Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 051803
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
203 PM 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 /THROUGH TONIGHT/...
AS OF 245 AM THURSDAY...

1206 PM... QUICK UPDATE THIS MORNING TO HANDLE EVOLVING SYSTEM
ACROSS NC AND VA. AS OF LATE MORNING THE UPPER LOW WAS LOCATED
ACROSS FAR EASTERN TN AND SOUTHEAST KY PLACING CENTRAL IN A
FAVORABLE REGION FOR PRIMARILY SHALLOW CONVECTION WITH A GOOD
DEAL PRIMARILY SUB-SEVERE HAIL AND LOCALLY HEAVY RAIN. LATEST SPC
SURFACE ANALYSIS SHOWS WEAK SURFACE BASED INSTABILITY IN AN AXIS
STRETCHING FROM ROXBORO SOUTHEAST ACROSS THE TRIANGLE REGION INTO
THE SOUTHERN PIEDMONT WITH SBCAPE VALUES RANGING ABOVE 500 J/KG IN
THE SANDHILLS AND SOUTHERN PIEDMONT. DEEP LAYER SHEAR IS
IMPRESSIVE AHEAD OF THE UPPER LOW RANGING FROM 40 TO 50 KTS FROM
US 1 EAST.

HAVE ADJUSTED POPS A BIT MORE FOR TODAY AND EXPANDED THE COVERAGE
AND INCLUSION OF THUNDER. TEMPERATURES WILL BE COMPLICATED BUT
HAVE GENERALLY ADJUSTED THEM DOWNWARD GIVEN PRECIPITATION AMOUNTS
AND A SLIGHT DECREASE IN DEW POINTS. -BLAES

PREVIOUS DISCUSSION...
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 /18Z THURSDAY THROUGH TUESDAY/...
AS OF 200 PM THURSDAY...

WIDESPREAD ADVERSE AVIATION CONDITIONS ARE EXPECTED THIS
AFTERNOON THROUGH EARLY FRIDAY MORNING. MVFR TO IFR CONDITIONS
WILL DOMINATE ACROSS MUCH OF CENTRAL NC THROUGH TONIGHT.

A STRONG UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE EAST ACROSS THE
CAROLINAS THIS AFTERNOON AND TONIGHT AND THEN LIFT NORTH TO NEAR
DELAWARE BY FRIDAY AFTERNOON. SEVERAL AREAS OR CLUSTERS OF SHOWERS
AND EVEN FEW THUNDERSTORMS THIS AFTERNOON WILL ROTATE AROUND THE
UPPER LOW THROUGH THE PERIOD. AN AREA OF WIDESPREAD RAIN ACROSS
THE EASTERN PIEDMONT AND THE COASTAL PLAIN EARLY THIS AFTERNOON
WILL PIVOT NORTH TOWARD EARLY EVENING WITH A LULL OVER MUCH OF THE
AREA BEFORE ANOTHER AREA OF WIDESPREAD SHOWERS DROP SOUTH FROM
SOUTHERN VA TONIGHT AND SPREADS EAST ACROSS THE AREA. SCATTERED
THUNDERSTORMS ARE EXPECTED THROUGH EARLY THIS EVENING...MAINLY
ACROSS THE EASTERN PIEDMONT...COASTAL PLAIN AND SANDHILLS
INCLUDING KRDU/KRWI/KFAY. EVEN WITH THE LULL OR BREAKS IN THE RAIN
TONIGHT...WIDESPREAD IFR CIGS AND MVFR/IFR VSBYS ARE EXPECTED.
CIGS AND VSBYS WILL BEGIN TO IMPROVE DURING THE LATE MORNING
FRIDAY WITH VFR CONDITIONS BECOMING MORE PROMINENT DURING THE
AFTERNOON.

LOOKING FURTHER AHEAD BEYOND 18Z FRIDAY... AVIATION CONDITIONS
WILL CONTINUE TO IMPROVE ON FRIDAY AND FRIDAY NIGHT WITH JUST A
SMALL CHANCE OF A SHOWER. OTHERWISE...MAINLY VFR CIGS AND VSBYS
ARE EXPECTED. DESPITE PERIODS OF CLOUDINESS AND A SMALL THREAT OF
A SHOWER...VFR CONDITIONS SHOULD PREVAIL OVER THE WEEKEND INTO
MONDAY BEFORE THE NEXT STORM SYSTEM APPROACHES ON TUESDAY. -BLAES
&&

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

&&

$$
SYNOPSIS...HARTFIELD
NEAR TERM...BLAES/HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...RE
AVIATION...BLAES



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