Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 012006 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 300 PM EST SUN FEB 1 2015 .SYNOPSIS... A STRONG COLD FRONT WILL APPROACHIN FROM THE WEST TONIGHT AND SWING ACROSS CENTRAL NC ON MONDAY. HIGHS PRESSURE WILL THEN BUILD OVER THE REGION THROUGH MIDWEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 300 PM SUNDAY... HIGH PRESSURE IS NOW OFFSHORE AND SOUTHERLY FLOW IS DRAWING MOISTURE NORTH ACROSS THE SOUTHEAST US AHEAD OF A SURFACE LOW AND A COLD FRONT OVER THE MID/LOWER MISSISSIPPI VALLEY. THE FEW BREAKS IN THE MID LEVEL CLOUD COVER STILL EVIDENT ON VIS IMAGERY OVER THE EASTERN HALF OF NC WILL FILL IN THIS EVENING AS MORE ROBUST DEEP MOISTURE MOVES IN. DESPITE THE OVERCAST... EMPS SHOULD FALL A FEW DEGREES EARLY THIS EVENING...WITH ACTUAL LOWS THE UPPER 40S TO LOWER 50S...BEFORE STRENGTHENING SOUTHERLY PRE-FRONTAL WINDS CAUSE TEMPS TO STARTING INCREASING INTO THE 50S BY MIDNIGHT. MOST GUIDANCE INDICATES WINDS WILL INCREASE TO NEAR 15KT AND GUST TO 20-25KT AFTER MIDNIGHT AS WELL. REGARDING POPS...REGIONAL RADAR SUGGESTS THE MOSTLY LIGHT WARM ADVECTION SHOWERS WELL OUT OF AHEAD OF THE DEVELOPING FRONTAL RAIN BAND ARE A COUPLE HOURS AHEAD OF SCHEDULE (OVER NORTHERN GEORGIA CURRENTLY)... SO WILL UP POPS IN THE WESTERN PIEDMONT IN THE 00-03Z PERIOD. THE WARM ADVECTION IS FORECAST TO WEAKEN WITH EASTWARD EXTENT THIS EVENING...AND WITH THE UPPER TROUGH AND COLD FRONT STILL WEST OF THE MOUNTAINS...THE INITIAL SURGE OF SHOWERS SHOULD ALSO WEAKEN AS IT MOVES INTO THE PIEDMONT. THIS 03-08Z TIME FRAME IS THE MOST UNCERTAIN REGARDING PRECIP COVERAGE. MODELS THEN SHOW THE PRIMARY BAND OF SHOWERS AND EFFECTIVE FRONTAL ZONE MOVING INTO THE WESTERN PIEDMONT BY 09Z AND PROGRESSING EAST THROUGH THE AREA BY 15Z. MOST CAMS INDICATE NUMEROUS SHOWERS OF LIGHT TO MODERATE INTENSITY...WITH FORECAST SOUNDINGS SHOWING VERY LITTLE INSTABILITY AMIDST OWING TO LAPSE RATES ALOFT. MODELS HAVE ALSO BEEN CONSISTENT IN THE PAST FEW ITERATIONS WITH AROUND A QUARTER OF AN INCH QPF WITH THIS SHOWERS. WILL HAVE CATEGORICAL POPS BETWEEN STARTING AFTER 08Z IN THE WEST.
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&& .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
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AS OF 300 PM SUNDAY... ONGOING SHOWERS MONDAY MORNING ARE EXPECTED TO PROGRESS EAST TO THE COASTAL PLAIN BY 15Z AS AN UPPER TROUGH AND COLD FRONT SWING ACROSS THE AREA. WHILE THE BULK OF THE PRECIP WILL BE TO THE EAST...THE NAM AND SOME OF THE CAMS SUGGEST ANOTHER BAND OF LOW-TOPPED SHOWERS ACCOMPANY THE ACTUAL FRONT BETWEEN 15-21Z. IF THESE MATERIALIZE...SOME ENHANCED WIND GUSTS WILL BE POSSIBLE IN ADDITION TO THE 30-35KT WESTERLY POST-FRONTAL WIND GUSTS ALREADY EXPECTED. 30-35KT WIND GUSTS ARE BELOW WIND ADVISORY CRITERIA SO NO ADVISORY IS NEEDED...BUT THIS POSSIBLE FINAL BAND WILL NEED TO BE MONITORED FOR LOCALLY ENHANCED WINDS. HIGHS RANGING FROM 51 TO 58 WILL LIKELY OCCUR DURING THE EARLY MORNING HOURS BEFORE CRASHING DURING THE AFTERNOON AND THE STRONG WINDS AND COLD ADVECTION SURGE ACROSS THE AREA. FINAL LOW TAMPS ARE A LITTLE UNCERTAIN GIVEN HOW FAR THEY THEY ARE EXPECTED TO FALL THROUGH THE DAY...BUT THERE IS SOME GENERAL MODEL CONSENSUS OF MID 20S FOR MUCH OF THE AREA AND UPPER 20S IN THE COASTAL PLAIN.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 250 AM SUNDAY... TUESDAY AND TUESDAY NIGHT...THE GUIDANCE HAS BEEN CONSISTENT MOVING A MID-LEVEL SHORTWAVE ACROSS CENTRAL NORTH CAROLINA DURING THE DAY...WITH THE LEFT EXIT REGION OF A 140KT 300MB JET MOVING THROUGH THE AREA TUESDAY MORNING WITH A 500MB JET JUST TO OUR SOUTH. AHEAD OF THE SHORTWAVE...AND IN VICINITY OF THE JETS ALOFT BOTH THE NAM AND THE GFS PROVIDE FOR SOME MOSTLY MID-LEVEL CLOUDINESS TUESDAY MORNING WITH COLUMN DRYING TO FOLLOW FOR THE AFTERNOON. CENTRAL NORTH CAROLINA IS IN AN 850MB THETA-E TROUGH WITH K INDICES NEGATIVE...AND THE MOISTURE ALOFT DOES NOT CURRENTLY GET BELOW ABOUT -20C AND THE AIR MASS BELOW THAT IS QUITE DRY. A PERIOD OF POSSIBLY BROKEN CLOUDS IS ONLY ANTICIPATED EARLY TUESDAY BEFORE LATE MORNING AND AFTERNOON INCREASING SUN. SUBSIDENCE TUESDAY NIGHT UNDER SURFACE HIGH PRESSURE MOVING SOUTHEAST...WITH POSSIBLY A FEW CLOUDS OVERNIGHT ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF A 70KT 500MB JET JUST TO OUR NORTH AND JUST MODEST MID-LEVEL MOISTURE. HIGHS TUESDAY AND LOWS TUESDAY NIGHT BOTH ABOUT A CATEGORY BELOW NORMAL...45 TO 50 FOR HIGHS TUESDAY AND MID TO UPPER 20S FOR LOWS TUESDAY NIGHT. WEDNESDAY THROUGH SATURDAY...PRIMARY CONCERN CONTINUES TO BE FOCUSED ON THE SYSTEM FOR THURSDAY...AS A COLD FRONT APPROACHES WEDNESDAY AND MOVES THROUGH MUCH IF NOT ALL OF CENTRAL NORTH CAROLINA WEDNESDAY NIGHT WITH A SURFACE LOW MOVING OVER SOME PART OF THE SOUTHEAST THURSDAY. THE GFS HAS TRENDED TOWARD THE PREVIOUS FEW VERSIONS OF THE ECMWF...WITH A DEEPER MID-LEVEL TROUGH MOVING SOUTHEAST ACROSS CANADA AND INTO THE GREAT LAKES WHICH SUPPRESSES THE SURFACE AND MID-LEVEL LOW TRACKS SUCH THAT CENTRAL NORTH CAROLINA WOULD RECEIVE LITTLE IF ANY PRECIPITATION. IT IS STILL CLOSE...THOUGH...AND FOR WHAT THEY ARE WORTH THE CANADIAN AND THE DGEX ARE STILL FARTHER NORTH AND WET FOR CENTRAL NORTH CAROLINA AT LEAST FOR THURSDAY. THE HIGHER QPF MODELS HAVE PARTIAL THICKNESSES THAT WOULD BE LIQUID ON THURSDAY FOR THE AREA...WHILE THE DRIER GUIDANCE IS COLDER. THE GFS HAS CERTAINLY TRENDED THE COLDER WAY...WITH HIGHS BY FRIDAY ON THE GFS MEX MOS GUIDANCE BARELY ABOVE FREEZING IN THE TRIAD. COMPLICATING THINGS...THE LATEST ECMWF IS SLOWER WITH THE TIMING OF THE MID-LEVEL TROUGH MOVING OUT OF CANADA...WITH A CORRESPONDINGLY SLOWER COLD FRONTAL PASSAGE AND A NOW SLIGHTLY FARTHER NORTH SURFACE LOW TRACK. LIKE THE CANADIAN AND THE DGEX...THICKNESSES ARE WARM FOR MUCH OF THURSDAY BEFORE COLDER AIR SETTLES IN. WHILE THE PROBABILITY OF PRECIPITATION MAY...OVERALL...HAVE LEANED SLIGHTLY LOWER...WITH THE OPERATIONAL GFS TRENDING PROGRESSIVELY DRIER IN EACH OF ITS LAST FOUR RUNS...GFS ENSEMBLES ON THURSDAY STILL HAVE SOME MEMBERS WITH A MORE MOIST AIR MASS AND PRECIPITATION. THE PRUDENT COURSE FOR THURSDAY IS TO MAINTAIN SOME CHANCES WITH SLIGHT CHANCES WEST OF ABOUT U.S. 1 AND CHANCES EAST...KEEPING PRECIPITATION LIQUID AND CONFINED TO THURSDAY UNTIL OVERALL FEATURES RESOLVE THEMSELVES MORE CLEARLY. THE WARMEST DAY SHOULD BE WEDNESDAY AHEAD OF THE COLD FRONT WITH THICKNESSES AND THE CURRENTLY EXPECTED DEGREE OF ANY MID- AND HIGH-LEVEL MOISTURE ALLOWING FOR HIGHS IN THE 50S. THERE HAVE BEEN HUGE SWINGS IN MOS GUIDANCE HIGHS FOR THURSDAY...40S TO 50S AND BACK AGAIN...AND 40S TO 50S TO 30S IN THE TRIAD ON PREVIOUS VERSIONS OF THE ECMWF MOS. BY FRIDAY SOME CONFIDENCE THAT MOST HIGHS SHOULD BE IN THE 30S MODERATING SOME FOR SATURDAY...BUT STILL BELOW NORMAL AND MOSTLY IN THE 40S THEN...AS 1000-850MB THICKNESSES RISE 40M TO 50M VERSUS VALUES OF AROUND 12Z FRIDAY. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 105 PM SUNDAY... CONDITIONS ARE CURRENTLY VFR ACROSS CENTRAL CENTRAL NC WITH CLOUD BASES AT OR ABOVE 10K FT AND A LIGHT SOUTH-SOUTHWESTERLY WIND. THE PRESSURE GRADIENT WILL CONTINUE TO STRENGTHEN THIS AFTERNOON AHEAD OF A LOW PRESSURE SYSTEM MOVING INTO THE OHIO VALLEY...AND AS SURFACE WINDS INCREASE TO 8-12KT...A FEW WIND GUSTS TO 15-20KT MAY OCCUR...MAINLY FROM KRDU WEST TO KINT/KGSO. PRECIP ASSOCIATED WITH THE AFOREMENTIONED LOW PRESSURE SYSTEM LOOKS TO BE AHEAD OF THE FORECAST BY AN HOUR OR TWO...SO WILL INTRODUCE MVFR CEILINGS AND A CHANCE OF RAIN IN THE TAFS JUST A LITTLE EARLIER. EXPECT CEILINGS TO BE NEAR MVFR (3-4K FT) BY 03Z AT KGSO/KINT AND MORE TOWARD 06Z FROM KRDU EAST. THE MAIN RAIN BAND WITH THIS SYSTEM WILL CROSS THE AREA BETWEEN 06Z AND 15Z...WITH PREDOMINATELY IFR CEILINGS POSSIBLE DURING THIS PERIOD. SOUTHERLY WINDS WILL INCREASE TO 15-20KT AND GUST TO NEAR 30KT OVERNIGHT AS THE PRECIP AND COLD FRONT APPROACH....THEN SHIFT TO WEST- NORTHWESTERLY AND GUST INTO THE 30-35KT RANGE BEHIND THE FRONT ON MONDAY. OUTLOOK... NW BREEZE AT 10-15 KT WILL PERSIST MON NIGHT AS HIGH PRESSURE BUILDS TOWARD THE REGION FROM THE WEST. VFR CONDITIONS WILL RULE THROUGH MID-WEEK AS DRY HIGH PRESSURE BUILDS OVER THE CAROLINAS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLS NEAR TERM...BLS SHORT TERM...BLS LONG TERM...DJF AVIATION...CBL/BLS

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