Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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385 FXUS62 KRAH 131747 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1247 PM EST SAT FEB 13 2016 .SYNOPSIS...ARCTIC HIGH PRESSURE WILL BUILD INTO CENTRAL NC TODAY AND SUNDAY. AN AREA OF LOW PRESSURE WILL APPROACH FROM THE WEST ON MONDAY AND CROSS THE REGION MONDAY NIGHT AND TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM SATURDAY... VERY COLD AND DRY ARCTIC AIRMASS FILTERING INTO CENTRAL NC VIA STRONG COLD AIR ADVECTION CURRENTLY TAKING PLACE OVER MUCH OF THE MID-ATLANTIC REGION. FAIRLY GOOD TEMPERATURE GRADIENT CURRENTLY IN PLACE FROM NORTH TO SOUTH ACROSS THE CWA WITH MID 20S STILL IN THE NORTH BUT AROUND FREEZING IN THE SOUTH. THIS GRADIENT WILL CONTINUE TODAY WITH HIGHS IN THE LOW 30S NORTH TO UPPER 30S TO NEAR 40 DEGREES ACROSS THE SOUTH. ASIDE FROM THE COLD...THE WEATHER STORY OF THE DAY WILL BE THE WINDS WITH A FEW GUSTS ALREADY OBSERVED TO BE BETWEEN 25-30 KTS. THIS WILL CONTINUE THROUGH THE MORNING AND INTO THE EARLY AFTERNOON BUT MAY BECOME MORE OF A HIGH SUSTAINED WIND IN THE 15-20 KT RANGE. COMBINING THE WINDS AND THE COLD WE EXPECT TO HAVE WIND CHILL VALUES IN THE MID 20S ACROSS MUCH OF THE AREA WITH A FEW LOW 30S IN THE SOUTH. DESPITE THE COLD...WITH HIGH PRESSURE OVERHEAD...EXPECT MOSTLY CLEAR SKIES FOR MUCH OF THE DAY. FOR TONIGHT...THICKNESSES PLUNGE INTO THE 1230-1240 METER RANGE...INDICATIVE OF THE POSSIBILITY OF SOME SINGLE DIGIT TEMPERATURES...HOWEVER WITH WINDS STIRRING FOR MUCH OF THE NIGHT...LOWS IN THE LOW TO MID TEENS SEEMS MORE LIKELY WITH A FEW SINGLE DIGITS POSSIBLE IN RURAL AREAS. WINDS SHOULD RELAX FOR THE MOST PART OVERNIGHT BUT STILL WIND CHILLS IN THE LOWER SINGLE DIGITS APPROACHING ZERO ARE NOT OUT OF THE QUESTION. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 340 AM SATURDAY... L/W TROUGH OVER THE EASTERN U.S. RELOADS AS A POTENT S/W DIGS SEWD FROM THE NORTHERN PLAINS INTO THE GREAT LAKES. THIS WILL BACK THE UPPER LEVEL FLOW OVER THE CAROLINAS..AND ADVECT HIGH LEVEL MOISTURE INTO OUR REGION BY LATE IN THE DAY. AT THE SURFACE...SFC HIGH DRIFTS OFFSHORE...INITIATING RETURN LOW LEVEL FLOW. THUS MOSTLY-PARTLY SUNNY SKIES IN THE MORNING WILL GIVE WAY TO THICKENING CLOUD COVER IN THE AFTERNOON. AFTERNOON TEMPS REMAIN WELL BELOW NORMAL...RANGING FROM NEAR 30 NORTH TO THE MID 30S SW. INCREASING ISENTROPIC UPGLIDE IN THE LOW LEVEL WAA PATTERN COUPLED WITH INCREASING DIVERGENCE ALOFT AHEAD OF THE APPROACHING S/W WILL INCREASE LIFT THROUGH THE COLUMN. THE LIFT APPEARS SUFFICIENT TO GENERATE PRECIPITATION OVER OUR WESTERN PIEDMONT LATE SUNDAY NIGHT. THERMAL PROFILES SUGGEST THAT PRECIP SHOULD INITIALLY START OUT AS FROZEN PRECIP (SNOW OR SNOW/SLEET MIX). PRECIP FALLING THROUGH DRY SUB CLOUD SHOULD TRIGGER A HYBRID/IN-SITU DAMMING EVENT OVER THE NW PIEDMONT. LOCKING THIS COLDER AIR IN PLACE SUGGEST A BETTER POTENTIAL FOR A LIGHT ACCUMULATION ACROSS THE NW PIEDMONT/TRIAD REGION BEFORE DAYBREAK MONDAY. MIN TEMPS LOW-MID 20S. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 4 AM SATURDAY... ...STORM SYSTEM LIKELY TO BRING WINTRY WEATHER THREAT SUN NIGHT/MON FOLLOWED BY HEAVY RAIN THREAT AND A FEW STORMS MON NIGHT/TUE... MONDAY THROUGH TUESDAY: S/W ENERGY ALOFT IS FORECAST TO DIG SOUTHEASTWARD FROM THE CENTRAL/SOUTHERN PLAINS SUNDAY NIGHT INTO MONDAY AND AMPLIFY ACROSS THE DEEP SOUTH...WITH A DEVELOPING SURFACE LOW. THE GFS AND ECMWF CONTINUE TO BE FURTHER WEST WITH THE TRACK OF THE SURFACE LOW COMPARED TO THE CANADIAN AND THE NAM (WITH GFS/ECMWF SHOWING LESS/WEAKER WINTER STORM). WILL CONTINUE TO TREND TO THE PREFERRED GFS... WHICH IS SIMILAR TO THE LATEST ECMWF. THIS WILL YIELD AN INSITU COLD AIR DAMMING EVENT FOR MONDAY... WITH GENERALLY LIGHT PRECIP. HOWEVER... GIVEN THE ANTECEDENT ARCTIC AIRMASS IN PLACE OVER CENTRAL NC ON SUNDAY... WE WILL LIKELY SEE A LIGHT WINTRY MIX ACROSS MOST/IF NOT ALL OF CENTRAL NC ON MONDAY MORNING... WITH A TRANSITION TO RAIN FROM SE TO NW THROUGHOUT THE DAY. THERE CONTINUES TO BE A LOT OF DISAGREEMENT WITH REGARD TO HOW FAST WARM AIR ABOVE THE COLD DOME WILL SURGE IN AND TURN ANY LIGHT PRECIP FROM SNOW OVER TO SLEET AND FREEZING RAIN. WITH THAT SAID... GIVEN THE SURFACE HIGH IS TRANSITORY WITH THIS SYSTEM (HINTS THE INSITU DAMMING) THE FREEZING RAIN WILL BE A SELF LIMITING PROCESS... WHICH WILL HELP KEEP TOTALS OF FREEZING RAIN BELOW WARNING CRITERIA AREA WIDE... THOUGH LOCATIONS ACROSS THE NORTHWEST PIEDMONT COULD SEE A COUPLE OF INCHES OF SNOW/SLEET... WITH UP TO A TENTH OF AN INCH OF ICE ACCRUAL BEFORE TEMPS CLIMB TO 33 LATE IN THE DAY/MONDAY EVENING... WITH LESSER AMOUNTS AS YOU GO SOUTH AND EASTWARD (THOUGH WE STILL MAY SEE SOME TRAVEL ISSUES ON MONDAY MORNING INTO THE AFTERNOON). THE BULK OF THE PRECIP THOUGH WILL OCCUR ON MONDAY NIGHT AS THE MAIN S/W ENERGY AND DEEPENING SURFACE LOW TRACK ACROSS THE AREA. WE COULD SEE UP TO 1 TO 2 INCHES OF RAIN WITH THIS SYSTEM... WITH EVEN A FEW THUNDERSTORMS POSSIBLE ACROSS THE AREA IF THE MID LEVEL TROUGH TAKES ON A NEGATIVE TILT. LOW TEMPS FOR THE PERIOD MONDAY NIGHT/TUESDAY MORNING MAY OCCUR EARLY (ESPECIALLY IN THE WEAKENING DAMMING REGION... NW PIEDMONT) WITH TEMPS HOLDING STEADY OR RISING OVERNIGHT. HIGH TEMPS WILL BE TRICK AND DEPEND ON THE TIMING OF THE ASSOCIATED SURFACE FRONT TRACKING THROUGH THE AREA AS THE SURFACE LOW LIFTS OFF TO THE NORTH AND EAST... AND HOW MUCH PARTIAL CLEARING WE MAY SEE ON TUESDAY AFTERNOON...ALONG WITH WESTERLY LOW LEVEL FLOW. FOR NOW WILL SHOW HIGHS RANGING FROM NEAR 50 NW TO NEAR 60S SE/E... WITH PRECIP EXITING THE AREA TUESDAY MORNING INTO THE AFTERNOON. TUESDAY NIGHT THROUGH FRIDAY: DRY WEATHER IS EXPECTED TO RETURN FOR THIS PERIOD... THOUGH A QUICK MOVING MOISTURE STARVED DISTURBANCE IS EXPECTED TO MOVE THROUGH THE AREA ON TUESDAY NIGHT/WEDNESDAY. OTHERWISE... HIGH PRESSURE AT THE SURFACE AND ALOFT WILL BUILD OVER THE REGION... RESULTING IN DRY AND QUITE WEATHER... WITH HIGH AND LOW TEMPS RETURNING TO NEAR NORMAL VALUES. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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AS OF 1245 PM SATURDAY 24 HOUR TAF PERIOD: HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. MOSTLY CLEAR SKIES TODAY AT ALL TAF SITES. THE MAIN CONCERN OF THE DAY WILL BE GUSTY WINDS AS MOST SITES REPORTING NORTHERLY SUSTAINED WINDS OF NEAR 10 KTS GUSTING TO 20-25 KTS AT TIMES. THIS ACTIVITY SHOULD CONTINUE THIS AFTERNOON BUT THE GUSTS COULD DROP INTO THE 15-20 KT RANGE FOR MUCH OF THE LATE AFTERNOON. AFTER SUNSET EXPECT SUSTAINED WINDS TO REMAIN NEAR 10 KTS GIVE OR TAKE. WINDS WILL SHIFT TO MORE NORTHEASTERLY ON SUNDAY AS THE GRADIENT RELAXES TO 5-10 KTS ACROSS THE AREA. SOME HIGH CLOUDS WILL MOVE IN FROM THE WEST AT THE END OF THE PERIOD. LONG TERM: THE NEXT EXPECTED PERIOD OF SUB-VFR CONDITIONS WILL BE ON MONDAY AS A LOW PRESSURE SYSTEM MOVES THROUGH THE AREA. SOME WINTER P-TYPE PROBLEMS MAY OCCUR ON MONDAY MORNING WITH KINT AND KGSO THE MOST LIKELY AFFECTED TAF SITES BUT ALL SITES COULD SEE SOME WINTER P- TYPES AT THE BEGINNING OF THE EVENT BEFORE AN EVENTUAL CHANGEOVER TO ALL RAIN LATER MONDAY. SUB-VFR CONDITIONS COULD LAST THROUGH TUESDAY BEFORE FINALLY RETURNING TO VFR FOR THE END OF THE WEEK.
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&& .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... NONE && $$ SYNOPSIS...WSS NEAR TERM...ELLIS SHORT TERM...WSS LONG TERM...BSD AVIATION...ELLIS CLIMATE...RAH

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