Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211156 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 756 AM EDT SUN SEP 21 2014 .SYNOPSIS...A COLD FRONT WILL APPROACH THE MOUNTAINS FROM THE WEST TODAY...AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST OFFSHORE THE CAROLINA COAST. HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH THROUGH MID-WEEK...IN THE WAKE OF A COLD FRONTAL PASSAGE MONDAY MORNING. && .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 300 AM SUNDAY... DRY/SUBSIDENT CONDITIONS WILL PREVAIL TODAY AS AN UPPER LEVEL LOW AND ATTENDANT SFC LOW PRESSURE SYSTEM TRACK NORTHEAST OFFSHORE THE CAROLINA COAST. POTENT SHORTWAVE ENERGY DIGGING THROUGH THE GREAT LAKES INTO THE OH VALLEY WILL PROPEL A COLD FRONT EAST TOWARD THE APPALACHIANS TODAY...WITH FROPA OCCURRING MID/LATE MONDAY MORNING IN CENTRAL NC AS THE AFOREMENTIONED SHORTWAVE ENERGY TRACKS ACROSS THE NORTHERN MID-ATLANTIC. POOR DIURNAL TIMING WILL LIKELY RULE MUCH IN THE WAY OF CONVECTION ALONG/AHEAD OF THE FRONT AT THIS LATITUDE... WITH CONVECTION MORE LIKELY TO ACCOMPANY THE FRONT FURTHER NORTH IN VA AND THE DELMARVA IN CLOSER VICINITY TO THE MORE VIGOROUS DPVA ASSOC/W THE AFOREMENTIONED SHORTWAVE. WILL KEEP THE FCST DRY THROUGH TONIGHT EVERYWHERE EXCEPT THE FAR N/NW PIEDMONT LATE THIS EVENING AND EARLY TONIGHT (22-05Z) WHEN ISOLD SHOWERS CANNOT BE RULED OUT. WARM ADVECTION FROM THE WEST THROUGHOUT THE DAY WILL RESULT IN WARMER TEMPS THAN IN PREVIOUS DAYS WITH HIGHS IN THE MID/UPPER 80S. TEMPS TONIGHT ARE EXPECTED TO FALL NO LOWER THAN THE MID/UPPER 60S (64-68F) IN MOST LOCATIONS GIVEN FROPA WILL OCCUR TOMORROW MORNING...THOUGH THE GFS IS NOTICEABLY FASTER WITH COLD ADVECTION IN THE WAKE OF THE FRONT IN COMPARISON TO THE NAM...SHOWING TEMPS AT INT/GSO FALLING INTO THE 50S PRIOR TO 12Z MON. GIVEN THAT THE GFS/NAM SHOW VIRTUALLY THE SAME PATTERN AND THAT COLD ADVECTION TYPICALLY LAGS FROPA DOWNSTREAM OF THE SOUTHERN APPALACHIANS...WILL TREND TOWARD THE NAM WITH LOWS IN THE MID/UPPER 60S. -VINCENT
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&& .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 300 AM SUNDAY... THE COLD FRONT WILL CROSS CENTRAL NC MONDAY MORNING...TEMPORARILY STALLING OVER THE COASTAL CAROLINAS MONDAY AFTERNOON AS STRONG HEIGHT FALLS /DPVA/ OVERSPREAD THE REGION IN ADVANCE OF POTENT SHORTWAVE ENERGY DIGGING ESE THROUGH THE TN VALLEY INTO THE CAROLINAS BY 00Z TUE. THOUGH COLD ADVECTION WILL BE PRESENT IN THE WAKE OF THE FRONT DURING THE DAY MON (ESP NW PIEDMONT)...THE STRONGEST COLD ADVECTION WILL NOT OCCUR IN EARNEST UNTIL MON EVENING (00-06Z TUE) WHEN STRONG SUBSIDENCE ENSUES IN THE WAKE OF THE AFOREMENTIONED SHORTWAVE AND HIGH PRESSURE BUILDS RAPIDLY SOUTHWARD INTO THE CAROLINAS. WITH THE FRONT EXPECTED TO TEMPORARILY STALL EAST OF CENTRAL NC PRIOR TO THE ONSET OF THE STRONGER CAA...EXPECT DRY CONDITIONS TO PREVAIL. HIGHS ARE EXPECTED TO RANGE FROM THE MID 70S NW TO LOWER 80S E/SE...WITH RELATIVELY CHILLY LOWS RANGING FROM THE UPPER 40S N/NW TO LOWER/MID 50S SE TUE MORNING. -VINCENT && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 323 AM SUNDAY... STRONG HIGH PRESSURE LOCATED OVER THE NEW ENGLAND STATES TUE AND WED WILL EXTEND DEEP INTO THE SE STATES. THE EVOLUTION OF A SMALL SCALE MID/UPPER LOW (AND CORRESPONDING COASTAL SURFACE TROUGH) SHOULD DETERMINE THE EXTENT OF COOLNESS AND POTENTIALLY WETNESS BEYOND WED. FORECAST CONFIDENCE CONTINUES LOW IN THE MIDDLE/END OF THE WEEK AS THERE CONTINUES TO BE DISAGREEMENT AMONG THE MODELS. A GIVEN WILL BE THAT THE LOW LEVEL FLOW AROUND THE HIGH WILL INCREASE AND BECOME INCREASING OFF THE ATLANTIC INTO OUR REGION WITH TIME WED-THU... INCREASING THE LOW LEVEL MOISTURE. JUST HOW MUCH DEEP MOISTURE CAN BE PULLED INTO THE REGION FOR THE PRODUCTION OF RAIN SHOULD BE DETERMINED BY THE CURRENT LOW PREDICTABILITY OF A POTENTIAL WEAKNESS IN THE MID/UPPER LEVELS LATER IN THE WEEK. THE GFS CONTINUES TO BE THE MOST SUPPRESSED SOLUTION AND THE EC WITH THE EC ENSEMBLES REMAINING THE FARTHEST NORTH AND NORTHWEST WITH THE DEEP MOISTURE INFLUX... COURTESY OF A WEAKNESS OVER THE SOUTHERN APPALACHIANS. BOTTOM LINE... EXPECT COOL AND DRY CONDITIONS TUE-WED... THEN INCREASING CLOUDS AND COOL THU-FRI. DAILY TEMPS SHOULD AVERAGE 5-10 DEGREES BELOW NORMAL BY WED-THU... AND EVEN COOLER IF THE EC VERIFIES WITH RAINY CONDITIONS THEN. THE WEEKEND CURRENTLY IS A TOSS UP - WITH THE LOW PREDICTABILITY OF THE POTENTIAL SYSTEM LATE IN THE WEEK. WE WILL KEEP THE SATURDAY FORECAST MOSTLY CLOUDY WITH LESS THAN 20 POP UNTIL SOME MODEL AGREEMENT IS ACHIEVED. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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AS OF 755 AM SUNDAY... 24-HR TAF PERIOD: VFR CONDITIONS WILL RULE THROUGH THE TAF PERIOD AS A COASTAL LOW PRESSURE SYSTEM TRACKS OFFSHORE THE CAROLINA COAST. NW WINDS AT 5 KT WILL BECOME WESTERLY AT 10-15 KT BY 15-18Z...THEN SOUTHWESTERLY AT ~10 KT BETWEEN 18-22Z AS A PRE-FRONTAL TROUGH SHARPENS OVER THE CAROLINAS/VA IN ADVANCE OF A COLD FRONT APPROACHING THE MOUNTAINS FROM THE WEST. ISOLD SHOWERS CANNOT BE RULED OUT AT THE INT/GSO TERMINALS...THOUGH PROBABILITIES ARE TOO LOW TO INCLUDE MENTION IN THE 12Z TAF ISSUANCE. WINDS WILL VEER TO THE NORTHWEST TONIGHT AND EARLY MONDAY MORNING IN THE WAKE OF THE FRONTAL PASSAGE. LOOKING AHEAD: EXPECT VFR CONDITIONS TO PREVAIL THROUGH MID-WEEK AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH IN THE WAKE OF A DRY COLD FRONTAL PASSAGE MONDAY MORNING. -VINCENT
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...PWB AVIATION...VINCENT

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