Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 040655 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 255 AM EDT SAT JUL 4 2015 .SYNOPSIS... A SERIES OF DISTURBANCES ALOFT WILL MOVE OVERHEAD AND INTERACT WITH A FRONTAL ZONE THAT WILL WAVER ACROSS VA AND NC THROUGH THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 PM FRIDAY... AFTERNOON/EVENING CONVECTION HAS BEEN RATHER BENIGN AS EXTENSIVE CLOUD COVER EARLIER TODAY KEPT TEMPERATURES DOWN...THUS LIMITING THE AMOUNT OF INSTABILITY. A SHORT WAVE LIFTING NORTHEAST TOWARDS THE MID ATLANTIC COAST IS LARGELY RESPONSIBLE FOR THE AREA OF CONVECTION CURRENTLY EXITING NORTHEASTERN NC. OTHERWISE...ANY REMAINING CONVECTION OVER OUR FORECAST AREA WILL CONTINUE TO WEAKEN AS INSTABILITY WANES EVEN MORE. HOWEVER...WEAK DISTURBANCES ALOFT COUPLED WITH THE MOISTURE RICH AIR MASS MAY SUPPORT A FEW SHOWERS THROUGH THE OVERNIGHT HOURS. OVERNIGHT LOWS WILL BE SIMILAR TO PREVIOUS NIGHTS...GENERALLY UPPER 60S TO LOWER 70S. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 340 PM FRIDAY... POSITIVELY TILTED MID-UPPER LEVEL TROUGH WILL REMAIN IN PLACE TO OUR WEST-NW WITH MINOR PERTURBATIONS LIFTING NEWD IN THE SW FLOW ALOFT. BULK OF THIS ENERGY WILL PASS TO OUR WEST-NW. WITH AFTERNOON HEATING...LOW LEVEL ATMOSPHERE SHOULD BECOME MODERATELY UNSTABLE...AND WITH AVAILABLE MOISTURE... GENERATE SCATTERED THUNDERSTORMS...MAINLY ACROSS THE NORTHERN PIEDMONT...BETWEEN 22Z- 03Z. LOW-MID LEVEL WIND STRENGTH OF 30-40KTS WILL CREATE DECENT SHEAR WITH STRAIGHT-LINE HODOGRAPHS HIGHLY PROBABLE. THIS SUGGEST BROKEN BANDS OF CONVECTION RATHER THAN SUPERCELLULAR STRUCTURE. STILL COULD SEE A STRONG/LOCALLY DAMAGING WINDS AND MARGINALLY LARGE HAIL (SIZE OF A QUARTER OR LESS) WITH THE STRONGER STORMS. PARTIAL-MOSTLY SUNNY SKIES THROUGH MID AFTERNOON SHOULD WARM TEMPS WELL INTO THE 80S TO AROUND 90. THE EXCEPTION WILL BE THE NW PIEDMONT WHERE CLOUDS MAY BE PROMINENT...HOLDING MAX TEMPS IN THE MID 80S. SIMILAR TO TONIGHT...EXPECT MAJORITY OF THE SHOWERS/STORMS TO DISSIPATE AROUND MIDNIGHT WITH A FEW SHOWERS PROBABLE WELL INTO THE NIGHT. MIN TEMPS 68-73. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 225 PM FRIDAY... A CLOSED MID-LEVEL LOW WILL DRIFT NNE ACROSS THE SOUTHERN AND CENTRAL APPALACHIANS ON SUNDAY...WHILE A SFC BOUNDARY REMAINS ALONG THE NC/VA BORDER. AS THE CLOSED LOW LIFTS TO THE N...SO WILL THE SFC BOUNDARY...MOVING N INTO VA SUNDAY NIGHT. AS SUCH...THE BEST CHANCE FOR RAIN AND GREATEST COVERAGE OF SHOWERS/TSTMS DURING THE DAY SUNDAY WILL BE INVOF OF THE BOUNDARY...BASICALLY AREAS N OF HWY 64. FORECAST SOUNDINGS SHOW MODEST CAPE AND SHEAR...WITH INSTABILITY LIMITED BY EXTENSIVE CLOUD COVERAGE. BUT WITH HIGH PWAT (>1.75") AND RELATIVELY SLOW STORM MOTION...WILL HAVE TO KEEP A CLOSE WATCH ON LOCALIZED FLOOD POTENTIAL. ON MONDAY...THE SFC BOUNDARY WILL BE WELL TO OUR NORTH. MODELS SHOW THAT A MID LEVEL DISTURBANCE ROTATING AROUND THE AFOREMENTIONED CLOSED LOW WILL MOVE UP FROM THE SOUTH AND CROSS THE EASTERN HALF OF THE STATE DURING THE AFTERNOON. WITH THIS BEING THE PRIMARY FEATURE OF THE DAY...THE BEST CHANCE FOR RAIN IS EXPECTED ACROSS LOCATIONS FROM THE COASTAL PLAIN AND EASTWARD...WITH PERHAPS MOST OF OUR CWA WEST OF I-95 REMAINING DRY. FOR TUESDAY THROUGH FRIDAY...ALL INDICATIONS AT THIS POINT SUGGEST THE SUB-TROPICAL RIDGE WILL BECOME ESTABLISHED OVER THE CAROLINAS AND SOUTHEAST IN THE WAKE OF THE AFOREMENTIONED CLOSED LOW GETTING ABSORBED INTO THE WESTERLY FLOW TO OUR NORTH. THIS PATTERN SHOULD KEEP THE DEEPEST MOISTURE...BEST SYNOPTIC SCALE FORCING...AND BEST CHANCE FOR RAIN MAINLY TO OUR NORTH. BUT THIS TIME OF YEAR... ISOLATED SHOWERS/TSTMS CAN NEVER BE RULED OUT...ESP INVOF OF THE PIEDMONT TROUGH AND TO OUR EAST INVOF THE SEA BREEZE...SO WILL MAINTAIN NEAR-CLIMO POPS FOR WIDELY SCATTERED MAINLY-DIURNAL SHOWERS/TSTMS ACROSS OUR AREA EACH DAY. AS FOR TEMPS DURING THE LONG TERM...NEAR-NORMAL TEMPS SUNDAY AND MONDAY WILL GRADUALLY WARM TO A DEGREE OR SO ABOVE NORMAL BY MID- WEEK AS THE SUBTROPICAL RIDGE SETS UP OVER THE CAROLINAS. NORMAL HIGHS ARE UPPER 80S TO AROUND 90...AND NORMAL LOWS IN THE UPPER 60S. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 250 AM SATURDAY... THE THREAT OF IFR-MVFR CEILINGS WILL CONTINUE IN THE VICINITY AND ESPECIALLY NORTH OF A FRONTAL ZONE DRAPED NEAR THE VA/NC BORDER THIS MORNING...WHILE THE PROBABILITY OF VFR CONDITIONS WILL INCREASE WITH SOUTHERN EXTENT FROM THE FRONT (IE. TOWARD KFAY). MEANWHILE...A SERIES OF DISTURBANCES OVER THE NORTHERN GULF COAST STATES TODAY WILL TRACK ENE ACROSS THE CAROLINAS THROUGH THIS EVENING...WITH AN ASSOCIATED CONVECTIVE CLUSTER PROBABLY ACCOMPANYING EACH...THE FIRST OF WHICH MAY AFFECT FAY/RDU/RWI BETWEEN 16-21Z BASED ON EXTRAPOLATION OF PAST MOVEMENT. STABILIZING EFFECTS OF EACH PASSING CLUSTER OF STORM SUGGESTS MUCH LOWER PREDICTABILITY WITH ANY SUBSEQUENT DISTURBANCE AND STORM CLUSTER FROM MID AFTERNOON ONWARD. OTHERWISE...A RELATIVELY STRONG PRESSURE GRADIENT BETWEEN LOW PRESSURE MOVING ACROSS THE DELMARVA AND HIGH PRESSURE ALONG THE GULF COAST WILL RESULT IN THE DEVELOPMENT OF BREEZY CONDITIONS BY 14- 15Z...AS SOUTHWEST WINDS STRENGTHEN INTO THE 10-20 KT RANGE WITH GUSTS IN THE 20S KTS - HIGHEST AT FAY AND RWI. OUTLOOK: THE FRONT WILL DRIFT SOUTH INTO NC LATE TONIGHT AND EARLY SUN. STRATUS WILL AGAIN BE POSSIBLE NEAR AND ESPECIALLY NORTH OF THE FRONT...NEAR AND MORE LIKELY JUST NORTH OF NORTHERN CENTRAL NC TAF SITES SUN MORNING. OTHERWISE...AN ABOVE AVERAGE PROBABILITY OF SHOWERS AND STORMS AND ASSOCIATED SUB-VFR CONDITIONS WILL ACCOMPANY THE APPROACH/PASSAGE OF AN UPPER LOW THROUGH THE SOUTHERN AND CENTRAL APPALACHIANS SUN-MON...BEFORE A RETURN TO MORE TYPICAL SUMMERTIME CONDITIONS FOR THE MIDDLE OF THE UPCOMING WEEK. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...KRD SHORT TERM...WSS LONG TERM...RAH AVIATION...26

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