Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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930 FXUS62 KRAH 011935 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 335 PM EDT SUN MAY 1 2016 .SYNOPSIS...
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A SERIES OF UPPER LEVEL DISTURBANCES WILL INTERACT WITH A MOIST AND UNSTABLE AIR MASS OVER CENTRAL NC TO TRIGGER SCATTERED CONVECTION THROUGH WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 335 PM SUNDAY... SUBSIDENCE BEHIND AN EXITING MCV HAS SUPPRESSED ADDITIONAL AFTERNOON CONVECTION THUS FAR ACROSS CENTRAL NC. STILL EXPECT SCATTERED CONVECTION TO DEVELOP OVER THE PIEDMONT AND SANDHILLS WITHIN THE 21Z- 00Z TIME FRAME AS WEAK VORTICES ALOFT INTERACT WITH AVAILABLE MOISTURE AND INSTABILITY. EXPECT BULK OF STORMS TO REMAIN BELOW SEVERE CRITERIA THOUGH AN ISOLATED STRONG/DAMAGING WIND GUSTS CANNOT BE RULED OUT. A SHEAR AXIS PROJECTED TO DROP SEWD OUT OF THE CENTRAL APPALACHIANS AND CROSS VA OVERNIGHT MAY TRIGGER A FEW SHOWERS ACROSS THE NORTHERN PIEDMONT OVERNIGHT. OTHERWISE EXPECT LOW CLOUDS TO REDEVELOP OVER MOST OF CENTRAL NC OVERNIGHT. MIN TEMPS LOW-MID 60S.
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&& .SHORT TERM /MONDAY AND MONDAY NIGHT/...
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AS OF 335 PM SUNDAY... ANOTHER MCV ASSOCIATED WITH THE CONVECTION NOW OCCURRING OVER SECTIONS OF THE LOWER MS VALLEY THIS AFTERNOON HAS THE POTENTIAL TO ENHANCE OUR CONVECTIVE PROBABILITIES ACROSS CENTRAL NC MONDAY AND MONDAY NIGHT. A LOW LEVEL JET ON THE ORDER OF 30-35KTS EXPECTED TO DEVELOP LATE IN THE DAY WHILE MID LEVEL LAPSE RATES WILL BE ON THE ORDER OF 6-7 DEG C/KM. IN ADDITION...CENTRAL NC SEE INCREASING DIVERGENCE ALOFT MONDAY AS WE BECOME UNDERNEATH THE RIGHT ENTRANCE REGION OF A 110+KT JET. THESE DYNAMICS SHOULD PROVIDE PLENTY OF LIFT OF A VERY MOIST AIR MASS (PRECIP WATER VALUES 1.5-1.7 INCHES OF >200 PERCENT OF NORMAL). THUS... SHOULD SEE SCATTERED TO NUMEROUS SHOWERS AND STORMS ERUPT...MAINLY DURING THE AFTERNOON AND CONTINUING WELL INTO MONDAY NIGHT. WHILE SEVERE PARAMETERS ARE MARGINAL...POTENTIAL WILL EXIST FOR LOCALIZED DAMAGING WIND GUSTS AND HAIL TO THE SIZE OF QUARTERS. MAIN CONCERN IS A HEAVY RAIN/FLASH FLOOD THREAT AS TRAINING CELLS OVER URBAN LOCATIONS COULD QUICKLY LEAD TO FLOODING OF STREETS AS WELL AS CREEKS/STREAMS. DO NOT BELIEVE THAT AREAL COVERAGE WILL BE ENOUGH TO WARRANT A FLASH FLOOD WATCH THOUGH COULD SEE THE NEEDED FOR A FEW URBAN/SMALL STREAM STATEMENTS AND POSSIBLY A FFW OR TWO. IF THE MCV RESPONSIBLE FOR THE DEEP SOUTH CONVECTION ARRIVES PRIOR TO 15Z...INITIATING SCATTERED CONVECTION SOONER THAN EXPECTED...THEN SEVERE WEATHER THREAT WILL BE GREATLY DIMINISHED BUT COULD SEE AN INCREASE THREAT FOR FLASH FLOODING. HIGH TEMPS MONDAY DEPENDENT ON PARTIAL SUN OCCURRING IN THE EARLY- MID AFTERNOON HOURS. IF CLOUDS SLOW TO DEPART OR SCATTERED CONVECTION COMMENCES SOONER THAN 20Z...THEN HIGH TEMPS MAY END UP BEING 3-4 DEGREES COOLER. MAX TEMPS 80-85. MIN TEMPS MONDAY NIGHT LOW-MID 60S.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/... AS OF 258 PM SUNDAY... A SERIES OF DISTURBANCES IN THE SW FLOW ALOFT WILL MOVE ACROSS THE CAROLINAS EARLY ON TUESDAY...WITH THE SFC COLD FRONT NOW PROGGED TO MOVE ACROSS OUR AREA AROUND MID-DAY. UNTIL FROPA...LOOK FOR RAIN CHANCES TO CONTINUE...THUS AREAS FROM THE TRIANGLE EASTWARD...AND PARTICULARLY DURING THE FIRST HALF OF THE DAY...SHOULD HAVE THE BEST CHANCE OF SEEING SHOWERS AND TSTMS. IN THE WAKE OF THE FRONT...LOOK FOR DRIER NW FLOW TO OVERSPREAD OUR CWA...RESULTING IN DRY WEATHER FOR THE SECOND HALF OF THE DAY. FAIR WEATHER WILL THEN CONTINUE TUESDAY NIGHT AND WEDNESDAY...UNTIL A FAIRLY DEEP CLOSED LOW... DROPPING SOUTH ACROSS THE GREAT LAKES...PUSHES ANOTHER COLD FRONT ACROSS OUR AREA WEDNESDAY NIGHT. WORTH NOTING THOUGH...THIS FRONT...AND THE AIRMASS JUST AHEAD OF IT...APPEARS TO HAVE LIMITED MOISTURE...RIGHT NOW WE`RE EXPECTING VERY MODEST RAINFALL AMOUNTS WITH THIS SYSTEM. IN THE WAKE OF THE FRONT...COOL NW FLOW WILL SET UP OVER OUR AREA WITH THE UPPER LOW NOW PROGGED TO TRANSIT VA AND NC. GIVEN THE THE ASSOC INSTABILITY...SCATTERED SHOWERS AND PERHAPS A TSTM OR TWO WILL REMAIN POSSIBLE THURSDAY AND FRIDAY. AS IT APPEARS RIGHT NOW...THE UPPER LOW IS PROGGED TO EXIT TO OUR EAST LATE FRIDAY...WITH SUBSIDENCE IN THE WAKE OF THIS FEATURE PROVIDING FAIR WEATHER FOR THE WEEKEND. TEMPS WILL BE WITHIN A FEW DEG OF NORMAL THROUGH THE WEEK...WITH THE EXCEPTION OF THURSDAY AND FRIDAY...WHEN TEMPS WILL RUN ABOUT 5-10 DEG BELOW NORMAL. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 200 PM SUNDAY... CEILINGS WILL CONTINUE TO GRADUALLY LIFT THROUGH THE REMAINDER OF THE AFTERNOON WITH MOST SITES EITHER HIGH END MVFR OR VFR CONDITIONS BY 21Z-22. AREAS OF SHOWERS WITH EMBEDDED THUNDERSTORMS WILL EXIT OUR COASTAL PLAIN COUNTIES BY 19Z. AFTER 20Z...COULD SEE RANDOM SHOWERS AND ISOLATED T-STORMS DEVELOP OVER THE PIEDMONT THOUGH COVERAGE EXPECTED TO BE LIMITED. BEST PROSPECTS ARE IN VICINITY OF THE TRIAD TERMINALS SO WILL HAVE A TEMPO FOR CONVECTION AT THOSE SITES. LATER TONIGHT...WIDESPREAD IFR/LIFR CEILINGS WILL DEVELOP AND PERSIST INTO MONDAY MORNING. POTENTIAL FOR A FEW SHOWERS TO SKIRT NEAR OR NORTH OF THE TRIAD TERMINALS AS WELL AS KRDU AND KRWI. LOW CLOUDS EXPECT TO LIFT BY MID DAY. WITH INCREASING SUNSHINE...ATMOSPHERE WILL DESTABILIZE...LEADING TO THE DEVELOPMENT OF SCATTERED-NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS. A FEW STORMS MAY BE STRONG-SEVERE BETWEEN 21Z-04Z. IN ADDITION...BLINDING HEAVY RAIN EXPECTED WITH THE HEAVIER SHOWERS/STORMS. AN UNSETTLED WEATHER PATTERN TUESDAY THROUGH THURSDAY IS EXPECTED TO RESULT IN VARIABLE AVIATION CONDITIONS. IT IS HIGHLY PROBABLE THAT PERIODS OF MVFR/IFR PARAMETERS WILL OCCUR DUE TO CEILINGS...IN ADDITION TO SCATTERED CONVECTION. IMPROVING AVIATION CONDITIONS EXPECTED BY LATE IN THE WORK WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...RAH AVIATION...WSS

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