-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 160159
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
955 PM EDT WED MAY 15 2013

.SYNOPSIS...
-- Changed Discussion --
A RIDGE OF HIGH PRESSURE OVER THE SOUTHEAST WILL CONTROL THE WEATHER
ACROSS CENTRAL NC THROUGH THURSDAY. A MID AND UPPER LEVEL AREA OF
LOW PRESSURE WILL APPROACH THE AREA FROM THE WEST THURSDAY NIGHT AND
FRIDAY. A COLD FRONT WILL SLOWLY MOVE SOUTH OVER OUR REGION DURING
THE WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 955 PM WEDNESDAY..

ONLY A FEW CIRRUS TRAVERSING THE SKY THIS EVENING AS THE WARM RIDGE
TAKES A FIRM GRIP OVER OUR REGION. THE LATEST OBSERVATIONAL DATA
INDICATED THE TEMPERATURES WERE STILL IN THE 75 TO 80 RANGE WITH DEW
POINTS IN THE UPPER 50S TO LOWER 60S. A SW BREEZE ALSO CONTINUED AT
NEAR 10 MPH KEEPING THE BOUNDARY LAYER MIXED. LOWS WILL STAY AT OR
ABOVE 65 AT MOST LOCATIONS.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
AS OF 200 PM WEDNESDAY...

FOR THURSDAY AND THURSDAY NIGHT...
THE RIDGE OF HIGH PRESSURE ACROSS THE SOUTHEAST FLATTENS DURING THE
PERIOD AND HEIGHTS ACROSS CENTRAL NC NUDGE DOWNWARD. A CLOSED AREA
OF LOW PRESSURE ACROSS OK TONIGHT WILL SLOWLY DRIFT EAST AND OPEN
UP. A DISTURBANCE IN THE CYCLONIC FLOW AHEAD OF THIS SYSTEM WILL
MOVE INTO CENTRAL NC ON THURSDAY AFTERNOON WITH A SECOND DISTURBANCE
LIKELY TO ROTATE THROUGH THE AREA ON THURSDAY NIGHT. AT THE SAME
TIME A COLD FRONT WILL DROP INTO THE MID ATLANTIC REGION AND LIKELY
TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS IN WV AND VA DURING THE
AFTERNOON. THE AIR MASS ACROSS CENTRAL NC ON THURSDAY AFTERNOON IS
NOT TERRIBLY SUPPORTIVE OF CONVECTION WITH WEAK INSTABILITY
GENERALLY LESS THAN 500 J/KG AND A RATHER DRY AIR MASS. IT IS
POSSIBLE THAT AFTERNOON CONVECTION IN WV/VA COULD SUSTAIN ITSELF IN
A REGION OF GREATER INSTABILITY AND MOVE SOUTH INTO NORTHERN NC ON
THURSDAY EVENING. FOR NOW WILL GO WITH A DRY FORECAST FOR THURSDAY
AND INCLUDE ONLY A SLIGHT CHANCE OF A THUNDERSTORM ACROSS THE
NORTHERN HALF ON THURSDAY EVENING.

EXPECT MID AND HIGH CLOUDINESS TO INCREASE ON THURSDAY RESULTING IN
PARTLY CLOUDY SKIES BY AFTERNOON. AFTERNOON LOW LEVEL THICKNESS
VALUES ON THURSDAY ARE ACTUALLY A FEW METERS COOLER THAN TODAY. THE
AXIS OF WARMEST CONDITIONS WHICH WAS LOCATED OVER WESTERN NC ON
WEDNESDAY SHIFTS EAST INTO THE COASTAL PLAIN ON THURSDAY. MOS
GUIDANCE IS ACTUALLY DEPICTING MAXES THAT ARE ROUGHLY A DEGREE
WARMER THAN WHAT THEY FORECASTED FOR WEDNESDAY. WHILE SOME HIGH/MID
LEVEL CLOUDINESS IS EXPECTED...STILL FEEL THAT THERE WILL BE
SUFFICIENT INSOLATION FOR MAXES TO WARM TO VALUES SIMILAR TO
WEDNESDAY WITH THE WARMEST TEMPS FLIP FLOPPED FROM WEST TO EAST.
WILL GO WITH HIGHS OF 85 NORTHWEST TO 90 NORTHEAST. MID AND HIGH
CLOUDINESS WILL CONTINUE TO THICKEN ON THURSDAY NIGHT AND A LIGHT
STIRRING OF SOUTHERLY WIND WILL RESULT IN A MILD NIGHT WITH LOWS IN
THE 60 TO 65 RANGE. -BLAES

FOR FRIDAY/FRIDAY NIGHT: THE WEAK SURFACE TROUGH IS EXPECTED TO
LINGER ACROSS CENTRAL/ERN NC INTO SC... WHILE THE PRIMARY FRONTAL
ZONE STRETCHES ACROSS MD BACK TOWARD CHICAGO. THE WEAK MID LEVEL LOW
NOW OVER NW TX WILL EASE EASTWARD ACROSS THE CAROLINAS AS A WEAK AND
SHEARING OPEN WAVE... ALTHOUGH DPVA SHOULD BE QUITE SMALL GIVEN THE
VERY LIGHT MID-LEVEL FLOW FROM THE NW. THE NOSE OF THE LOW LEVEL JET
SITS WELL WEST OVER THE LOWER-MID MISS VALLEY (NRN LA/NRN AL/WRN
TN/KY) BUT MODELS DEVELOP AFTERNOON STORMS ALL ALONG AND SOUTH OF
THE 925 MB FRONT FROM NRN IL ACROSS WV TO SE VA... WITHIN AN OVERALL
WEAK WIND FIELD AND LOW DEEP LAYER SHEAR BUT POSSESSING MODERATE
INSTABILITY (MLCAPE UP TO 1000-1500 J/KG). CURRENT CONFIGURATION OF
CONVECTION CHANCES WITH THE BEST CHANCES NEAR THE VA BORDER AND IN
THE NORTHEAST PORTIONS OF THE FORECAST AREA HANDLES THIS WELL. THE
ECMWF AND ESPECIALLY THE GFS KEEP CONVECTION GOING OVERNIGHT OVER
MUCH OF EASTERN NC NEAR THE POORLY DEFINED INTERSECTION OF THE
AFOREMENTIONED TROUGH AND WHAT LOOKS TO BE A SSW-MOVING OUTFLOW
BOUNDARY. GIVEN THE LINGERING MARGINAL ELEVATED INSTABILITY
OVERNIGHT AND PRECIP WATER OVER 150% OF NORMAL... SCATTERED
SLOW-MOVING SHOWERS AND ISOLATED STORMS IN THE EAST THROUGH THE
NIGHT HERE SEEMS REASONABLE. HIGHS 82-87 WITH THICKNESSES 15-20
METERS ABOVE NORMAL AND INCREASING CLOUD COVER. LOWS 62-66 WITH
MOSTLY CLOUDY SKIES... INCLUDING LOW STRATUS TOWARD DAYBREAK.

FOR SATURDAY/SATURDAY NIGHT: THE MID LEVEL WAVE OBSERVED OVER NV/UT
THIS MORNING IS EXPECTED TO TRACK TOWARD THE ESE TOWARD NC BY THE
WEEKEND... ALTHOUGH ITS STRENGTH ON THE MODELS MAY BE ERRONEOUSLY
ENHANCED BY CONVECTIVE FEEDBACK ALONG ITS JOURNEY. THE WEAK STEERING
FLOW OVER NC WILL STILL LIMIT THE FORCING FOR ASCENT VIA DPVA AS THE
WAVE ARRIVES LATE SATURDAY INTO SATURDAY NIGHT... AND THE WEAK LOW
LEVEL FLOW WILL CURB MASS CONVERGENCE ALONG ANY RESIDUAL ILL-DEFINED
TROUGH OR OUTFLOW. BUT DESPITE THIS AND MID LEVEL LAPSE RATES OF
JUST 5.5-6.0 C/KM... THE CONTINUED PRESENCE OF ABOVE-NORMAL PRECIP
WATER (NEAR 1.5 INCHES OR OVER 150% OF NORMAL) AND INCREASING
INFLUENCE OF LOW LEVEL CONFLUENT AND ONSHORE-DIRECTED ATLANTIC
INFLOW NECESSITATES A MENTION OF AT LEAST SCATTERED STORMS FOCUSED
IN (BUT NOT RESTRICTED TO) THE AFTERNOON/EVENING HOURS. INSTABILITY
IS IN QUESTION WITH 500-M MLCAPE OF 500-1000 J/KG ON THE ECMWF AND
1000-2000 J/KG ON THE GFS... AND IF WE DO ACHIEVE GREATER
INSTABILITY... POPS MAY NEED TO GO UP INTO THE LIKELY RANGE IN LATER
FORECASTS. HIGHS 79-85 WITH CONSIDERABLE CLOUDINESS. LOWS 62-66
UNDER CLOUDY SKIES. -GIH
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 305 PM WEDNESDAY...

FOR SUNDAY/SUNDAY NIGHT: THE WEAK WAVE WILL CONTINUE TO MEANDER TO
THE SE ACROSS THE CAROLINAS SUNDAY... ALTHOUGH IT WILL BE EMBEDDED
WITHIN A LARGE RIDGE EXTENDING FROM THE GREAT LAKES DOWN TO THE
INTERIOR SOUTHEAST... WHILE BROAD TROUGHING SITS OVER THE WESTERN
CONUS. THE GFS RETAINS A STRONGER MID LEVEL WAVE AND AS SUCH FORMS A
POTENT INVERTED TROUGH OVER ERN NC INTO CENTRAL SC WITH A WEDGE-LIKE
NNE SURFACE FLOW PATTERN OVER THE WRN PIEDMONT... WHEREAS THE ECMWF
WITH ITS WEAKER WAVE DEPICTS A LARGE SURFACE HIGH CENTERED OFF NEW
ENGLAND EXTENDING SOUTHWARD JUST OFF THE EAST COAST WITH A BROAD
SOUTHEASTERLY ATLANTIC INFLOW AND NO SUCH TROUGHING FEATURE. BOTH
HAVE BEEN CONSISTENT BUT SUSPECT THE GFS MAY BE ADVERSELY AFFECTED
BY GRIDSCALE FEEDBACK AND THUS LOWERING SURFACE PRESSURES TOO
MUCH... SO WILL LEAN TOWARD THE ECMWF. THIS FAVORS A MORE
LOW-LEVEL-STEERED INFLUX OF A TROPICAL-LIKE AIR MASS INTO NC
SUNDAY... SUGGESTING GOOD COVERAGE OF LOW-BASED SHOWERS AND A FEW
STORMS (PARTICULARLY IN THE WEST WHERE UPSLOPE FLOW MAY AUGMENT RAIN
COVERAGE) BUT WITH SOME HOLES IN THE CLOUD COVER. HIGHS 77-83 AND
LOWS 64-67.

FOR MONDAY THROUGH WEDNESDAY: AGAIN FOLLOWING THE ECMWF... THE
SURFACE HIGH OFF THE NORTHEAST COAST STARTS TO DRIFT SOUTHWARD...
PUSHED BY MID LEVEL TROUGHING LOCATED TO ITS EAST... WHILE THE MID
LEVEL ANTICYCLONE BECOMES CENTERED OVER THE REGION. THIS RESULTS IN
ANOTHER DAY OF WARM TEMPS ALOFT AND LONG-FETCH SOUTHEAST LOW LEVEL
FLOW INTO NC... AND ANOTHER DAY OF AT LEAST SCATTERED SHOWERS AND A
FEW STORMS WITH MORE CLOUDS THAN SUNSHINE. AS THE OFFSHORE SURFACE
HIGH DRIFTS FURTHER SOUTHWARD... LOW LEVEL FLOW OVER NC WILL WEAKEN
AND VEER TO BE MORE FROM A SOUTHERLY DIRECTION... AND THIS MORE
OVER-LAND DIRECTION AND CONTINUED WARM MID-LEVEL TEMPS SHOULD LEAD
TO REDUCED SHOWERS/STORM COVERAGE ON TUESDAY INTO WEDNESDAY... WITH
A BIT MORE SUNSHINE AND HIGHS REBOUNDING BACK ABOVE NORMAL. MID
LEVEL HEIGHTS WILL CONTINUE TO FALL WITH A CYCLONE CENTER FORMING
OVER THE MIDWEST... AND THIS IS PROJECTED TO BE SLOW TO DRIFT TO THE
SSE OVER THE MID MISS VALLEY... WHICH SHOULD KEEP ITS ASSOCIATED
COLD FRONT (AND FRONTAL PRECIP) WELL TO OUR NORTHWEST THROUGH
WEDNESDAY. WILL KEEP POPS NEAR OR BELOW CLIMATOLOGY ON WEDNESDAY AS
WELL... WITH TEMPS ABOUT A CATEGORY ABOVE NORMAL. -GIH

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 800 PM WEDNESDAY...

24-HR TAF PERIOD:
VFR CONDITIONS WILL RULE THROUGH THE TAF PERIOD. LIGHT SOUTHWEST
WINDS WILL PREVAIL OVERNIGHT...BECOMING WSW OR WESTERLY AT 10-15 KT
DURING THE DAY THURSDAY. SUB-VFR CONDITIONS WILL ONLY BE POSSIBLE IN
ASSOCIATION WITH A SMALL POTENTIAL FOR ISOLD SHOWERS AND
THUNDERSTORMS THURSDAY EVENING INTO THURSDAY NIGHT.

LOOKING AHEAD:
VFR CONDITIONS SHOULD LARGELY PREVAIL INTO THE WEEKEND. HOWEVER...
EXPECT AN INCREASING POTENTIAL FOR DIURNAL CONVECTION FRIDAY THROUGH
THE WEEKEND...WITH SUB-VFR CONDITIONS POSSIBLE IN ASSOCIATION WITH
ISOLD TO SCT SHOWERS AND THUNDERSTORMS...PRIMARILY DURING THE LATE
AFTERNOON AND EVENING...AND A CHANCE OF FOG OR LOW CEILINGS DURING
THE EARLY MORNING HOURS...PRIMARILY SUN/MON. -VINCENT

&&

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

&&

$$

SYNOPSIS...BLAES
NEAR TERM...BADGETT
SHORT TERM...BLAES/HARTFIELD
LONG TERM...HARTFIELD
AVIATION...VINCENT