000
FXUS62 KRAH 171915
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
315 PM EDT WED SEP 17 2014

.SYNOPSIS...HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE NORTH
TONIGHT... AND REMAIN OVER THE AREA THROUGH SATURDAY. A COLD FRONT
WILL APPROACH FROM THE NORTHWEST SUNDAY... THEN MOVE SOUTHEAST
THROUGH THE REGION MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 PM WEDNESDAY...

THROUGH TONIGHT: A FEW SHOWERS/STORMS ARE POSSIBLE MAINLY IN THE
COASTAL PLAIN THIS EVENING... BUT OTHERWISE EXPECT QUIET WEATHER
TONIGHT WITH PARTLY TO MOSTLY CLOUDY SKIES. THE SURFACE FRONT
REMAINS WELL TO OUR SOUTH THIS AFTERNOON... WITH SOMEWHAT WEAK HIGH
PRESSURE BUILDING IN FROM THE NORTH. THE RESULTING LOW LEVEL
EASTERLY FLOW OFF THE ATLANTIC CONTINUES TO DRAW SUFFICIENT MOISTURE
INTO CENTRAL NC FOR BROKEN CLOUD COVER... ESPECIALLY OVER THE HIGHER
TERRAIN WHERE FORCED UPGLIDE IS LEADING TO MORE DENSE CLOUD
DEVELOPMENT. CINH AND LOW CAPE VALUES DOMINATE THE FAR NRN AND WRN
CWA ACCORDING TO MESOANALYSES... ALTHOUGH IN EASTERN SECTIONS FROM
RALEIGH TO THE EAST AND SOUTHEAST...MLCAPE HAS RISEN ABOVE 500
J/KG... AND EFFECTIVE SHEAR HERE A WEAK MID LEVEL WAVE NOW
TRAVERSING THE REGION MAY PROVIDE A SLIGHT BIT OF DEEPER FORCING FOR
ASCENT TO AUGMENT THE INSTABILITY... ALTHOUGH DYNAMICS ARE GENERALLY
QUITE WEAK. OTHERWISE... THE COLUMN IS DRIER IN THE WRN CWA WITH
BELOW-NORMAL PW... AND CONVECTION FOR THE REMAINDER OF TODAY INTO
TONIGHT APPEARS UNLIKELY HERE. MODELS WITH BOTH EXPLICIT AND
PARAMETERIZED CONVECTION HAVE GENERALLY OVERDONE PRECIP OVER THE
AREA SO FAR TODAY... AND EVEN THESE ARE TRENDING DRIER OVERNIGHT.
WILL HOLD INTO LOW CHANCE POPS FROM THE TRIANGLE EAST INTO EARLY
EVENING... TRENDING DOWN BY LATE EVENING/OVERNIGHT. HAVE RETAINED A
MENTION OF PATCHY DRIZZLE OVERNIGHT... AS WE KEEP A PREDOMINANTLY
EASTERLY MOIST LOW LEVEL FLOW... HOWEVER THE MODELS` DEPICTION OF
MOIST ISENTROPIC UPGLIDE IS WEAK AT BEST TONIGHT... SO EXPECT
MINIMAL IMPACT. WE SHOULD CONTINUE TO SEE BROKEN CLOUDS OVERNIGHT
HOWEVER... ESPECIALLY IN THE WRN PIEDMONT AND SOUTHWEST... WHERE WE
SHOULD HAVE ADDITIONAL MID/HIGH CLOUDS AS A RESULT OF THE REMNANT
MCV -- NOW OVER SRN MO/NRN AR -- EXPECTED TO SKIRT BY JUST TO OUR
SOUTHWEST LATE TONIGHT. LOWS 58-63. -GIH

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 310 PM WEDNESDAY...

THE MCV RESULTING FROM THE MCS NOW OVER THE MO/AR BORDER IS STILL
EXPECTED TO PUSH SOUTHEAST AWAY FROM THE AREA THU MORNING. THE
MODELS SHOW TRAILING WEAK VORTICITY INSTIGATING ISOLATED CONVECTION
OVER THE MOUNTAINS AND FAR SWRN PIEDMONT THU MORNING... AND THIS IS
REASONABLE CONSIDERING THE POTENTIALLY DEEPER MOISTURE HERE AND
UPSLOPE-DIRECTED LOW LEVEL FLOW... SO WILL LEAVE IN A MENTION OF
ISOLATED SHOWERS OVER THE WRN/SRN CWA THU MORNING. BY AFTERNOON...
EXPECT THE RISK OF ISOLATED SHOWERS TO SHIFT TO THE SOUTHEASTERN AND
FAR ERN CWA WHERE WE SHOULD ONCE AGAIN SEE MARGINAL INSTABILITY
(MUCAPE AROUND 1000 J/KG) AND SOMEWHAT IMPROVED DEEP LAYER SHEAR
CLOSER TO 30 KTS. THE MID LEVELS REMAIN DRY AND FAIRLY STABLE
HOWEVER... SO WILL RESTRICT POPS TO JUST ISOLATED SHOWERS OVER THE
E/SE SECTIONS THU AFTERNOON... WITH NO POPS AFTER NIGHTFALL... AS
HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTH. ANOTHER ROUND OF
LOW CLOUDS/FOG IS POSSIBLE LATE THU NIGHT... FOLLOWING PERSISTENCE.
HIGHS 78-81... ON THE LOW END OF GUIDANCE BASED ON AT LEAST SOME
CLOUDINESS AND SLIGHTLY BELOW NORMAL THICKNESSES. NEAR-NORMAL LOWS
OF 59-63 LOOK GOOD. -GIH

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
AS OF 253 PM WEDNESDAY...

FRIDAY THROUGH SATURDAY: EASTERN US TROUGH WILL PULL EAST AND OUT TO
SEA OUT ON FRIDAY... BUT NOT WITHOUT LEAVING BEHIND A REMNANT MID-
LEVEL CIRCULATION TO MEANDER OFF THE SE COAST THROUGH EARLY SUNDAY.
AT THE SURFACE...PROGRESSIVE CANADIAN HIGH OVER NEW ENGLAND WILL
QUICKLY MOVE EAST OUT INTO THE NORTHERN ATLANTIC...BECOMING
ELONGATED AS IT SHIFTS FARTHER OFFSHORE. IN THE WAKE OF THE EXITING
TROUGH...HEIGHTS INCREASE OVER THE AREA...WHICH SHOULD KEEP THE MID-
LEVEL CIRCULATION OFF THE SE COAST AT BAY AND SECURE DRY CONDITIONS
ACROSS CENTRAL NC.

AS FAR AS TEMPERATURES...PROGRESSIVE NATURE OF THE PARENT HIGH AND
ORIENTATION OF THE ASSOCIATED RIDGE AXIS IS EXPECTED TO YIELD A LONG
FETCH OF EAST-NORTHEASTERLY LOW-LEVEL MARITIME FLOW INTO THE AREA
AND KEEP THE BRUNT OF THE COOLER AND DRIER AIR TO OUR NORTH...WHILE
SUPPORTING PERIODIC PARTLY TO BROKEN CLOUDINESS IN THE WAY OF
MORNING STRATUS AND A DIURNALLY ENHANCED CU FIELD. HIGHS IN THE MID
70S NORTH TO AROUND 80 SOUTH. LOWS FRIDAY NIGHT IN THE MID 50S NORTH
TO NEAR 60 SOUTH. LOWS SATURDAY NIGHT A GOOD CATEGORY WARMER...IN
THE UPPER 50S TO LOWER 60S.

SUNDAY THROUGH MONDAY: 40 TO 60 METER HEIGHT FALLS TRAVERSING THE
REGION IN ADVANCE OF THE AMPLIFYING UPPER LEVEL TROUGH SWINGING
EASTWARD ACROSS THE EASTERN US WILL DRIVE A SURFACE COLD FRONT
THROUGH THE AREA MONDAY AFTERNOON. IN ADVANCE OF THE UPPER
TROUGH...AFOREMENTIONED MID-LEVEL CIRCULATION/LOW OFF THE SOUTHEAST
COAST WILL FINALLY GET KICKED EAST-NORTHEASTWARD...LIFTING UP THE NC
COAST AND THEN OUT INTO THE ATLANTIC ON SUNDAY. THE LATEST 12Z/17
GFS IS STRONGER WITH THIS FEATURE AND SUGGEST IT COULD POTENTIALLY
ENHANCE THE ONSHORE MARITIME FLOW...POSSIBLY RESULTING IN SLIGHTLY
CLOUDIER/COOLER CONDITIONS...MAINLY ACROSS EASTERN PORTIONS OF THE
FORECAST AREA ON SUNDAY. OTHERWISE...WITH LOW-LEVEL THICKNESSES
PROJECTED TO CLIMB 20 METERS ABOVE NORMAL...HIGHS IN THE LOWER TO
MID 80S.

THERE ARE SOME MINOR MODEL TIMING DIFFERENCES WITH FROPA ON
MONDAY...WITH THE EC A GOOD 12 HOURS FASTER TO PUSH THE FRONT
THROUGH THE AREA. GIVEN LIMITED/SHALLOW MOISTURE
AVAILABILITY...CONVECTION ALONG THE FRONT WILL NEED TO UTILIZE
FAVORABLE DIURNAL TIMING/INSTABILITY TO SUPPORT SLIGHT/SMALL CHANCE
POPS MONDAY AFTERNOON/EARLY EVENING.

TUESDAY AND WEDNESDAY: BELOW NORMAL TEMPERATURES ARE EXPECTED
UNDERNEATH THE EASTERN US TROUGH AND SUPPORTED IN THE LOW-LEVELS BY
NORTHERLY FLOW VIA BUILDING STRONG ~1030MB SURFACE HIGH. HIGHS 70 TO
75. LOWS IN THE 50S.


&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 150 PM WEDNESDAY...

CURRENT PREDOMINATING MVFR CONDITIONS ARE EXPECTED TO SLOWLY RISE TO
LOW-END VFR PRIOR TO 22Z. THESE VFR CONDITIONS SHOULD HOLD UNTIL THE
04Z-07Z TIME FRAME... WHEN IFR CIGS MAY DEVELOP ACROSS THE AREA...
LASTING UNTIL AROUND 12Z-13Z THU MORNING.

A COLD FRONT HAS SETTLED SOUTH OF NC... WITH COOL HIGH PRESSURE
BUILDING IN FROM THE NORTH. A MOIST EASTERLY FLOW OF AIR IN THE LOW
LEVELS OFF THE ATLANTIC IS GENERATING THE CURRENT CLOUD COVER OVER
CENTRAL NC. THIS FLOW WILL PERSIST THROUGH TONIGHT... WITH
REDEVELOPMENT OF LOW CLOUDS LATE TONIGHT AS THE LOWER LEVELS
STABILIZE. ANY LOW CLOUDS TONIGHT SHOULD MIX OUT AND LIFT TO VFR
BETWEEN 13Z AND 15Z THU. THERE IS A RISK OF STORMS NEAR RWI/FAY THIS
AFTERNOON UNTIL AROUND 22Z OR 23Z... BUT OTHERWISE MOSTLY DRY
WEATHER IS EXPECTED. HOWEVER... PATCHY MVFR VSBY IN DRIZZLE IS
POSSIBLE TONIGHT BETWEEN 07Z AND 12Z.

LOOKING BEYOND 18Z THU... VFR CONDITIONS SHOULD DOMINATE THU
AFTERNOON AND EVENING. IFR CIGS AND MVFR/IFR VSBYS ARE POSSIBLE THU
NIGHT FROM 06Z UNTIL 13Z FRI MORNING... AND AGAIN BETWEEN 08Z AND
12Z SAT MORNING... AS THE LIGHT ONSHORE LOW LEVEL FLOW PERSISTS.
OTHERWISE... VFR CONDITIONS ARE EXPECTED AT CENTRAL NC TERMINAL
FORECAST SITES... AS A RIDGE OF HIGH PRESSURE EXTENDS THROUGH THE
AREA. -GIH

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...CBL
AVIATION...HARTFIELD

NWS RAH Office Area Forecast Discussion