Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210710 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 310 AM EDT MON APR 21 2014 .SYNOPSIS...LOW PRESSURE OFF THE CAROLINA COAST WILL SLOWLY DRIFT OUT TO SEA TODAY... AS HIGH PRESSURE BUILDS OVER THE SOUTHEAST STATES. A COLD FRONT WILL CROSS THE REGION TUESDAY EVENING. HIGH PRESSURE WILL BUILD BACK IN FOR WEDNESDAY THROUGH THURSDAY. && .NEAR TERM /THROUGH TUESDAY NIGHT/... AS OF 245 AM MONDAY... FOR TODAY/TONIGHT: EXPECT A FAIRLY QUIET DAY AND NIGHT WITH CONTINUED IMPROVING WEATHER CONDITIONS. THE STRONG OFFSHORE LOW IS LOCATED ROUGHLY EAST OF CHS AND DRIFTING TO THE ENE... WHILE THE NARROW RIDGE OF HIGH PRESSURE CENTERED WELL EAST OF NEW ENGLAND EXTENDS NARROWLY TO THE SW INTO CENTRAL NC THIS MORNING. WHILE THIS HIGH WILL CONTINUE TO PUSH NE AWAY FROM THE US... THE SOUTHERN PORTION OF THIS RIDGE WILL STEADILY STRENGTHEN AND MODIFY WHILE DRIFTING SOUTHWARD TOWARD THE GULF COAST AND COVERING THE GULF AND SOUTHEAST STATES. THE SURFACE FLOW FROM THE NE AND NNE AROUND THE OFFSHORE LOW IS STILL BRINGING LOW LEVEL MOISTURE AND CLOUDS INTO THE SE AND FAR ERN CWA. THESE CLOUDS ARE LIKELY TO PERSIST FOR SEVERAL MORE HOURS... HOWEVER THE STRENGTHENING RIDGING FROM THE SURFACE UP THROUGH 850 MB AND ENSUING SUBSIDENCE AND MIXING/DRYING SHOULD YIELD INCREASING SUNSHINE BY MID TO LATE MORNING OVER ALL OF CENTRAL NC. THICKNESSES START THE DAY AROUND 15 M BELOW NORMAL BUT RECOVER NICELY DURING THE DAY... AND WITH PLENTIFUL SUNSHINE... EXPECT HIGHS OF 70-74. LOWS TONIGHT 48-52 WITH HIGH CLOUDS DRIFTING OVER THE AREA. FOR TUE/TUE NIGHT: THE COLD FRONT NOW OVER THE MIDWEST AND ITS ASSOCIATED MID LEVEL TROUGH WILL APPROACH NC LATE TUE... MOVING SE THROUGH THE AREA TUE EVENING INTO THE EARLY OVERNIGHT HOURS. AHEAD OF THE FRONT... SURFACE WINDS WILL STRENGTHEN FROM THE WSW... AND MAINLY WESTERLY WINDS AT 850-700 MB WILL MINIMIZE THE POTENTIAL FOR MOISTURE RETURN... EXEMPLIFIED BY PRECIP WATER PROGS SHOWING A NARROW TIME WINDOW OF VALUES NEAR OR JUST ABOVE 1.0 INCH... WHICH IS JUST SLIGHTLY ABOVE THE NORMAL FOR THIS TIME OF YEAR. EXPECT INCREASING CLOUD COVER STARTING EARLY IN THE DAY WITH THE MID LEVEL FRONT PASSAGE AND WEAK DPVA. SOMEWHAT BETTER MOISTURE IS EXPECTED TO ARRIVE IN THE AFTERNOON THROUGH EARLY EVENING AHEAD OF THE FRONT... AND THIS WILL BRING OUR WINDOW OF OPPORTUNITY FOR SHOWERS AND A FEW STORMS. IN ADDITION TO THE MARGINAL MOISTURE... DEEP LAYER SHEAR WILL ALSO NOT BE TOO IMPRESSIVE... JUST AROUND 20-25 KTS. MUCAPE IS EXPECTED TO TOP OUT AT 500-1000 J/KG... STARTING IN THE NW CWA NEAR 21Z AND SPREADING QUICKLY ACROSS THE REST OF CENTRAL/ERN NC BY 03Z. COVERAGE SHOULD BE ON THE LOW END BASED ON THE LIMITED OVERALL MOISTURE... PEAKING AT 40-50%. WHILE THE DEEP LAYER SHEAR AND INSTABILITY ARE BOTH MARGINAL... THE NAM DEPICTS A DRY SUBCLOUD LAYER SUGGESTING ENHANCED WIND GUSTS WITH ANY CONVECTION. EXPECT COOLING/CLEARING OVERNIGHT BEHIND THE FRONT WITH HIGH PRESSURE STARTING TO BUILD IN FROM THE NW. HIGHS 77-83 WITH ABOVE NORMAL THICKNESSES. LOWS TUE NIGHT FROM 47 NW TO 56 SE. -GIH && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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AS OF 305 AM MONDAY... A COLD FRONT WILL MOVE THROUGH THE AREA TUESDAY NIGHT...WITH NORTHWESTERLY FLOW ALOFT OVER THE REGION ON WEDNESDAY. CANADIAN HIGH PRESSURE WILL BUILD FROM THE UPPER MIDWEST TOWARD THE MID- ATLANTIC STATES BY THURSDAY...WHICH WILL KNOCK TEMPS BACK SLIGHTLY BELOW NORMAL ON WEDNESDAY AND THURSDAY AS THICKNESSES FALL BELOW 1350M. ANY WIND GUSTS WEDNESDAY MORNING SHOULD ABATE DURING THE AFTERNOON AS THE MID-LEVEL SHORTWAVE RIDGING BUILDS EAST TOWARD THE AREA. RH HUMIDITY VALUES ALSO LOOK TO STAY ABOVE 30 PERCENT AND LIMIT ANY FIRE WEATHER CONCERNS. HIGHS 69-73. THE SURFACE RIDGE WILL SETTLE OVERHEAD WEDNESDAY NIGHT AND THICKNESS FORECASTS SUGGEST SOME UPPER 30S COULD OCCUR ACROSS NORTHERN AREAS BY THURSDAY MORNING. LOWS MOSTLY 40-45.
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&& .LONG TERM /THUSDAY THROUGH SUNDAY/...
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AS OF 305 AM MONDAY... HIGH PRESSURE WILL SETTLE OFFSHORE DURING THE DAY ON THURSDAY AND GIVE WAY TO MODERATING RETURN FLOW...WITH HIGHS IN THE LOW/MID 70S THURSDAY AND UPPER 70S TO LOWER 80S ON FRIDAY. ANOTHER COLD FRONT WILL APPROACH FROM THE WEST ON FRIDAY...THOUGH THIS TIME WITH THE PRIMARY SHORTWAVE FORECAST TO LIFT THROUGH THE OHIO VALLEY REGION. MOISTURE AVAILABILITY WILL AGAIN BE QUESTIONABLE AS THE MID-LEVEL FLOW BECOMES WESTERLY BY EARLY FRIDAY. MODELS ARE SLIGHTLY FASTER WITH THE ARRIVAL OF THE COLD FRONT...WITH POPS AS EARLY AS 12-15Z ACROSS THE WESTERN PIEDMONT ON FRIDAY. BEYOND FRIDAY...THE GFS AND ECMWF DIVERGE REGARDING THE EVOLUTION OF THE LONGWAVE PATTERN...WITH THE GFS SHOWING ADDITIONAL SHORTWAVE ENERGY SWINGING THROUGH THE MIDWEST AND ANOTHER COLD FRONT LATE SATURDAY INTO SUNDAY. THE ECMWF ON THE OTHER HAND BUILDS A RIDGE QUICKLY TOWARD THE EASTERN US. GIVEN THESE DIFFERENCES...PREFER TO STAY THE COURSE WITH THE CURRENT DRY FORECAST ON SATURDAY/SUNDAY...WITH HIGHS SLIGHTLY ABOVE NORMAL.
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&& .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 105 AM MONDAY... AT INT/GSO... HIGH CONFIDENCE IN VFR CONDITIONS WITH UNRESTRICTED VSBYS AND MOSTLY CLEAR SKIES WITH LIGHT WINDS TODAY AND TONIGHT... AS HIGH PRESSURE BUILDS OVER THE SOUTHEAST STATES AND GULF COAST. AT RDU AND ESPECIALLY AT RWI/FAY... FORECAST IS NOT AS STRAIGHTFORWARD DUE TO THE LINGERING EFFECTS OF THE STRONG LOW PRESSURE AREA LOCATED OFF THE CAROLINA COAST EARLY THIS MORNING. THE MOIST FLOW FROM THE NORTHEAST WILL CONTINUE TO BRING ATLANTIC MOISTURE INTO THE ERN TERMINALS. CONTINUED VFR IS THE MOST LIKELY SCENARIO AT RDU... WHICH WILL BE ON THE WESTWARD EDGE OF THE STRATUS SHIELD. HOWEVER AT FAY/RWI... CIGS ARE LIKELY TO HOVER IN THE 3000 TO 3500 FT AGL RANGE FROM NOW THROUGH THIS MORNING UNTIL AROUND 12Z-14Z... WHEN THE DEPARTURE OF THE OFFSHORE LOW AND BUILDING HIGH PRESSURE WILL LEAD TO CLEARING SKIES. FAY/RWI WILL ALSO SEE LINGERING BRISK WINDS FROM THE NORTHEAST AND NNE WITH SPORADIC GUSTS TO 15-20 KTS UNTIL EARLY AFTERNOON... WHEN WINDS WILL BECOME LIGHT OVER ALL OF CENTRAL NC. HIGH CONFIDENCE IN VFR CONDITIONS AT ALL SITES FROM LATE AFTERNOON THROUGH TONIGHT WITH ONLY HIGH CLOUDS PASSING OVERHEAD. LOOKING BEYOND 06Z EARLY TUE MORNING: CONTINUED VFR THROUGH MUCH OF TUE WITH SURFACE WINDS BECOMING SOUTHWESTERLY AT 8-13 KTS. A COLD FRONT WILL PUSH TOWARD THE SOUTHEAST TUE EVENING INTO THE EARLY OVERNIGHT... BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS GENERATING MVFR CONDITIONS AND LOCALLY ENHANCED WIND GUSTS OVER 30 MPH. CLEARING SKIES AND VFR CONDITIONS LIKELY BEHIND THE FRONT LATE TUE NIGHT THROUGH THU WITH HIGH PRESSURE BUILDING IN FROM THE NW. MOIST SW FLOW RETURNS THU NIGHT... BRINGING POTENTIAL SUB-VFR CIGS EARLY FRI MORNING... THEN MVFR CIGS WITH SCT SHOWERS ARE POSSIBLE FRI AFTERNOON IN THE WARM SECTOR AHEAD OF AN APPROACHING FRONT. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...SMITH LONG TERM...SMITH AVIATION...HARTFIELD

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