Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 031924
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
325 PM EDT THU SEP 3 2015

.SYNOPSIS...A WEAK DISTURBANCE WILL PASS OVER NORTHERN NORTH
CAROLINA TONIGHT. A BACKDOOR COLD FRONT WILL APPROACH FROM THE NORTH
LATE FRIDAY... THEN PUSH SOUTHWARD THROUGH THE AREA FRIDAY NIGHT...
BEFORE SETTLING TO OUR SOUTH ON SATURDAY. HIGH PRESSURE WILL NOSE IN
FROM THE NORTH OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 235 PM THURSDAY...

CONVECTION CHANCES STILL LOOK PRETTY SLIM FOR THE REST OF THE
DAYLIGHT HOURS IN CENTRAL NC. THE LATEST MESOANALYSES INDICATE PW
VALUES NEAR OR BELOW NORMAL OVER THE NRN TWO THIRDS OF THE CWA...
WITH SMALL MLCAPE OF 500 J/KG OR LOWER WITH CINH PERSISTING IN THE
NORTHEAST CWA... AND VERY WEAK DEEP LAYER SHEAR. THE ONLY CONVECTION
THUS FAR OUTSIDE OF THE VA MOUNTAINS HAS BEEN ACROSS EXTREME SE NC
ALONG THE OLD OUTFLOW BOUNDARY AND BENEATH THE WEAK MID LEVEL SHEAR
AXIS. BASED ON THE BOUNDARY LOCATION AND ATTENDANT LOW LEVEL MASS
CONVERGENCE AS WELL AS MOISTURE AVAILABILITY... CONTINUE TO THINK
THAT THE FAR SRN AND SE FRINGE OF THE CWA MAY STILL SEE ISOLATED
SHOWERS AND STORMS OVER THE NEXT SEVERAL HOURS... GIVEN THAT LOW AND
MID LEVEL LAPSE RATES ARE BEST ACROSS THIS SRN TIER. LOWER PW AND
LOWER POTENTIAL FOR INSTABILITY ELSEWHERE WITH A LACK OF TRIGGER
SHOULD PRECLUDE SHOWER/STORM DEVELOPMENT OVER THE REST OF THE CWA
THROUGH EARLY EVENING. THEN AFTER NIGHTFALL... IT`S A TOUGH CALL ON
WHETHER OR NOT WE`LL SEE ISOLATED SHOWERS OVERNIGHT. SOME SREF
MEMBERS AS WELL AS THE NAM AND GFS SPIT OUT A LITTLE LIGHT PRECIP
MAINLY N AND NE OF RDU... LIKELY A RESULT OF WEAK DPVA DRIFTING
SOUTHWARD FROM VA AND/OR WEAK UPPER DIVERGENCE ALONG A SUBTLE UPPER
SHEAR AXIS THAT WILL EXTEND FROM WV ACROSS NE NC LATE TONIGHT. IN
EITHER CASE... COVERAGE AND AMOUNTS DO NOT APPEAR TO BE VERY HIGH...
GIVEN THE WEAKNESS OF ANY POSSIBLE FORCING FEATURES AND THE ABSENCE
OF ANY PRECIP LATE TONIGHT ON OTHER MODELS SUCH AS THE NSSL WRF.
HOWEVER... WILL LEAVE IN A SLIGHT CHANCE OF SHOWERS ACROSS THE FAR N
AND NE GIVEN THE GOOD AGREEMENT ON THE UPPER DIVERGENCE BAND. LOWS
67-72. -GIH

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 325 PM THURSDAY...

OUR BEST SHOT AT SCATTERED TO NUMEROUS SHOWERS AND STORMS WILL BE
LATE FRI INTO FRI NIGHT... WITH SEVERAL FAVORABLE FACTORS IN PLAY.
FIRST... MODELS DEPICT A POCKET OF ABOVE-NORMAL PW SLIDING SOUTHWARD
FROM VA INTO/THROUGH CENTRAL NC TOMORROW... IN CONJUNCTION WITH WEAK
DPVA SPREADING IN FROM THE NW AND NE AND IMPROVING UPPER DIVERGENCE
FROM THE NORTH... ALL AHEAD OF THE INCOMING BACKDOOR COLD FRONT. THE
LARGE-SCALE MODELS INCLUDING THE NAM/GFS/ECMWF/SREF ARE IN AGREEMENT
ON CONVECTION DEVELOPING DURING THE EARLY TO MID AFTERNOON OVER
CENTRAL NC... FOCUSING THE BEST COVERAGE AND HIGHEST AMOUNTS OVER
THE FAR NW PIEDMONT. GIVEN THE EXPECTED MID-UPPER LEVEL DYNAMIC
CONTRIBUTIONS TO ASCENT... DESTABILIZATION WITH GOOD HEATING DURING
THE DAY... AND RISING MOISTURE THROUGH THE COLUMN... CONVECTIVE
COVERAGE LOOKS SUFFICIENT TO RAISE POPS A BIT... TO LIKELY IN THE NW
CWA WITH GOOD CHANCES ELSEWHERE FOR NOW (ALTHOUGH THESE MAY GO UP TO
LIKELY HERE AS WELL IN LATER FORECASTS IF TRENDS HOLD). THE WEAK
DEEP LAYER SHEAR SHOULD LIMIT STORM STRENGTH... ALTHOUGH THE PROFILE
AND DCAPE NOTED ON NAM FORECAST SOUNDINGS WOULD SUGGEST A MARGINAL
WIND THREAT. THE ANTICIPATED SLOW MOVEMENT WITH HIGH WATER CONTENT
WILL BRING A RISK OF SLOW-MOVING STORMS GENERATING URBAN FLOODING.
EXPECT HIGHS OF 90-95 WITH DECENT PREFRONTAL HEATING AND CONTINUED
ABOVE NORMAL THICKNESSES. POPS SHOULD TREND DOWNWARD AFTER NIGHTFALL
WITH LOSS OF INSOLATION... HOWEVER WITH LOW LEVEL CONFLUENT FLOW
NEAR THE BACKDOOR FRONT AND INCREASED ATLANTIC-SOURCE FEED WITH
PERSISTENT UPPER DIVERGENCE OVERNIGHT... WILL KEEP A MENTION OF
SCATTERED SHOWERS AND STORMS THROUGH THE NIGHT... WITH THE BEST
CHANCES WEST. LOWS 67-71. -GIH

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 150 PM THURSDAY...

COOLER TEMPERATURES EXPECTED FOR MUCH OF THE LONG TERM AS THE COLD
FRONT THAT IS PROGGED TO COME THROUGH FRIDAY NIGHT WILL BRING A
CHANGE IN AIRMASS FROM THE NORTHEAST. WITH THIS WILL COME A GREATER
FETCH OF MOISTURE FROM OFFSHORE...DRIVEN BY SEVERAL SHORTWAVE
IMPULSES THAT ARE EXPECTED TO MOVE INTO THE STATE DURING THE WEEKEND
AND INTO EARLY NEXT WEEK.

FOR THE WEEKEND...THE GREATEST THREAT FOR RAIN WILL BE IN THE WEST
ON SATURDAY AS THE FRONT MOVES THROUGH AND A CAD-LIKE SCENARIO SETS
UP. AS THE WEEKEND PROGRESSES HOWEVER...AN INVERTED TROUGH ALONG THE
EAST COAST WILL SHARPEN AND THUS BRING A MORE NORTHERLY COMPONENT TO
THE WIND AND SHUT OFFSHORE MOISTURE FEED INTO THE NW PIEDMONT AND
INSTEAD BEGIN TO FOCUS THE BEST CHANCE FOR CONVECTION OVER THE
EASTERN PART OF THE STATE. THUS RAIN CHANCES FOR SUNDAY WILL BE
BETTER IN THE EAST THAN IN THE WEST. THIS PATTERN WILL CONTINUE INTO
LABOR DAY WITH SOUTHEASTERN COUNTIES HAVING THE BEST CHANCE FOR
SHOWERS AND THUNDERSTORMS. HIGHS IN THE LOW TO MID 80S FOR THIS
PERIOD WITH THE POTENTIAL FOR SOME UPPER 70S IN THE NW IF CLOUD
COVER LOCKS IN.

THE BERMUDA HIGH BEGINS TO TAKE BACK OVER FOR MIDWEEK AND THE
SURFACE HIGH OVER OUR AREA AND THE INVERTED TROUGH WILL BEGIN TO
BREAK DOWN. THIS WILL SEE A RETURN TO WARMER TEMPERATURES...ALTHOUGH
GRADUALLY...WITH DIURNAL CHANCES FOR SHOWERS AND ISOLATED
THUNDERSTORMS THROUGH THURSDAY. AT THIS TIME...ANY THUNDERSTORMS
THAT DO OCCUR EITHER THIS WEEKEND OR NEXT WEEK ARE NOT EXPECTED TO
BE SEVERE...BUT A FEW STRONG STORMS CANNOT BE RULED OUT.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 105 PM THURSDAY...

VFR CONDITIONS WILL HOLD TODAY INTO THIS EVENING. A WEAK LOW
PRESSURE TROUGH WILL REMAIN STRETCHED ACROSS SE NC AS WEAK HIGH
PRESSURE HOLDS OVER NRN AND WRN NC. THERE IS A SMALL CHANCE OF A
SHOWER OR STORM GENERATING BRIEF SUB-VFR CONDITIONS AT FAY TODAY
MAINLY 19Z-01Z... BUT CHANCES ARE TOO LOW TO MENTION AT THIS TIME.
THERE IS A RISK OF MVFR-IFR FOG LATE TONIGHT INTO EARLY FRI MORNING
AT RDU/FAY AND ESPECIALLY RWI... WITH WINDS GOING CALM AND LITTLE IN
THE WAY OF CLOUD COVER WITH RESIDUAL GROUND MOISTURE ALL
FACILITATING FOG DEVELOPMENT ESPECIALLY IN LOW LYING AREAS. ISOLATED
SHOWERS ARE POSSIBLE TONIGHT NEAR RDU/RWI... HOWEVER MODELS ARE NOT
IN GOOD AGREEMENT ON THIS... AND ANY COVERAGE SHOULD BE LOW
ANYWAY... SO WILL NOT MENTION IN THE TERMINAL FORECASTS FOR NOW. VFR
CONDITIONS WILL AGAIN DOMINATE MID-LATE MORNING FRI... HOWEVER WE`LL
SEE A TREND TOWARD NUMEROUS SHOWERS AND STORMS AREAWIDE TOWARD THE
END OF THIS 24-HR FORECAST PERIOD... LIKELY STARTING NEAR OR JUST
AFTER 16Z... AS A BACKDOOR COLD FRONT APPROACHES FROM THE NORTH.
OUTSIDE OF ANY SHOWERS/STORMS... SURFACE WINDS WILL REMAIN LIGHT.

LOOKING BEYOND 18Z FRI... CONFIDENCE IS HIGH THAT NUMEROUS SHOWERS
AND STORMS WITH SLOW MOVEMENT WILL BRING A PERIOD OF ADVERSE
AVIATION CONDITIONS TO ALL CENTRAL NC TERMINALS FRI AFTERNOON
THROUGH MID EVENING. SUB-VFR CIGS/VSBYS... HEAVY DOWNPOURS... AND
ENHANCED SURFACE WIND GUSTS WILL BE POSSIBLE IN/NEAR THIS ACTIVITY.
THE COLD FRONT WILL PUSH SOUTHWARD THROUGH CENTRAL NC FRI NIGHT AND
SETTLE TO OUR SOUTH SAT... HOLDING THERE WHILE WEAKENING THROUGH TUE
AS HIGH PRESSURE NOSES IN FROM THE NORTH AND NE. SUB-VFR LOW CLOUDS
AND FOG ARE LIKELY AT ALL SITES EACH LATE NIGHT/EARLY MORNING
SAT/SUN/MON. -GIH

&&

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

&&

$$

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



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