Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 050713
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
310 AM EDT THU MAY 5 2016

.SYNOPSIS...
DEEP LOW PRESSURE WILL WOBBLE SLOWLY EASTWARD OVER THE MIDATLANTIC
REGION AND CAROLINAS THROUGH FRIDAY NIGHT... BRINGING UNSETTLED
WEATHER. THIS LOW PRESSURE WILL MOVE NORTHEAST AWAY FROM THE AREA
EARLY SATURDAY... BRINGING IMPROVING WEATHER FOR SATURDAY INTO
SUNDAY. A COLD FRONT APPROACHING FROM THE NORTHWEST WILL STALL OUT
NEAR THE VIRGINIA NORTH CAROLINA BORDER LATE SUNDAY INTO MONDAY.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 245 AM THURSDAY...

QUITE AN UNSETTLED PATTERN IS EXPECTED FOR THE NEXT 24-30 HRS...
WITH A GREATER CHANCE OF PRECIP ESPECIALLY IN THE TRIANGLE AND TO
THE NORTH AND EAST. THE LATEST SURFACE MAP SHOWS ONE FRONT AND LOW
HEADING OFFSHORE WHILE ANOTHER FRONT AND LOW APPROACH FROM THE NW.
THE MID-UPPER LEVEL VORTEX THAT WILL DRIVE OUR WEATHER FOR THE NEXT
COUPLE OF DAYS IS CLEARLY NOTED ON WATER VAPOR IMAGERY OVER THE OH
VALLEY AND IS POISED TO DRIFT SLOWLY SOUTHEAST TO A POSITION
CENTERED OVER THE CAROLINAS TODAY... WITH MULTIPLE LOBES OF
VORTICITY ROTATING ABOUT ITS CENTER. ONE SUCH WAVE IS NOW SWINGING
THROUGH THE WRN PIEDMONT BRINGING A BROAD BUT BROKEN BAND OF SHOWERS
INTO OUR WRN COUNTIES... FUELED IN PART BY STEEP MID LEVEL LAPSE
RATES OF 6.8-7.0 C/KM ACTING ON ELEVATED PW AROUND 0.75 IN. MODELS
INCLUDING CONVECTION-ALLOWING AND TRADITIONAL MODELS ALL SHOW
UPSCALE GROWTH OF THIS PRECIP AS IT SHIFTS SLOWLY EASTWARD THROUGH
CENTRAL NC... CULMINATING IN A BAND OF MODERATE TO HEAVY PRECIP
PIVOTING OVER THE CENTRAL THEN NE CWA... SUPPORTED BY FOCUSED UPPER
DIVERGENCE ATOP LOW LEVEL MASS CONVERGENCE ALONG A SURFACE TROUGH
EXTENDING FROM THE JUST-OFFSHORE LOW BACK ACROSS ERN/NRN NC AND
THROUGH CENTRAL VA... AS WELL AS WEAK INSTABILITY WITH DAYTIME
HEATING... EXACERBATED BY MID LEVEL LAPSE RATES OF 6.5-7.5 C/KM AS
THE LOW TRACKS OVER THE REGION. WITH PLENTIFUL LIFT AND MOISTURE...
HAVE RAISED POPS ACROSS THE BOARD... STARTING WITH CHANCE POPS
MAINLY IN THE WRN HALF EARLY THIS MORNING SPREADING EASTWARD AND
TRENDING UP TO CATEGORICAL NE TAPERING TO GOOD CHANCE SOUTH AND WEST
(FARTHER FROM THE BEST STACKED FORCING FOR ASCENT) FOR THE AFTERNOON
INTO THE NIGHT. DESPITE THE MODEST INSTABILITY... THE STEEP LAPSE
RATES STILL PRESENT A THREAT FOR A FEW STORMS... ALONG WITH SMALL
HAIL... PARTICULARLY IN AND NEAR AREAS THAT SEE SOME HEATING THIS
AFTERNOON. WHILE ANY INSTABILITY IS APT TO DECREASE AFTER
NIGHTFALL... OTHER LIFT MECHANISMS PERSIST... INCLUDING MID LEVEL
DPVA AS WAVES ROTATE AROUND THE LOW AND LOW LEVEL CONFLUENT FLOW
ALONG THE PERSISTENT TROUGH... AND WILL MAINTAIN HIGH POPS THROUGH
THE NIGHT... ESPECIALLY NE. SUCH AN EXTENDED PERIOD OF A FOCUSED
MODERATE TO HEAVY RAIN OVER THE NE CWA WOULD BRING ABOUT CONCERN FOR
FLOODING... HOWEVER FLASH FLOOD GUIDANCE IS RATHER HIGH HERE (2.5-
3.5" IN 3 HRS)... SUGGESTING MORE OF AN URBAN AND SMALL STREAM FLOOD
THREAT. AS SUCH... WILL NOT ISSUE A FLASH FLOOD WATCH... BUT WILL
KEEP A CLOSE EYE ON THIS POTENTIAL THROUGH TODAY. THICKNESSES WILL
BE HELD DOWN BY CONSIDERABLE CLOUD COVER THROUGH MUCH OF THE DAY AND
COLD AIR ADVECTION WITH PERIODS OF SHOWERS... SO EXPECT CHILLY WELL-
BELOW-NORMAL HIGHS IN THE UPPER 50S TO LOWER 60S ALONG/NORTH OF
HIGHWAY 64 WITH MID 60S SOUTH WHERE PRECIP WILL BE MORE PATCHY AND
LIGHTER. LOWS TONIGHT IN THE MID 40S TO AROUND 50. -GIH

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
AS OF 310 AM THURSDAY...

THE STACKED LOW PRESSURE WILL HOLD OVER ERN VA AND THE DELMARVA
THROUGH FRI BEFORE THE SURFACE LOW WEAKENS AND THE LOW ALOFT WOBBLES
NORTHWARD. WHILE LIFT-INDUCING FEATURES SUCH AS THE LOW LEVEL
CONFLUENT FLOW AND UPPER DIVERGENCE ARE LIKELY TO BE WEAKER FRI WITH
VERY MARGINAL INSTABILITY PREDICTED... THE SWATHS OF DPVA WILL
CONTINUE AS WAVES SWING AROUND THE LOW CENTER... AND ONE VORTICITY
MAX IN PARTICULAR DROPPING SE FROM THE OH VALLEY FRI WILL ONCE AGAIN
LEAD TO STEEP MID LEVEL LAPSE RATES IN THE AFTERNOON OVER THE
CAROLINAS... AS PW REMAINS QUITE HIGH AT 0.80-1.0". SEE NO REASON
WHY WE WON`T SEE ANOTHER ROUND OF SCATTERED TO NUMEROUS SHOWERS AND
PERHAPS A STORM OR TWO MAINLY IN THE AFTERNOON WITH HEATING... AND
ESPECIALLY OVER THE NRN AND ERN CWA... WHERE LIFT AND MOISTURE WILL
BE BEST. THIS ACTIVITY WILL DWINDLE AFTER NIGHTFALL WITH NOCTURNAL
COOLING AND THE DEPARTURE OF THE MID LEVEL LOW WITH SUBSEQUENT
RISING HEIGHTS AND DECREASING MOISTURE THROUGH THE COLUMN. WILL
TREND POPS DOWN TO SLIGHTLY CHANCE NORTH AND EAST IN THE EVENING
WITH NO POPS OVERNIGHT AND DECREASING CLOUDS. EXPECT HIGHS FRI FROM
THE LOW 60S NORTH TO UPPER 60S SOUTH... AND LOWS FRI NIGHT IN THE
UPPER 40S TO LOWER 50S. -GIH

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 AM THURSDAY...

SATURDAY AND SUNDAY: INTERESTING FORECAST FOR THE WEEKEND AS THE
UPPER LEVEL LOW WILL BE WELL NORTH OF THE AREA WITH THE ASSOCIATED
UPPER TROUGH MOVING OFF OF THE ATLANTIC COAST. BOTH OF THESE
FEATURES ARE BEING USHERED ON BY A NEWLY DEVELOPING UPPER TROUGH
OVER THE GREAT LAKES ON SATURDAY WHICH WILL QUICKLY DIG INTO NY AND
NEW ENGLAND BY SUNDAY. THIS WILL PUSH A WEAK COLD FRONT THROUGH THE
AREA EARLY SUNDAY MORNING ASSOCIATED WITH A SURFACE LOW OVER
SOUTHERN QUEBEC. THIS WONT HOLD LONG HOWEVER AS THE UPPER TROUGH
BECOMES NEGATIVELY TILTED...ALMOST PULLING THE SURFACE FRONT
OFFSHORE AND THEN SURFACE HIGH PRESSURE OVER FLORIDA BUILDS
NORTHWARD OVER CENTRAL NC. THE SENSIBLE WEATHER UPSHOT OF ALL OF
THIS IS THAT DESPITE THE COLD FRONT MOVING THROUGH EARLY
SUNDAY...TEMPERATURES ON SUNDAY AFTERNOON WILL ACTUALLY BE WARMER
THEN ON SATURDAY. EXPECT MID 70S ON SATURDAY AFTERNOON BUT RISING TO
AT LEAST THE LOW IF NOT MID 80S BY LATER IN THE AFTERNOON ON SUNDAY.
ANY PRECIP CHANCES LOOK TO BE ACROSS THE NORTH ON SUNDAY MORNING
WITH THE FRONT BUT ONLY SLIGHT CHANCES AT THIS TIME. CERTAINLY
NOTHING TO DETER OUTDOOR PLANS AT THIS TIME. NIGHTTIME LOWS DURING
THIS PERIOD IN THE UPPER 50S TO LOWER 60S.

MONDAY THROUGH WEDNESDAY: A FAIRLY STRAIGHT FORWARD FORECAST FOR THE
BEGINNING OF NEXT WEEK AS HIGH PRESSURE OVER THE WESTERN ATLANTIC
WILL CONTROL THE WEATHER ON MONDAY...KEEPING CONDITIONS DRY AND WITH
SOUTHERLY RETURN FLOW...FAIRLY WARM. ON TUESDAY...A RAGGED LOW
PRESSURE SYSTEM OVER THE MISSISSIPPI VALLEY WILL GRADUALLY WORK
EASTWARD. WHILE DETAILS REGARDING TIMING AND LOCATION HAVE YET TO BE
RESOLVED...THE TREND IS THE SAME. PRECIPITATION CHANCES WILL
INCREASE ON TUESDAY...WITH BEST CHANCES FOR ANY SHOWERS OR
POTENTIALLY A THUNDERSTORM IN THE NORTHWEST PIEDMONT. BY
WEDNESDAY...THE LOW IS EVEN MORE DISORGANIZED BUT WILL BE POSITIONED
OVER NY AND THE MID ATLANTIC STATES...FURTHER INCREASING
PRECIPITATION CHANCES WEDNESDAY AFTERNOON. THIS WOULD ALSO BE THE
BEST CHANCE FOR THUNDER IN THE FORECAST BUT TOO FAR OUT TO TELL WHAT
SEVERE CHANCES WOULD BE. RIGHT NOW...SEVERE PARAMETERS ARE NOT ALL
THAT FAVORABLE FOR SEVERE WX...ESPECIALLY GIVEN THE LACK OF DYNAMICS
AS THE UPPER JET BASICALLY DISSOLVES. HIGHS DURING THIS TIME IN THE
LOW TO MID 80S WITH LOWS IN THE LOW TO MID 60S.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 150 AM THURSDAY...

CONFIDENCE IS GROWING THAT WE`LL SEE DETERIORATING AVIATION
CONDITIONS THIS MORNING AT ALL SITES... WITH MVFR TO IFR CONDITIONS
DOMINATING THROUGH MUCH OF THIS AFTERNOON AND INTO TONIGHT. A STRONG
UPPER LEVEL LOW WILL DROP FROM THE OH VALLEY SE TO OVER NC TODAY...
WITH ACCOMPANYING LOW PRESSURE AT THE SURFACE. IN THE EAST... IFR TO
LIFR STRATUS AND MVFR WILL CONTINUE SPREADING INTO RWI AND NEARING
RDU/FAY AS WELL IN THE PREDAWN HOURS. AND IN THE WEST... A BAND OF
SHOWERS WILL MOVE INTO THE INT/GSO VICINITIES THIS MORNING BEFORE
SPREADING SLOWLY EASTWARD TO THE REMAINING TAF SITES THROUGH THE
LATE MORNING AND AFTERNOON. RDU AND RWI HAVE THE GREATEST CHANCE OF
SEEING PROLONGED SUB-VFR CONDITIONS TODAY WITH PERIODS OF SHOWERS
GENERATING MOSTLY MVFR VSBYS WITH IFR CIGS. A COUPLE OF
THUNDERSTORMS ARE ALSO POSSIBLE THIS AFTERNOON AT ALL SITES...
HOWEVER COVERAGE SHOULD BE LOW AND TIMING IS TOO UNCERTAIN TO
INCLUDE IN THE FORECASTS AT THIS TIME. THE RAIN IS EXPECTED TO TAPER
DOWN FROM SW TO NE THROUGH THE EVENING... HOWEVER RAIN WITH MVFR TO
IFR VSBYS SHOULD REMAIN DOMINANT AT RDU/RWI WITH SUB-VFR CIGS
PERSISTING THROUGH THE END OF THE FORECAST PERIOD.

LOOKING BEYOND 06Z EARLY FRI MORNING... RDU/RWI SHOULD REMAIN
IFR/LIFR UNTIL MID MORNING FRI... HOWEVER INT/GSO/FAY ARE EXPECTED
TO SLOWLY IMPROVE TO MVFR. ALL SITES SHOULD BE VFR (OR HIGH-END MVFR
AT WORST) BY LATE MORNING FRI... ALTHOUGH THE CHANCE REMAINS FOR
BRIEF SUB-VFR CONDITIONS IN SHOWERS FRI AFTERNOON. VFR CONDITIONS
SHOULD PREVAIL FRI NIGHT THROUGH MON AS THE LOW MOVES AWAY FROM THE
REGION. -GIH

&&

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

&&

$$

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



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