Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221851 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 250 PM EDT FRI AUG 22 2014 .SYNOPSIS...UPPER LEVEL DISTURBANCES WILL CONTINUE TO MOVE SOUTHEAST ACROSS THE REGION THROUGH THE EARLY PART OF THE WEEKEND. A COLD FRONT WILL MOVE SOUTH THROUGH MUCH OF THE CAROLINAS BY SUNDAY MORNING. HIGH PRESSURE WILL THEN SOUTH BEHIND THE FRONT AT LEAST FOR THE EARLY PART OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 250 PM FRIDAY... PERTURBED NORTHWESTERLY FLOW CONTINUES OVER THE REGION TODAY BETWEEN A MID-LEVEL RIDGE OVER THE DEEP SOUTH AND A TROUGH OVER THE NORTHEAST. THE COUPLE OF DISTURBANCES MOVING IN FROM THE NORTHWEST APPEAR TO HAVE WEAKENED CONSIDERABLY TODAY AND ALL OF THE ASSOCIATED SHOWERS HAVE ESSENTIALLY DISSIPATED BEFORE CROSSING THE NC/VA BORDER. CLOUDS HAVE BEEN INCREASING ACROSS THE NORTH SINCE LATE MORNING...BUT STRONG HEATING HAS STILL RESULTED IN MLCAPE OF 1000-2000 J/KG. WINDS OVER THE AREA ARE RELATIVELY WEAK...WITH SLIGHTLY HIGHER SHEAR ACROSS THE NORTHERN COASTAL PLAIN AS A NORTHWESTERLY SPEED MAX CROSSES THE CENTRAL APPALACHIANS. OUTSIDE OF WEAK DISTURBANCES ALOFT...MUCH OF THE AREA IS VOID OF ANY STRONG FORCING. ANY AREA OF CONVECTION CURRENTLY OVER WV MAY BRING A BETTER CHANCE OF SHOWERS/STORMS LATER THIS EVENING...SO WILL CONTINUE POPS INTO THE OVERNIGHT HOURS BEFORE TRENDING DOWN AFTER MIDNIGHT. IF CONVECTION CAN GET GOING...ESPECIALLY BY EARLY EVENING...DCAPE WILL BE FAIRLY HIGH ACROSS THE SOUTHERN HALF OF THE AREA WHERE BETTER MIXING HAS TAKEN PLACE AND A WIND THREAT MAY STILL EXIST. LOWS TONIGHT IN THE LOWER 70S WITH THE POTENTIAL FOR SOME STRATUS ON THE NORTHEAST AS A WEAK BOUNDARY SLIPS INTO THER AREA FROM THE NORTHEAST. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 220 PM FRIDAY... A WEAK BOUNDARY...POTENTIALLY OUTFLOW INDUCED...FORECAST TO MOVE INTO THE AREA TONIGHT WILL SETTLE ACROSS THE SOUTHERN PORTIONS OF THE AREA...WHILE THE TRUE COLD FRONT REMAINS TO OUR NORTHEAST. AHEAD OF THE FRONT...H85 TEMPS REMAIN ABOVE 18C...THOUGH MIXING SHOULD STOP SHORT OF THAT LEVEL WITH PW NEAR 2 INCHES. PERIODS OF HIGH CLOUDS IN NORTHWEST FLOW ALOFT SHOULD ALSO TEMPER HIGHS A BIT...ESPECIALLY ACROSS THE NORTHEAST AS THE FRONT BEGINS TO PUSH INTO THE AREA LATE IN THE DAY. COOLER GUIDANCE GIVES A WIDE RANGE OF TEMPS FROM LOWER 90S SOUTHWEST TO MID 80S NORTHEAST. DUE TO THIS...INSTABILITY WILL BE GREATEST ACROSS THE SOUTHEAST...WITH MARGINALLY STRONGER SHEAR BACK TO THE NORTHEASTER CLOSER TO THE FRONTAL ZONE. THERE IS STILL THE POTENTIAL FOR ANOTHER DISTURBANCE TO APPROACH FROM THE NORTHEAST...WHICH COMBINED WITH INCREASINGLY CONVERGENT LOW LEVEL FLOW AND HIGH PW...SHOULD LEAD TO A BETTER CHANCE OF SHOWERS AREAWIDE. THE BACKDOOR COLD FRONT WILL MAKE ITS WAY INTO THE AREA LATE SATURDAY AND OVERNIGHT...WITH DRYING ALOFT BEHIND THE FRONT ZONE. MOIST NORTHEASTERLY FLOW WILL LIKELY LEAD TO FAIRLY WIDESPREAD STRATUS...AND POSSIBLY A FEW LIGHT SHOWERS AS A SHORTWAVE ROTATES SOUTH ACROSS THE AREA. LOWS WILL BE IN THE UPPER 60S NORTHEAST TO LOWER 70S SOUTHWEST. 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/... 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. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... 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. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF/BLS NEAR TERM...BLS SHORT TERM...BLS LONG TERM...MLM AVIATION...BLS

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