Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 110319 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1019 PM EST WED FEB 10 2016 .SYNOPSIS...
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AN UPPER LEVEL DISTURBANCE WILL CROSS THE SOUTHEAST STATES LATE THURSDAY THROUGH FRIDAY...WHILE A SURFACE FRONTAL ZONE RETREATS NORTH AND SUPPORTS COASTAL CYCLOGENESIS OFF THE SOUTHEAST UNITED STATES COAST. ARCTIC HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST LATE FRIDAY THROUGH THE WEEKEND. A COMPLEX STORM SYSTEM WILL AFFECT THE REGION EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH THURSDAY NIGHT/...
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AS OF 1010 PM WEDNESDAY... TONIGHT: 00Z RAOB DATA INDICATE HEIGHTS ALOFT CONTINUE TO RISE THROUGHOUT THE SOUTHEAST AND MIDDLE ATLANTIC STATES...AS AN EASTERN CONUS TROUGH BRIEFLY RETREATS/LIFTS UP THE NORTHEAST COAST. A STRONG LOW-MID LEVEL WAA REGIME AND AXIS OF LOW-MID LEVEL FGEN ON THE WEST SIDE OF THE DEPARTING TROUGH --BENEATH THE EXIT REGION OF A NEARLY 150 KT NORTHWESTERLY UPPER JET STREAK FROM THE UPPER MIDWEST TO THE TN VALLEY-- HAS SUPPORTED A NARROW STRIPE OF LIGHT SNOW FROM THE NORTHERN PLAINS TO MOSTLY RECENTLY...THE SOUTHERN APPALACHIANS. THE NWP MODELS INSIST THAT THE UPPER JET AND ASSOCIATED FORCING BELOW WILL WEAKEN AS IT MIGRATES ACROSS THE CAROLINAS...AROUND THE BASE OF THE DEPARTING TROUGH AXIS...OVERNIGHT. THIS WEAKENING FORCING AND DISPERSING OF MOISTURE/CLOUDS...IN CONJUNCTION WITH THE NORTHWESTERLY FLOW RAIN-SHADOW EFFECT IN THE LEE OF THE APPALACHIANS...SUPPORTS THIS WEAKENING TREND ALREADY NOTED IN REGIONAL RADAR IMAGERY DURING THE PAST COUPLE OF HOURS. DRY CONDITIONS ARE CONSEQUENTLY ANTICIPATED THROUGHOUT CENTRAL NC OVERNIGHT. AT THE SURFACE...A WEAK/SECONDARY COLD FRONT NOW CROSSING CENTRAL NC WILL RESULT IN A SECONDARY SURGE OF CAA AND BL MIXING TONIGHT... BUT WITH PERIODS OF CALM AND MAXIMIZED RADIATIONAL COOLING OVER THE PIEDMONT ESPECIALLY LATE TONIGHT...AS A WEAK (1024 MB) SURFACE HIGH ACROSS THE TN VALLEY BUILDS EAST INTO THE CENTRAL-SOUTHERN APPALACHIANS. ASSOCIATED FORECAST LOW TEMPERATURES ARE CLOSE TO THE PREVIOUS FORECASTS...IN THE MID TEENS TO LOWER 20S...WITH MINIMUM WIND CHILL VALUES RANGING FROM THE HIGH SINGLE DIGITS TO MIDDLE TEENS. -26 THURSDAY AND THURSDAY NIGHT: THE UPPER TROUGH WILL BEGIN TO RELAX AS THE SURFACE LOW PRESSURE SYSTEM OFF OF NEW ENGLAND CONTINUES OUT TO SEA. THICKNESSES WILL TAKE A WHILE TO RECOVER HOWEVER AND THE WARMER THICKNESSES WILL REMAIN TO OUR SOUTH. THEREFORE NOT MUCH CHANGE IN HIGH TEMPERATURE FOR THURSDAY WITH UPPER 30S TO LOWER 40S ACROSS THE AREA. SKIES WILL BE MOSTLY CLEAR WITH PLENTY OF SUN HOWEVER WITH BUT STILL A LITTLE BREEZY WITH GUSTS UP TO 15 KTS OR SO. THURSDAY NIGHT WILL FEATURE A GRADIENT IN THE LOW TEMPERATURE FROM NORTH TO SOUTH WITH UPPER TEENS NORTH TO MIDDLE 20S SOUTH AS A LOW PRESSURE SYSTEM BEGINS TO DEVELOP SOUTH OF THE AREA LATE THURSDAY NIGHT INTO FRIDAY MORNING.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 230 PM WEDNESDAY... WITH THE LONGWAVE TROUGH HOLDING OVER ERN NOAM... A PERTURBATION NOW COMING INTO THE PACIFIC NORTHWEST WILL RIDE ATOP THE WESTERN RIDGE AND SHEAR OUT AS IT DIVES INTO THE TROUGH BASE AND EVENTUALLY CROSSES THE CAROLINAS FRI GENERATING WEAK DPVA. THE FORCING FOR ASCENT WITH THIS FEATURE WILL BE AUGMENTED BY UPPER DIVERGENCE IN THE LEFT EXIT REGION OF THE JET DIVING INTO THE CENTRAL CONUS TOWARD THE SOUTHEAST STATES... AND THIS WILL SUPPORT SURFACE LOW PRESSURE DEVELOPMENT... TRACKING ACROSS AR AND THE GULF STATES/SRN GA/SRN SC THU/THU NIGHT BEFORE SHIFTING OFF THE SC COAST FRI MORNING. THE OVERALL LIFT IS NOT TERRIBLY IMPRESSIVE HOWEVER... AND THE LATEST MODEL RUNS DO NOT SUBSTANTIALLY DEEPEN THE SURFACE LOW UNTIL IT IS ALREADY WELL OFF THE COAST AND MOVING ENE AWAY FROM NC... KEEPING IT RATHER WEAK AND FLAT WITHOUT A STRONG THERMAL ADVECTION PATTERN. MOISTURE IS ALSO UNIMPRESSIVE... WITH FORECAST SOUNDINGS INDICATING MULTIPLE UNSATURATED LAYERS AND INCONSISTENT MOISTENING ABOVE -10C THAT BRINGS DOUBT AS TO THE PRESENCE OF ICE ALOFT. WITH MODELS CONTINUING TO DEPICT VERY LIGHT TO NO QPF EXCEPT AS ONE GETS CLOSER TO THE CENTRAL COASTAL AREA... WILL TAKE POPS AND AMOUNTS DOWNWARD OVER MUCH OF THE CWA. THICKNESSES AND THE VERTICAL THERMAL STRUCTURES NOTED ON FORECAST SOUNDINGS SUPPORT A MOSTLY RAIN/SNOW MIX OVER THE FAR SE CWA... AND WHILE THIS IS THE AREA THAT IS MOST LIKELY TO SEE SOME SLIGHTLY HEAVIER BANDED PRECIP ON THE NW SIDE OF THE DEPARTING LOW... THE HIGH PROBABILITY OF A MIXTURE WILL KEEP ANY ACCUMULATIONS VERY LOW... WITH ONLY A SLUSHY COATING AT MOST. FURTHER INLAND... WITHIN THE COLDER THICKNESSES... ANY PRECIP SHOULD BE LIGHT FLURRIES... YIELDING LITTLE MORE THAN A LIGHT DUSTING WITH NO TRAVEL IMPACTS. EXPECT CONSIDERABLE CLOUD COVER FRI... WITH CLEARING FRI NIGHT AS THE POLAR FRONT DROPS SOUTHEAST THROUGH THE AREA... MOST LIKELY OCCURRING AFTER MIDNIGHT. HIGHS 36-42 FRI AND LOWS 21-28. -GIH && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 330 PM WEDNESDAY... ...BITTERLY COLD AIR THIS WEEKEND WITH A WINTRY WEATHER THREAT EARLY NEXT WEEK... SAT/SUN: THE AFOREMENTIONED ARCTIC FRONT DROPPING SE THROUGH THE CWA DURING THE PREDAWN HOURS SAT WILL INTRODUCE STRONG COLD AIR ADVECTION AND A PLUNGE IN THICKNESSES (TO AROUND 80 M BELOW NORMAL) AS A DENSE POLAR SURFACE HIGH STARTS TO BUILD IN FROM THE NW. THE CORE OF THE HIGH WILL MOVE FROM THE MIDWEST FRI NIGHT ACROSS THE SRN GREAT LAKES AND OH VALLEY TO THE MIDATLANTIC BY SUN EVENING WHILE EXTENDING DOWN THROUGH NC. EXPECT DECENT SUNSHINE WITH LITTLE MORE THAN FLAT CU SAT AFTERNOON WITH MIXING AND RESIDUAL MOISTURE BENEATH THE SUBSIDENCE INVERSION ALOFT... AND INCREASING HIGH CLOUDS SUNDAY AHEAD OF THE NEXT STORM SYSTEM. THE THICKNESSES PROJECTED BY THE MODELS SUGGEST HIGHS BELOW FREEZING SAT ALONG/NORTH OF HIGHWAY 64... AND BELOW FREEZING AREAWIDE ON SUNDAY... WITH LOWS AROUND 8 TO 15 SAT NIGHT. THE THICKNESS CLIMATOLOGY INDICATES THAT SINGLE DIGIT LOWS ARE POSSIBLE SAT NIGHT... BUT WITH EXPECTATIONS OF SOME MIXING PERSISTING OVERNIGHT... HAVE OPTED ON THE "WARM" SIDE OF THIS CLIMATOLOGY. SEE CLIMATE SECTION BELOW. LOWS SUN NIGHT IN THE UPPER TEENS TO LOWER 20S AS THE SURFACE HIGH DRIFTS NE TOWARD NEW ENGLAND. MON THROUGH WED: MODEL DIFFERENCES WIDEN HEADING INTO MON AS ANOTHER ROUND OF ENERGY SHIFTS INTO THE PLAINS BEFORE AMPLIFYING OVER THE ERN STATES BY MID WEEK. IN SHORT... THE ECMWF SOLUTION (AND THE CANADIAN IS SIMILAR) WAS PREFERRED OVER THE GFS... WITH THE FORMER APPEARING MORE REASONABLE AND FITTING BETTER WITH CLIMATOLOGY. ACCORDING TO THIS SOLUTION... A POTENT PERTURBATION WILL SWING THROUGH OK MON THEN DEEPEN OVER THE LOWER MISS VALLEY MON NIGHT BEFORE CROSSING THE TN VALLEY/SE/CAROLINAS/MIDATLANTIC TUE INTO WED. THE ECMWF BRINGS STRONG MOISTURE ADVECTION AND DEEP LIFT STARTING MON AND CONTINUING THROUGH TUE NIGHT... FINALLY SHIFTING TO OUR NE WED... ALL THE WHILE TAKING A MILLER-B TYPE CYCLOGENESIS PATTERN THROUGH THE REGION. THERE REMAINS A GREAT DEAL OF UNCERTAINTY REGARDING THE VERTICAL THERMAL STRUCTURE AS WELL AS QPF... BUT CONFIDENCE IN AT LEAST SOME PRECIP MON THROUGH TUE NIGHT IS HIGH ENOUGH TO BUMP UP POPS INTO THE LIKELY CATEGORY. AND IF THE ECMWF IS CORRECT... WE`D BE LOOKING AT A VERY WET EVENT... WITH A CHANCE OF MOSTLY SNOW MON TRENDING UP TO MOSTLY RAIN MON NIGHT AS POPS INCREASE... INDICATING A LOWER OVERALL IMPACT FROM WINTRY WEATHER. BUT A LOT CAN CHANGE OVER THE NEXT SEVERAL MODEL RUNS... SO EVERYONE SHOULD KEEP A CLOSE EYE ON THE LATEST FORECASTS. TEMPS SHOULD START TO WARM UP INTO THE 30S MON... INTO THE 40S TUE AS WE GET INTO THE WARM SECTOR... AND PERHAPS LOW 50S (CLOSE TO NORMAL) WED AS THE MID LEVEL LOW MOVES NE AWAY FROM OUR AREA. -GIH && .AVIATION /00Z THROUGH MONDAY/... AS OF 635 PM WEDNESDAY... 24 HOUR TAF PERIOD: HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. WIND GUSTS WILL BE THE ISSUE THAT LINGERS THIS EVENING. WEST NORTHWESTERLY WINDS AT 10 KTS GUSTING 15-20 KTS WILL BE POSSIBLE AT ALL TAF SITES BUT ESPECIALLY AT KGSO/KINT THROUGH THE EVENING. VFR CONDITIONS ARE EXPECTED THROUGH THURSDAY. LONG TERM: A COASTAL SYSTEM ON FRIDAY WITH A SHORTWAVE MOVING ACROSS THE NORTH WILL BRING A CHANCE FOR SUB-VFR CONDITIONS PARTICULARLY AT EASTERN TAF SITES. THE NEXT MORE SIGNIFICANT SYSTEM IS PROGGED TO ENTER THE REGION MONDAY NIGHT INTO TUESDAY. && .CLIMATE... HERE ARE THE RECORD LOWS AND RECORD LOW MAXIMUM TEMPERATURES FOR SAT FEB 13TH AND SUN FEB 14TH AT GSO... RDU... AND FAY: REC YR REC YR LOW LOW MAX ---------------------------------------------- GSO: 02/13 11 1955 31 1986 02/14 6 1905 22 1914 RDU: 02/13 4 1899 10 1899 02/14 -2 1899 27 1916 FAY: 02/13 14 1973 32 1955 02/14 12 1968 33 1916 && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...26/ELLIS SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...BADGETT CLIMATE...HARTFIELD

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