Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 302014 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 314 PM EST FRI JAN 30 2015 .SYNOPSIS...BREEZY NORTHWESTERLY WINDS TODAY WILL GIVE WAY TO HIGH PRESSURE BUILDING IN FROM THE WEST OVER THE WEEKEND. A LOW PRESSURE SYSTEM WILL THEN CROSS THE REGION LATE SUNDAY AND MONDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1030 AM FRIDAY... AN UPPER TROUGH IS CURRENTLY SWINGING ACROSS THE AREA WITH A COLD FRONT DEPARTING TO THE EAST. STRONG POST-FRONTAL COLD ADVECTION IS SETTING UP ACROSS THE AREA THIS MORNING WITH THE 12Z KGSO RAOB SHOWING AN ALREADY DEEP MIXED LAYER UP TO 5000 FT AND A GUST TO 38KT AT KGSO. NORTHWESTERLY WINDS ARE STEADILY INCREASING AND GUSTS ARE STARTING TO REACH THE UPPER 20S TO AROUND 30KT AREAWIDE. IT APPEARS THE GUSTS WILL PEAK LATE THIS MORNING AND VERY EARLY AFTERNOON...AS MUCH AS 30-35KT IN SOME AREAS...BEFORE THE PRESSURE GRADIENT BEGINS TO SLOWLY WEAKEN. MEANWHILE...REGIONAL VIS SHOWS A FEW STREAMS OF MOISTURE (JUST ABOVE 850MB PER KGSO/KRNK RAOBS) SPILLING EAST ACROSS THE NORTHERN CWA. THE STRONG INVERSION JUST ABOVE AND STRENGTHENING SUBSIDENCE BEHIND THE UPPER TROUGH WILL KEEP THIS MOISTURE TRAPPED AND THE STRATOCU FAIRLY SHALLOW...SO WE MAINLY EXPECT SKIES VARYING FROM PARTLY CLOUDY SOUTHWEST TO A PERIOD OF MOSTLY CLOUDY NORTHEAST. DRY ADIABATIC MIXING TO 850MB WHILE ACCOUNTING FOR SOME DOWNSLOPE WARMING YIELDS HIGHS IN THE 43-50 RANGE...ONLY ABOUT 3-4 DEGREES OFF CURRENT READINGS. -BLS && .SHORT TERM /TONIGHT THROUGH MONDAY/...
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AS OF 308 PM FRIDAY... WINDS WILL DIMINISH TONIGHT UNDER CLEAR SKIES. THERE SHOULD BE ENOUGH OF A GRADIENT FOR AT LEAST A SLIGHT STIR TO THE WIND THROUGH THE NIGHT...AS 925MB WINDS REMAIN TO 35KT. SURFACE DEW POINTS SHOULD CONTINUE TO DRY...AND 1000-850MB THICKNESSES WOULD SUGGEST LOWS FROM THE TEENS TO THE LOWER 20S. THIS WILL ESSENTIALLY BE THE FORECAST FOR LOWS OVERNIGHT...19 TO 20 IN THE NORTHWEST PIEDMONT TO NEAR 25 TOWARD KFAY...CLOSE TO THE AVERAGE OF THE MET AND MAV MOS. ON SATURDAY...925MB WINDS DIMINISH TO AROUND 15KT BY 18Z...AND BUFR SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST A FEW WIND GUSTS IN THE TEENS KNOTS WITH INITIAL MIXING BEFORE THE WINDS DIMINISH AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTHWEST. SATURDAY AFTERNOON...A FLAT RIDGE AXIS ALOFT GETS CLOSE TO CENTRAL NORTH CAROLINA AS SOME MID-LEVEL VORTICITY ADVECTION MOVES INTO AND ACROSS CENTRAL NORTH CAROLINA DURING THE LATE AFTERNOON AND NIGHTTIME HOURS...FORECAST BY BOTH THE GFS AND NAM. GFS AND NAM BUFR SOUNDINGS SUGGEST INCREASING UPPER-LEVEL MOISTURE SUCH THAT INCREASING HIGH CLOUDS SHOULD GRADUALLY OCCUR FROM SATURDAY AFTERNOON INTO SATURDAY NIGHT. WITH MOST IF NOT ALL OF CENTRAL NORTH CAROLINA EXPECTED TO BE MOSTLY CLOUDY BY THE MIDDLE OF THE NIGHT SATURDAY...OVERNIGHT LOWS SHOULD BE WARMER...MID TO UPPER 20S IN THE NORTHERN COASTAL PLAIN TO AROUND 30 ELSEWHERE. -DJF HIGH PRESSURE WILL MOVE OFF THE EAST COAST SUNDAY... AS A LOW PRESSURE SYSTEM MOVES INTO THE OHIO VALLEY. SOUTHWESTERLY LOW LEVEL FLOW... AND INCREASING THICKNESSES WILL BRING HIGHS A FEW DEGREES WARMER ON SUNDAY... AROUND 50. COLD FRONT WILL MOVE THROUGH THE AREA ON MONDAY. A STRONG PRESSURE GRADIENT WILL DEVELOP AS THE LOW DEEPENS OFF THE MIDATLANTIC COAST... AND HIGH PRESSURE BUILDS IN TO THE MIDWEST... LEADING TO BREEZY CONDITIONS MONDAY AFTERNOON. STRONG COLD ADVECTION WILL OVERTAKE THE REGION DURING THIS TIME... LEADING TO A LIKELY NONDIURNAL TEMPERATURE TREND... WITH TEMPS FALLING THROUGH THE 40S DURING THE DAY.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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AS OF 309 PM FRIDAY... HIGH PRESSURE WILL EXTEND ACROSS THE AREA TUESDAY AND WEDNESDAY... AS ENERGY CURRENTLY OVER THE BAJA MOVES EASTWARD TO THE GULF COAST. AN AREA OF LOW PRESSURE WILL DEVELOP IN RESPONSE OVER THE NORTHERN GULF OF MEXICO ON WEDNESDAY... POTENTIALLY MOVING ALONG THE SOUTHEAST COAST IN THE THURS/FRI TIMEFRAME. GFS REMAINS CLOSE TO THE COAST WITH PRECIP MOVING IN LATER ON WEDNESDAY... 12Z ECMWF TAKES THE LOW OUT TO SEA WITH LITTLE LOCAL IMPACT... AND GFS ENSEMBLE HAS CONSIDERABLE VARIATION IN STRENGTH AND PROXIMITY TO THE COAST... SO CONFIDENCE AT THIS TIME REMAINS LOW. TIMING WILL HAVE A GREAT IMPACT ON PTYPE... WITH ANY OVERNIGHT PRECIP POTENTIALLY BRINGING PTYPE ISSUES. AT THIS POINT... WILL CONTINUE WITH CHANCE OF RAIN UNTIL TIMING/DEVELOPMENT CAN BE BETTER ASCERTAINED. TEMPERATURES WILL CONTINUE TO BE BELOW NORMAL THROUGH THE END OF THE WEEK.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 100 PM FRIDAY... STRONG NORTHWESTERLY WIND GUSTS (CROSSWINDS FOR MANY RUNWAYS) OF ANYWHERE FROM 25KT TO 35KT ARE OCCURRING ACROSS CENTRAL NC THIS MORNING IN THE WAKE OF A DEPARTING COLD FRONT. THESE GUSTS WILL CONTINUE THIS AFTERNOON AND MAY LINGER INTO THE EVENING HOURS BEFORE SUBSIDING AFTER MIDNIGHT. SCATTERED STRATOCU WILL BE MOSTLY CONCENTRATED FROM KRDU NORTH AND EAST BUT REMAIN ABOVE 5000 FT THIS AFTERNOON. OTHERWISE...HIGH PRESSURE WILL BUILD IN FROM THE WEST THROUGH SATURDAY AND VFR CONDITIONS ARE EXPECTED TO PREVAIL. BEYOND THE 12Z VALID TAF PERIOD... VFR CONDITIONS WILL CONTINUE THROUGH EARLY SUNDAY. A LOW PRESSURE SYSTEM WILL CROSS THE CENTRAL APPALACHIANS SUNDAY NIGHT...WITH A CHANCE OF RAIN AND SUB-VFR CONDITIONS FROM LATE SUNDAY AFTERNOON THROUGH MONDAY AFTERNOON. HIGH PRESSURE AND VFR CONDITIONS WILL RETURN FOR TUESDAY...WITH ANOTHER SYSTEM TO APPROACH THE REGION ON WEDNESDAY. && .FIRE WEATHER... AS OF 300 AM FRIDAY... WIND GUSTS TO 30KT TODAY...OR TO AROUND 35 MPH...ARE CERTAINLY POSSIBLE AS THE SURFACE GRADIENT TIGHTENS BEHIND THE COLD FRONT. SURFACE DEW POINTS WILL FALL BEHIND THE FRONT AS WELL...WITH THE LOWEST GUIDANCE OF THE RAP SUGGESTING SOME DEW POINTS IN SINGLE FIGURES LATE IN THE DAY IN THE NORTHWEST PIEDMONT. THE GFS IS HIGHER...AND THE NAM IS MORE OF A COMPROMISE...WHICH IS CONSISTENT WITH THE MOS GUIDANCE. BY 00Z SATURDAY...THE GRIDDED FORECAST WILL SHOW A DEW POINT NEAR 10F IN THE TRIAD...BUT EVEN THERE THE MINIMUM RELATIVE HUMIDITY IS IN THE UPPER 20S PERCENT. BASED THOSE DEW POINTS...RECENT RAIN...AND EARLIER FORECAST SERVICE COORDINATION... WILL FOR NOW HIGHLIGHT THE ADVERSE CONDITIONS OF THE WIND GUSTS IN THE DISCUSSION OF THE FIRE WEATHER FORECAST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...DJF/BLS SHORT TERM...DJF/SEC LONG TERM...SEC AVIATION...BLS FIRE WEATHER...DJF

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