Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 311857
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
300 PM EDT THU JUL 31 2014

.SYNOPSIS...MOISTURE WILL INCREASE ACROSS CENTRAL NORTH CAROLINA
THIS EVENING...BEGINNING A PROLONGED PERIOD OF UNSETTLED WEATHER
THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM THURSDAY...

THINGS ARE PROGRESSING ALONG THIS AFTERNOON PRETTY MUCH AS EXPECTED
WITH MOISTURE SPREADING NORTH AND EAST OUT OF UPSTATE SOUTH CAROLINA
AND INTO THE WESTERN PIEDMONT. LARGELY LIGHT RAIN BUT A FEW CELLS IN
THE TRIAD AT THIS TIME HAVE CAUSED A FEW LIGHTNING STRIKES. LOOKING
AT THE SPC MESOANALYSIS...THE BEST COMBINATION OF SHEAR AND
INSTABILITY THIS AFTERNOON COULD BE IN THE SOUTHWEST
PIEDMONT...MAINLY SOUTH OF HIGHWAY 64 AND WEST OF OF US HIGHWAY 1.
IF THERE WAS TO BE A STRONGER STORM OR TWO THIS AFTERNOON...THIS MAY
BE THE MOST LIKELY REGION...ALTHOUGH EFFECTIVE SHEAR IS EXPECTED TO
FALL OFF OVER THE NEXT SEVERAL HOURS. FOR CENTRAL AND EASTERN
AREAS...A MOSTLY CLOUDY AFTERNOON WITH THE LEAST CHANCE OF RAIN IN
THE FAR EASTERN COUNTIES. THIS IS HOW THE TEMPERATURE SPREAD WILL
PLAY OUT AS WELL WITH FAR THE FAR SOUTHERN AND EASTERN AREAS
RECEIVING THE GREATEST INSOLATION AND POINTS NORTH AND WEST
SIGNIFICANTLY COOLER. EXPECT HIGHS IN THE LOW 80S NW WITH MID TO
UPPER 80S IN THE SOUTH AND EAST.

FOR TONIGHT A SHORTWAVE IS EXPECTED TO PROGRESS THROUGH THE UPPER
TROUGH AND OVER THE NORTHWEST PIEDMONT...ENHANCING RAINFALL
SOMEWHERE AROUND MIDNIGHT. STILL EXPECTING THE EAST TO REMAIN
LARGELY DRY ALTHOUGH MOISTURE WILL BEGIN TO FILTER INTO THE AREA
FROM EASTERN SOUTH CAROLINA. THE INCREASE IN MOISTURE WILL INCREASE
THE CHANCES FOR MVFR/IFR VISIBILITIES/CEILINGS OVERNIGHT AT MOST
LOCATIONS AFTER 9Z. IN ADDITION THE UPTICK IN MOISTURE WILL ALSO
MODERATE LOW TEMPERATURES TO THE MID 60S NW TO UPPER 60S SE.

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 300 PM THURSDAY...

ON FRIDAY THE UPPER TROUGH WILL CONTINUE TO HOVER WEST OF THE AREA.
AT THE SURFACE...THERE WILL BE STRONG SURFACE CONVERGENCE OVER
CENTRAL NC AS DISTURBANCES MOVE THROUGH THE TROUGH ACROSS THE
WESTERN PIEDMONT AND AT THE SAME TIME A SEPARATE PLUME OF MOISTURE
WILL APPROACH CENTRAL NC FROM THE SSE. THE ONSLAUGHT OF MOISTURE
WILL BEGIN IN EARNEST AS PRECIPITABLE WATER VALUES CLIMB OVER 2
INCHES ACROSS THE AREA. MODEL FORECAST SOUNDINGS AS SEEN IN BUFKIT
ARE VERY WET FROM TOP TO BOTTOM BUT THERE STILL REMAINS A QUESTION
OF HOW MUCH INSTABILITY WILL BE PRESENT. THE NAM IS VERY BULLISH AND
THE GFS NOT AS MUCH BUT THEY BOTH AGREE THAT THE SOUTHEAST WILL
CARRY THE MOST CAPE. PLENTY OF FORCING WILL BE PRESENT WITH 30-40
KTS OF BULK SHEAR ACROSS THE EAST AND POTENTIALLY SOME DECENT 0-3 KM
HELICITY VALUES. SPC OUTLOOK NOT CALLING FOR A SLIGHT RISK AT THIS
POINT BUT WOULD NOT BE SURPRISED TO SEE A FEW STRONGER OR ROTATING
CELLS IN THE SOUTHEAST FRIDAY AFTERNOON. ALL THIS ASIDE THE MAIN
STORY WILL STILL BE THE RAINFALL WITH A HALF OF AN INCH TO AN INCH
(LOCALLY HIGHER) EXPECTED ACROSS THE AREA WITH HEAVIER TOTALS IN
MORE CONVECTIVE CELLS IN THE EAST. MAX TEMPS IN THE UPPER 70S TO
LOWER 80S NW TO SE.

CHANCES FOR RAIN WILL CONTINUE THROUGH FRIDAY NIGHT WITH THE EAST
EXPECTED TO SEE MORE OF THE ACTIVITY MAINLY IN THE FORM OF SHOWERS
AS CONDITIONS BECOME SLIGHTLY MORE STABLE OVERNIGHT. FOG AND/OR LOW
STRATUS SHOULD BE PREVALENT ACROSS THE AREA BEFORE DAYBREAK ON
SATURDAY. LOWS 65-70 DEGREES.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 300 PM THURSDAY...

...AN UNSETTLED AND ACTIVE PERIOD THROUGH AT LEAST THE WEEKEND WITH
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY
RAIN...

A BROAD UPPER LEVEL TROUGH PERSISTS JUST WEST OF THE APPALACHIANS
INTO EARLY NEXT WEEK. AT THE SAME TIME A SURFACE TROUGH SETS UP
ACROSS EASTERN NC WITH A FLOW OF DEEP MOISTURE MOVING ACROSS THE
AREA. THIS WILL RESULT IN A PERIOD OF UNSETTLED WEATHER AND THE
POTENTIAL FOR SOME SIGNIFICANT RAIN. THE TROUGH WEAKENS EARLY TO
MIDDLE PORTION OF NEXT WEEK AS PART OF IT LIFTS ACROSS NEW ENGLAND
AND ANOTHER PORTION BREAKS OFF OVER THE LOWER MISSISSIPPI VALLEY.
THIS RESULTS IN A DECREASE IN PRECIPITATION COVERAGE AND A WARMING
TEMPERATURES TO NEAR OR OR JUST ABOVE AVERAGE TOWARD THE MIDDLE OF
THE WEEK.

GUIDANCE SUGGESTS THAT ONE SHORT WAVE TROUGH WILL BE DEPARTING THE
REGION EARLY SATURDAY MORNING WITH ANOTHER WAVE POISED TO MOVE
ACROSS THE AREA SATURDAY NIGHT...BUT TRYING TO TIME THESE FEATURES
TOO PRECISELY IS FOOLHARDY. IN ADDITION... GUIDANCE VARIES WITH THE
INLAND PROGRESSION OF THE COASTAL TROUGH. THE END RESULT THOUGH
SHOULD BE A FAIRLY ACTIVE CONVECTIVE PATTERN SATURDAY WITH THE BULK
OF THE SHOWERS AND THUNDERSTORMS OCCURRING DURING THE AFTERNOON
THROUGH THE EVENING INTO THE EARLY OVERNIGHT HOURS. THE NAM
GENERATES A LOT MORE PRECIPITATION THAN THE GFS/ECMWF DURING THE DAY
AND IS ACCORDINGLY COOLER AND MORE STABLE THAN THE GFS WHICH
GENERATES MLCAPE VALUES UP TO 1000-1500 J/KG ACROSS THE EASTERN
PIEDMONT AND COASTAL PLAIN. IT WILL BE DIFFICULT GETTING A BETTER
READ ON THE INSTABILITY UNTIL A BETTER UNDERSTANDING OF THE
EVOLUTION OF THE DIURNAL CONVECTIVE CYCLE ON FRIDAY IS COMPLETE.
GREATER CONFIDENCE IS IN THE AMOUNT OF SHEAR WITH THE GFS NOTING
STRONGER DEEP LAYER FLOW WITH BULK SHEAR VALUES OF 20-30KTS WHICH
WOULD SUPPORT SOME STORM ORGANIZATION. THE NAM HAS WEAKER
FLOW...AROUND 20KTS OR SO WITH THE SREF ENSEMBLE DISTRIBUTION SPREAD
FROM 20-30 KTS. THE GREATEST SHEAR SHOULD BE LOCATED FROM THE TRIAD
NORTH AND WEST WITH THE GREAT INSTABILITY TO THE SOUTHEAST. STILL
ANY STORM ELEMENTS THAT DEVELOP NEAR THE SURFACE BOUNDARY WILL NEED
TO BE MONITORED. FOR NOW THE MOST LIKELY THREAT IS FROM EFFICIENT
RAIN MAKING STORMS THAT REPEATEDLY TRACK OVER THE SAME LOCATION
RESULTING IN POTENTIAL FLOODING ISSUES.

ACTIVE WEATHER CONTINUES ON SUNDAY AS MULTIPLE SHORT WAVE TROUGHS
APPROACH THE REGION WITH A VERY MOIST AIR MASS IN PLACE. THE RESULT
SHOULD BE AN ACTIVE CONVECTIVE DAY ONCE AGAIN WITH LIKELY POPS
WARRANTED AND THE GREATEST PRECIPITATION COVERAGE ACROSS THE EASTERN
PORTION OF THE FORECAST AREA. INSTABILITY PARAMETERS ARE WEAKER THAN
SUNDAY WITH MID LEVEL LAPSE RATES PROGGED TO BE MORE THAN 0.5 C DEG
LESS AS THE MID LEVELS WARM SOMEWHAT WITH THE DEPARTING TROUGH.

THE PATTERN TRANSITIONS INTO A MORE TYPICAL SUMMERTIME APPEARANCE ON
ON MONDAY AND ESPECIALLY TUESDAY THROUGH WEDNESDAY AS THE UPPER
TROUGH WEAKENS AND THE UPPER FLOW BECOMES NOTICEABLY MORE WESTERLY.
RAIN CHANCES ACCORDINGLY DROP DURING THE EARLY TO MID WEEK
PERIOD...ESPECIALLY DURING THE A-TYPICAL DIURNAL HOURS. LOW CHANCE
TO SLIGHT CHANCE POPS WILL BE INCLUDED IN THE FORECAST FOR PRIMARILY
THE AFTERNOON AND EVENING HOURS.

TEMPERATURES AT THE BEGINNING OF THE LONG TERM WILL BE QUITE COOL AS
DICTATED BY THE COOL AIR MASS WITH MORNING 1000-850MB THICKNESSES
VALUES IN THE 1385-1395 RANGE ALONG WITH LOTS OF CLOUDS AND
PRECIPITATION. HIGHS ON SATURDAY AND SUNDAY SHOULD RANGE IN THE
UPPER 70S IN THE NORTHWEST PIEDMONT TO LOWER 80S IN THE SOUTHERN
COASTAL PLAIN. HIGHS WILL MODERATE BEGINNING TUESDAY AND WARM INTO
THE UPPER 80S TO AROUND 90 BY THURSDAY. -BLAES
&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 200 PM THURSDAY...

WHILE MOSTLY VFR CONDITIONS SHOULD PERSIST FOR THE REST OF THE
AFTERNOON SOME SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL
MOVE THROUGH THE NORTHWEST PIEDMONT THIS AFTERNOON MAINLY AFFECTING
KGSO AND KINT. WINDS WILL CONTINUE TO BE LIGHT AND VARIABLE WITH
CEILINGS MAINLY BEGINNING AT 5-10 KFT. THESE CONDITIONS WILL BEGIN
TO DETERIORATE AFTER 9Z WHEN ALL SITES ARE EXPECTED TO GO BELOW VFR
THRESHOLDS WITH MVFR VISIBILITIES AND/OR IFR CEILINGS. EXPECT
PERIODS OF HEAVIER RAIN TO BEGIN AND PERSIST THROUGH THE END OF THE
TAF PERIOD FOR WESTERN SITES. FOR CENTRAL AND EASTERN
TERMINALS...AFTER SCATTERED SHOWERS THIS AFTERNOON...SHOULD HAVE A
LULL IN PRECIP UNTIL LATER IN THE PERIOD WHEN MORE SUBSTANTIAL
SHOWERS AND THUNDERSTORMS ARE EXPECTED MAINLY AFTER 15Z. WINDS WILL
CONTINUE TO BE LIGHT AND VARIABLE AND CEILINGS SHOULD RECOVER TO AT
LEAST MVFR LEVELS BY AFTERNOON.

LONG TERM: A PROLONGED PERIOD OF UNSETTLED WEATHER WILL PROMOTE
ADVERSE AVIATION CONDITIONS THROUGH EARLY NEXT WEEK.

&&

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

&&

$$

SYNOPSIS...ELLIS
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...BLAES
AVIATION...ELLIS



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