Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 040605
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
200 AM EDT MON MAY 4 2015

.SYNOPSIS....SYNOPSIS... HIGH PRESSURE OFF THE MID ATLANTIC COAST
WILL EXTEND INTO THE REGION THROUGH MID WEEK. AN AREA OF
LOW PRESSURE WILL FORM NEAR THE BAHAMAS DURING THE MIDDLE OF THE
WEEK AND MOVE SLOWLY NORTH TOWARD THE SOUTHEAST COAST.
&&

.NEAR TERM /OVERNIGHT/...
AS OF 950 PM SUNDAY...

AN AREA OF HIGH PRESSURE IN THE LOW-MID LEVELS OF THE ATMOSPHERE AND
A DRY WLY FLOW ALOFT WILL MAINTAIN MOSTLY CLEAR SKIES ACROSS THE
AREA THROUGH THE OVERNIGHT HOURS. LOW LEVEL AIR MASS CONTINUES TO
GRADUALLY MODIFY AS TEMPS ARE A SOLID 3-6 DEGREES WARMER AT 01Z MON
COMPARED TO 24 HOURS AGO. THIS SUGGEST MIN TEMPS WILL LIKELY BE MUCH
WARMER THAN LAST NIGHT. MIN TEMPS 50-55.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 230 PM SUNDAY...

HIGH PRESSURE WILL SET UP OFFSHORE MONDAY WITH A RIDGE AXIS
STRETCHING ACROSS THE STATE. THE MOISTURE RETURN AROUND THE HIGH IS
PRETTY LIMITED AND MOST OF CENTRAL NC WILL STAY WELL CAPPED AS
DEWPOINTS AGAIN MIX OUT INTO THE UPPER 40S.  THE WEAK DISTURBANCE
ALOFT (MENTIONED ABOVE) LOOKS TO HAVE LITTLE IMPACT GIVEN THE
STABILITY AS DRIFTS EAST TOWARD THE COAST MONDAY AFTERNOON.
INSTEAD...THE ONLY CHANCE OF PRECIP...AND A VERY SLIGHT CHANCE AT
THAT...MAY COME FROM SOME DIURNALLY DRIVEN SHOWERS OVER THE HIGHER
TERRAIN DRIFTING EAST TOWARD THE NORTHWEST PIEDMONT LATER IN THE
AFTERNOON.  850MB TEMPS WILL BE COMPARABLE TO TODAY...AROUND
10C...AND WHILE MIXING ISN`T AS DEEP IT SHOULD EXTEND THROUGH
850MB...SUGGESTING HIGHS SIMILAR TO TODAY...78-81. LOWS MONDAY NIGHT
INTO THE MID 50S.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
AS OF 230 PM SUNDAY...

FOR THE PERIOD TUESDAY THROUGH WEDNESDAY...BOTH THE NAM AND THE GFS
FORECAST LIMITED OVERALL LIFT WITH RIDGING OVERHEAD. A SURFACE FRONT
APPROACHES FROM THE NORTH LATE WEDNESDAY...WITH THE NAM A LITTLE
FARTHER SOUTH COMPARED TO THE GFS AND WITH BOTH MODELS APPARENTLY
KEEPING THE BOUNDARY NORTH OF CENTRAL NORTH CAROLINA AT LEAST
THROUGH THE DAY WEDNESDAY. WINDS ARE GENERALLY LIGHT SURFACE THROUGH
500MB...AND EVEN THROUGH 300MB SAVE FOR THE GFS FORECAST OF A MODEST
INCREASE IN 300MB WINDS FROM THE EAST LATE WEDNESDAY. WITH FORCING
EXPECTED TO LIE AWAY FROM CENTRAL NORTH CAROLINA...CHANCES FOR ANY
SHOWER OR THUNDERSTORM WILL BE PREDICATED ON WHERE ANY WOULD DEVELOP
AND MOVE INTO CENTRAL NORTH CAROLINA.

ON TUESDAY...BUFR SOUNDINGS FROM THE GFS AND NAM ARE CAPPED ACROSS
MUCH IF NOT ALL OF CENTRAL NORTH CAROLINA. THE BEST 850MB THETA-E
AIR IS NORTHWEST OF CENTRAL NORTH CAROLINA...TOWARD THE MOUNTAINS
AND FOOTHILLS...WHERE THE 0-3KM MUCAPE IS FORECAST TO BE TO NEAR
1500J/KG. BASED ON THE THICKNESS FORECAST...A SHOWER OR STORM COULD
MOVE OFF THE HIGHER TERRAIN TOWARD THE FAR NORTHWEST PIEDMONT LATE
IN THE DAY...AND WILL FORECAST A SLIGHT CHANCE OF A THUNDERSTORM
LATE TUESDAY AFTERNOON AND EARLY TUESDAY EVENING MAINLY OVER FORSYTH
COUNTY...AS EVEN THE KGSO BUFR SOUNDING IS CAPPED THROUGH 00Z
WEDNESDAY BUT NAM AND GFS QPF EEK A VERY MINOR AMOUNT INTO THE KINT
AREA LATE IN THE DAY. ON WEDNESDAY...MUCAPE IN THAT 0-3KM LAYER
INCREASES OVER THE HIGHER TERRAIN AND NEAR THE SURFACE BOUNDARY TO
2000-2500J/KG...WHERE THE HIGHER 850MB THETA-E AIR SHOULD BE. BUFR
SOUNDINGS AGAIN ARE LARGELY CAPPED...ALTHOUGH EVEN ON THE LESS
UNSTABLE GFS THERE IS FORECAST MODEST MID-LEVEL COOLING ON THE KGSO
BUFR SOUNDING LATE IN THE DAY. 850MB CONVERGENCE IS NEGLIGIBLE AND
CENTRAL NORTH CAROLINA REMAINS UNDER UPPER CONVERGENCE...BUT IT IS
POSSIBLE AN ISOLATED THUNDERSTORM MOVES OFF OF THE HIGHER TERRAIN OR
AWAY FROM THE SURFACE FRONT AND FOLLOWS THE THICKNESSES SOUTH. WILL
HAVE A SLIGHT CHANCE OF A THUNDERSTORM WEDNESDAY AFTERNOON AND EARLY
EVENING PRIMARILY IN THE INTERSTATE 85 CORRIDOR...WHICH IS CLOSE TO
THE CONSENSUS OF THE SOUTHERN EXTENT OF MEASURABLE QPF BETWEEN THE
GFS AND NAM FOR WEDNESDAY AFTERNOON AND JUST SOUTH OF THE FORECAST
850MB LIFT. HIGHS 80 TO 85 WITH THE AVERAGE A DEGREE OR TWO HIGHER
WEDNESDAY WITH HIGHER 1000-850MB THICKNESSES. LOWS TUESDAY NIGHT IN
THE 50S.

FOR THE PERIOD WEDNESDAY NIGHT THROUGH SUNDAY...FAIR UNCERTAINTY
CONTINUES REGARDING THE DEVELOPMENT OF SURFACE LOW PRESSURE OFFSHORE
OF THE SOUTHEAST CONUS IN WEAK...BROAD LOW PRESSURE ALOFT. FOR THE
MOST PART...THE LONG-TERM GUIDANCE HAS BEEN CONSISTENT WITH
THEMSELVES. THE GFS HAS GENERALLY BEEN FARTHER SOUTH WITH ANY LOW
PRESSURE TRACK GIVEN STRONGER SURFACE HIGH PRESSURE TO THE NORTH...
WHILE THE ECMWF HAS GENERALLY WEAKENED THE SURFACE HIGH SUFFICIENTLY
THAT SURFACE LOW PRESSURE IS ABLE TO MOVE FARTHER NORTH. COARSE
MODEL SOUNDINGS SHOW DIFFERENCES IN MOISTURE AND THE AVAILABLE CAP
DEPENDING ON THE DAY...BUT WHAT BOTH THE GFS AND ECMWF SEEM TO HAVE
IN COMMON ARE LIMITED INSTABILITY IN GENERAL...LIMITED LOW-LEVEL
CONVERGENCE AWAY FROM ANY SURFACE LOW PRESSURE...AND RELATIVELY WEAK
WINDS ALOFT. FOR THIS FORECAST...CONSIDERING WHAT THE LONG-TERM
GUIDANCE HAS IN COMMON...DO NOT HAVE CONFIDENCE TO GO BEYOND A
SLIGHT CHANCE OR ISOLATED SHOWERS AND THUNDERSTORMS. FOR THURSDAY...
FOCUSED THE SLIGHT CHANCE MAINLY TOWARD THE NORTHWEST PIEDMONT
CLOSER TO THE SURFACE BOUNDARY AND A LITTLE BETTER INSTABILITY GIVEN
A CONSENSUS APPROACH TO THE LONG-TERM GUIDANCE...AND FOR FRIDAY HAVE
MORE OF A FOCUS FOR THE SLIGHT CHANCE OVER THE FAR NORTHWEST
PIEDMONT AND THE COASTAL PLAIN...THE LATTER DUE TO A CONSENSUS
INCREASE IN THE MEAN MOISTURE. SLIGHT CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT CENTRAL NORTH CAROLINA SATURDAY AND SUNDAY
DUE TO UNCERTAINTY...LEANING TOWARD CLIMATOLOGY AND...FOR
SATURDAY...WHERE 00Z GFS ENSEMBLES SHOW HIGHER POPS. HIGHS IN THE
NORMAL RANGE TO A CATEGORY OR TWO ABOVE...MOSTLY AROUND 80 EXCEPT 80
TO 85 SUNDAY WHEN 1000-850MB THICKNESSES ARE FORECAST HIGHEST. LOWS
UPPER 50S TO MID 60S.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 200 AM MONDAY...

MODERATE CONFIDENCE OF VFR CONDITIONS THROUGH THE 24 HOUR TAF
PERIOD AS HIGH PRESSURE CENTERED TO OUR SOUTH SLOWLY SLIPS OFF THE
COAST BUT EXTENDS INTO THE REGION THROUGH TUESDAY. AN UPPER
LEVEL SHORT WAVE TROUGH WILL SLOWLY MOVE ACROSS CENTRAL NC TODAY AND
OFF THE COAST TONIGHT. WHILE A FEW SHOWERS ARE LIKELY TO DEVELOP
ACROSS MOUNTAINS TODAY AND DRIFT EAST...THE PROBABILITY OF ANY OF
THESE SHOWERS REACHING THE TRIAD REMAINS VERY SMALL AND WILL BE
OMITTED FROM THE TAF. THE ONLY OTHER POTENTIALLY ADVERSE WEATHER
COULD BE A BRIEF PERIOD OF MVFR RADIATION FOG AT KRWI TOWARD
DAYBREAK TODAY. OTHERWISE SCT CLOUDS AT 6-10KFT THIS MORNING WILL
GIVE WAY TO A MORE PROMINENT CLOUD DECK OF SCT-BKN CUMULUS THIS
AFTERNOON AT AROUND 6-8KFT. A LIGHT MAINLY SOUTHERLY WIND FROM 190-
220 DEGREES AT 5-10 KTS IS EXPECTED TODAY.

OUTLOOK...GENERALLY FAIR WEATHER IS EXPECTED FOR LATE TONIGHT INTO
TUESDAY NIGHT WITH SHOWERS DEVELOPING ACROSS THE
MOUNTAINS TUESDAY AND WEDNESDAY AFTERNOONS. AN ONSHORE FLOW
WILL INCREASE AND PERSIST DURING THE MID AND LATE WEEK AS LOW
PRESSURE DEVELOPS NEAR THE BAHAMAS AND DRIFTS NORTH. A WEAK
FRONT WILL ALSO DROP INTO THE REGION LATE WEDNESDAY INTO THURSDAY.
MOISTURE IS EXPECTED TO INCREASE DURING THE WEEK ALONG WITH
THE THREAT OF EARLY MORNING STRATUS/FOG. THERE IS THE POTENTIAL FOR
MORE WIDESPREAD ADVERSE AVIATION CONDITIONS ASSOCIATED WITH THE
COASTAL STORM SYSTEM TO ARRIVE LATE IN THE WORK WEEK. -BLAES
&&

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

&&

$$

SYNOPSIS...BLAES
NEAR TERM...WSS
SHORT TERM...22
LONG TERM...DJF
AVIATION...BLAES


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