Severe Thunderstorm Warning 72, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
235 PM EDT SAT MAY 9 2009

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE REGION THIS EVENING AND MOVE THROUGH
THE AREA OVERNIGHT. ALONG AND AHEAD OF THE FRONT...EXPECT AT LEAST
SCATTERED THUNDERSTORMS. BEHIND THE COLD FRONT...COOLER HIGH
TEMPERATURES WILL OCCUR FOR LATE IN THE WEEKEND THROUGH AT LEAST THE
EARLY PART OF NEXT WEEK. HIGHS WILL BE NOTICEABLY COOLER MONDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 205 PM SATURDAY...

DISCRETE THUNDERSTORMS HAD DEVELOPED DURING THE EARLY AFTERNOON
ALONG AND JUST EAST OF HIGHER ELEVATIONS IN AREAS WHERE MSAS IN
PARTICULAR SHOWED THE HIGHEST INSTABILITY THIS AFTERNOON...TO -7C IN
TERMS OF LIFTED INDICES. SPC MESOANALYSIS ALSO INDICATED THE BEST
SURFACE-BASED CAPE THERE...AROUND 2000J/KG. WHILE INITIALLY
THUNDERSTORMS MAY HAVE A LITTLE DIFFICULTY PENETRATING INTO CENTRAL
NORTH CAROLINA...BOTH THE 12Z GFS AND NAM ARE CONSISTENT WITH
EARLIER THINKING IN THAT THE CAP BETWEEN 700MB AND 850MB WILL ERODE
DURING THE REST OF THE AFTERNOON...WITH GOOD CAPE DEVELOPING OVER
THE WESTERN PIEDMONT AROUND 21Z. ALTHOUGH BOTH THE GFS AND NAM BUFR
SOUNDINGS SHOW GREATER CIN TOWARD KFAY AND KRWI DURING THE EVENING
WITH THE GREATER 0-6KM SHEAR AND LIFT FARTHER NORTH TOWARD THE
VIRGINIA BORDER...THOSE SOUNDINGS STILL SHOW NARROW CAPE WHICH
SHOULD ALLOW AT LEAST SCATTERED THUNDERSTORMS TO MOVE EAST THROUGH
CENTRAL NORTH CAROLINA THIS EVENING. HELICITY VALUES ARE GENERALLY
100M2/S2 OR LESS...AND MODEL SOUNDINGS ALSO SHOW ONLY A SLIGHT CURVE
AT BEST TO HODOGRAPHS WHICH PROMPTS THE PRIMARY SEVERE WEATHER
THREAT BEING DAMAGING WIND WITH 925MB AND 850MB WINDS NEAR 35KT.
LARGE HAIL IS A POSSIBILITY WITH THE MOST ROBUST UPDRAFTS...AS THE
FREEZING LEVELS ARE EXPECTED TO BE NEAR 15KFT.

THE FRONT WILL NOT MOVE THROUGH CENTRAL NORTH CAROLINA UNTIL LATE
TONIGHT...BUT UPPER DIVERGENCE AND MID-LEVEL SHORTWAVE ENERGY MOVE
EAST OF CENTRAL NORTH CAROLINA BY 06Z WITH 850MB THETA-E IN
PARTICULAR DIMINISHING QUICKLY OVERNIGHT. THE NAM IS FASTER THAN THE
GFS WITH THE LATTER...AND THE GFS MAY BE SLIGHTLY MORE ACCURATE WITH
THE ACTUAL FRONT NOT MOVING THROUGH UNTIL LATE. CHANCES FOR SHOWERS
SHOULD BECOME PRETTY LOW OVERNIGHT AS BOTH NAM AND GFS BUFR
SOUNDINGS BECOME FAIRLY STABLE AS DRY AIR MOVES IN. LOWS SHOULD BE
IN THE UPPER 50S TO MID 60S.

GENERALLY DRY AND STABLE CONDITIONS ARE ANTICIPATED SUNDAY. WHILE
THE FRONT SLOWLY MOVES SOUTH OF CENTRAL NORTH CAROLINA...BOTH THE
GFS AND THE NAM SUGGEST A PERIOD OF MID-LEVEL CLOUDS MOVING ACROSS
THE REGION DURING THE MORNING. THESE GENERALLY WANE BY EARLY
AFTERNOON. THE GFS IS CLOSE TO THE SANDHILLS AND SOUTHERN COASTAL
PLAIN WITH MINIMAL QPF SUNDAY...BUT AGAIN SOUNDINGS ARE STABLE AND
MOISTURE ALOFT IS NOT COLDER THAN -10C. AS A RESULT...WILL KEEP THE
FORECAST DRY WITH HIGHS WITHIN A DEGREE OR THREE OF 80.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 235 PM...

FAST ZONAL FLOW ALOFT ALWAYS DIFFICULT FOR MODELS TO HANDLE. MODELS
HOWEVER ARE IN ROUGH AGREEMENT IN DRIVING A TROUGH THROUGH NEW
ENGLAND SUNDAY NIGHT WHILE MOISTURE UNDERCUTS A WEAK LOW LEVEL HIGH
PRESSURE SYSTEM IN THE MIDWEST. THE GFS HAS FEEDBACK PROBLEMS AT
THIS TIME AND IS SUSPECT. OTHER MODELS DEVELOP WEAK LEE SIDE
TROUGHING BEFORE SUNRISE MONDAY. THUS HAVE CONFINED RAIN CHANCES
SUNDAY NIGHT TO LATE AND IN THE WEST WHERE WEAK LIFT FROM THIS
TROUGH MAY AID LIFT.

THERE ARE TIMING DIFFERENCES IN PUSHING THIS TROUGH THROUGH CENTRAL
NORTH CAROLINA MONDAY...AND THE SYSTEM IS QUITE WEAK. GIVEN THE
DIFFICULT PATTERN WILL LEAVE RAIN CHANCES MONDAY AT FORTY PERCENT.

THIS WEAK LOW LEVEL TROUGH WILL EXIT BY SUNSET MONDAY... AND MONDAY
NIGHT AND TUESDAY SHOULD BE DRY.

THE GFS HAS DROPPED LOW LEVEL THICKNESS SIGNIFICANTLY FOR MONDAY TO
MATCH THE NAM MODELS LATEST TWO RUNS. VALUES SUGGEST AFTERNOON HIGHS
AT LEAST TEN DEGREES BELOW NORMAL...AND IF PRECIPITATION LINGERS
INTO THE AFTERNOON...THOSE VALUES MAY BE TOO WARM.  ALTHOUGH SURFACE
WINDS WILL BE FROM THE NORTHEAST TUESDAY... FLOW IS WEAK AND
SUNSHINE SHOULD ALLOW AFTERNOON HIGHS TO SETTLE CLOSE TO SEASONAL
NORMALS. AFTERNOON HIGHS 65 TO 70 MONDAY...MID TO UPPER 70S TUESDAY.
OVERNIGHT LOWS IN THE FIFTIES SUNDAY NIGHT...NEAR 50 MONDAY NIGHT.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 205 PM SATURDAY...

A SURFACE HIGH PRESSURE RIDGE WILL RESIDE DOWN THE EASTERN SEABOARD
AND INTO CENTRAL NORTH CAROLINA ON WEDNESDAY...WHICH LOOKS TO BE
VERY NICE DAY WITH LIMITED CLOUD COVER AND NORMAL TO SLIGHTLY ABOVE
NORMAL TEMPS.  THE SURFACE HIGH PRESSURE AXIS SLIDES OFFSHORE ON
WEDNESDAY...ALLOWING THE RETURN OF SOUTHERLY FLOW ON THURSDAY.
MEANWHILE...AN UPPER-LEVEL SHORTWAVE IS PROGGED TO TRAVERSE THE
NORTHERN HALF OF THE COUNTRY...DRIVING A SURFACE FRONTAL SYSTEM
TOWARD OUR AREA. DEEP MOISTURE AND RAIN CHANCES WILL INCREASE ON
THURSDAY...ALTHOUGH SHORTWAVE RIDGING BETWEEN THE APPROACHING SYSTEM
AND A CUTOFF LOW OVER THE ATLANTIC COULD INITIALLY LIMIT SHOWER AND
THUNDERSTORM DEVELOPMENT ON THURSDAY. MODEL DIFFERENCES EXIST ON THE
TIMING OF FRONTAL PASSAGE ON FRIDAY...WITH THE GFS POTENTIALLY AS
MUCH AS 12 HORUS FASTER ON FRIDAY MORNING...WITH THE ECMWF LATER ON
FRIDAY.  THE ECMWF HAS BEEN PREFERRED...LEANING A LITTLE BIT MORE
TOWARDS THE GFS ENSEMBLE MEAN PER HPC THIS MORNING. THEREFORE...WILL
CONTINUE TO CARRY A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH
FRIDAY EVENING.  GUIDANCE NOT SUGGESTIVE OF MUCH OF AN AIRMASS
CHANGE WITH THE FRONT...CONTINUING HIGHS IN THE UPPER 70S TO LOWER
80S INTO THE WEEKEND.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 205 PM SATURDAY...

PRIMARY HAZARDS FOR ALL TAF SITES IN CENTRAL NORTH CAROLINA THROUGH
THE EVENING WILL BE SCATTERED THUNDERSTORMS. SOME OF THE STORMS
COULD LOCALLY BE SEVERE. OUTSIDE OF THUNDERSTORMS...VFR CONDITIONS
ARE ANTICIPATED WITH GUSTY...SOUTHWEST WINDS GRADUALLY DIMINISHING
IN SPEED LATE THIS AFTERNOON AND INTO THE EVENING AS THE DIRECTION
VEERS TO THE WEST. OVERNIGHT...AS THE FRONT MOVES SOUTH THROUGH
CENTRAL NORTH CAROLINA...WINDS WILL CONTINUE TO VEER TO NORTHWEST TO
NORTH.

DESPITE A PERIOD OF MID-LEVEL CLOUDS LATE TONIGHT THROUGH SUNDAY
MORNING...VFR CONDITIONS ARE EXPECTED THROUGH THE DAY SUNDAY. WINDS
WILL BE NORTHERLY BUT GENERALLY 10KT OR LESS WITH A FEW WIND GUSTS
IN THE TEENS KTS. BEYOND THE 18Z TAF PERIOD INTO SUNDAY NIGHT...
CLOUDS ARE EXPECTED TO THICKEN AND LOWER ONCE AGAIN.

AREAS OF LIGHT RAIN ARE POSSIBLE LATE SUNDAY NIGHT INTO MONDAY WITH
CONDITIONS PREDOMINANTLY VFR. AREAS OF MVFR CONDITIONS ARE POSSIBLE
ESPECIALLY MONDAY...AND LOCAL IFR CONDITIONS CANNOT BE COMPLETELY
RULED OUT THEN.

&&

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

&&

SYNOPSIS...DJF
NEAR TERM...DJF
LONG TERM...BLS
AVIATION...DJF

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
632 PM EDT SAT MAY 9 2009

NCZ011-026>028-041>043-077-078-085-086-088-089-102245-
HALIFAX-FRANKLIN-NASH-EDGECOMBE-WAKE-JOHNSTON-WILSON-HARNETT-WAYNE-
SCOTLAND-HOKE-CUMBERLAND-SAMPSON-
632 PM EDT SAT MAY 9 2009

...SEVERE THUNDERSTORM WATCH 284 IN EFFECT UNTIL 1 AM EDT SUNDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THROUGH TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

A LINE OF SEVERE THUNDERSTORMS WILL RACE EAST ACROSS MUCH OF CENTRAL
NORTH CAROLINA THROUGH THE MID EVENING HOURS. WIND GUSTS TO 60 OR
70 MPH WILL PRODUCE DAMAGE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

NCZ007>010-021>025-038>040-073>076-083-084-102245-
PERSON-GRANVILLE-VANCE-WARREN-FORSYTH-GUILFORD-ALAMANCE-ORANGE-
DURHAM-DAVIDSON-RANDOLPH-CHATHAM-STANLY-MONTGOMERY-MOORE-LEE-ANSON-
RICHMOND-
632 PM EDT SAT MAY 9 2009

...SEVERE THUNDERSTORM WATCH 281 IN EFFECT UNTIL 9 PM EDT THIS
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...THROUGH TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

A LINE OF SEVERE THUNDERSTORMS WILL RACE EAST ACROSS MUCH OF CENTRAL
NORTH CAROLINA THROUGH THE MID EVENING HOURS. WIND GUSTS TO 60 OR
70 MPH WILL PRODUCE DAMAGE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

BADGETT

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