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538
FXUS62 KRAH 010009
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
809 PM EDT TUE SEP 30 2014

.SYNOPSIS...WEAK HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
NORTH THROUGH THURSDAY. A STRONG COLD FRONT WILL CROSS THE CAROLINAS
FROM THE WEST LATE FRIDAY AND EARLY SATURDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
AS OF 1230 PM TUESDAY...

THROUGH TONIGHT: EXPECT LOW STRATUS TO GRADUALLY MIX OUT THIS
AFTERNOON AS VERTICAL MIXING INCREASES IN ASSOC/W INSOLATION. EXPECT
HIGHS REBOUNDING INTO THE UPPER 70S TO LOWER 80S AS LONG AS CLOUD
COVER SCATTERS OUT BY ~18Z. AN UPPER LEVEL LOW DIGGING ACROSS THE
LOWER GREAT LAKES TODAY WILL PROGRESS ACROSS THE MID-ATLANTIC NEAR
OR JUST NORTH OF THE MASON DIXON LINE TONIGHT. UPPER LEVEL FORCING
(AND PRECIPITATION POTENTIAL) ASSOC/W THIS FEATURE SHOULD LARGELY
REMAIN NORTH OF CENTRAL NC...THOUGH A PERIOD OF CLOUD COVER AND
PERHAPS AN ISOLD SHOWER COULD NOT BE ENTIRELY RULED OUT BETWEEN 00-
06Z WED IN THE N/NW PIEDMONT. EXPECT LOWS IN THE UPPER 50S TO NEAR
60F.

WED/WED NIGHT: COMPLEX PATTERN IN THIS PERIOD WITH A NON-ZERO CHANCE
FOR PRECIPITATION. THE UPPER LOW PROGRESSING THROUGH THE MID-
ATLANTIC TONIGHT WILL MOVE OFFSHORE THE MID-ATLANTIC COAST ON WED AS
A SHORTWAVE RIDGE BUILDS OVER THE TN/OH VALLEY. SMALL AMPLITUDE
WAVES DIGGING SE INTO VA ON THE WESTERN PERIPHERY OF THE EXITING
UPPER LOW ON WED COULD PERHAPS PROVIDE A GLANCING BOUT OF DPVA
DURING THE DAY...OTHERWISE...ONE WOULD EXPECT SUBSIDENCE TO
GRADUALLY TAKE HOLD LATE WED INTO WED NIGHT AS THE SHORTWAVE RIDGE
PROGRESSES TO THE SPINE OF THE APPALACHIANS. BOTH THE GFS/NAM
DEVELOP VERY LIGHT PRECIP OVER THE NORTHERN PIEDMONT WED...WHILE THE
NAM GENERATES ADDITIONAL PRECIP WED NIGHT. IT IS DIFFICULT TO
ASCERTAIN WHY MODEL GUIDANCE IS DEVELOPING PRECIPITATION WED/WED
NIGHT...ESP WITH WEAK LOW-LEVEL FLOW AND MARGINAL/SHALLOW
INSTABILITY (EQUILIBRIUM LEVEL ~10 KFT). AT THIS TIME WILL CONTINUE
TO INDICATE A DRY FCST. HIGHS WED SLIGHTLY WARMER THAN TODAY...IN
THE LOWER 80S. LOWS WED NIGHT IN THE UPPER 50S/LOWER 60S. -VINCENT

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 235 PM TUESDAY...

THURSDAY AND THURSDAY NIGHT: SYNOPTIC SCALE SUBSIDENCE WILL PREVAIL
ACROSS CENTRAL NC ON THURSDAY AS HEIGHTS INCREASE OVER THE
AREA...DOWNSTREAM OF THE SOUTHERN STREAM TROUGH EJECTING EASTWARD
OUT OF THE CENTRAL/SOUTHERN ROCKIES...PROGRESSING EASTWARD INTO THE
SOUTHERN PLAINS/LOWER MS VALLEY THURSDAY NIGHT. IF CURRENT TIMING
HOLDS UP...IT SHOULD REMAIN DRY THROUGH THURSDAY NIGHT AS GFS BUFR
SOUNDINGS REMAIN STRONGLY CAPPED ALOFT...WITH STRENGTHENING
SOUTHERLY RETURN FLOW LEADING TO AN INCREASE IN CLOUDS FROM WEST-
EAST. HIGHS 80 TO 85. LOWS IN THE LOWER TO MID 60S.

FRIDAY AND FRIDAY NIGHT: MODELS INDICATE PHASING NORTHERN STREAM AND
SOUTHERN STREAM TROUGHS ACROSS THE UPPER MS VALLEY/UPR MIDWEST AND
INTO THE GREAT LAKES FRIDAY AND FRIDAY NIGHT. MODELS ARE IN REALLY
GOOD AGREEMENT WITH THE TIMING OF THE ACCOMPANYING COLD FRONT
PASSAGE INTO THE AREA LATE FRIDAY AFTERNOON/FRIDAY EVENING...EXITING
EASTERN PORTIONS OF THE FORECAST AREA BY DAYBREAK SATURDAY.  THE
LEAD SOUTHERN STREAM WAVE OVER THE LOWER MS VALLEY/TN VALLEY FRIDAY
MORNING REALLY SHEARS OUT/DAMPENS AS IT LIFTS NORTHWARD INTO MID-
ATLANTIC REGION FRIDAY EVENING/NIGHT...RESULTING IN WEAK UPPER LEVEL
SUPPORT WITH EASTWARD ADVANCING 30-35KT SWLY LLJ FOCUSING STRONG
MOISTURE TRANSPORT AND LOW-LEVEL CONVERGENCE WITHIN A BAND OF
CONVECTION ALONG THE FRONT. LATE DIURNAL TIMING AND MODEST LAPSE
RATES ALOFT WILL RESULT IN LIMITED/WEAK INSTABILITY(200-400
MUCAPE)...THWARTING ANY SEVERE THREAT. HAVE INCREASED POPS TO LIKELY
ACROSS THE FORECAST AREA FRIDAY NIGHT...DECREASING WEST TO EAST
DURING THE PREDAWN HOURS AS FRONT MOVES EASTWARD TOWARDS THE COAST.
PROGRESSIVE NATURE OF SYSTEM WILL LIMIT RAINFALL AMOUNTS...WITH
AVERAGE QPF AMOUNTS OF A 0.25-0.50".

MAX TEMPS FRIDAY AFTERNOON WILL DEPEND ON ARRIVAL/ONSET OF
SHOWERS/CONVECTION...ESPECIALLY IN THE WEST. UNDER THICKENING CLOUD
COVER...A BIT COOLER THAN THURSDAY RANGING FROM MID 70S WEST TO
LOWER 80S EAST. MIN TEMPS WILL DEPEND ON WEST-EAST TIMING OF FROPA
FRIDAY NIGHT THROUGH THE AREA...RANGING FROM LOWER/MID 50S NORTHWEST
TO LOWER/MID 60S SE.


&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 235 PM TUESDAY...

IN THE WAKE OF THE FRONTAL PASSAGE SATURDAY MORNING...DRY CONDITIONS
WILL PREVAIL THROUGH EARLY NEXT WEEK AS SFC HIGH PRESSURE OVER THE
SOUTHERN PLAINS/LOWER MS VALLEY BUILDS EAST THROUGH THE
PERIOD...SHIFTING EAST OFF THE SOUTHEAST COAST ON MONDAY. AFTER A
CHILLY SATURDAY NIGHT/SUNDAY MORNING IN WHICH FAVORABLE RADIATIONAL
CONDITIONS WILL HELP SUPPORT MIN TEMPS IN THE MID TO UPPER 40S
ACROSS A LARGE PORTION OF THE FORECAST AREA...TEMPERATURES WILL
MODERATE TO NEAR NORMAL BY MONDAY.

TIMING/MAGNITUDE OF THE NEXT SYSTEM STILL IN QUESTION AS NORTHERN
STREAM ENERGY ROTATING SOUTHEASTWARD THROUGH THE BASE OF THE
AMPLIFIED TROUGH LOOKS TO IMPACT THE REGION LATE MONDAY-TUESDAY TIME
FRAME. UNTIL MODEL DISCREPANCIES CAN BE IRONED OUT WITH THIS CLIPPER-
LIKE TROUGH...WILL INDICATE CONSERVATIVE/SLIGHT CHANCE
POPS...ESPECIALLY GIVEN POTENTIAL FOR LIMITED MOISTURE AVAILABILITY.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 800 PM TUESDAY...

HIGH PRESSURE OVER THE AREA HAS LEAD TO MOSTLY CLEAR SKIES THIS
EVENING. IN ADDITION...WINDS WILL BECOME MOSTLY CALM OVER THE NEXT
COUPLE OF HOURS. THESE CLEAR SKIES AND LIGHT/CALM WINDS SHOULD LEAD
TO ANOTHER NIGHT OF FOG. HOWEVER...IT IS NOT A SURE BET AS MODELS
ARE IN DISAGREEMENT (WITH ONE SHOWING PREDOMINATELY VFR CONDITIONS
ALL NIGHT). NEVERTHELESS... GIVEN A SIMILAR SET UP TO LAST NIGHT
(MINUS THE LIGHT RAIN THAT OCCURRED ON MONDAY)...WENT AHEAD AND
INCLUDED IFR/LIFR VSBYS/CIGS IN ALL TAF SITES EXCEPT THE TRIAD WHERE
THERE IS SLIGHTLY DRIER AIR (BUT STILL INCLUDED SOME SUB-VFR
CONDITIONS). CONDITIONS SHOULD IMPROVE TO VFR BY THE MID MORNING
HOURS OF WEDNESDAY...WITH JUST SOME MID/HIGH CLOUDS AND LIGHT AND
VARIABLE WINDS FOR THE REMAINDER OF THE TAF PERIOD GIVEN THE HIGH
PRESSURE OVERHEAD.

OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH LATE
WEDNESDAY/EARLY THURSDAY MORNING AS WEAK HIGH PRESSURE EXTENDS INTO
THE REGION FROM THE NORTH. MVFR/IFR CIGS/VSBYS MAY DEVELOP EARLY
THURSDAY MORNING AS THE HIGH BEGINS TO SHIFT OFFSHORE. OTHERWISE...
THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS WILL BE LATE FRI AND
EARLY SAT AS A STRONG COLD FRONT CROSSES THE CAROLINAS FROM THE
WEST.

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...KRD/VINCENT




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