Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281139 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 639 AM EST WED JAN 28 2015 .SYNOPSIS...HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH EARLY THURSDAY... BEFORE PUSHING TO OUR SOUTH. A CLIPPER LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE AREA LATE THURSDAY AND THURSDAY NIGHT. COOL HIGH PRESSURE WILL BUILD BACK IN FROM THE WEST FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 244 AM WEDNESDAY... VERY STRONG LOW PRESSURE SYSTEM OFF OF THE NEW ENGLAND COAST WILL CONTINUE TO GRADUALLY SLIDE NORTHEASTWARD TODAY. IN ITS WAKE SURFACE HIGH PRESSURE WILL BUILD IN FROM THE OHIO VALLEY WITH AN UPPER LEVEL RIGE CENTERED OVER THE MIDWEST. THIS WILL KEEP FLOW AT THE SURFACE NORTHERLY AND AS A RESULT TEMPERATURES WILL BE BELOW NORMAL TODAY WITH HIGHS IN THE MID 40S. DESPITE THE COLD THERE WILL BE PLENTY OF SUNSHINE AS SKIES REMAIN CLEAR. WEATHER IS EXPECTED TO REMAIN SETTLED AS THE PARADE OF SHORTWAVES ON THE BACK SIDE OF THE EXITING LOW PRESSURE SYSTEM CEASES. MAYBE A FEW WIND GUSTS TO 15-20 KTS IN THE EAST THIS MORNING AS BUT OTHERWISE QUIET WEATHER IS EXPECTED. WINDS WILL CALM LATER ON TONIGHT INTO THURSDAY MORNING BUT UPPER LEVEL CLOUDS WILL ENCROACH ON NORTHERN AREAS OVERNIGHT WEDNESDAY NIGHT...ESPECIALLY ACROSS THE NORTH...HAMPERING OPTIMAL RADIATIONAL COOLING. THICKNESS VALUES ALSO WILL BE HIGHER IN THE WEST THAN IN THE EAST...THEREFORE BETWEEN THE CLOUDS AND THE THICKNESS VALUES..EXPECT THE LOWEST TEMPERATURES OVERNIGHT IN OUR SOUTHERN AND EASTERN RURAL AREAS. LOWS IN THE LOW TO MID 20S. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 245 AM WEDNESDAY... HIGH PRESSURE WILL REMAIN IN CONTROL ON THURSDAY FOR MUCH OF THE DAY AS IT MOVE ACROSS EASTERN NC AND EVENTUALLY OUT INTO THE WESTERN ATLANTIC. THIS WILL PUT CENTRAL NC ON THE WARM SIDE OF THE HIGH IN THE SOUTHERLY RETURN FLOW WHICH WILL HELP TEMPERATURES RECOVER BUT ONLY LIMITED AS HIGH AND MID-LEVEL CLOUDS WILL OVERSPREAD THE AREA DURING PEAK HEATING AND LIMIT THE AMOUNT OF INSOLATION. THEREFORE WE WILL HAVE TO SETTLE FOR UPPER 40S NORTH TO LOWER 50S SOUTH. BY THURSDAY EVENING A LOW PRESSURE SYSTEM WILL BE CENTERED OVER THE GREAT LAKES WITH A COLD FRONT EXTENDING DOWN THE APPALACHIANS. IN OUR AREA...MOISTURE WILL BE VERY LIMITED AND THEREFORE PRECIPITATION IS A LOW CONFIDENCE FORECAST AT THE MOMENT. PRECIPITABLE WATER VALUES ONLY RISE TO A HALF OF AN INCH OF WATER AND ALL MODELS HINT AT PRECIPITATION FIZZLING OUT OVER CENTRAL NC AND THEN PICKING UP AGAIN OFFSHORE. FORCING WITH THIS SYSTEM IS MOSTLY IN THE UPPER LEVELS WITH THE LEFT EXIT REGION OF A 120 KT 500 MB JET STREAM MOVING ACROSS THE CWA FROM WEST TO EAST CREATING A 500 MB VORT MAX THAT WILL PROVIDE SUBSTANTIAL UPPER LEVEL LIFT FOR A PERIOD OF TIME BETWEEN 00Z AND 06Z FRIDAY MORNING BUT WHETHER OR NOT ENOUGH MOISTURE REMAINS TO PRODUCE SHOWERS THAT ARE ABLE TO OVERCOME LOW LEVEL DRY AIR REMAINS TO BE SEEN. WILL CARRY A SLIGHT CHANCE THROUGH THAT 0-6Z TIMEFRAME BUT OTHERWISE WILL KEEP THE FORECAST DRY. LOWS THURSDAY NIGHT IN THE LOW 30S NW TO UPPER 30S SE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 225 AM WEDNESDAY... FRI-SAT NIGHT: DRY AND COOL. LATEST MODEL RUNS UNANIMOUSLY SHOW THE SURFACE FRONT OFF THE NC COAST FRI MORNING WITH COLD AIR ADVECTION COMMENCING... AS SURFACE HIGH PRESSURE INITIALLY CENTERED OVER THE UPPER MIDWEST PUSHES EASTWARD WHILE BUILDING SOUTH INTO NC. GOOD MIXING AND A TIGHT MSLP GRADIENT WILL BRING BRISK NORTHWEST WINDS SUSTAINED UP TO 15-20 MPH... AND MOMENTUM TRANSFER SUPPORTS GUSTS TO 25-30 MPH FROM LATE MORNING THROUGH THE AFTERNOON... ABATING SLOWLY IN THE EVENING WITH THE GRADUAL LOSS OF MIXING. FALLING THICKNESSES FRI INDICATE HIGHS IN THE MID 40S TO AROUND 50 DESPITE PLENTY OF SUNSHINE. WINDS FALL OFF FRI NIGHT BUT DON`T GO COMPLETELY CALM... YET THE CHILLY AIR MASS BUILDING IN WITH CLEAR SKIES AND OTHERWISE DECENT RADIATIONAL COOLING STILL FAVORS LOWS IN THE LOW-MID 20S... AND WOULD NOT BE SURPRISED TO SEE A FEW TEENS IN OUTLYING AREAS. SUNSHINE CONTINUES SAT AS THE HIGH RIDGES SOUTHWARD INTO NC. HIGHS STILL BELOW NORMAL... 44-48. THE MID LEVEL RIDGE AXIS SHIFTS OVER AND JUST EAST OF THE CAROLINAS SAT NIGHT AS THE SURFACE RIDGE MOVES SSE AND OFFSHORE... AND WE SHOULD SEE INCREASING HIGH CLOUDS LATE AS WSW MID LEVEL FLOW STARTS DRAWING IN WEAK SOUTHERN STREAM VORTICITY FROM THE BAJA LOW. LOWS IN THE UPPER 20S TO AROUND 30. SUN-TUE: CONFIDENCE INCREASING THAT WE`LL SEE A GOOD SHOT OF RAIN... LIKELY FOCUSED IN THE SUN NIGHT-MON TIME FRAME. THE ECWMF IS A BIT FASTER THAN THE GFS BY ABOUT 3-6 HRS... AND WILL GO WITH A COMPROMISE TIMING SOLUTION FOR NOW... BUT OTHERWISE THE TWO MODELS ARE IN GOOD AGREEMENT ON AMPLIFICATION AND PRECIP PLACEMENT. A POTENT NORTHERN STREAM SHORTWAVE TROUGH TRACKS THROUGH THE CENTRAL MISS VALLEY SUNDAY/SUN NIGHT AS ITS ASSOCIATED PRIMARY SURFACE LOW MOVES JUST AHEAD OF IT THROUGH THE OH VALLEY... ALL THE WHILE PULLING INCREASING SOUTHERN-STREAM MOISTURE FROM EAST OF THE NW- MEXICO LOW... ALONG AND AHEAD OF THE TRAILING SURFACE COLD FRONT INTO THE GULF STATES AND MID SOUTH. THE ECMWF/GFS COMPROMISE TIMING SUPPORTS BRINGING A CHANCE OF RAIN INTO THE FAR WRN CWA LATE SUN... FOLLOWED BY WIDESPREAD RAIN SPREADING EASTWARD SUN EVENING THROUGH THE FIRST HALF OF MONDAY... AS THE NORTHERN STREAM SHORTWAVE TROUGH CROSSES THE OH VALLEY/CENTRAL APPALACHIANS INTO THE NORTHEAST/MID ATLANTIC REGION. HAVE SLOWED DOWN BOTH THE ARRIVAL AND EXIT OF PRECIP BY A FEW HOURS... AND HAVE RAISED POPS A BIT MORE AT THE EVENT`S PEAK BASED ON GOOD AGREEMENT AMONG THE MODELS AND THEIR ENSEMBLE MEMBERS... AND VERY HIGH VALUES OF LOW LEVEL MOISTURE FLUX AND VIGOROUS DYNAMIC FORCING FOR ASCENT. LOW LEVEL THICKNESSES SOAR OVER CENTRAL NC SUNDAY THROUGH AT LEAST THE FIRST HALF OF MON... ALTHOUGH THERE IS STILL A CHANCE OF A LINGERING COOL STABLE POOL OVER THE NW PIEDMONT. SO WE SHOULD SEE ABOVE NORMAL TEMPS... MAINLY OVER THE SRN AND ERN CWA... DESPITE THE HIGH CHANCE OF SHOWERS. THE GFS DEPICTS A COUPLE HUNDRED J/KG OF MUCAPE AHEAD OF THE FRONT... AND IF THIS WEAK INSTABILITY PERSISTS IN LATER RUNS... A RISK OF THUNDER MAY NEED TO BE ADDED. FRONTAL PASSAGE IS MOST LIKELY MON AFTERNOON... WITH PLUNGING THICKNESSES POST-FRONT AS ANOTHER CANADIAN SOURCE HIGH BUILDS IN FROM THE NW. EXPECT CLEARING SKIES MON EVENING WITH TEMPS RETURNING TO BELOW NORMAL VALUES MON NIGHT THROUGH TUE. -GIH && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 640 AM WEDNESDAY... 24 HOUR TAF PERIOD: VERY HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. LIGHT NORTHERLY WINDS THIS MORNING WILL GO TO CALM LATER THIS EVENING. MOSTLY CLEAR SKIES TODAY WITH SOME HIGH CLOUDS POSSIBLY CREEPING IN AT THE END OF THE TAF PERIOD. LONG TERM: THE NEXT THREAT TO AVIATION CONDITIONS WILL BE THURSDAY NIGHT INTO FRIDAY MORNING AS A FRONTAL SYSTEM CROSSES THE AREA AND THEN ANOTHER SYSTEM SUNDAY NIGHT THROUGH MONDAY. FORECAST CONFIDENCE IN THE THURSDAY EVENT IS LOWER THAN NORMAL AND CONDITIONS COULD REMAIN VFR THROUGH THE EVENT. THERE IS HIGHER CONFIDENCE IN THE SUNDAY EVENT BRINGING SOME ADVERSE AVIATION CONDITIONS.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...ELLIS

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