-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 200704
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
303 AM EDT SUN APR 20 2014

.SYNOPSIS...LOW PRESSURE OFF THE SOUTH CAROLINA COAST WILL CONTINUE
MOVING SLOWLY TO THE NORTHEAST TODAY... AS COOL HIGH PRESSURE NOSES
INTO THE REGION FROM THE NORTHEAST. THE OFFSHORE LOW WILL MOVE OUT
OVER THE ATLANTIC TONIGHT AND MONDAY... AS MILD HIGH PRESSURE BUILDS
INTO THE AREA FROM THE SOUTHWEST THROUGH TUESDAY.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
AS OF 235 AM SUNDAY...

FOR TODAY/TONIGHT: BROKEN BANDS OF PATCHY VERY LIGHT RAIN AND
DRIZZLE CONTINUE TO PROPAGATE TO THE WSW ACROSS THE CENTRAL/SRN CWA
THIS MORNING... FED BY CONFLUENT LOW LEVEL ONSHORE FLOW AROUND LOW
PRESSURE LOCATED OFF THE SC COAST. AS THIS LOW MAKES ONLY SLOW
PROGRESS GENERALLY TOWARD THE NE TODAY/TONIGHT... THIS FETCH OF
ATLANTIC MOISTURE THROUGH A DEEP LAYER SHOULD ALLOW FOR A CONTINUED
RISK OF PATCHY AND MOSTLY TRACE AMOUNTS OF PRECIP OVER THE ERN AND
SRN CWA. MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THIS PATTERN...
DEPICTING A GRADUAL DISSOLUTION OF THE 925-700 MB MASS CONVERGENCE
OVER THE NW CWA WITH THE FOCUS OF DEEPER MOISTURE AND LIGHT PRECIP
SHIFTING TO THE SOUTHEAST. LATEST MODELS SHOW A FAIRLY SHARP NW EDGE
TO THE DEEPER MOISTURE... SUGGESTING THAT THERE WILL BE A TIGHT
GRADIENT IN CLOUDS AND LIGHT PRECIP POTENTIAL TODAY THAT IS
DIFFICULT TO PINPOINT... AND THESE CLOUDS (OR LACK OF SAME) WILL
IMPACT TODAY`S HIGH TEMPS. HAVE CHOSEN TO FOLLOW THE PATTERN OF THE
SREF PROBABILITIES OF ANY MEASURABLE RAIN... KEEPING A HIGH CHANCE
OF LIGHT RAIN OR DRIZZLE (LIKELY POPS TO START THEN TRENDING DOWN TO
CHANCE THROUGH THE DAY) ROUGHLY SE OF A LINE FROM KIXA TO KRDU TO
KAFP... WITH A TREND TO NO CHANCE NW OF THIS LINE AND GREATER
SUNSHINE. ACCORDINGLY... WITH MORE SOLAR INSOLATION EXPECTED ACROSS
THE FAR NRN AND NW CWA... HAVE NUDGED UP HIGHS A BIT THERE... WHILE
KEEPING THEM STEADY OR A DEGREE OR SO LOWER IN THE FAR ERN CWA WHERE
THERE SHOULD BE ONLY A BRIEF WINDOW OF PARTIAL SUNSHINE THIS
AFTERNOON. HIGHS 60 EAST TO 68 NW. WITH THE MSLP GRADIENT STAYING
TIGHT ESPECIALLY FROM THE TRIANGLE SOUTH AND EAST... EXPECT THE
STEADY BRISK AND OCCASIONALLY GUSTY WINDS TO CONTINUE TODAY... MOST
MARKEDLY IN THE ERN CWA. THE PARENT HIGH CENTERED OFF THE NEW
ENGLAND COAST CONTINUES PROGRESSING EASTWARD AND ITS NARROW RIDGE SW
THROUGH CENTRAL NC STEADILY WEAKENS... AND AS THE OFFSHORE CYCLONE
CONTINUES MOVING NE... EXPECT OUR SURFACE WINDS TO BACK SLIGHTLY TO
A MORE NNE DIRECTION... DRAWING IN INCREASINGLY DRY LOW LEVEL AIR
INTO CENTRAL NC. BUT THERE IS CONSIDERABLE MODEL DISCREPANCY AS TO
THE DEGREE OF REMAINING LOW LEVEL MOISTURE OVER THE ERN CWA... WITH
THE NAM SHOWING THICK CLOUDS ROLLING BACK IN LATE AFTERNOON THROUGH
THE NIGHT WITH LOWERING BASES... WHILE THE GFS TRENDS TO MOSTLY
CLEAR SKIES BUT INDICATES LOW STRATUS FORMING LATE TONIGHT WITHIN
THE SURFACE-BASED STABLE LAYER. THERE ARE FEW HINTS AT THIS TIME AS
TO WHICH SOLUTION IS BEST... AS THE INCOMING AIR ADVECTING IN
THROUGH A DEEP LAYER IS COMING FROM THE RATHER DATA-SPARSE ATLANTIC
OCEAN. BUT THE PATTERN WOULD SUGGEST THAT WE`LL MOST LIKELY SEE AT
LEAST SOME RETURN OF CLOUDS IN THE ERN CWA THIS EVENING... AND WILL
INDICATE THIS IN THE FORECAST. EXPECT MOSTLY CLEAR SKIES IN THE NW
TRENDING TO MOSTLY CLOUDY SE TONIGHT... WITH ANY PATCHY DRIZZLE
EXITING THE SE CWA EARLY. WITH THE LOW LEVELS REMAINING AT LEAST A
LITTLE STIRRED AND POSSIBLE CLOUD COVER... HAVE UPPED LOWS JUST
SLIGHTLY... TO 40-46. -GIH

FOR MONDAY/MONDAY NIGHT: QUIET WEATHER ANTICIPATED BETWEEN STORM
SYSTEMS. THE CHILLY HIGH TO OUR NE AS WELL AS THE OFFSHORE LOW
SHOULD BE WELL AWAY FROM OUR REGION BY MONDAY MORNING... ALLOWING
MID LEVEL SHORTWAVE RIDGING TO BUILD IN FROM THE WEST WITH A WEAK
SURFACE RIDGE SETTLING BRIEFLY OVER THE GULF COAST AND INTERIOR
SOUTHEAST STATES AHEAD OF THE NEXT COLD FRONT. WILL HAVE MOSTLY
SUNNY SKIES... WITH ANY MORNING STRATUS QUICKLY MIXING OUT BOTH
HORIZONTALLY AND VERTICALLY. THICKNESSES SUPPORT HIGHS OF 69-72.
EXPECT MOSTLY CLEAR SKIES MUCH OF MONDAY NIGHT BUT TRENDING TOWARD
FAIR SKIES WITH INCREASING HIGH CLOUDS AS THE TROUGH NOW OVER THE
DESERT SOUTHWEST HEADS EASTWARD THROUGH THE MISS VALLEY. NEAR-NORMAL
LOWS OF 49-53. -GIH

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
AS OF 300 AM SATURDAY...

WITH THE DEPARTURE OF THE UPPER LOW ON MONDAY...THE LARGE SCALE FLOW
WILL BECOME MUCH MORE PROGRESSIVE FOR THE UPCOMING WEEK.  AN UPPER
LEVEL TROUGH AND ASSOCIATED WEAK FRONTAL ZONE WILL CROSS CENTRAL NC
TUESDAY AFTERNOON AND EVENING...AND THE MAIN FORECAST CONCERN DURING
THIS PERIOD WILL BE MOISTURE RETURN AND WHETHER OR NOT CONVECTION IS
ABLE TO MAKE IT ACROSS THE MOUNTAINS.  SURFACE HIGH PRESSURE OVER
THE SOUTHEAST US AND MOSTLY WEST-SOUTHWESTERLY MID-LEVEL FLOW SHOULD
LIMIT SIGNIFICANT MOISTURE RETURN AHEAD OF THE FRONT.  THUS...MODEL
DEWPOINTS CAPE APPEAR TO BE TOO HIGH TUESDAY AFTERNOON.  DRY
ADIABATIC MIXING TO 900-850MB SUGGESTS HIGHS IN THE UPPER 70S TO
AROUND 80.  THIS WILL AID IN SOME WEAK DESTABILIZATION...BUT OVERALL
THE THREAT OF MORE THAN JUST A FEW STRONG STORMS APPEARS LIMITED AND
MOST LIKELY OVER WESTERN NC...WITH CONVECTIVE POTENTIAL BECOMING
LESS FAVORABLE TO THE EAST AS THE FRONT MOVES TOWARD THE COAST
TUESDAY EVENING.  LOWS TUESDAY NIGHT IN THE LOW TO MID 50S.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 300 AM SATURDAY...

WITHIN THE PROGRESSIVE FLOW ALOFT...CANADIAN HIGH PRESSURE WILL
BRIEFLY BUILD OVER THE MID-ATLANTIC STATES AND CAROLINAS WEDNESDAY
AND THURSDAY BEFORE SHIFT OFFSHORE BY THURSDAY NIGHT.  THIS WILL
LEAD TO A COUPLE DAYS OF HIGHS SLIGHTLY BELOW NORMAL IN THE UPPER
60S AND LOWER 70S...WITH RETURN FLOW AND WARMING FOR FRIDAY.
ANOTHER FRONTAL SYSTEM WILL APPROACH ON FRIDAY...WITH A SLIGHTLY
BETTER WINDOW FOR MOISTURE RETURN OFF THE GULF.  HOWEVER...STRONGER
DYNAMIC FORCING AGAIN LOOKS TO LIFT OFF TO THE NORTH AND BEST
INSTABILITY LIKELY STAYS TO OUR SOUTH.  THUS...THIS SYSTEM COLD BE
ANOTHER ONE THAT BECOMES DRIER AS IT MOVES EAST OF THE MOUNTAINS.
SLIGHT CHANCE POPS FOR NOW...WITH HIGHS MOSTLY IN THE 75-80 RANGE.
-- End Changed Discussion --

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 1255 PM SATURDAY...

THE COMBINATION OF STRONG LOW PRESSURE OFF THE SC COAST AND A NARROW
WEDGE OF COOL HIGH PRESSURE NOSING INTO NC FROM THE NORTH IS KEEPING
THICK MAINLY VFR CLOUDS OVER CENTRAL NC... AND THIS SHOULD PERSIST
THROUGH THE MORNING. CONFIDENCE IN THE DETAILS OF THE AVIATION
FORECAST FOR CENTRAL NC IS LOW... GIVEN POOR MODEL PERFORMANCE IN
THE LAST DAY OR SO AND LACK OF MODEL AGREEMENT ON A SOLUTION. BUT
BASED ON EXTRAPOLATION OF UPSTREAM CONDITIONS AND THE MOST PLAUSIBLE
MODEL SOLUTION... EXPECT CENTRAL NC TAF SITES TO SEE THICK VFR
CLOUDS HOLD THROUGH MIDDAY (AROUND 17Z) WITH PATCHY SPRINKLES OR
DRIZZLE... ALTHOUGH FAY HAS THE BEST CHANCE OF SEEING A FEW HOURS OF
LOWER MVFR CIGS THIS MORNING. THERE MAY EVEN BE A PERIOD OF FAIR
SKIES WITH A THIN DECK OF MID CLOUDS BASED AOA 8 000 FT AGL THIS
MORNING. FORECAST CONFIDENCE DROPS THIS AFTERNOON WITH THE NAM
SHOWING VFR CLOUDS RETURNING... AROUND 4 000 FT THICK... TRENDING
SLOWLY DOWN TO MVFR BY MID EVENING... WHILE THE GFS SHOWS A TREND TO
MOSTLY CLEAR SKIES BY EVENING. PREFER THE PESSIMISTIC SOLUTION WITH
GREATER CLOUD COVER... BUT TAFS WILL FEATURE CLOUDS HOLDING MAINLY
VFR WITH A CHANCE OF MVFR TOWARD THE END OF THE FORECAST PERIOD.
VSBYS SHOULD REMAIN PREDOMINANTLY VFR THROUGHOUT. SURFACE WINDS WILL
REMAIN BRISK FROM THE NE AT 12-17 KT SUSTAINED WITH SPORADIC GUSTS
TO 22-30 KTS AT ALL SITES THROUGH THE TAF FORECAST PERIOD.

LOOKING BEYOND 06Z EARLY MONDAY MORNING... AS THE OFFSHORE LOW MOVES
AWAY AND OUT TO SEA... VFR CONDITIONS ARE EXPECTED TO DOMINATE
THROUGH MONDAY NIGHT... ALTHOUGH RWI/FAY MAY SEE A PERIOD OF OVC IFR
STRATUS LATE TONIGHT THROUGH MONDAY MORNING. THE NEXT SYSTEM WILL
IMPACT THE AREA ON TUESDAY... BRINGING ANOTHER CHANCE FOR RAIN AND
ASSOCIATED ADVERSE AVIATION CONDITIONS. HOWEVER... THIS WILL BE A
MUCH MORE PROGRESSIVE SYSTEM THAN THE CURRENT ONE... WITH CONDITIONS
IMPROVING TO VFR LATE TUESDAY NIGHT INTO WEDNESDAY. VFR CONDITIONS
SHOULD THEN PERSIST THROUGH THURSDAY AS HIGH PRESSURE DOMINATES. -GIH

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...SMITH
LONG TERM...SMITH
AVIATION...HARTFIELD/KRD