Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 201403
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1003 AM EDT SUN APR 20 2014

.SYNOPSIS...LOW PRESSURE OFF THE SE COAST WILL CONTINUE MOVING EAST
AND OUT INTO THE ATLANTIC...LEAVING BEHIND A COOL WEDGE OF HIGH
PRESSURE ON MONDAY. A COLD FRONT WILL CROSS THE REGION ON
TUESDAY...WITH HIGH PRESSURE RETURNING FOR MIDWEEK.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
AS OF 10 AM SUNDAY...

TODAY: VERTICALLY STACKED LOW WILL DRIFT SLOWLY EASTWARD AND AWAY
FROM SHORE THROUGH TONIGHT. EXPECT VERY DELIBERATE...IN FACT SLOTH-
LIKE IMPROVEMENT SPREAD EASTWARD THROUGH TONIGHT WITH WESTERN
PORTIONS UNDER THE INFLUENCE OF THE DRY AIR RIDGE FROM THE
NORTH...YIELDING DRY CONDITIONS WITH FULL COMPLIMENTS OF SUN TODAY.
MEANWHILE...EASTERN PORTIONS OF TEH FORECAST AREA WILL REMAIN MOSTLY
CLOUDY FOR A GOOD PART OF THE TODAY WITH WANING ONSHORE CONVERGENT
FLOW SUPPORTIVE OF PATCHY AND MOSTLY TRACE AMOUNTS OF PRECIP.

THIS WEST TO EAST CLOUD GRADIENT WILL GOVERN HIGHS TODAY...WITH
STRONGER ISOLATION OUT WEST WILL SUPPORT SOME OF THE WARMEST
READINGS. HIGHS RANGING FROM UPPER 60S WEST TO UPPER 50S/NEAR 60
SOUTHEAST.  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.

TONIGHT:
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 THIS EVENING WITH LOWERING
BASES... WHILE THE GFS TRENDS TO MOSTLY CLEAR SKIES BUT INDICATES
LOW STRATUS FORMING LATE TONIGHT WITHIN THE SURFACE-BASED STABLE
LAYER. GIVEN CONTINUED NELY ONSHORE FLOW...EXPECT WE WILL SEE AT
LEAST SOME RETURN OF CLOUDS INTO THE COASTAL PLAIN...AND AS POSSIBLY
FAR INLAND AS SAY THE EASTERN PIEDMONT. WILL INDICATE THIS IN THE
FORECAST. EXPECT MOSTLY CLEAR SKIES IN THE NW TRENDING TO MOSTLY
CLOUDY SE TONIGHT. LOWS IN THE LOWER 40 TO MID 40S...COOLEST ACROSS
THE NW.

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/...
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.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 725 AM SUNDAY...

HIGH AND MID LEVEL CLOUD DECKS AND SCT-BKN VFR STRATOCUMULUS WILL
CONTINUE TO SPREAD TOWARD THE WEST-SOUTHWEST OVER NC... A RESULT OF
THE COMBINATION OF STRONG LOW PRESSURE OFF THE SC COAST AND A NARROW
WEDGE OF COOL HIGH PRESSURE NOSING INTO NC FROM THE NORTH. THESE VFR
CLOUDS SHOULD PERSIST THROUGH THE DAY. CONFIDENCE IN THE DETAILS OF
THE AVIATION FORECAST FOR CENTRAL NC IS LOW BEYOND 00Z THIS
EVENING... DUE TO POOR MODEL PERFORMANCE REGARDING CLOUD HEIGHTS AND
EXTENT 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
NO WORSE THAN VFR CLOUDS HOLD THROUGH THE DAY (LOWEST AT FAY/RWI)...
WITH PATCHY SPRINKLES OR DRIZZLE POSSIBLE AT RWI. FAY HAS A CHANCE
OF SEEING A TREND TO MVFR CIGS LATE TONIGHT INTO MONDAY MORNING.
FORECAST CONFIDENCE DROPS THIS AFTERNOON WITH THE NAM SHOWING VFR
CLOUDS RETURNING... AROUND 4 000 FT THICK... TRENDING SLOWLY DOWN TO
MVFR THIS EVENING... WHILE THE GFS SHOWS 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 12-16 KT SUSTAINED WITH SPORADIC GUSTS TO 18-25 KTS AT ALL
SITES THROUGH THE TAF FORECAST PERIOD.

LOOKING BEYOND 12Z 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 MID MORNING MONDAY. 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...CBL
NEAR TERM...CBL/HARTFIELD
SHORT TERM...SMITH
LONG TERM...SMITH
AVIATION...HARTFIELD/KRD



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