Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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767 FXUS62 KRAH 131143 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 642 AM 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 340 AM SATURDAY... ARCTIC HIGH PRESSURE WILL BUILD INTO CENTRAL NC TODAY AND SETTLE OVERHEAD TONIGHT-EARLY SUNDAY. THIS AIR MASS WILL BE SOME OF THE COLDEST SO FAR THIS WINTER. THE LEADING EDGE OF THE COLD AIRMASS WAS ENTERING THE PIEDMONT AT 08Z. WHILE PRE DAWN TEMPERATURES WERE IN THE UPPER 20S-LOWER 30S...MOST PLACES DIP INTO THE MID-UPPER 20S SHORTLY AFTER DAYBREAK. IN SPITE OF ABUNDANT SUNSHINE...STRONG LOW LEVEL CAA WILL DETER TEMP RECOVERY. DAYTIME HIGH TEMPS SHOULD VARY FROM NEAR 30 ACROSS THE FAR NORTH-NW TO THE MID-UPPER 30S SOUTH. CALENDAR DAY MIN TEMPS MAY ACTUALLY OCCUR JUST BEFORE MIDNIGHT THIS EVENING. LOW LEVEL THICKNESSES TONIGHT DROP INTO THE 1235-1240M RANGE. IN PAST EVENTS...THIS RESULTED IN MIN TEMPS IN THE 5-10 ABOVE RANGE. MOS CONSENSUS CLUSTERING A LITTLE ABOVE THESE VALUES AND WILL FOLLOW SUIT. MIN TEMPS 10-15 ABOVE. WITH SUSTAINED WINDS 5-10 MPH OVERNIGHT...WIND CHILL VALUES AROUND 5 ABOVE WILL BE COMMON. WILL CONTINUE TO HIGHLIGHT COLD WIND CHILLS IN THE HWO. && .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 /12Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 642 AM SATURDAY HIGH CONFIDENCE THAT VFR WILL EXIST ACROSS CENTRAL SUNDAY THROUGH SUNDAY. EXCEPT FOR A FEW-SCATTERED STRATOCU TODAY...SKIES WILL BE CLEAR. SFC WINDS WILL BE BRISK WITH GUSTS 22-27KTS HIGHLY PROBABLE FROM THE NW. THESE BRISK WINDS WILL SLOWLY SUBSIDE LATER TONIGHT. VFR CONDITIONS TO CONTINUE INTO SUNDAY THOUGH MID-HIGH LEVEL CLOUDS WILL BE INCREASING DURING THE DAY AS AN AREA OF LOW PRESSURE APPROACHES FROM THE WEST. MOISTURE AHEAD OF THIS SYSTEM WILL LEAD TO SUB VFR CEILINGS ALONG WITH PATCHES OF PRECIPITATION LATE SUNDAY NIGHT INTO MONDAY. AT ONSET...THIS PRECIPITATION MAY OCCUR AS A WINTRY MIX. THE SUB VFR CONDITIONS MAY LINGER INTO EARLY TUESDAY WITH IMPROVING CONDITIONS LATE TUESDAY INTO WEDNESDAY.
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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...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS CLIMATE...RAH

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