Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 102315
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
710 PM EDT THU JUL 10 2014

.SYNOPSIS...A WEAKENING COLD FRONT WILL SHIFT THROUGH THE REGION
THROUGH TONIGHT... THEN MOVE TOWARD THE COAST FRIDAY. WEAK HIGH
PRESSURE WILL SETTLE OVER THE REGION SATURDAY INTO SUNDAY.

&&


.NEAR TERM /THROUGH FRIDAY NIGHT/...
AS OF 710 PM THURSDAY...

EARLY UPDATE... THE SEVERE THUNDERSTORM WATCH FOR THE EASTERN CWA
HAS BEEN CANCELLED.  MUCH OF THE WATCH AREA HAS BEEN OVERTURNED BY
CONVECTION....SO THE THREAT OF WIDESPREAD SEVERE STORMS HAS
DIMINISHED.  THERE IS STILL SUPPORT FOR ADDITIONAL STORMS WITH THE
UPPER TROUGH TO THE WEST...ESPECIALLY FOR AREAS WEST OF US HWY 1
WHICH REMAIN SLIGHTLY UNSTABLE. -BLS

PREVIOUS DISCUSSION...
THROUGH TONIGHT: FOCUS REMAINS ON THE EASTERN
HALF OF CENTRAL NC... MAINLY ALONG/EAST OF HIGHWAY 1... FOR NUMEROUS
SHOWERS AND STORMS THROUGH THIS EVENING. STORMS THUS FAR HAVE BEEN
PRIMARILY MULTICELL CLUSTERS WITH A COUPLE OF PROMINENT
SUPERCELLS... AND THIS MODE OF CONVECTION IS LIKELY TO PERSIST FOR
SEVERAL MORE HOURS. CONFLUENT SSW FLOW ALOFT AHEAD OF A MID LEVEL
SHEAR AXIS SITTING JUST TO OUR WEST WILL CONTINUE TO DRAW POCKETS OF
SRN STREAM VORTICITY ACROSS NC... ALONG AND AHEAD OF A WEAK SURFACE
TROUGH. THIS FORCING FOR ASCENT COMBINED WITH WEAK HEIGHT FALLS AND
NRN-STREAM ENERGY... ENHANCED LIFT WITHIN THE RIGHT ENTRANCE REGION
OF THE 100+ KT UPPER JET CORE CENTERED OVER THE NORTHEAST STATES...
AND ABOVE NORMAL PW (1.8-2.0 IN.) WILL ALL SUPPORT A CONTINUED
THREAT OF NUMEROUS SHOWERS AND STORMS IN THE EAST... WITH LESSER
COVERAGE IN THE WEST WITHIN LOWER PW AND SLIGHTLY MORE STABLE AIR
DUE TO THIS MORNING`S SHOWERS/CLOUDS. THIS SCENARIO IS SUPPORTED BY
THE LATEST HRRR GUIDANCE AS WELL AS THE WRF-ARW/NMM. CONCERN
PERSISTS FOR A FEW SEVERE STORMS INTO EARLY EVENING IN THE EASTERN
CWA (PARTICULARLY SOUTHEAST SECTIONS SE OF RALEIGH) WHERE MODERATE
INSTABILITY IS ALIGNED WITH DECENT DEEP LAYER EFFECTIVE SHEAR OF 25-
30 KTS... 500 MB WINDS OF 30-40 KTS... AND D-CAPE OF 800-1200 J/KG.
AS THE WEAKENING MID LEVEL SHEAR AXIS SHIFTS SLOWLY EASTWARD AND
OVERHEAD OVERNIGHT... STORM COVERAGE SHOULD SLOWLY SHRINK AS WE LOSE
HEATING... ENDING LAST OVER THE ERN COASTAL PLAIN... AS THE SURFACE
BOUNDARY SETTLES OVER SE NC. PLENTIFUL LOW LEVEL MOISTURE AND WEAK
MASS CONVERGENCE SHOULD RESULT IN POCKETS OF FOG/STRATUS AREAWIDE
OVERNIGHT. HIGH-RES GUIDANCE AND PERSISTENCE SUGGEST LOWS TONIGHT OF
67-73.

FOR FRI/FRI NIGHT: AS THE DAMPENING SHEAR AXIS SHIFTS TO OUR SE IN
LINE WITH THE DISSIPATING SURFACE TROUGH... THE HIGHER PW VALUES
WILL ACCORDINGLY SHIFT TO THE COASTAL PLAIN... LEAVING A LIGHT NNE
LOW LEVEL FLOW AND RELATIVELY (FOR JULY) DRY COLUMN OVER THE NRN AND
WRN CWA. MODELS GENERALLY INDICATE VERY LITTLE PRECIP COVERAGE...
CONFINING AFTERNOON CONVECTION TO THE COASTAL PLAIN AND SE SANDHILLS
WHERE MODELS PROJECT MUCAPE PEAKING AT 1000-1500 J/KG. WILL RETAIN
CHANCE POPS HERE WITH ISOLATED CHANCES TO THE NW. A DIP IN
THICKNESSES TO SLIGHTLY BELOW NORMAL VALUES SUPPORTS HIGHS OF 85-90.
EXPECT LITTLE MORE THAN PATCHY SHOWERS FRI NIGHT. LOWS 66-71. -GIH

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 315 PM THURSDAY...

THE MID LEVEL TROUGH AXIS (CURRENTLY MOVING TOWARDS THE AREA) WILL
PUSH OFFSHORE ON SATURDAY...WHILE THE MID LEVEL RIDGE TRIES TO BUILD
EASTWARD TOWARDS THE REGION. MODELS HAVE TRENDED DRIER FOR THE
WEEKEND...ESPECIALLY ON SATURDAY GIVEN THE DRIER AIR FILTERING INTO
THE REGION BEHIND THE DEPARTING TROUGH. IN FACT...FORECAST SOUNDINGS
INDICATE VERY LIMITED DEEP LAYER MOISTURE...WITH PWAT VALUES PROGGED
TO RANGE BETWEEN 1-1.25 INCHES (WELL BELOW NORMAL). THEREFORE...
WILL GO WITH A MOSTLY DRY FORECAST FOR SATURDAY. MOISTURE WILL START
TO RECOVER SOME ON SUNDAY AND A SURFACE TROUGH WILL SHARPEN UP OVER
THE REGION...LEADING TO A BETTER CHANCE OF MOSTLY DIURNAL TYPE
STORMS...ALTHOUGH OVERALL COVERAGE SHOULD STILL BE RATHER LOW. LOW
LEVEL THICKNESS VALUES ARE PROGGED TO BE NEAR 1420M ON SATURDAY AND
GIVEN EXPECTED LACK OF PRECIP...TEMPS SHOULD RISE INTO THE UPPER 80S
TO LOWER 90S. BY SUNDAY...LOW LEVEL THICKNESS VALUES ARE EXPECTED TO
CLIMB ANOTHER 5-10M...RESULTING HIGH TEMPS A FEW DEGREES
WARMER...GENERALLY LOW TO MID 90S (ALTHOUGH MORE CLOUDS MAY BE
AROUND WHICH WOULD TEMPER THE WARMING SOME).

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 315 PM THURSDAY...

A DEEP VORTEX IS PROGGED TO MOVE SOUTH OUT OF CANADA AND EVENTUALLY
ACROSS THE GREAT LAKES THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL
RESULT IN A DEEP TROUGH DEVELOPING OVER THE EASTERN HALF OF THE
CONUS. THEREFORE...PRECIP CHANCES WILL BE ON THE INCREASE FOR NEXT
WEEK...ESPECIALLY LATE TUESDAY INTO EARLY WEDNESDAY AS A FRONT
APPROACHES THE AREA. ALSO...GIVEN THIS UNSEASONABLY STRONG TROUGH...
THE MID LEVEL FLOW IS EXPECTED TO STRENGTHEN AND THEREFORE THE
POSSIBILITY OF AN ORGANIZED SEVERE THREAT WILL EXIST AND THIS WILL BE
MONITORED OVER THE NEXT SEVERAL DAYS. THEN THERE IS STILL A GOOD BIT
OF UNCERTAINTY WITH REGARDS TO IF THIS FRONT WILL PUSH ALL THE WAY
THROUGH THE AREA...BUT FOR NOW IT LOOKS LIKE THE FRONT WILL STALL
SOMEWHERE ACROSS THE CAROLINAS. THUS...WILL SHOW A LITTLE DECREASE
IN POPS FOR THE LATTER HALF OF THE WEEK...BUT WILL KEEP A CHANCE IN
GIVEN THE UNCERTAINTY WITH REGARDS TO WHERE THE FRONT ENDS UP. HIGH
TEMPS AHEAD OF THE FRONT ARE EXPECTED TO BE IN THE LOW TO MID 90S ON
MONDAY AND POSSIBLY TUESDAY...ALTHOUGH DEPENDING ON THE TIMING OF
THE PRECIP...TEMPS COULD BE SLIGHTLY LOWER ON TUESDAY. THEN SLIGHTLY
COOLER TEMPS ARE EXPECTED WEDNESDAY AND THURSDAY GIVEN THE DEEP
TROUGHING OVER THE EAST COAST AND THE POSSIBILITY THAT THE FRONT
WILL PUSH THROUGH THE AREA.

&&

AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 1250 PM THURSDAY...

WHILE A FEW CLOUDS BASED AT 2000-3000 FT AGL PERSIST OVER CENTRAL
NC... VFR CONDITIONS ARE EXPECTED TO DOMINATE AT CENTRAL NC TERMINAL
SITES THROUGH 04Z THIS EVENING... ALTHOUGH A SHORT PERIOD OF MVFR
CIGS AND IFR VSBYS WITH HEAVY RAIN AND STRONG/VARIABLE WIND GUSTS
ARE POSSIBLE IN/NEAR SHOWERS/STORMS. STORMS COULD AFFECT TAF SITES
AT ANY TIME THROUGH MID EVENING BUT ARE MOST LIKELY TO IMPACT
INT/GSO IN THE 18Z-21Z WINDOW... RDU IN THE 20Z-02Z WINDOW... AND
FAY/RWI IN THE 21Z-04Z WINDOW. STARTING NEAR 04Z... SHOWERS AND
ISOLATED STORMS WITH SUB-VFR CONDITIONS MAY BE ONGOING NEAR RWI/FAY
AND PERHAPS RDU... ALTHOUGH COVERAGE SHOULD STEADILY SHRINK
OVERNIGHT. WIDESPREAD MVFR TO IFR FOG AND STRATUS ARE EXPECTED TO
FORM AFTER 06Z AND PERSIST UNTIL 12Z FRI MORNING... AFTER WHICH TIME
AN IMPROVEMENT TO VFR IS EXPECTED THROUGH 14Z. AWAY FROM STORMS...
PREVAILING WINDS WILL REMAIN LIGHT... UNDER 10 KTS... MAINLY FROM
THE S AND SW (EXCEPT VARIABLE AT INT/GSO).

LOOKING BEYOND 18Z FRI... VFR CONDITIONS WILL AGAIN DOMINATE BUT A
FEW STORMS WITH GUSTY WINDS AND SUB-VFR CONDITIONS ARE EXPECTED AT
RDU AND PARTICULARLY RWI/FAY FRI AFTERNOON/EVENING. ARRIVAL OF A
DRIER AND MORE STABLE AIR MASS FRI NIGHT THROUGH SUN WILL LEAD TO A
HIGH CONFIDENCE IN VFR CONDITIONS OVER THE WEEKEND. A RETURN TO
SCATTERED LATE DAY SHOWERS AND STORMS IS EXPECTED MON-TUE... WITH A
CHANCE OF LIGHT SUB-VFR FOG WITHIN A FEW HOURS OF DAWN BOTH MON AND
TUE. -GIH

&&

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

&&

$$

SYNOPSIS...WSS/HARTFIELD
NEAR TERM...HARTFIELD/BLS
SHORT TERM...KRD
LONG TERM...KRD
AVIATION...HARTFIELD


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