CONVECTION WILL
LIKELY SHIFT SOUTH...PRIMARILY DRIVEN BY THE COOL POOL BUT
POTENTIALLY ENHANCED BY DISTURANCES IN THE W/NW FLOW ALOFT. STILL
NOT TERRIBLY CONFIDENT ABOUT THE AMOUNT OF CONVECTIVE COVERAGE BUT
FEEL THAT CURRENT FORECAST OF AROUND 40 POPS IS APPROPRIATE. SPC HAS
PLACED NORTHEASTERN NC IN THE SLIGHT RISK FOR WEDNESDAY WITH THE
PRIMARY THREAT OF DAMAGING DOWNBURST WINDS. AHEAD OF THE FRONT
TEMPERATURES WILL CLIMB INTO THE 80S WITH HIGHS OF 81-85 EXPECTED.
-BLAES

&&

.SHORT TERM /WEDNESDAY NIGHT AND THURSDAY/...
AS OF 302 PM TUESDAY...

THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL GRADUALLY SHIFT SOUTH
AND EAST THROUGH NORTH CAROLINA WEDNESDAY EVENING INTO THE OVERNIGHT
HOURS. AN UPPER LEVEL DISTURBANCE IN THE NW FLOW WILL COMBINE WITH
THE COLD FRONT TO ENHANCE THE CONVECTION THROUGH THE EVENING. THE
SLIGHT RISK OF SEVERE STORMS WITH LARGE HAIL MAY CONTINUE THROUGH AT
LEAST 00Z AND MAY LAST THROUGH MIDNIGHT OR SO ALONG AND AHEAD OF THE
COLD FRONT. OTHERWISE... POP WILL DECREASE FROM NORTH TO SOUTH TO
ONLY A SLIGHT CHANCE BY 12Z THURSDAY. THE WINDS WILL SHIFT TO THE NE
AND COOLER AIR WILL BEGIN TO FILTER IN FROM THE NE OVERNIGHT. SKIES
WILL BECOME PARTLY CLOUDY LATE WITH LOWS IN THE MID 50S NE RANGING
INTO THE LOWER 60S SOUTH.

A CHILLY HIGH PRESSURE OVER THE GREAT LAKES WILL BUILD SOUTH INTO
NC/SC THURSDAY. THIS WILL BRING AN INCREASING NE-E FLOW THAT WILL
BEGIN TO TAP ATLANTIC MOISTURE DURING THE DAY. A WAA PATTERN ALOFT
WILL ALSO TAP THE ATLANTIC AND GULF OF MEXICO AS A MID/UPPER LOW
APPROACH LATE IN THE DAY FROM THE TENNESSEE VALLEY REGION. WE WILL
MAINTAIN THE CHANCE OF RAIN LATE IN THE WEST. OTHERWISE... MUCH
COOLER AND MOSTLY CLOUDY BECOMING CLOUDY. HIGHS IN THE 60S EXCEPT
LOWER 70S ACROSS THE SOUTHERN ZONES FROM WADESBORO TO FAYETTEVILLE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 324 PM TUESDAY..

MODELS ARE STILL SHOWING ENOUGH SPREAD IN THE TRACK/STRENGTH OF THE
APPROACHING MID/UPPER LOW AS IT PUSHES EITHER EAST OR EAST-SOUTHEAST
ACROSS THE SOUTHEASTERN UNITED STATES THURSDAY NIGHT AND FRIDAY. THE
GUIDANCE MOST PREFERRED WOULD BRING THE MID/UPPER LEVEL LOW ESE
ACROSS SC THEN OFFSHORE. THIS TRACK WOULD KEEP ALL OF CENTRAL NORTH
CAROLINA IN THE COOL/DAMP SECTOR THROUGH THE EVENT AS HIGH PRESSURE
TO OUR NORTH SUPPLIES A FEED OF CHILLY MOIST AIR IN FROM OFF THE
ATLANTIC. WARM AND MOIST ADVECTION ALOFT WILL FEED THE SYSTEM WITH
PW'S EXPECTED TO INCREASE TO 150-200 PERCENT OF NORMAL ACROSS SC
INTO SOUTHERN NC. A HYBRID COLD AIR DAMMING EVENT LOOKS LIKELY WITH
HIGHS POSSIBLY STAYING IN THE 50S OVER THE PIEDMONT REGION FRIDAY IF
IT RAINS INTO THE COOL STABLE AIR MASS MOST OF THE DAY. WE WILL
CARRY LIKELY POP FOR RAIN THROUGHOUT THE REGION WITH POPS HIGHEST
SOUTH AND LOWEST IN THE FAR NE BOTH THURSDAY NIGHT AND FRIDAY.
CURRENT QPF OF BETWEEN 0.25 AND 0.50 EXPECTED NORTH WITH 0.50 TO
1.00 INCH SOUTH. THIS MAY SWING A BIT NORTHWARD OR SOUTHWARD
DEPENDING ON THE TRACK/STRENGTH OF THE MID/UPPER LEVEL LOW/TROUGH.
LOWS SHOULD DIP TO BETWEEN 50-55 WITH SOME UPPER 40S NORTH. HIGHS
SHOULD BE AROUND 60 WITH 50S NW AND MID 60S SE. RAIN IS LIKELY BOTH
PERIODS.

THE H5 TROUGH IS FORECAST TO AMPLIFY OVER THE EASTERN UNITED STATES
FRI NIGHT AND SATURDAY DRIVING A CHILLY AIR MASS SOUTHWARD INTO THE
REGION AS THE MID-UPPER TROUGH MOVES OFF THE SC/NC COAST FRI NIGHT.
THERE IS A CHANCE OF LINGERING RAIN IN THE EAST FRI EVENING. THEN
CLEARING IS EXPECTED ALL ZONES WITH LOWS IN THE UPPER 30S TO MID
40S. MOSTLY SUNNY AND COOL CONDITIONS ARE EXPECTED SATURDAY WITH
HIGHS IN THE 65-70 RANGE.

THE H5 TROUGH WILL BECOME ESTABLISHED OVER THE EASTERN UNITED STATES
WITH THE NEXT COLD FRONT EXPECTED TO PUSH INTO OUR REGION LATE
MONDAY. SUNDAY AND MONDAY SHOULD BE MOSTLY CLEAR/MOSTLY SUNNY AND
MILDER OUT AHEAD OF THE NEXT COLD FRONT WITH LOWS IN THE 40S. HIGHS
WILL BE IN THE 70-75 RANGE SUNDAY... AND MID TO UPPER 70S MONDAY.

A TURN TO COLDER TEMPERATURES IS EXPECTED TO FOLLOW TUESDAY AND
WEDNESDAY AS THE H5 TROUGH BECOMES ESTABLISHED OVER THE EASTERN
STATES PUSHING SURFACE HIGH PRESSURE OUT OF CANADA TOWARD NC. LOWS
MAY DIP INTO THE MID/UPPER 30S BY THE MIDDLE OF THE WEEK... WITH
HIGHS IN THE 50S/60S. THIS WOULD SUGGEST AT LEAST SOME FROST RISK
MID TO LATE NEXT WEEK.

&&

.AVIATION /00Z WEDNESDAY THROUGH SATURDAY/...
AS OF 735 PM TUESDAY...

VFR CONDITIONS ARE EXPECTED THIS EVENING...WITH THE EXCEPTION OF
SOME BRIEF SUB MVFR CONDITIONS ASSOCIATED WITH AREA OF STORMS
DRIFTING OFF THE HIGHER TERRAIN AND INTO THE TRIAD ATTM.
AS THE STORMS CONTINUE TO MOVE SOUTHEAST...THEY ARE EXPECTED TO
WEAKEN AS THEY MOVE INTO A MORE STABLE ENVIRONMENT...AND THUS WILL
NOT INCLUDE TS IN ANY OTHER TAF SITE EAST OF THE TRIAD AT THIS
TIME.  A WARM FRONT WILL LIFT NORTH ACROSS THE AREA OVERNIGHT.
LOW-LEVEL MOISTURE RETURN IN THE WAKE OF THE WARM FRONT COULD
RESULT IN THE DEVELOPMENT OF FOG/STRATUS AT OR JUST PRIOR TO
DAYBREAK...WITH NAM/GFS BUFR SOUNDINGS INDICATING THE BEST POTENTIAL
AT KRDU/KFAY/KRWI. ANY STRATUS AND FOG SHOULD BURN ON BY 14 TO
15Z...WITH VFR CONDITIONS INTO THE AFTERNOON.

CONVECTIVE COVERAGE IS EXPECTED TO BE GREATER LATE WEDNESDAY
AFTERNOON AND EVENING...ESPECIALLY ACROSS THE NORTH AS A
BACK-DOOR COLD FRONT DROPS SOUTH INTO THE AREA BETWEEN 21 TO 03Z
THURSDAY.

LOOKING FURTHER AHEAD...THE BACK-DOOR COLD FRONT AND ASSOCIATED
CONVECTION WILL SPREAD SOUTH THROUGH THE AREA WEDNESDAY NIGHT.
THEN A PERIOD OF UNSETTLED WEATHER IS EXPECTED THURSDAY THROUGH MUCH
OF FRIDAY AS AN AREA OF LOW PRESSURE MOVES ACROSS THE REGION.
DRY HIGH PRESSURE WILL BUILD INTO THE AREA LATE FRIDAY AND INTO
SATURDAY LEADING TO IMPROVING AVIATION CONDITIONS.

&&

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

&&

SYNOPSIS...BADGETT
NEAR TERM...BLAES
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...CBL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
353 PM EDT TUE APR 3 2012

NCZ007>011-021>028-038>043-073>078-083>086-088-089-042000-
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-
353 PM EDT TUE APR 3 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
WEDNESDAY AFTERNOON AND EVENING IN ADVANCE OF A COLD FRONT
APPROACHING THE AREA FROM VIRGINIA. ISOLATED SEVERE STORMS WILL
BE POSSIBLE...WITH A PRIMARY THREAT OF DAMAGING WINDS. THE
GREATEST THREAT OF SEVERE WEATHER WILL BE ACROSS THE COASTAL
PLAIN AND THE NORTHERN PIEDMONT BETWEEN 400 PM AND 1000 PM
WEDNESDAY.

BLAES