Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221759 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 155 PM EDT FRI AUG 22 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL DIVE SOUTHEAST INTO OUR REGION FROM THE OHIO VALLEY AND MIDWEST. A BACK-DOOR COLD WILL SETTLE SLOWLY SOUTH THROUGH THE AREA ON SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1025 AM FRIDAY... PERTURBED NORTHWESTERLY FLOW CONTINUES OVER THE REGION TODAY BETWEEN A MID-LEVEL RIDGE OVER THE DEEP SOUTH AND A TROUGH OVER THE NORTHEAST. A LEAD...DECAYING DISTURBANCE CROSSING WV HS AIDING AN AREA OF MOSTLY LIGHT SHOWERS NOW OVER SOUTHWESTERN VA. AHEAD OF THIS FEATURE...AMPLE SUNSHINE OVER CENTRAL NC WILL ALLOW TEMPS TO RISE INTO THE LOW TO MID 90S...BASED ON H85 TEMPS OF 19-20C PER REGIONAL RAOBS. DEWPOINTS SHOULD AGAIN MIX OUT INTO THE MID/UPPER 60S...ESPECIALLY ACROSS THE SOUTHWESTERN AND WESTERN AREAS WHERE 925MB DEWPOINTS ARE AT A RELATIVE MIN. MLCAPE VALUES AREA FORECAST TO RANGE FROM 1000 J/KG IN THE WEST TO NEAR 2000 J/KG IN THE EAST. A BELT OF STRONGER NORTHWESTERLY MID-LEVEL FLOW WILL SHIFT SOUTHEAST ACROSS VA AND THE NORTHERN PORTIONS OF NC AS A SPEED MAX CROSSES THE CENTRAL APPALACHIANS. EFFECTIVE BULK SHEAR SHOULD REACH AROUND 25- 30 KTS NORTHEAST OF THE TRIANGLE THIS AFTERNOON AND EVENING...WHICH COMBINED WITH MODERATE INSTABILITY WILL SUPPORT THE POTENTIAL FOR SOME STRONG MULTI-CELL CLUSTERS. THE BIGGEST UNCERTAINTY CONTINUES TO BE WITH CONVECTIVE INITIATION AHEAD OF THE DISTURBANCE. IF THE SHOWERS AHEAD OF THE DISTURBANCE HOLD TOGETHER INTO THE NORTHERN PIEDMONT IN THE NEXT 2-3 HOURS...THEY MAY LIMIT DESTABILIZATION. HOWEVER... WITH TIME EXPECT ADDITIONAL STORMS TO POPS UP AND PROPAGATE TOWARD THE SOUTH-SOUTHEAST TOWARD WHAT SHOULD BE MODEST DCAPE ACROSS THE SOUTHERN TIER...FURTHER ENHANCING THE THREAT OF SOME DAMAGING WIND GUSTS. LINGERING SFC OUTFLOW AND SURFACE FRONT DROPPING SOUTH INTO THE AREA WILL SUPPORT SMALL TO SLIGHT POPS OVERNIGHT. LOWS IN THE UPPER 60S NE TO LOWER 70S SE. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 320 AM FRIDAY... SATURDAY AND SATURDAY NIGHT: HIGH PRESSURE OVER NEW ENGLAND WILL BEGIN TO RIDGE SOUTH DOWN THE MID-ATLANTIC SEABOARD WHICH SHOULD PUSH THE BACK-DOOR FRONT SLOWLY SOUTH INTO THE AREA ON SATURDAY. AS USUAL...TIMING OF THESE BACK-DOOR FRONTS THIS TIME OF YEAR IS SUSPECT(USUALLY SLOWER IS BETTER)...WITH DIURNAL HEATING AND RESULTANT DESTABILIZATION AIDING IN SCATTERED COVERAGE. THE LATE ARRIVAL OF A SHORTWAVE TROUGH ROTATING SOUTHWARD DOWN THE BACK-SIDE OF THE UPPER TROUGH SATURDAY NIGHT MAY EVEN SUPPORT A FEW ANAFRONTAL SHOWERS OVERNIGHT. COOLER ON SATURDAY WITH CLOUDS AND NELY FLOW NORTH OF THE FRONT. HIGHS RANGING FROM LOWER/MID 80S NORTH TO LOWER 90S SOUTH. LOWS SATURDAY NIGHT IN THE UPPER 60S TO LOWER 70S. SUNDAY AND SUNDAY NIGHT: AS THE UPPER AIR PATTERN AMPLIFIES (RIDGE BUILDING OVER THE MISSISSIPPI RIVER VALLEY...TROUGH DEEPENING ACROSS THE WESTERN ATLANTIC) ON SUNDAY...CENTRAL NC WILL BE UNDER NORTHWEST/NORTHERLY FLOW ALOFT. AT THE SURFACE...A COLD FRONT WILL BE SHUNTED SOUTH OF THE REGION AS HIGH PRESSURE BEGINS TO RIDGE DOWN FROM THE NORTHEAST. AS THIS OCCURS...DRIER AIR WILL FILTER INTO THE REGION THROUGHOUT THE DAY...BUT SOME DEEP MOISTURE WILL REMAIN IN PLACE...MOSTLY ACROSS THE SOUTH AND WEST WHERE PWAT VALUES ARE PROGGED TO HOVER BETWEEN 1.5-1.75 INCHES THROUGH SUNDAY NIGHT. GIVEN THIS AND THE LINGERING FRONT...AND THE POSSIBILITY OF ANY WEAK DISTURBANCES MOVING OVER THE AREA WITHIN THE NORTHWESTERLY FLOW ALOFT...WILL MAINTAIN SLIGHT CHANCE TO CHANCE POPS...HIGHEST ACROSS THE SOUTH AND WEST. IN FACT...NORTHEASTERN PORTIONS OF THE FORECAST AREA MAY STAY DRY. TEMPS WILL RANGE FROM NEAR 80 DEGREES TO THE MID 80S...WITH OVERNIGHT LOWS GENERALLY IN THE MID 60S. && .LONG TERM /SUNDAY THROUGH FRIDAY/...
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AS OF 1250 PM FRIDAY... AN AMPLIFIED UPPER PATTERN WILL PERSIST THROUGH EARLY NEXT WEEK... WITH AN UPPER RIDGE GRADUALLY BUILDING EAST TOWARDS THE REGION. A COLD FRONT WILL BE SUPPRESSED SOUTH OF THE AREA BY LATE SUNDAY AS DRY AND COOLER SURFACE HIGH PRESSURE BECOMES FIRMLY ENTRENCHED DOWN THE ATLANTIC COAST. THERE WILL BE A LINGERING CHANCE OF SHOWERS SUNDAY AS THE FRONT SURGES SOUTH...FOLLOWED BY DRY CONDITIONS THROUGH THURSDAY. THE UPPER RIDGE WILL DEAMPLIFY/FLATTEN OUT AS THE NEXT UPPER TROUGH AND ASSOCIATED SURFACE FRONT APPROACHES THE AREA LATE THURSDAY INTO FRIDAY...BRINGING INCREASING PRECIPITATION CHANCES BY THE END OF THE WEEK. POST FRONTAL CONDITIONS WILL BE PLEASANT...WITH CONSIDERABLY COOLER TEMPERATURES AND LOWER HUMIDITY. LOW LEVEL THICKNESS VALUES WILL FALL THROUGH EARLY NEXT WEEK...TO THE TUNE OF 30 METERS EQUATING TO AROUND A 10 DEGREE COOL OFF. HIGHS SUNDAY THROUGH TUESDAY WILL BE WELL BELOW...5-7 DEGREES...NORMAL WITH UPPER 70S TO LOWER 80S OVER ALL BUT THE FAR SOUTHERN TIER WHICH MAY SEE MID 80S. TEMPS WILL BEGIN TO MODERATE WEDNESDAY THROUGH FRIDAY AS THE UPPER RIDGE SHIFTS EAST... WITH MID/UPPER 80S EXPECTED BY THE END OF THE WEEK. OVERNIGHT LOWS WILL FOLLOW THE SAME PATTERN...WITH MOSTLY LOW TO MID 60S EARLY NEXT WEEK WARMING TO MID AND UPPER 60S BY LATE WEEK.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 155 PM FRIDAY... VFR CONDITIONS ACROSS CENTRAL NC THIS AFTERNOON. SHOWERS AND STORMS STREAMING ACROSS WV AND VA IN NORTHWEST FLOW ALOFT SHOULD EVENTUALLY MOVE INTO THE NORTHERN AND NORTH EASTERN PORTIONS OF NC THIS AFTERNOON AND EVENING. WHILE A SHOWER OR STORMS CANNOT BE RULED OUT AT ANY SITE...PROBABILITIES ARE HIGHEST AT KRDU AND KRWI AFTER 20Z. LATER TONIGHT...A WEAK BOUNDARY IS FORECAST TO SURGE INTO NC FROM THE NORTH...AHEAD OF A COLD FRONT SET TO MOVE INTO THE AREA ON SATURDAY NIGHT. NORTHEASTERLY WIND BEHIND THE BOUNDARY SHOULD LEAD TO SOME LOW CLOUDS...MAINLY NORTH AND EAST OF KRDU...THOUGH IT ISNT CLEAR FROM GUIDANCE HOW WIDESPREAD ANY STRATUS WOULD BE. MOSTLY VFR CONDITIONS AND A CONTINUED CHANCE OF SHOWERS/STORMS ARE EXPECTED DURING THE DAY ON SATURDAY. OUTLOOK... A COLD FRONT WILL PUSH INTO NC FROM THE NORTHEAST ON SATURDAY NIGHT...WITH WIDESPREAD LOW CEILINGS EXPECTED BEHIND THE FRONT ON SUNDAY MORNING. A DRYING TREND WILL ENSUE HEADING INTO NEXT WEEK AS HIGH PRESSURE BUILDS INTO THE AREA BEHIND THE FRONT.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL/BLS SHORT TERM...CBL/KRD LONG TERM...MLM AVIATION...BLS

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