Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250123 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 922 PM EDT SUN AUG 24 2014 .SYNOPSIS...SURFACE HIGH PRESSURE CENTERED OVER THE MID-ATLANTIC WILL EXTEND SOUTHWARD INTO THE CAROLINAS THROUGH MID-WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 922 PM SUNDAY... MAIN ISSUES FOR THE OVERNIGHT INCLUDE LINGERING CLOUDINESS... SURFACE MIXING... AND THE AFFECTS ON AREA TEMPERATURES. THE LATEST DATA ANALYSIS INDICATED THE SURFACE HIGH PRESSURE CONTINUED TO BUILD SOUTH AND WEST ACROSS OUR REGION FROM THE NORTHEASTERN STATES. THE CENTER OF THE HIGH (1022 MB) WAS LOCATED OVER NY/PA. THE MAIN COLD FRONT HAD SETTLED ALL THE WAY SOUTHWARD INTO SOUTHERN SOUTH CAROLINA AND GEORGIA (UNUSUAL FOR LATE AUGUST). MUCH DRIER AIR WAS ASSOCIATED WITH THE HIGH PRESSURE OVER THE MID- ATLANTIC STATES ADVECTING SOUTH AND WEST INTO EASTERN VA AND EASTERN NC (PER THE LATEST SATELLITE DATA). THE LATEST RAOBS FROM WALLOPS ISLAND... PITTSBURGH... AND MOREHEAD CITY ALL INDICATE SIGNIFICANT DRYING MOST NOTABLY IN THE MID LAYERS EXTENDING DOWN THE SURFACE OVER PA/VA. HOWEVER... THE NC RAOBS CONTINUED TO INDICATE AN INVERSION (STRONGEST OVER THE WESTERN SECTIONS) AT 4500 TO 5500 FEET AGL. ALTHOUGH MOISTURE WAS DECREASING FROM THE TOP DOWN AND FROM SURFACE DRY AIR ADVECTION FROM THE NE... IT WILL TAKE SEVERAL MORE HOURS TO SCOUR OUT ALL THE LEFT OVER MOISTURE OVER THE WESTERN HALF OF CENTRAL NC. IN FACT... IT MAY TAKE UNTIL AFTER SUNRISE MONDAY BEFORE THE SKIES CLEAR OVER THE TRIAD REGION. EVEN THROUGH THE SKIES HAVE CLEARED NEAR THE COAST INLAND TO NEAR THE RDU TO FAY AREAS... SOME MODELS INDICATE THE DEVELOPED OF AT LEAST PATCHY TO BROKEN LAYERS OF LOW STRATUS LATER TONIGHT AND EARLY MONDAY INTO THE COASTAL PLAIN. THE NE SURFACE WINDS ALSO HAVE BEEN 5-12 MPH THROUGH MID-EVENING. THIS HAS KEPT THE BOUNDARY LAYER WELL MIXED. THIS MIXING AND THE LINGERING CLOUDS HAVE KEPT THE TEMPERATURES FROM DROPPING OVER THE PIEDMONT AND FOOTHILLS. WE WILL RAISE LOWS A FEW DEGREES FROM THE PREVIOUS FORECAST... FORECASTING LOWER TO MID 60S OVER THE WESTERN PIEDMONT WHERE THE CLOUDINESS AND SOME MIXING WILL BE AROUND MUCH OF THE NIGHT. LOWS OVER THE COASTAL PLAIN SHOULD DIP INTO THE UPPER 50S AS FAR SOUTH AS NEAR GOLDSBORO... A REAL TREAT FOR THE LAST WEEK OF AUGUST OF ANY YEAR. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 255 PM SUNDAY... A RIDGE OF HIGH PRESSURE ALOFT WILL EXTEND INTO THE OH VALLEY AND SOUTHERN APPALACHIANS ON MONDAY AND MONDAY NIGHT WHILE SURFACE HIGH PRESSURE CENTERED OVER NY/PA EXTENDS INTO THE CAROLINAS. PARTLY TO MOSTLY SUNNY SKIES ARE EXPECTED ON MONDAY AS ANOTHER BUT LESS PRONOUNCED ROUND OF STRATO CUMULUS IS EXPECTED. THE GREATEST CLOUD COVERAGE SHOULD BE CONFINED TO THE COASTAL PLAIN. MOST OF THESE CLOUDS SHOULD DISSIPATE MONDAY EVENING RESULTING IN MAINLY CLEAR SKIES WITH A FEW MORE CLOUDS PERSISTING IN THE COASTAL PLAIN WHERE A NORTHEAST FLOW WILL PROVIDE SOME ENHANCED MOISTURE. NORTHEAST WINDS ON MONDAY WILL RANGE BETWEEN 8-12 MPH WITH GUSTS OF 14-18 MPH. THE COOL AIR MASS SHOULD SUPPORT HIGHS ONLY IN THE 80-85 RANGE WITH OVERNIGHT LOWS WITHIN A FEW DEGREES OF 60. -BLAES FOR TUE/TUE NIGHT: ANOTHER QUIET/DRY/STABLE DAY. SURFACE HIGH PRESSURE RIDGING WILL BE CENTERED TO OUR NE BUT EXTEND STRONGLY SW THROUGH CENTRAL NC... WHILE ALOFT... STRONG RIDGING CENTERED TO OUR WEST WILL EXPAND EASTWARD. MODELS PREDICT CONTINUED VERY LOW PRECIP WATER (NEAR 2 STANDARD DEVIATIONS BELOW NORMAL)... AND BUFR FORECAST SOUNDINGS SHOW DRY AND STABLE MID LEVELS. MAY SEE AREAS OF LOW STRATUS IN THE HOURS AROUND SUNRISE... AS WELL AS A FEW HIGH CLOUDS... BUT OTHERWISE EXPECT ABUNDANT SUNSHINE. A DRY ADIABATIC LOW LEVEL PROFILE SUGGESTS HIGHS IN THE MID 80S... IN LINE WITH STATISTICAL GUIDANCE. A FEW HIGH CLOUDS TUE NIGHT... BUT OTHERWISE CLEAR SKIES ARE ANTICIPATED TUE NIGHT WITH THE SURFACE RIDGE ON TOP OF THE REGION. COOL LOWS OF 58-63. -GIH && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 255 PM SUNDAY... FOR WED/WED NIGHT: MORE QUIET WEATHER IS EXPECTED... ALTHOUGH A CHANGE IN OVERALL PATTERN IS ON THE HORIZON. THE SURFACE HIGH WILL CONTINUE TO WEAKEN AND SHIFT SW... IN RESPONSE TO MID LEVEL TROUGHING DIGGING OVER SE CANADA INTO THE ST LAWRENCE VALLEY... AND THE CORRESPONDING SURFACE COLD FRONT PUSHING SOUTHWARD INTO THE OH VALLEY. MID LEVEL FLOW WILL REMAIN LIGHT BUT INCREASE FROM THE WNW IN RESPONSE TO THE RIDGE SHIFTING TO OUR SOUTH. PW REMAINS WELL BELOW NORMAL WITH STABLE PROFILES NOTED IN FORECAST SOUNDINGS THROUGH WED... ALTHOUGH AN E-W BAND OF HIGHER PW ASSOCIATED WITH THE COLD FRONT APPROACHING FROM THE NORTH WILL SLOWLY PUSH TOWARD NC WED NIGHT. THIS RETURN TO MORE TYPICAL VALUES ESPECIALLY ACROSS NRN NC SHOULD TRANSLATE INTO THICKENING HIGH CLOUDS WED NIGHT... BUT THE COLUMN REMAINS TOO DRY AND STABLE FOR ANY PRECIP. HIGHS AROUND 85-88 AS THICKNESSES START TRENDING BACK UP TO NORMAL VALUES. LOWS 62-66. FOR THU THROUGH SUN: WHAT IS NOW TS CRISTOBAL IS EXPECTED TO MOVE NORTHEASTWARD WELL OFF THE CAROLINA COAST THU/FRI... WITH NO TANGIBLE IMPACT ON CENTRAL NC. THE DIGGING TROUGH TO OUR NORTH SHIFTS EAST AND DEEPENS DOWN THROUGH AND JUST EAST OF THE CANADIAN MARITIMES/NEW ENGLAND... PUSHING THE BACKDOOR FRONT SOUTHWARD INTO NC... MOST LIKELY IN THE THU NIGHT/FRI MORNING TIME FRAME. THE ECMWF/GFS SPREAD JUST LIGHT FRONTAL PRECIP ACROSS MAINLY THE NRN THIRD OF THE CWA DURING THIS TIME WINDOW... AND GIVEN THE LACK OF A GOOD INFLUX OF MOISTURE WITH THIS FEATURE AND WEAK NW FLOW ALOFT... AS WELL AS THE SUB-500 J/KG MUCAPE AND WEAK SHEAR... MINIMIZING THE SHOWER/STORM POTENTIAL WITH FRONTAL PASSAGE LOOKS LIKE A GOOD MOVE. THE PROGRESSIVE PATTERN ACROSS NRN/CENTRAL NOAM SHOULD LEAD TO A SWIFT SHIFT OF THE TROUGH TO OUT OVER THE NRN ATLANTIC... WITH WEAK/BRIEF MID LEVEL RIDGING OVER THE SOUTHEAST. THE SURFACE HIGH TO OUR NORTH (BEHIND THE FRONT) SHOULD CORRESPONDINGLY MOVE TO OUR NE THEN EAST... AND AS A RESULT... EXPECT THE FRONT TO STALL OUT NEAR THE NC/SC BORDER AND UP THROUGH WRN NC OVER THE WEEKEND BEFORE WASHING OUT. MODELS START TO DIFFER QUITE A BIT IN TERMS OF PLACEMENT AND TIMING OF CONVECTION OVER THE WEEKEND. DESPITE THE PRESENCE OF THE FRONTAL ZONE... THIS PATTERN DOESN`T APPEAR CONDUCIVE FOR HIGH COVERAGE OF SHOWERS/STORMS... ALTHOUGH THE WEAK STEERING COULD MEAN ANY STORMS MAY BE SLOW-MOVING. WILL TREND POPS UP TO NEAR-CLIMATOLOGICAL CHANCES BY SAT/SUN... WITH INCREASING THICKNESSES AND HUMIDITY. EXPECT DAILY HIGHS IN THE MID-UPPER 80S... AND LOWS IN THE MID 60S TO AROUND 70. -GIH && .AVIATION /00Z MONDAY THROUGH THURSDAY/... AS OF 700 PM SUNDAY... 24-HR TAF PERIOD: VFR CONDITIONS AND A STEADY NORTHEAST BREEZE SHOULD PREVAIL THROUGH THE TAF PERIOD AS DRY SURFACE HIGH PRESSURE OVER THE MID-ATLANTIC EXTENDS SOUTHWARD INTO THE CAROLINAS. VFR CEILINGS WITH BASES AT 4000-6000 FT WILL PERSIST OVERNIGHT...ALBEIT SCATTERING OUT IN SOME LOCATIONS MONDAY MORNING AS A DRIER H85 AIRMASS ADVECTS INTO THE REGION FROM THE NNE/NE. LOW-LEVEL (H925) MOISTURE ADVECTING INTO EASTERN PORTIONS OF THE STATE MAY RESULT IN A PERIOD OF MVFR CEILINGS AT THE FAY/RWI TERMINALS MONDAY MORNING BETWEEN 12-18Z...THOUGH CONFIDENCE IS TOO LOW TO WARRANT MENTION WITH THE 00Z TAF ISSUANCE. A NORTHEAST BREEZE AT 4-8 KT OVERNIGHT WILL INCREASE TO 10-15 KT DURING THE DAY MONDAY. LOOKING AHEAD: VFR CONDITIONS SHOULD PREVAIL THROUGH MID-WEEK AS SURFACE HIGH PRESSURE OVER THE MID-ATLANTIC CONTINUES TO EXTEND SOUTHWARD INTO THE CAROLINAS AND TROPICAL CYCLONE CRISTOBAL MAINTAINS A HEALTHY DISTANCE OFFSHORE THE SOUTHEAST COAST AS IT TRACKS NORTH OF THE BAHAMAS. SOME POTENTIAL (ALBEIT LOW) FOR CONVECTION WILL BE POSSIBLE BY THE END OF THE WEEK (THU/FRI) IN ASSOC/W NW FLOW ALOFT DOWNSTREAM OF AN APPROACHING UPPER LEVEL RIDGE. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PWB NEAR TERM...PWB SHORT TERM...BLAES/HARTFIELD LONG TERM...HARTFIELD AVIATION...VINCENT

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