-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 231837
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
235 PM EDT WED JUL 23 2014

.SYNOPSIS...ATLANTIC HIGH PRESSURE WILL EXTEND WESTWARD OVER THE
CAROLINAS TODAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST
TONIGHT... THEN PUSH SOUTHEAST THROUGH NORTH CAROLINA THURSDAY AND
THURSDAY NIGHT. WEAK HIGH PRESSURE WILL PUSH IN FROM THE NORTH ON
FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 955 AM WEDNESDAY...

UPDATE...MORNING FOG HAS DISSIPATED AND WILL DELAY POPS AND DECREASE
CLOUD COVERAGE THROUGH THE AFTERNOON. HIGH TEMPERATURES ARE ON TRACK...
BUT THE SOUTHEAST SHOULD GET A LITTLE WARMER THAN ONGOING 90-ISH...WILL
RAISE TO 92-93 DUE TO CURRENT RISING TREND AND STRONG INSOLATION.

PREVIOUS DISCUSSION...FOR TODAY/TONIGHT: ISOLATED SHOWERS ON THE
PERIPHERY OF THE ATLANTIC RIDGE OFF THE SOUTHEAST COAST HAVE ALL BUT
DIED OFF THIS MORNING. PATCHY FOG AND STRATUS WILL HOLD UNTIL SOON AFTER
DAYBREAK (PRIMARILY OVER THE ERN HALF OF THE CWA)... FOLLOWED BY A TREND
TO PARTLY TO MOSTLY SKIES AS A LIGHT SW SURFACE BREEZE INDUCES MIXING
AND DISPERSION OF THE LOW LEVEL MOISTURE. DEEP LAYER SHEAR REMAINS
LOW TODAY (10-15 KTS) WITH MARGINAL INSTABILITY (MLCAPE PEAKING AT
500-1000 J/KG) WITH MODEST MID LEVEL LAPSE RATES OF 5.5-6.0 C/KM.
DYNAMICALLY WE SHOULD BE IN A RELATIVE LULL ZONE TODAY WITH THE MID
LEVEL RIDGE CENTERED OFF THE SE COAST CONTINUING TO NOSE WESTWARD
OVER THE SOUTHEAST... WHILE ENERGY DIVES FROM THE UPPER MIDWEST
SOUTHEASTWARD TOWARD THE WRN OH VALLEY... HELPING DIG THE TROUGH
JUST TO OUR NW TONIGHT AS THE ASSOCIATED SURFACE FRONT APPROACHES.
PW VALUES REMAIN ELEVATED (1.7-2.1)... SO STILL EXPECT SCATTERED
SHOWER/STORM ACTIVITY TODAY... BUT THE LACK OF DEEP SHEAR AND
CONVECTIVE FOCUS AND THE WEAK MID LEVEL FLOW WILL HAMPER STORM
ORGANIZATION AND STRENGTH. BOTH THE TRADITIONAL AND CONVECTION-
ALLOWING MODELS BEAR THIS OUT WITH LIMITED COVERAGE TODAY... ALONG
WITH A SHIFT IN BEST LOW LEVEL MOISTURE TRANSPORT TO COASTAL
SECTIONS. WILL KEEP POPS AT 25-35% TODAY... PEAKING DURING THE
TYPICAL MID-LATE AFTERNOON... AND TAPERING DOWN IN THE MID-LATE
EVENING AS THE BOUNDARY LAYER STABILIZES AND PW DIPS SLIGHTLY. HIGHS
89-93 WITH NEAR-NORMAL THICKNESSES AND SOME SUNSHINE. LOWS 69-74
UNDER PARTLY TO MOSTLY CLOUDY SKIES. -GIH

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
AS OF 315 AM WEDNESDAY...

MUCH OF THE CWA SHOULD SEE SHOWERS/STORMS AT SOME POINT THU. THE MID
LEVEL TROUGH DIGS JUST WEST OF THE FORECAST AREA EARLY THU... WITH
PROJECTED HEIGHT FALLS OF 30-50 M OVER NC. THE ACCOMPANYING SURFACE
FRONT IS EXPECTED TO REACH THE SPINE OF THE APPALACHIANS EARLY THU
MORNING... THEN EASE SLOWLY EASTWARD INTO CENTRAL NC DURING THE
AFTERNOON WITH SURFACE LOW PRESSURE FORMING ALONG THE FRONT AS DPVA
ALOFT STRENGTHENS. THIS IMPROVING DYNAMIC FORCING FOR ASCENT WILL
ATTEND STRENGTHENING MID LEVEL WINDS AND GREATER DEEP LAYER SHEAR OF
30-35 KTS. INSTABILITY COULD HOLD ON THE LOW SIDE HOWEVER... AS
MODELS SHOW MUCAPE TOPPING OUT AT 1000-2000 J/KG OVER THE
CENTRAL/ERN CWA... WHICH COULD BE A FUNCTION OF THE EARLY ARRIVAL OF
THE DYNAMIC LIFT AS SUGGESTED BY TRADITIONAL MODELS (WHICH SHOW GOOD
QPF COVERAGE OVER THE NRN/WRN CWA PRIOR TO 18Z) AS WELL AS THE HIGH-
RES WRF-NMM/ARW AND THE (NAM-HEAVY) SREF PROBABILITIES. WILL BRING
IN MID RANGE CHANCE POPS OVER THE NW CWA BY LATE MORNING...
SPREADING EAST OVER THE REST OF THE CWA DURING THE AFTERNOON...
BEFORE ENDING WNW TO ESE FROM LATE AFTERNOON THROUGH THE EVENING.
DID KEEP A LOW CHANCE OF LINGERING SHOWERS OVER THE SOUTHEAST CWA
THROUGH THE NIGHT GIVEN THAT THE FRONTAL ZONE COULD BECOME STALLED
OUT THERE... AND THE INCOMING SURFACE HIGH PRESSURE WILL STILL BE
CENTERED OVER IN/OH OVERNIGHT... NOT A FAVORABLE LOCATION FOR THE
MORE DENSE AIR TO BE ABLE TO GET OVER THE MOUNTAINS. THE RISK OF A
FEW SEVERE STORMS REMAINS... BOOSTED BY THE LARGE SCALE FORCING FOR
ASCENT AND THE IMPROVING KINEMATICS... BUT IF THE CONVECTION COMES
IN EARLIER IN THE DAY AS EXPECTED... THIS WILL CUT DOWN ON HEATING
AND RESULTING INSTABILITY OVER ALL BUT THE FAR SE CWA. AND MARGINAL
MID LEVEL LAPSE RATES (BARELY APPROACHING 6.0) SHOULD LIMIT THE
LARGE HAIL THREAT. BUT WITH THE RELATIVE VIGOROUS NATURE OF THIS
SYSTEM (FOR JULY) AND POSSIBLE MODERATE INSTABILITY... WILL CONTINUE
THE MENTION OF AN ISOLATED SEVERE STORM OR TWO ESPECIALLY FROM THE
TRIANGLE SOUTH AND EAST... HIGHLIGHTING DAMAGING WINDS AS THE
PRIMARY THREAT. HIGHS 84 NW TO 93 SE. LOWS 64 NW TO 73 SE.
-GIH

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 235 PM WEDNESDAY...

NWP GUIDANCE IS RELATIVELY CONSISTENT IN BRINGING THE SURFACE COLD
FRONT TO THE COASTAL PLAIN OF THE CAROLINAS BY 12 UTC FRIDAY AS THE
UPPER LEVEL TROUGH AXIS CROSSES THE APPALACHIANS. THE UPPER LEVEL
TROUGH AXIS MAKES LIMITED PROGRESS EAST ON FRIDAY AS THE NEXT
SHORTWAVE TROUGH OVER THE OH VALLEY EARLY FRIDAY SPLITS WITH ONE
PIECE OF ENERGY MOVING EAST INTO THE NORTHEAST AND THE OTHER DROPS
TOWARD THE SAVANNAH RIVER VALLEY. THE FRONT DRIFTS SOUTH AND BRIEFLY
STALLS BEFORE MOVING NORTH INTO THE MID ATLANTIC AS A WARM FRONT
SATURDAY. DEEP MOISTURE DECREASES ON FRIDAY COMPARED TO THURSDAY
WITH THE BULK OF THE MOISTURE CONFINED TO THE 925 TO 700 MB LAYER IN
A REGION OF RELATIVELY STEEP LAPSE RATES. THIS PATTERN SUGGESTS THE
BEST CONVECTIVE COVERAGE ON FRIDAY WILL BE ACROSS THE FAR SOUTHEAST
PIEDMONT AND ESPECIALLY THE COASTAL PLAIN AND EASTERN SANDHILLS
FRIDAY AFTERNOON AND EVENING. POPS IN THE SLIGHT CHANCE TO LOW
CHANCE RANGE SHOULD SUFFICE. HIGHS ON FRIDAY WILL RANGE IN THE MID
TO UPPER 80S. PARTLY CLOUDY SKIES ARE EXPECTED FRIDAY NIGHT WITH
LOWS IN THE MID 60S TO NEAR 70. SATURDAY WILL FEATURE PARTLY CLOUDY
SKIES WITH THE BULK OF THE CONVECTION SUPPRESSED TOWARD THE COAST.
THERE IS JUST A LIMITED THREAT OF PRECIPITATION IN CENTRAL NC WITH
THE BEST CHANCE OF STORMS ON SATURDAY ACROSS THE EASTERN COASTAL
PLAIN WITH ONLY SLIGHT CHANCE POPS WARRANTED. SATURDAY SHOULD
FEATURE THE FAIRER WEATHER OF THE WEEKEND WITH VERY LIMITED
PRECIPITATION COVERAGE AND NEAR SEASONABLE TEMPERATURES.
TEMPERATURES WILL MODERATE A BIT ON SATURDAY WITH HIGHS IN THE 87 TO
92 RANGE.

THE NEXT UPPER TROUGH APPROACHES FROM THE NORTHWEST ON SUNDAY WITH A
COLD FRONT DROPPING ACROSS THE OH VALLEY. A LEE TROUGH AHEAD OF THE
FRONT ACROSS THE PIEDMONT OF VA AND THE CAROLINAS IS EXPECTED TO
BECOME CONVECTIVELY ACTIVE DURING THE AFTERNOON AND EVENING WITH
SCATTERED CONVECTION. THE SOUTHERLY FLOW AHEAD OF THE UPPER
TROUGH... COMBINED WITH DEEP MIXING WILL RESULT IN HIGHS IN THE
LOWER 90S. THE UPPER TROUGH AXIS AND COLD FRONT WILL CROSS CENTRAL
NC ON MONDAY WITH GOOD CONVECTIVE COVERAGE ANTICIPATED. WILL
INCREASE POPS INTO THE HIGH CHANCE RANGE. WITH THE APPROACHING
TROUGH...THE LOW AND MID LEVEL FLOW INCREASES WITH BULK SHEAR VALUES
OF 30-40 KTS EXPECTED SUGGESTING SOME HIGH-BASED STORM ORGANIZATION
IS POSSIBLE.  SLIGHTLY COOLER TEMPERATURES ARE EXPECTED ON MONDAY
WITH THE CLOUD COVER AND PRECIPITATION...HIGHS SHOULD RANGE IN THE
86 TO 91 RANGE WITH LOWS MONDAY MORNING IN THE 69 TO 74 RANGE.

THE LARGE AMPLITUDE UPPER LEVEL TROUGH SLOWLY MOVES EAST ON TUESDAY
WITH THE COLD FRONT PROGGED TO MOVE INTO THE COASTAL PLAIN MONDAY
NIGHT AND SLOWLY PUSH TOWARD THE COAST ON TUESDAY. COOL HIGH
PRESSURE BUILDS INTO THE REGION WITH ANY PRECIPITATION ON TUESDAY
LIKELY CONFINED TO THE COASTAL PLAIN AND POINTS EAST. MAINLY DRY
CONDITIONS ARE EXPECTED ON WEDNESDAY BUT IT IS WORTH NOTING THAT THE
GFS/ECMWF BOTH INDICATE THE STALLED FRONT NEAR THE COAST MAY TRY TO
WORK WEST. FOR NOW WILL INCLUDE A DRY FORECAST. THE MUCH COOLER AIR
MASS WITH LOW LEVEL THICKNESS VALUES FALLING INTO THE 1375-1390M
RANGE FOR TUESDAY AND WEDNESDAY MORNINGS. THIS WOULD SUPPORT LOWS IN
THE 60S AND PERHAPS UPPER 50S IN THE TRIAD OR NEAR THE VA BORDER ON
WEDNESDAY MORNING WITH HIGHS OF 79-86. -BLAES
-- End Changed Discussion --
&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 652 AM WEDNESDAY...

AT INT/GSO... VFR CONDITIONS HAVE PREVAILED... WHILE CIGS/VSBYS HAVE
DROPPED TO IFR/LIFR AT RDU/FAY/RWI OVER THE LAST SEVERAL HOURS DUE
TO WET GROUND AND LIGHT WINDS. THESE POOR AVIATION CONDITIONS WILL
GRADUALLY IMPROVE THROUGH 14Z... RISING TO MVFR THEN VFR WITH THE
ONSET OF HEATING AND MIXING TO DISPERSE THE FOG AND STRATUS. VFR
CONDITIONS ARE LIKELY FROM 15Z ON THROUGH THE DAY AS CIGS LIFT AND
BREAK UP WITH MIXING... WITH SURFACE WINDS FROM THE SW AT 8-12 KTS.
ANY SHOWERS/STORMS WILL BE ISOLATED OR IN SMALL CLUSTERS... AND THE
CHANCE OF THEM AFFECTING TAF SITES IS TOO SMALL TO INCLUDE IN THE
TAFS AT THIS TIME. VFR CONDITIONS SHOULD PREVAIL THROUGH 06Z EXCEPT
AT RWI... WHICH MAY SEE MVFR VSBYS IN FOG AFTER 03Z. EXCEPT FOR THIS
LIGHT FOG AT RWI... VFR CONDITIONS SHOULD HOLD ELSEWHERE OVERNIGHT
WITH A LIGHT BREEZE FROM THE SW.

LOOKING BEYOND 12Z EARLY THU MORNING... AN APPROACHING COLD FRONT
WILL BRING NUMEROUS SHOWERS AND STORMS WITH SUB-VFR CONDITIONS
STARTING LATE THU MORNING (15Z-18Z) AT INT/GSO BEFORE SPREADING EAST
TO RDU DURING THE EARLY AFTERNOON AND TO RWI/FAY DURING THE MID-LATE
AFTERNOON. THE FRONT MAY SLOW DOWN OVER COASTAL SECTIONS THU
NIGHT/FRI... KEEPING A CHANCE OF SUB-VFR SHOWERS/STORMS FRI
AFTERNOON... BUT OTHERWISE VFR CONDITIONS ARE EXPECTED FRI-SAT AS
HIGH PRESSURE NOSES IN FROM THE NORTH. AN UPPER LEVEL DISTURBANCE
WILL MOVE IN FROM THE NORTHWEST ON SUNDAY... POTENTIALLY BRINGING
ANOTHER ROUND OF SHOWERS/STORMS. -GIH

&&

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

&&

$$

SYNOPSIS..HARTFIELD
NEAR TERM...MLM/HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...BLAES
AVIATION...HARTFIELD