Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 090721 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 320 AM EDT WED JUL 9 2014 .SYNOPSIS...A SURFACE TROUGH WILL PERSIST OVER CENTRAL NORTH CAROLINA TODAY. A WEAKENING COLD FRONT WILL MOVE INTO OUR REGION THURSDAY...THEN DRIFT TOWARD THE COAST FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 320 AM WEDNESDAY... PERTURBATIONS ROTATING THROUGH THE BASE OF A BROAD L/W TROUGH OVER THE OH AND TN VALLEYS WILL INTERACT WITH AVAILABLE MOISTURE AND INSTABILITY TO TRIGGER SCATTERED THUNDERSTORMS ACROSS MOST OF THE PIEDMONT LATER TODAY. BULK OF MODEL GUIDANCE SUGGEST GREATEST LIKELIHOOD FOR CONVECTION WILL BE FROM MID/LATE AFTERNOON INTO THE EVENING HOURS. A SIDE NOTE...ONE OR TWO OF THE WRF MODELS SUGGEST CONVECTION POSSIBLY STARTING AS EARLY AS 15Z IN THE NW PIEDMONT. IN ANTICIPATION OF HEATING THROUGH EARLY AFTERNOON...LOW LEVEL LAPSE RATES APPROACHING 9 DEG C/KM MAY BE REALIZED. THIS ALSO SUPPORTED BY MODEL SOUNDINGS DEPICTING A WELL DEFINED INVERTED V SIGNATURE. BULK WIND SHEAR VALUES NOT AS ROBUST AS PREDICTED 24 HOURS AGO WITH VALUES NOW IN THE 20-25KT RANGE. STILL...CONSIDERING THE TIME OF YEAR...THESE WIND PARAMETERS MAY STILL BE ENOUGH TO CAUSE CONVECTION TO ORGANIZE INTO BROKEN BOW SEGMENTS. IF THIS OCCURS...THREAT FOR DAMAGING WIND GUSTS WILL INCREASE. THUS...EXPECT SLIGHT CHANCE POPS THIS MORNING ACROSS THE PIEDMONT TO INCREASE TO HIGH CHANCE BY MID- LATE AFTERNOON WITH A STRONG-SEVERE STORM POSSIBLE ACROSS THE NORTHERN PIEDMONT. CONVECTIVE CHANCES APPEAR LESS TO THE SOUTH AND SE OF RALEIGH AS THIS REGION A BIT REMOVED FROM THE BETTER DYNAMIC SUPPORT ALOFT. EXPECT CONVECTION COVERAGE IN THIS REGION TO BE ISOLATED. MAX TEMPS THIS AFTERNOON DEPENDENT UPON HOW EXTENSIVE THE CLOUDS ARE AND WHEN CONVECTION BEGINS TO POP. BASED ON LATEST MODEL PROJECTION OF BETTER COVERAGE AROUND MID-LATE AFTERNOON...FEEL THAT ENOUGH HEATING WILL OCCUR TO BOOST TEMPS AN ADDITIONAL 2-4 DEGREES ACROSS THE PIEDMONT FROM PREVIOUS FORECAST. MAX TEMPS NEAR 90 NW TO THE MID 90S EAST AND SOUTH. EXPECT CONVECTION TO SLOWLY WANE THIS EVENING WITH ISOLATED TO POSSIBLY SCATTERED CONVECTION OCCURRING WELL PAST MIDNIGHT. MIN TEMPS IN THE UPPER 60S-LOWER 70S. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 320 AM WEDNESDAY... MID LEVEL SHEAR AXIS AND ASSORTED PERTURBATIONS WILL DRIFT OVER THE REGION THURSDAY. ATTENDANT SFC FRONT WILL AID TO FOCUS LOW LEVEL MOISTURE AND CONVERGENCE...LEADING TO A LIKELIHOOD OF SCATTERED/NUMEROUS SHOWERS AND THUNDERSTORMS. SEVERE WEATHER THREAT APPEARS LESS THAN TODAY...THOUGH STORMS WITH SUSTAINED UPDRAFTS MAY CAUSE STRONG/LOCALLY DAMAGING WINDS DUE TO PRECIP LOADING. THIS ASPECT APPEARS MORE LIKELY ACROSS THE SANDHILLS AND COASTAL PLAIN. DEEP UNIDIRECTIONAL FLOW SUGGEST THAT SHOWERS AND STORMS MAY TRAIN REPEATEDLY OVER THE SAME LOCATION FOR A COUPLE OF HOURS. WITH THE MOISTURE RICH AIR MASS IN PLACE (PW VALUES 1.7-2 INCHES PROJECTED)...THIS MAY LEAD TO LOCALIZED FLOODING...ESPECIALLY IN URBANIZED AREAS. PLAN TO MAINTAIN LIKELY POPS OVER BULK OF THE FORECAST AREA. MAX TEMPS WILL BE HELD DOWN DUE TO EXTENSIVE CLOUD COVERAGE AND COVERAGE OF SHOWERS AND STORMS. HIGH TEMPS MID 80S NW TO LOWER 90S FAR SOUTH. MIN TEMPS UPPER 60S-LOWER 70S. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 310 AM WEDNESDAY... FRIDAY THROUGH SUNDAY NIGHT: THE WEAK MID LEVEL TROUGH IS EXPECTED TO PUSH TO THE EAST OF CENTRAL NC LATE FRIDAY AFTERNOON/EVENING... WITH THE WEAK SURFACE TROUGH STALLING ACROSS THE COASTAL PLAIN LATE FRIDAY AFTERNOON/EVENING. BEHIND THE MID LEVEL TROUGH... WE SHOULD SEE DRIER MID/UPPER LEVEL AIR. THUS... WILL LOWER POPS IN THE WEST/NORTHWESTERN PIEDMONT TO SLIGHT CHANCE FRIDAY. EXPECT THE BEST CHANCE OF SHOWERS AND STORMS WILL BE ACROSS THE COASTAL PLAIN AND SANDHILLS (WHERE THE BEST INSTABILITY AND WEAK SURFACE CONVERGENCE WILL BE DURING THE AFTERNOON... AND BETTER MOISTURE AS MENTIONED ABOVE). DEEP LAYER SHEAR LOOKS TO BE LESS THAN 20 KTS WHERE THE BEST INSTABILITY IS EXPECTED (ACROSS COASTAL PLAIN/SANDHILLS) FRIDAY AFTERNOON/EVENING. THUS... EXPECT ANY SEVERE THREAT WILL BE QUITE MARGINAL AT BEST. HOWEVER... EXPECT WE COULD SEE SOME ISOLATED STRONG TO SEVERE STORMS... WITH THE MAIN THREAT FROM DAMAGING DOWNBURST WINDS. GIVEN THE LINGERING HIGH PW`S ACROSS OUR EASTERN COUNTIES... A LOCALIZED FLASH FLOODING THREAT CANNOT BE RULED OUT... ESPECIALLY WITH A FAIRLY WEAK STEERING FLOW. EXPECT HIGH TEMPS WILL GENERALLY BE IN THE UPPER 80S... WITH PERHAPS EVEN A FEW MID 80S ACROSS OUR FAR EAST WHERE CLOUDS/SCATTERED CONVECTION WILL HELP LIMIT INCOMING SOLAR RADIATION. ANY LINGERING CONVECTION LATE FRIDAY EVENING SHOULD GENERALLY PUSH TO THE EAST/SOUTHEAST OF THE AREA AND/OR DISSIPATE WITH THE LOSS OF HEATING. LOWS SATURDAY MORNING ARE EXPECTED TO BE IN THE UPPER 60S TO LOWER 70S. MID LEVEL FLOW WILL BECOME MORE NORTHWESTERLY TO WEST-NORTHWESTERLY OVER THE WEEKEND... WITH THE POTENTIAL OF UPSTREAM CONVECTION/MCV`S TO TRACK ACROSS CENTRAL NC. THE LATEST GUIDANCES HAS SHIFTED THE MORE ACTIVE DAY TO SUNDAY NOW... AS THE MID/UPPER LEVEL TROUGH BEGINS TO AMPLIFY ACROSS THE UPPER MIDWEST/NORTHERN PLAINS AND GREAT LAKES REGION. GIVEN SUCH DISTURBANCES IN NORTHWEST FLOW ARE HARD TO TRACK WILL LIMIT POPS TO LOW END CHANCE FOR THE WEEKEND... HIGHEST ON SUNDAY. LOW LEVEL THICKNESS VALUES ARE EXPECTED TO SLOWLY INCREASE THIS WEEKEND. THIS WILL RESULT IN HIGH TEMPS IN THE UPPER 80S TO LOWER 90S SATURDAY TO THE LOWER 90S SUNDAY (TO PERHAPS EVEN SOME MID 90S ACROSS THE SOUTH). LOW TEMPS ARE EXPECTED TO GENERALLY BE AROUND 70/LOWER 70S. MONDAY AND TUESDAY: A DEEP TROUGH IS EXPECTED TO DEVELOP ACROSS THE EASTERN HALF OF THE COUNTRY EARLY NEXT WEEK. THIS SHOULD RESULT IN THE INCREASING LIKELIHOOD OF SHOWERS AND STORMS EARLY NEXT WEEK AS A SURFACE COLD FRONT APPROACHES THE REGION FROM THE NORTHWEST... POSSIBLY MOVING INTO THE AREA ON TUESDAY. GIVEN WE ARE TALKING ABOUT DAY 6 AND 7 OF THE FORECAST WILL LIMIT POPS TO THE 30-40 PERCENT RANGE FOR NOW. AFTERNOON LOW LEVEL THICKNESS VALUES ARE PROGGED TO INCREASE TO AROUND 1430 METERS DURING THIS TIME. THIS WOULD SUPPORT AT LEAST HIGH TEMPS IN THE LOWER TO MID 90S... WITH PERHAPS SOME UPPER 90S. FOR NOW WILL LIMIT HIGH TEMPS TO THE LOWER 90S... TO A FEW MID 90S ACROSS THE SOUTH.... GIVEN THE INCREASED CHANCES FOR SHOWERS AND STORMS. LOWS DURING THE PERIOD ARE EXPECTED TO BE IN THE LOWER 70S... WITH EVEN SOME MID 70S POSSIBLE. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 125 AM WEDNESDAY... VFR CONDITIONS WILL GENERALLY PERSIST THROUGH 18Z. AFTER 18Z...A SERIES OF UPPER LEVEL DISTURBANCES COUPLED WITH A SLOWLY WEAKENING SURFACE COLD FRONT WILL INCREASE THE THREAT FOR SCATTERED CONVECTION ACROSS CENTRAL NC. BETWEEN 20Z AND 01Z...THE THREAT FOR SCATTERED CONVECTION AND ASSOCIATED MVFR/IFR CEILINGS AND VISIBILITIES WILL BE GREATEST ON VICINITY OF THE TRIAD TERMINALS AS WELL AS KRDU. IN VICINITY OF THE STRONGER CONVECTION...WIND GUSTS UP TO 40KTS PROBABLE. THE ATMOSPHERE WILL REMAIN UNSETTLED TONIGHT THROUGH THURSDAY NIGHT AS THE SURFACE COLD FRONT GRADUALLY DRIFTS SEWD ACROSS THE REGION AND THE SERIES OF DISTURBANCES LIFT ACROSS THE REGION. WHILE CONVECTIVE COVERAGE AND INTENSITY WILL DWINDLE OVERNIGHT...ISOLATED TO SCATTERED SHOWERS AND T-STORMS WILL STILL OCCUR WELL PAST MIDNIGHT. THE CONVECTIVE ACTIVITY IS EXPECTED TO REACH ITS PEAK COVERAGE THURSDAY AFTERNOON AND EVENING WHEN SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE NUMEROUS. BETTER AVIATION CONDITIONS ANTICIPATED FRIDAY THROUGH SATURDAY AS A SLIGHTLY DRIER MORE STABLE AIR MASS ENCOMPASSES MOST OF THE REGION. SCATTERED AFTERNOON-EARLY EVENING CONVECTION WILL STILL BE PROBABLE IN VICINITY OF KFAY AND KRWI WHERE AVAILABLE MOISTURE AND LOW LEVEL INSTABILITY WILL BE BEST. BY SUNDAY...REMNANTS OF DECAYING THUNDERSTORM COMPLEXES ORIGINATING IN THE MIDWEST MAY BEGIN TO AFFECT CENTRAL NC...LEADING TO A BETTER CHANCE FOR SCATTERED CONVECTION AND ASSOCIATED MVFR CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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