Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 140233 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 930 PM EST SAT FEB 13 2016 .SYNOPSIS...ARCTIC HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH SUNDAY. A DEVELOPING STORM SYSTEM WILL APPROACH FROM THE WEST SUNDAY NIGHT AND THEN MOVE EASTWARD THROUGH THE AREA MONDAY THROUGH TUESDAY. HIGH PRESSURE WILL GRADUALLY BUILD IN FROM THE NORTHWEST TUESDAY NIGHT THROUGH THE END OF THE WEEK. && .NEAR TERM /THROUGH SUNDAY/... AS OF 930 PM SATURDAY... 1036MB SURFACE HIGH OVER INDIANA/OHIO WILL BUILD ACROSS THE APPALACHIANS AND VIRGINIA OVERNIGHT...WITH THE RIDGE AXIS SHIFTING OVER CENTRAL NC LATE TONIGHT. LOW-LEVEL THICKNESSES ARE EXPECTED TO DROP TO AROUND 1240M...WHICH SHOULD RESULT IN SOME SINGLE DIGIT LOWS IN OUTLYING AREAS. HIGH CLOUDS ACCELERATING THROUGH THE MID- MISSISSIPPI RIVER VALLEY WILL REACH THE WESTERN CWA LATE TONIGHT AS WELL...AND THE UPPER LEVEL PATTERN SUGGESTS SOME OROGRAPHIC ENHANCEMENT IS POSSIBLE AS NORTHWEST FLOW INCREASES ACROSS THE APPALACHIAN RIDGES. RIGHT NOW GUIDANCE INDICATES THE CLOUDS WILL BE HIGH AND THIN AT FIRST...WITH MORE SUBSTANTIAL MID CLOUDS TO FOLLOW LATER IN THE MORNING. THIS FORECAST UPDATE WILL LOWER MIN TEMPS A FEW DEGREES IN THE TYPICALLY COLDEST SPOTS OF THE PIEDMONT AND COASTAL PLAIN...WITH LOWS RANGING FROM 9-15. SINGLE DIGIT WIND CHILLS FOR MOST AREAS. SUNDAY: ON SUNDAY SURFACE HIGH PRESSURE MOVES DIRECTLY OVERHEAD AND THE UPPER LEVEL FLOW BECOMES VERY ZONAL. THIS WILL ALLOW WINDS TO CALM AND SKIES TO REMAIN CLEAR FOR THE MORNING...BUT IT ALSO MEANS THAT THE ARCTIC AIR THAT WAS BROUGHT INTO PLACE TODAY WILL HAVE VERY LITTLE PLACE TO GO AND TEMPERATURES WILL REMAIN VERY COLD WITH EXPECTED HIGHS ON SUNDAY ONLY IN THE LOW TO MID 30S. FURTHER HINDERING ANY EFFECTS OF INSOLATION...A MID-LEVEL CLOUD DECK WILL MOVE IN FROM THE WEST DURING THE AFTERNOON HOURS SO WE WONT GET ANY HELP WITH TEMPERATURES THERE...PERHAPS IN THE EAST WHERE IT WILL TAKE LONGER TO OVERSPREAD THE AREA. NO PRECIPITATION IS EXPECTED && .SHORT TERM /SUNDAY NIGHT THROUGH WED NIGHT/... AS OF 320 PM SATURDAY... ...WINTRY WEATHER STILL EXPECTED SUN NIGHT/MON/MON NIGHT ESPECIALLY OVER THE NC PIEDMONT... SUN NIGHT THROUGH TUE: OVERVIEW: CONFIDENCE CONTINUES TO INCREASE REGARDING THE TIMING... MOST PROBABLE PRECIP TYPE PATTERN... AND PRIMARY WEATHER THREATS FOR THE INCOMING SYSTEM. LATEST GUIDANCE SHOWS THE ONSET OF PRECIP SUN NIGHT MOSTLY AFTER MIDNIGHT... AND AN EARLIER ENDING BY THE LUNCH HOUR TUE. LONGWAVE TROUGHING WILL CONTINUE TO AMPLIFY ALONG THE MISS VALLEY SUN NIGHT/MON AS NRN STREAM ENERGY DROPS INTO ITS BASE OVER THE GULF STATES... CULMINATING IN A NARROW DEEP SHORTWAVE TROUGH TAKING ON A SLIGHT POSITIVE TILT AS IT SWINGS ENE THROUGH THE CAROLINAS/VA LATE MON NIGHT THROUGH TUE MORNING. AT THE SURFACE... THE POLAR HIGH SITUATED OVER THE NORTHEAST AND MIDATLANTIC STATES SUN NIGHT WILL PUSH STEADILY NORTHEAST AND OUT OVER THE NW ATLANTIC THROUGH MON... WHILE A COASTAL FRONT FORMS ALONG THE CAROLINA COAST EXTENDING BACK TO DEVELOPING LOW PRESSURE OVER THE CENTRAL GULF STATES. THIS LOW THEN TRACKS EAST THEN NE THROUGH NC MON EVENING THROUGH EARLY TUE MORNING BEFORE MOVING QUICKLY INTO THE NORTHEAST STATES... WITH A TRAILING FRONT SWEEPING OFF THE NC COAST BY EARLY TUE AFTERNOON. SOME UNCERTAINTY PERSISTS REGARDING THE PATTERN OF CYCLOGENESIS BUT IT`S LOOKING MORE LIKE A MILLER-A WITH THE COASTAL FRONT JUMPING INLAND MON NIGHT AND A PRIMARY LOW TRACKING NORTHEASTWARD ALONG THIS FRONT EAST OF THE APPALACHIANS. WHILE THE SURFACE HIGH WILL HAVE INITIALLY DEPOSITED PLENTY OF COLD STABLE AIR... THE HIGH ITSELF WILL BE TRANSITORY AND THE STABLE POOL SHOULD EVENTUALLY BECOME VULNERABLE TO THE STRENGTHENING WARM NOSE AT 850- 900 MB. PRECIPITATION CHANCES: AT THE BEGINNING OF THE EVENT... THE PROCESSES TO FORCE ASCENT SUNDAY NIGHT INTO EARLY MONDAY INCLUDING DPVA AND MOIST ISENTROPIC UPGLIDE ARE RATHER WEAK AND FOCUSED PRIMARILY ON WRN AND NRN PORTIONS OF CENTRAL NC. IT WILL ALSO TAKE A FEW HOURS FOR THE INITIALLY DRY SUBCLOUD LAYER TO MOISTEN SUN NIGHT. WILL TREND POPS UP TO LIKELY IN THE NW WITH LOWER CHANCE POPS TO THE SOUTH AND EAST SUN NIGHT... THEN EXPAND POPS TO THE EAST AND SOUTH TO LIKELY S/E AND CATEGORICAL NW DURING MON... BUT WITH FAIRLY LIGHT QPF... UNDER A QUARTER INCH MAINLY IN THE NW FOR THE SUN NIGHT/MON PERIOD. THIS CHANGES HOWEVER MON EVENING/NIGHT AS STRONG UPPER DIVERGENCE (DUE TO IDEALLY JUXTAPOSED POLAR AND SUBTROPICAL JETS) AND VIGOROUS LOW LEVEL MOISTURE TRANSPORT EAST OF THE LOW STRENGTHEN DEEP LAYER LIFT. WILL RAMP UP POPS FURTHER TO CATEGORICAL WEST/LIKELY EAST LATE MON... THEN TO CATEGORICAL EVERYWHERE MON NIGHT INTO TUE MORNING... ENDING W TO E MID MORNING THROUGH EARLY TUE AFTERNOON. PTYPES: USING THE TOP-DOWN METHODOLOGY WITH CONSIDERATION OF (A) THE INITIALLY VERY COLD/DENSE NATURE OF THE SURFACE AIR MASS... (B) THE STRENGTHENING WARM NOSE ALOFT... AND (C) THE STRONG LOW LEVEL WARM ADVECTION AND WARM HYDROMETEORS ALOFT THAT SHOULD DISLODGE/DISSOLVE THE WEDGE AIR MASS SE TO NW MON AFTERNOON/EVENING... EXPECT THIS TO START AS MOSTLY LIGHT SNOW WITH PERHAPS PATCHY LIGHT SLEET SUN NIGHT ACROSS THE NRN AND WRN CWA... FOLLOWED BY A TRANSITION FROM SSE TO NNW TO FREEZING RAIN/SLEET THEN TO ALL RAIN... WITH THE FAR NW COUNTIES INCLUDING THE TRIAD THE LAST TO SEE AN END TO THE WINTRY PRECIP MON EVENING. THE LATEST MODEL TIMING AND VERTICAL THERMAL STRUCTURE SUGGESTS A SLIGHTLY LONGER-LASTING AND MORE AREALLY EXPANSIVE ICING THREAT THAN WHAT WAS INDICATED YESTERDAY... ALTHOUGH THIS OVERALL LOOKS LIKE ADVISORY CRITERIA ACCUMULATIONS AT MOST OVER ALL BUT PERHAPS THE FAR NW. TENTATIVE ACCUMULATIONS WILL BE FROM ONE TO THREE HUNDREDTHS OF AN INCH OF ICING (MAINLY TRACE AMOUNTS) ALONG/NW OF HIGHWAY 1 EXCEPT FOR FOUR TO SIX HUNDREDTHS IN THE NW PIEDMONT... AND SNOW TOTALS OF 1-3" NW QUARTER WITH A QUARTER INCH TO ONE INCH ELSEWHERE (JUST A TRACE SE)... ALL OF WHICH SHOULD BE QUICKLY SWEPT AWAY BY MODERATE TO POTENTIALLY HEAVY RAINFALL MON NIGHT INTO TUE MORNING. WILL ISSUE A WINTER STORM WATCH FOR AREAS ALONG AND NW OF A LINE FROM ALBEMARLE TO CARTHAGE TO RALEIGH TO WARRENTON FOR SUN NIGHT THROUGH LATE MON. PRECIP TOTALS: STORM TOTAL LIQUID QPF IS EXPECTED TO BE 1 TO 1 1/2" WITH LOCALLY HIGHER AMOUNTS POSSIBLE... GIVEN THE HIGH WATER CONTENT AND STRONG LIFT MON NIGHT/TUE MORNING. BASED ON THE ANTECEDENT CONDITIONS AND WITH SEVERAL RIVERS AND CREEKS RUNNING HIGH... A FLOOD WATCH MAY BE NEEDED FOR SOME PORTION OF THE AREA FOR MON NIGHT INTO TUE MORNING. STORM POTENTIAL: WHILE LAPSE RATES WILL LIKELY BE MARGINAL (NEARING 6.5 C/KM LATE MON NIGHT INTO TUE MORNING MAINLY IN THE EAST)... THE STRONG AND FOCUSED LIFT POSSIBLE WITH THIS SYSTEM AND WARMING LOW LEVELS ESPECIALLY IN THE SANDHILLS AND COASTAL PLAIN MAY SUPPORT A FEW LIGHTNING STRIKES LATE MON NIGHT INTO TUE MORNING. TEMPS: EXPECT LOWS SUN NIGHT OF 22-27. TEMPS SHOULD SLOWLY RISE MON THROUGH MON NIGHT... REACHING THE LOW 30S NW TO LOW 40S SE LATE MON... RISING TO THE MID 30S NW TO UPPER 40S SE MON NIGHT... AND PEAKING AT 50-60 TUE WITH CLEARING SKIES IN THE AFTERNOON AND MINIMAL DIP IN THICKNESSES. TUE NIGHT THROUGH WED NIGHT: A SECONDARY POTENT VORTICITY MAX WILL DIVE THROUGH THE CENTRAL MISS VALLEY TUE AND CROSS VA AND NRN NC TUE NIGHT... HOWEVER THIS IS FAIRLY MOISTURE STARVED AND SHOULD GENERATE LITTLE MORE THAN SOME CLOUDS. OTHERWISE WE WILL SEE HIGH PRESSURE BUILDING IN GRADUALLY FROM THE NW THROUGH WED NIGHT... WITH A NET RESULT OF DRY WEATHER AND NEAR TO SLIGHTLY ABOVE NORMAL TEMPS FOR CENTRAL NC. -GIH && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM SATURDAY... FAIRLY QUIET WEATHER FOR THE END OF THE FORECAST PERIOD AS SURFACE HIGH PRESSURE MOVES TO THE NORTH OF THE AREA ON THURSDAY. A LITTLE BIG COOLER THAN WEDNESDAY BECAUSE OF A SMALL EXTRA SURGE OF COLD AIR THAT WILL MOVE THROUGH THURSDAY MORNING WITH THE PASSAGE OF THE UPPER TROUGH AXIS. THIS SHOULD KEEP HIGHS IN THE LOW 50S BUT WITH PLENTY OF SUN. THERE WILL BE A WARMING TREND FOR FRIDAY AND SATURDAY AS A FAIRLY STRONG UPPER RIDGE EXTENDS UP FROM THE GULF OF MEXICO AND HIGH PRESSURE MOVES OFFSHORE...PUTTING CENTRAL NC IN THE WARM RETURN FLOW REGIME. MODELS ARE NOT IN AGREEMENT ON THE HANDLING OF THE NEXT LOW PRESSURE SYSTEM FROM WHICH AN ASSOCIATED COLD FRONT IS EXPECTED TO MOVE THROUGH CENTRAL NC AT SOME POINT NEXT WEEKEND. THERE IS A CHANCE THAT THE FRONT COULD MOVE THROUGH ON SATURDAY BUT WITH LITTLE MOISTURE. REGARDLESS...TEMPERATURES WILL BE WARM AHEAD OF THE FRONT WITH HIGHS ON SATURDAY IN THE LOW TO MID 60S...FINALLY BACK ABOVE NORMAL FOR THIS TIME OF YEAR. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 730 PM SATURDAY... EXPANSIVE ARCTIC HIGH PRESSURE WILL BUILD ACROSS THE EASTERN UNITED STATES AND MAINTAIN VFR CONDITIONS THROUGHOUT CENTRAL NC THROUGH SUNDAY. A DISTURBANCE IN WNW FLOW ALOFT WILL CAUSE AN AREA OF MID- HIGH LEVEL CEILINGS TO SPREAD EAST OF THE APPALACHIANS LATE SUNDAY...AND PARTICULARLY SO SUNDAY NIGHT WHEN LIGHT WINTRY PRECIPITATION --INITIALLY ALOFT-- WILL BEGIN TO REACH THE SURFACE. A PERIOD OF IFR-MVFR CONDITIONS...WITH PERIODS OF WINTRY PRECIPITATION THAT WILL GRADUALLY CHANGE TO RAIN FROM SOUTHEAST TO NORTHWEST MONDAY AFTERNOON THROUGH MONDAY NIGHT...WILL THEN FOLLOW THROUGH EARLY TUE. && .CLIMATE... HERE ARE THE RECORD LOWS AND RECORD LOW MAXIMUM TEMPERATURES FOR FEB 13TH AND FEB 14TH AT GSO... RDU... AND FAY: REC YR REC YR LOW LOW MAX ---------------------------------------------- GSO: 02/13 31 1986 02/14 6 1905 22 1914 RDU: 02/13 10 1899 02/14 -2 1899 27 1916 FAY: 02/13 32 1955 02/14 12 1968 33 1916 && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING FOR NCZ007-021>023-038-039. WINTER STORM WATCH FROM MONDAY MORNING THROUGH MONDAY AFTERNOON FOR NCZ008>010-024>026-040-041-073>076. && $$ SYNOPSIS...HARTFIELD NEAR TERM...ELLIS/SMITH SHORT TERM...HARTFIELD LONG TERM...ELLIS AVIATION...2 CLIMATE...RAH

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