Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 032340
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
740 PM EDT MON AUG 3 2015

.SYNOPSIS... A STATIONARY FRONT WILL CONTINUE TO EXTEND THROUGH
CENTRAL NORTH CAROLINA... FROM THE SANDHILLS THROUGH THE NORTHERN
OUTER BANKS... THROUGH MIDWEEK. A COLD FRONT APPROACHING FROM THE
NORTHWEST WILL STALL NEAR THE NORTH CAROLINA VIRGINIA BORDER EARLY
WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 325 PM MONDAY...

COASTAL SHOWERS HAVE THUS FAR HELD MAINLY SE OF THE FORECAST AREA...
WITHIN THE ABOVE-NORMAL PW AND HIGHER SURFACE THETA-E AIR. ISOLATED
SHOWERS FORMED CLOSED TO MIDDAY OVER THE FAR NRN PIEDMONT ALONG AN
OLD OUTFLOW FROM LAST NIGHT`S OH VALLEY CONVECTION. THESE FAILED TO
GATHER A LOT OF STEAM DUE TO THE DRY AIR... HOWEVER HAVE HELD ONTO
ISOLATED POPS OVER THE FAR NE FOR A FEW MORE HOURS GIVEN THE STEEP
LOW LEVEL LAPSE RATES AND 35-40 KTS OF EFFECTIVE DEEP LAYER SHEAR.
ANY SHOWERS SHOULD BE GONE CLOSE TO SUNSET WITH THE LOSS OF HEATING.
WILL ALSO MAINTAIN SMALL CHANCE POPS AS OUTFLOW FROM COLLAPSING
COASTAL CONVECTION MAY YIELD SECONDARY SHALLOW SHOWERS/STORMS INTO
THE FAR SE CWA. OTHERWISE... EXPECT DRY WEATHER WITH DECREASING
CLOUDS BY MID EVENING. LOW LEVEL MOISTURE LATE TONIGHT SHOULD BE
NEAR TO SLIGHTLY HIGHER THAN IT WAS EARLY THIS MORNING WITH WEAK
MASS CONVERGENCE ALONG THE 925 MB INVERTED TROUGH... FAVORING
ANOTHER ROUND OF PATCHY LOW STRATUS AND FOG OVERNIGHT... ESPECIALLY
OVER THE EASTERN TWO THIRDS OF THE CWA. THIS IS SUPPORTED BY HIGH
SREF PROBABILITIES OF LOW VSBYS OVERNIGHT. LOWS OF 68-73. -GIH

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 350 PM MONDAY...

THE SYNOPTIC FRONT NOW JUST NW OF THE OH VALLEY IS EXPECTED TO
PROGRESS STEADILY TO THE ESE THROUGH TUE NIGHT... AS THE OLD FRONTAL
ZONE OVER CENTRAL/ERN NC GETS NEW LIFE AS A PREFRONTAL PIEDMONT
TROUGH... CAUSING AN INCREASE IN SURFACE DEWPOINTS ACROSS CENTRAL NC
AND A RISING RISK OF LATE-DAY STORMS. THE LATEST MODEL RUNS CONTINUE
TO DISAGREE ON THE DETAILS OF QPF. WHILE ALL FAVOR A CONTINUED HIGH
COVERAGE OF CONVECTION OVER COASTAL NC ESPECIALLY SOUTH OF
HATTERAS... THE NAM/SREF AND ECMWF SUPPORT SHOWERS/STORMS DEVELOPING
JUST SOUTH OF THE FRONT... ACROSS SRN KY INTO SRN VA AND NW NC IN
THE AFTERNOON. THE ECMWF SHOWS A QUICKLY DIMINISHING TREND AFTER
00Z... RESULTING IN DRY WEATHER FOR ALL BUT THE FAR NORTH AND FAR
ERN CWA... HOWEVER THE NAM LEANS WETTER WITH APPARENT SOUTHEAST-
MOVING OUTFLOW CONTINUING TO SUPPORT CONVECTION INTO THE NIGHT OVER
CENTRAL NC. THE NSSL WRF IS SIMILAR IN THAT IT GENERATES ISOLATED TO
SCATTERED CELLS OVER THE PIEDMONT LATE TUE... HOWEVER THE COVERAGE
IS QUITE SPARSE. AND THE GFS STAYS LARGELY DRY OUTSIDE OF COASTAL
NC. TOUGH CALL ON WHICH IS CORRECT... BUT I`M INCLINED TO THINK THAT
THE NAM HAS THE MOST VALIDITY... AS THE MODELS SOMETIMES HAVE A
DIFFICULT TIME DEALING WITH SUBSTANTIAL OUTFLOWS EMANATING FROM
ORGANIZED CONVECTIVE COMPLEXES. WILL HAVE CHANCE POPS IN THE SE ONLY
FOR MUCH OF TUE... THEN REDUCE POPS TO ISOLATED BUT EXPAND THEM
ACROSS CENTRAL NC BY EVENING... CONTINUING OVERNIGHT... AS THERE MAY
BE SUFFICIENT INSTABILITY AND STEEP LAPSE RATES IN THE COLUMN
LINGERING AFTER NIGHTFALL. BUT CONFIDENCE IS NOT HIGH.
ACCORDINGLY... THE RISK OF ANY STORMS BECOMING SEVERE IS ALSO HARD
TO DETERMINE... BUT GIVEN THE UPTICK IN SURFACE DEWPOINTS... THE
POTENTIAL CERTAINLY EXISTS FOR MODERATE INSTABILITY AND 30+ KTS OF
EFFECTIVE DEEP LAYER SHEAR THAT WOULD SUPPORT A FEW STRONG TO SEVERE
CELLS ACROSS THE NRN CWA. THICKNESSES AND GUIDANCE INDICATE HIGHS OF
90-94. LOWS 69-74. -GIH

&&

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

OVERALL THE SYNOPTIC PATTERN THROUGHOUT THE LONG TERM PERIOD WILL
FEATURE RIDGING OVER THE SOUTHWEST CONUS AND TROUGHING (WITH VARYING
STRENGTHS) OVER THE EAST. GIVEN THIS UPPER LEVEL FLOW PATTERN...
MUCH OF OUR WEATHER WILL BE DICTATED BY NUMEROUS SHORTWAVES (WHICH
ARE IMPOSSIBLE TO ACCURATELY PREDICT THIS FAR OUT). BESIDES SEVERAL
WEAKER DISTURBANCES DURING THE MIDDLE PART OF THE WEEK TRIGGERING
WIDELY SCATTERED SHOWERS/STORMS...THE FIRST SIGNIFICANT SHORT WAVE
IS PROGGED TO CROSS THE REGION LATE THURSDAY INTO FRIDAY. THE GFS
AND ECMWF DIFFER QUITE SIGNIFICANTLY...WITH THE GFS MUCH WEAKER AND
DISORGANIZED...WHILE THE ECMWF SPINS UP QUITE A STRONG LOW THAT
CROSSES VIRGINIA BEFORE EXITING OFF OF THE DELMARVA COAST. GIVEN
THAT THE ECMWF IS MORE SIMILAR TO THE NAM (AT LEAST THROUGH 84
HOURS)...WILL FOLLOW ITS SOLUTION MORE CLOSELY. THIS WOULD RESULT IN
PRECIP CHANCES RAMPING UP LATE THURSDAY INTO FRIDAY WITH THE
APPROACH OF THE DEEPER SHORT WAVE/SURFACE FRONT BEFORE DECREASING
LATE FRIDAY NIGHT AS THE NEXT KICKER WAVE PUSHES THE FRONT EAST. THE
GFS DOES SHOW THIS OVERALL PATTERN (SHORT WAVE(S)/SURFACE
FRONT)...BUT JUST IS NOT AS DEEP/ORGANIZED WITH THE SYSTEM...THUS
THE PRECIP IS MORE SCATTERED IN NATURE.

BY THE WEEKEND...BOTH MODELS ARE THEN IN FAIRLY GOOD AGREEMENT WITH
THE FRONT BEING PUSHED TO OUR EAST...AND BECOMING NEARLY STATIONARY
THERE. THIS SHOULD RESULT IN A MOSTLY DRY FORECAST...WITH ONLY SOME
ISOLATED DIURNAL TYPE ACTIVITY...MOSTLY ACROSS THE EAST IN CLOSER
PROXIMITY TO THE BOUNDARY.

TEMPS WILL BE RATHER WARM TO START THE PERIOD (HIGHS IN THE
MID/UPPER 90S...LOWS IN THE LOW/MID 70S)...BUT BY THE WEEKEND THEY
SHOULD FALL SOME BEHIND THE FRONT (HIGHS IN THE MID/UPPER 80S...LOWS
IN THE MID/UPPER 60S).

&&

.AVIATION /00Z WEDNESDAY THROUGH SATURDAY/...
AS OF 740 PM MONDAY...

WHILE VFR CONDITIONS ACROSS CENTRAL NC ARE LIKELY TO PERSIST
THROUGH MUCH OF THE TAF PERIOD...A PERIOD OF MVFR/POSSIBLY IFR
CONDITIONS IS POSSIBLE IN EARLY MORNING STRATUS AND FOG ACROSS THE
COASTAL PLAIN AND EASTERN PIEDMONT ON TUESDAY MORNING. AN ISOLATED
THUNDERSTORM IS POSSIBLE THIS EVENING BUT THE COVERAGE SHOULD BE
EXTREMELY LIMITED AND GENERALLY CONFINED TO LOCATIONS SOUTH AND EAST
OF U.S. ROUTE 1. PERSISTENCE AND VARIOUS SETS OF GUIDANCE SUGGEST
AREAS OF STRATUS AND/OR FOG ARE POSSIBLE ON TUESDAY MORNING...MOST
LIKELY IMPACTING THE KFAY AND KRWI TERMINALS WITH A SMALLER THREAT
AT KRDU. THESE CONDITIONS SHOULD BE FOCUSED TO A PERIOD OF BETWEEN
09 AND 13Z IN MOST LOCATIONS WITH RESIDUAL RESTRICTIONS CLEARED BY
15Z. VFR CONDITIONS SHOULD PREAIL OVERNIGHT AT KINT AND KGSO. WITH
HEATING...SCT CUMULUS IS LIKELY TO DEVELOP TOWARD MIDDAY WITH BASES
OF BETWEEN 4-6KFT. LIGHT MAINLY SOUTH TO SOUTHWEST WINDS ARE
EXPECTED THROUGH THE PERIOD...ALTHOUGH AN HOUR OR TWO OF SLIGHTLY
STRONGER AND GUSTY SOUTHERLY WINDS IS POSSIBLE NEAR AND BEHIND A
NORTHWARD MOVING BOUNDARY THAT CROSSES THE KRDU/KRWI/KFAY TERMINALS.

LOOKING BEYOND 00Z WED... ADVERSE AVIATION CONDITIONS ON WED AND THU
ARE LIKELY TO BE ASSOCIATED WITH SOME EARLY MORNING FOG AND STRATUS
ALONG WITH SCT MAINLY AFTN AND EVENING THUNDERSTORMS ON WED AND A
BETTER CHANCE OF STORMS ON THU AND THU NIGHT. A LINGERING COLD FRONT
WILL LIKELY BRING A CONTINUED THREAT OF SCT MAINLY AFTN AND EVENING
SHOWERS AND STORMS TO THE AREA ON FRI AND SAT. -BLAES
&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...KRD
AVIATION...BLAES



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