Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 280214
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1015 PM EDT SUN JUL 27 2014

.SYNOPSIS...A STRONG COLD FRONT WILL CROSS THE AREA ON MONDAY...
BRINGING NOTICEABLY COOLER AND LESS HUMID AIR INTO THE AREA. HIGH
PRESSURE BUILDS OVER MUCH OF THE REGION FOR TUESDAY INTO WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 815 PM SUNDAY...

A S/W ROUNDING THE BASE OF THE L/W TROUGH OVER THE LOWER OH AND TN
VALLEY WILL CONTINUE TO PUSH E-SE THROUGH THE OVERNIGHT. THIS
FEATURE WILL INTERACT WITH THE MOIST AND SLIGHT-MODERATELY UNSTABLE
AIR MASS OVER CENTRAL NC TO SUPPORT THE DEVELOPMENT OF SCATTERED
THUNDERSTORMS...SOME OF WHICH MAY BE STRONG TO SEVERE OWING TO
EFFECTIVE BULK SHEAR IN THE NEIGHBORHOOD OF 45-50KTS. MOST OF THE
SEVERE STORM PARAMETERS FAVOR THE WESTERN PIEDMONT...MAINLY SOUTH OF
THE TRIAD TOWARD THE CLT METRO AREA. AS THE NEAR SURFACE AIR MASS IS
BEGINNING TO STABILIZE WITH LOSS OF HEATING...TORNADIC THREAT IS
BECOMING LESS OF A CONCERN. HOWEVER...LARGE HAIL AND DAMAGING WINDS
REMAIN A VIABLE THREAT...POSSIBLY INTO THE WEE HOURS OF MONDAY
MORNING IF STORMS ORGANIZE/STRENGTHEN ONCE THEY CROSS THE HIGHER
TERRAIN OF WESTERN NC.

IF STORMS DO ORGANIZE...WILL NEED TO INCREASE POPS OVERNIGHT ACROSS
THE EASTERN PIEDMONT INTO THE SANDHILLS AND COASTAL PLAIN. BEHIND
THE CONVECTIVE STORMS...MAY SEE PATCHES/AREAS OF FOG
DEVELOP...MAINLY OVER THE WESTERN PIEDMONT BY DAYBREAK MONDAY.

MIN TEMPS IN THE LOW-MID 70S.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 325 PM SUNDAY...

NWP GUIDANCE CONTINUES TO SUGGEST DESTABILIZATION WILL BE LIMITED
AND CONFINED TO THE SANDHILLS ANTO THE STATE. GUIDANCE POPS ARE LOW
IN GENERAL...AND THE CONVECTIVE ALLOWING MODELS HAVE NOT BEEN
HELPFUL OVERALL IN THEIR FORECASTS OF SHOWER AND THUNDERSTORM
DEVELOPMENT IN AND NEAR CENTRAL NORTH CAROLINA. A FEW SHOWERS HAVE
DEVELOPED JUST WEST AND SOUTHWEST OF THE TRIAD...AND AHEAD OF THE
COMPLEX OF STORMS...THINK THERE IS ENOUGH SHEAR AND
INSTABILITY...AND SIMPLE DYNAMICS FROM THE ONGOING STORMS...SIMILAR
TO THE LATEST TREND OF RAP FORECASTS...TO ALLOW FOR SOME CONTINUED
PROGRESSION OF ACTIVITY INTO AND THROUGH CENTRAL NORTH CAROLINA.
TAFS WILL LIKELY INCLUDE A MENTION OF THUNDER AND GUSTY
WINDS...SHOWERS AND LESSER GUSTS CURRENTLY TOWARD KRWI. CONFIDENCE
IS ONLY MODEST...AND ND COASTAL PLAIN...GIVEN THE FASTER TREND NOTED
IN NWP GUIDANCE WITH THE PASSAGE OF THE COLD FRONT THROUGH ALL BUT
THE SOUTHEASTERN THIRD OF THE FORECAST AREA BY 18Z MON.
INDEED...WESTERLY DOWNSLOPE FLOW WILL VEER THE SFC FLOW/LIMIT
CONVERGENCE AND AUGMENT DRY ADVECTION BEHIND THE FRONT (AND LIKELY
CAUSE THE FRONT TO ACCELERATE/MERGE WITH THE PRECEDING LEE
TROUGH)...AND CONSEQUENTLY CAUSE SFC DEWPOINTS TO MIX INTO THE LOWER
60S (AND EVEN SOME UPPER 50S POSSIBLE) OVER THE PIEDMONT - YIELDING
LITTLE BOUYANCY. TO THE EAST...IN THE PRE-FRONTAL AIR MASS OVER THE
SANDHILLS AND SOUTHERN AND CENTRAL COASTAL PLAIN...A RESERVOIR OF
UPPER 60S TO LOWER 70S SFC DEWPOINTS WILL REMAIN UNTIL THE FRONT
CROSSES THOSE AREAS DURING THE MID-AFTERNOON HOURS. MORE FAVORABLE
DIURNAL FRONTAL TIMING THERE WILL ALLOW FOR STRONG DIURNAL
HEATING/DESTABILIZATION/STEEPENING OF LOW LEVEL LAPSE RATES...
BENEATH A LINGERING PLUME OF STEEP MID LEVEL LAPSE RATES IN EXCESS
OF 7 C/KM. THESE EXPECTED STEEP LOW-MID LEVEL LAPSE RATES AMIDST
UNSEASONABLY STRONG MID LEVEL FLOW IN THE 40-50 KT RANGE - AND
ASSOCIATED LONG AND STRAIGHT FORECAST HODOGRAPHS AT KFAY AT TIME OF
FROPA AROUND 21Z - WILL SUPPORT A CONDITIONAL RISK OF DAMAGING WIND
GUSTS AND LARGE HAIL LIKELY FROM SPLITTING SUPERCELLS...PROVIDED
STORMS INDEED DEVELOP. THIS RISK WILL BE GREATEST ROUGHLY FROM
GOLDSBORO TO FAYETTEVILLE TO LAURINBURG AND ESPECIALLY POINTS
EAST...TO COASTAL AREAS.

LOW LEVEL THICKNESS VALUES AROUND 1425 METERS SUPPORT HIGH
TEMPERATURES IN THE MID-UPPER 80S NW TO LOWER-MID 90S SE. COOLER MON
NIGHT...WITH LOWS RANGING FROM LOWER 60W NW TO MID-UPPER 60 SE.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
AS OF 315 PM SUNDAY...

STRONGLY BLOCKED FLOW AROUND THE NORTHERN HEMISPHERE WILL LEAD TO A
RELATIVELY UNCHANGED WEATHER PATTERN FROM TUESDAY THROUGH THE END OF
NEXT WEEK.   THE TROUGH/RIDGE PATTERN OVER THE CONUS WILL AMPLIFY
WITH AN UNSEASONABLY DEEP UPPER TROUGH OVER THE EASTERN US.  IN THE
WAKE OF MONDAY`S SYSTEM...PW DROPS BELOW ONE INCH AND THE MEAN
TROUGH AXIS SETS UP NEARLY OVERHEAD.  DEWPOINTS ARE PROGGED TO DROP
WELL INTO THE 50S IN THE PIEDMONT...WITH THICKNESSES SUGGESTING
TEMPS 5-10 DEGREES BELOW NORMAL IN THE LOW TO MID 80S. THUS...
PRECIP CHANCES LOOK VERY SMALL THROUGH THURSDAY.  HEADING INTO NEXT
WEEKEND...MODELS SHOW ANOTHER SHORTWAVE REINFORCING THE UPPER TROUGH
OVER THE EASTERN CONUS...THOUGH ALSO SHIFTING THE TROUGH AXIS
WESTWARD TOWARD THE MIDWEST STATES. WITH AN FRONTAL ZONE/INVERTED
TROUGH LINGERING NEAR THE COAST OR SLOWLY DRIFTING
INLAND....MOISTURE RETURN AND A MORE FAVORABLE POSITION FOR
INFLUENCE FROM DISTURBANCES ROUNDING THE BASE OF THE TROUGH SHOULD
SLOWLY INCREASE CHANCES FOR PRECIP...WITH INCREASING CLOUD COVER
THROUGH THE WEEKEND.  HIGHS LOOK TO REMAIN A GOOD 5-10 DEGREES BELOW
NORMAL.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
AS OF 1015 PM SUNDAY...

GOOD INSTABILITY REMAINED LATE IN THE EVENING EAST OF THE MOUNTAINS
INTO CENTRAL NORTH CAROLINA...WHILE A COMPLEX OF SHOWERS AND
THUNDERSTORMS MOVED SOUTHEAST ACROSS THE WESTERN PART OF THE STATE.
BASED ON THE LATEST SPC MESOANALYSIS...THE LEADING COMPLEX OF
SHOWERS AND STORMS TENDED TO HEAD TOWARD THE BETTER MID-LEVEL
INSTABILITY/LAPSE RATES TOWARD UPSTATE SOUTH CAROLINA...AND JUST
WEST OF CENTRAL NORTH CAROLINA. SOME PARAMETERS STILL FAVOR THE
POTENTIAL FOR DEEP CONVECTION UPSTREAM TO MAKE IT INTO CENTRAL NORTH
CAROLINA...AND THE LATEST GUIDANCE VARIES FROM DRY CONDITIONS OVER
THE AREA ON THE RAP MODEL...A STARK CHANGE FROM AFTERNOON RUNS...TO
STILL A FEW SHOWERS AND ISOLATED STORMS INTO THE OVERNIGHT. BASED ON
THE GUIDANCE TRENDS AND THE KGSO 00Z UPPER-AIR SOUNDING...UPDATED
TAFS TO BE A LITTLE MORE OPTIMISTIC IN CONDITIONS...BUT LEFT STILL
THE POTENTIAL FOR A FEW SHOWERS WITH A GUSTY WIND GIVEN CONTINUED
INSTABILITY...SURFACE WINDS REMAINING GUSTY ESPECIALLY FROM THE
TRIANGLE WEST...AND ONLY MODEST CONFIDENCE IN EVOLVING CONDITIONS.
AVIATION INTERESTS SHOULD KEEP ABREAST OF THE LATEST OBSERVATIONAL
AND RADAR TRENDS INTO THE OVERNIGHT HOURS.

LATE TONIGHT INTO MONDAY...OVERALL DRIER AIR MOVES INTO CENTRAL
NORTH CAROLINA. WITH MIXING MONDAY...WINDS SHOULD BECOME 250-290 AND
WITH MODEST GUSTS TO AT OR SLIGHTLY ABOVE 20KT. A SHOWER OR
THUNDERSTORM IS POSSIBLE TOWARD KFAY AND KRWI MONDAY AFTERNOON BUT
CONFIDENCE IN THEIR DEVELOPMENT AND LOCATION IS TOO LOW TO INCLUDE
IN THE 00Z TAF. BEYOND THE 00Z VALID TAF PERIOD...VFR CONDITIONS
SHOULD PREVAIL FOR MUCH OF THE REST OF THE WORK WEEK...WITH
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS FROM FRIDAY INTO
THE WEEKEND.

&&

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

&&

$$

SYNOPSIS...MWS/DJF
NEAR TERM...WSS
SHORT TERM...MWS
LONG TERM...BLS
AVIATION...DJF



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