Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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031 FXUS62 KRAH 120333 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1033 PM EST THU FEB 11 2016 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE WILL TRACK ACROSS THE CAROLINAS ON FRIDAY. IN THE WAKE OF THE DISTURBANCE...ARCTIC HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTHWEST OVER THE WEEKEND. && .NEAR TERM /OVERNIGHT/... AS OF 1030 PM THURSDAY... POTENT SHORTWAVE ENERGY EMBEDDED WITHIN BROAD CYCLONIC FLOW OVER MISSOURI (PER 03Z SAT IMAGERY/RAP DATA) THIS EVENING WILL DIG RAPIDLY ESE TO THE WESTERN SLOPES OF THE SOUTHERN APPALACHIANS BY 12Z FRI MORNING...PRECEDED BY A SMALL AMPLITUDE WAVE (OR WAVES) TRACKING ESE FROM WESTERN TN INTO WESTERN NC/SC BY SUNRISE FRI. IN RESPONSE TO DPVA ATTENDANT THE LEAD SHORTWAVE ENERGY...LOW-LEVEL WARM ADVECTION IS ALREADY UNDERWAY OVER GA/SC...AS EVIDENCED BY THE RECENT DEVELOPMENT OF LOW CEILINGS (3000-6000 FT AGL) EXTENDING NORTHEAST FROM TALLAHASSEE TO SAVANNAH. EXPECT LOW-LEVEL CLOUD COVER TO EXPAND IN COVERAGE AND EXTEND NORTHWARD OVER THE CAROLINAS BY SUNRISE AS LOW-LEVEL FLOW CONTINUES TO BACK/STRENGTHEN IN RESPONSE TO APPROACHING DPVA. AS A RESULT...LOW TEMPS FRI MORNING MAY BE REACHED BY 06-09Z IN SOUTHERN PORTIONS OF CENTRAL NC...ESPECIALLY NEAR THE SC BORDER WHERE TEMPS MAY BOTTOM OUT IN THE MID/UPPER 20S BEFORE LEVELING OFF. OTHERWISE...EXPECT LOWS IN THE LOWER/MID 20S NORTH OF HWY 64 WHERE CLOUD COVER WILL INCREASE LATER. -VINCENT && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 320 PM THURSDAY... ...WINTERY MIX EVENT TO OCCUR ACROSS THE EASTERN THIRD OF NC FRIDAY... LOW PRESSURE WILL DEVELOP OFF OF THE SOUTH CAROLINA COAST AND LIFT OFF TO THE NORTHEAST AS IT DOES SO. COLD ANTECEDENT CONDITIONS WILL SET THE STAGE FOR WINTER P-TYPES AT THE ONSET OF THE EVENT. AS THE LOW MOVES OFF THE COAST AND DEVELOPS IT WILL DO SO FROM A MORE WEST SOUTHWEST TO NORTHEAST DIRECTION AND THEREFORE WONT HAVE AS MUCH TIME TO TAP INTO ATLANTIC MOISTURE AS MAY SOMETIMES BE THE CASE WITH COASTAL SYSTEMS. THEREFORE MODEL QPF AMOUNTS ARE FAIRLY LOW AT THIS TIME AND IT IS EXPECTED THAT MOST OF THE PRECIPITATION SHOULD BE CONFINED TO AREAS EAST OF US HIGHWAY 1. LOOKING AT MODEL FORECAST SOUNDINGS...PTYPE FOR AREAS GENERALLY EAST OF HIGHWAY 1 AND NORTH OF HIGHWAY 70 SHOULD REMAIN A MOSTLY SNOW EVENT WITH PERHAPS SOME SLEET MIXED IN. SNOW ACCUMULATIONS WILL INCREASE TO THE NORTH AND EAST WITH HIGHEST AMOUNTS APPROACHING OR JUST OVER AN INCH OF SNOW. BACK TOWARDS THE TRIANGLE A DUSTING TO A HALF OF AN INCH IS MORE LIKELY BUT CONFIDENCE IN THIS AREA IS LACKING AND THIS WILL BE THE POTENTIAL BUST ZONE THAT MAY NOT GET ANY ACCUMULATION AT ALL. IF THE FORECAST WERE TO BUST ON THE HIGH SIDE IT WOULD MOST LIKELY BE IN THE EXTREME NORTHEAST OR IN ANY AREAS OF POTENTIAL SNOW BANDING WHERE SNOWFALL RATES COULD BE HIGHER AT TIMES. THESE WILL MOST LIKELY NOT BE ABLE TO BE EVALUATED IN DETAIL UNTIL THE EVENT BEGINS TO UNFOLD. SOUTH OF HIGHWAY 70 AND EAST OF US 1 A WARM NOSE DEVELOPS IN THE SOUNDINGS SUGGESTING MORE OF A SLEET AND FREEZING RAIN EVENT WITH SOME SNOW AT THE ONSET. WHILE FREEZING RAIN WILL BE POSSIBLE IN THIS AREA...THE TIMING WINDOW WILL BE SMALL FOR THIS TO OCCUR AS TEMPERATURES BEGIN TO WARM AFTER THE ONSET OF PRECIP AND THE TIME SPENT BELOW FREEZING SHOULD BE CONFINED TO A COUPLE OF HOURS. AFTER 18Z THESE AREAS SHOULD TRANSITION TO RAIN. THEREFORE IMPACTS IN THESE AREAS SHOULD BE LIMITED. TIMING OF THE EVENT WILL BEGIN AFTER 12Z WITH FIRST RETURNS ON RADAR COMING INTO THE SOUTHERN COUNTIES WITH MAIN ONSET OF HEAVIER PRECIPITATION OCCURRING IN THE HOURS BETWEEN 15-21Z. PRECIPITATION OF ALL TYPES SHOULD BE WRAPPING UP IN THE EAST NO LATER THAN 00Z SATURDAY. WITH THE ABOVE IN MIND HAVE DECIDED TO ISSUE A WINTER WEATHER ADVISORY BEGINNING 12Z FRIDAY THROUGH 00Z SATURDAY FOR MOST COUNTIES EAST OF HIGHWAY 1...MAINLY FOR POTENTIAL SNOW ACCUMULATIONS OF AN INCH OR GREATER IN THE NORTHEAST AND A POTENTIAL GLAZE OF FREEZING RAIN IN THE SOUTHERN COUNTIES. WILL MONITOR THE SITUATION FOR THE POTENTIAL OF EXTENDING THE ADVISORY BEYOND 0Z SATURDAY FOR LINGERING IMPACTS ON THE ROADS FOR FRIDAY NIGHT INTO SATURDAY MORNING. TEMPERATURES ON FRIDAY WILL REMAIN IN THE LOW TO MID 30S WITH LOWS SATURDAY MORNING IN THE LOW TO MID 20S. && .LONG TERM /SATURDAY THROUGH THURSDAY/... AS OF 325 PM THURSDAY... BITTERLY COLD AIR THIS WEEKEND WITH A WINTRY WEATHER THREAT EARLY NEXT WEEK. CONFIDENCE IN THE DETAILS OF THE POTENTIAL WINTER EVENT FOR MON/TUE IS LOW... SO STAY TUNED. SAT/SUN: AN 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 SCATTERED FLAT CU SAT AFTERNOON RESULTING FROM MIXING AND RESIDUAL MOISTURE BENEATH THE SUBSIDENCE INVERSION ALOFT... AND INCREASING MID CLOUDS SUNDAY AHEAD OF THE NEXT STORM SYSTEM. THE THICKNESSES PROJECTED BY THE MODELS ALONG WITH STATISTICAL GUIDANCE SUGGEST HIGHS SAT OF 29- 38 (HOLDING AT OR BELOW FREEZING ALONG/NORTH OF HIGHWAY 64) AND 28- 34... WITH LOWS AROUND 9 TO 17 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 HIGHER END OF CLIMATOLOGY. LOWS SUN NIGHT IN THE 20-25 RANGE AS THE SURFACE HIGH DRIFTS NE TOWARD NEW ENGLAND AND CLOUDS CONTINUE TO INCREASE AND THICKEN FROM THE WEST. MON/TUE: IMPORTANT MODEL DIFFERENCES PERSIST REGARDING THE DETAILS OF THE PRECIP EVENT EARLY NEXT WEEK. THEY AGREE ON A POTENT AND DIGGING SHORTWAVE TROUGH DIVING TROUGH THE SOUTHERN PLAINS MON... THROUGH THE GULF STATES AND TN VALLEY MON NIGHT... AND TAKING ON A NEGATIVE TILT AS IT SWINGS THROUGH THE CAROLINAS AND MIDATLANTIC REGION TUE... AND THEY ALL AGREE THAT WE WILL UNDOUBTEDLY GET PRECIP OF SOME KIND... ESPECIALLY LATE MON NIGHT INTO TUE WHEN PRECIP MAY BE HEAVY. THE GFS IS SLOWER (BY ABOUT 6 HRS) AND DEEPER THAN THE ECMWF STARTING AS EARLY AS MON MORNING... BUT ITS PARENT HIGH TO OUR NE IS A BIT MORE PROGRESSIVE. THE CANADIAN BY CONTRAST IS EVEN SLOWER THAN THE GFS WITH THE MID LEVEL TROUGH. THE MODELS ALSO DON`T AGREE ON THE PATTERN OF CYCLOGENESIS... WITH NO REAL CONSENSUS AS TO WHETHER THIS IS LIKELY TO BE A MILLER-A OR MILLER-B TYPE EVENT. THESE DIFFERENCES ALL HAVE MAJOR RAMIFICATIONS WITH RESPECT TO THE VERTICAL THERMAL STRUCTURE AND RESULTING P-TYPES... AND UNFORTUNATELY... WE CANNOT PROVIDE MUCH IN THE WAY OF DETAILS AT THIS TIME WITH ANY AMOUNT OF CONFIDENCE. HOWEVER... MOST MODELS AND ENSEMBLE MEMBERS FAVOR A LOW TRACK WELL INLAND... EVEN WITH A MILLER- B SECONDARY LOW... WHICH RAISES CONFIDENCE THAT THE EASTERN CWA WILL SEE A SWIFT TRANSITION TO ALL RAIN BY LATE MON. CONSIDERING THAT THE PRECEDING POLAR AIR MASS WILL HAVE BROUGHT VERY COLD TEMPS AND EVEN COLDER DEWPOINTS... THE STABLE AIR MAY PROVE MORE DIFFICULT TO DISLODGE OVER THE CLIMATOLOGICALLY FAVORED AREAS OF THE NW PIEDMONT... YIELDING A LONGER DURATION WINTER EVENT THERE. MODELS ALSO TEND TO AGREE ON AN OVERALL PATTERN OF LIGHTER PRECIP ON MONDAY WITH WEAKER FORCING FOR ASCENT FOLLOWED BY STRONGER LIFT AND GREATER MOISTURE TRANSPORT GENERATING A HEAVY PRECIP THREAT FOR LATE MON NIGHT INTO TUE. 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 TO LOW 40S MON... INTO THE 40S TO LOW 50S TUE AS WE GET INTO THE WARM SECTOR. WED/THU: PRECIP SHOULD END BY TUE NIGHT. THE MID LEVEL TROUGH SLOWLY SHIFTS EASTWARD OUT OF THE EASTERN STATES WED... WITH AN INCOMING MID LEVEL RIDGE GENERATING RISING HEIGHTS FOR THU... AS SURFACE HIGH PRESSURE BUILDS IN FROM THE NW. EXPECT FAIR SKIES... DRY WEATHER... AND A TREND OF TEMPS UP CLOSER TO SEASONAL NORMALS. -GIH && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 715 PM THURSDAY... VFR CONDITIONS WILL PERSIST THROUGH THE OVERNIGHT HOURS BEFORE DETERIORATING DURING THE MORNING HOURS ON FRIDAY AS A QUICK MOVING LOW PRESSURE SYSTEM IMPACTS THE AREA. CLOUDS WILL INCREASE FROM THE SOUTHWEST...INITIALLY WITH CIGS AROUND 5 KFT BUT THEN DROPPING TO 1500 FEET OR SO AS PRECIPITATION BEGINS. PRECIPITATION IS EXPECTED TO BEGIN JUST AFTER SUNRISE AT KFAY AND THEN OVERSPREAD INTO KRDU AND KRWI. PRECIPITATION TYPE FOR KFAY IS EXPECTED TO BE A WINTERY MIX WITH SLEET AND FREEZING RAIN POSSIBLE. FURTHER NORTH...THE PRIMARY PRECIP TYPE IS EXPECTED TO BE SNOW...WITH SOME SLEET POTENTIALLY MIXED IN. GIVEN THAT THE LOW PRESSURE SYSTEM WILL TRACK JUST OFFSHORE...PRECIP IS EXPECTED TO REMAIN ACROSS THE EASTERN HALF OF THE FORECAST AREA. THEREFORE...KGSO AND KINT SHOULD REMAIN PRECIP FREE...ALTHOUGH CLOUDS MAY TEMPORARILY LOWER INTO THE MVFR RANGE. PRECIP SHOULD PULL OUT OF THE AREA DURING THE LATE AFTERNOON/EARLY EVENING HOURS...ALTHOUGH LOW CIGS MAY PERSIST THROUGH THE EVENING HOURS. OUTLOOK...VFR CONDITIONS WILL RETURN FOR THE WEEKEND AS HIGH PRESSURE BUILDS TOWARDS AND EVENTUALLY OVER THE AREA. THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS WILL COME MONDAY INTO TUESDAY AS ANOTHER LOW PRESSURE SYSTEM IMPACTS THE AREA. && .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... WINTER WEATHER ADVISORY FROM 7 AM TO 7 PM EST FRIDAY FOR NCZ010-011-026>028-041>043-077-078-085-086-088-089. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...KRD

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