Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 130841 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 340 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/...
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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.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
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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.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 315 PM FRIDAY... ...STORM SYSTEM LIKELY TO BRING WINTRY WEATHER THREAT SUN NIGHT/MON FOLLOWED BY HEAVY RAIN THREAT AND A FEW STORMS MON NIGHT/TUE... SUNDAY: CONTINUED CHILLY WITH THE ARCTIC HIGH PRESSURE EXTENDING FROM THE ERN GREAT LAKES DOWN THROUGH NC. WILL HAVE INCREASING CLOUDS AHEAD OF THE APPROACHING STORM... AS OUR MID LEVEL FLOW SHIFTS FROM FAST NORTHWESTERLY TO WEST-SOUTHWEST... A FUNCTION OF PACIFIC NORTHWEST ENERGY DIVING INTO AN INITIALLY FLAT/BROAD CENTRAL CONUS TROUGH CAUSING ITS AMPLIFICATION. STATISTICAL GUIDANCE STILL SUPPORTS HIGHS FROM 29 NE TO 35 SW. -GIH SUN NIGHT THROUGH TUE: OVERVIEW: CONFIDENCE IS BEGINNING TO INCREASE REGARDING THE TIMING... MOST PROBABLE PRECIP TYPE PATTERN... AND PRIMARY WEATHER THREATS FOR THE INCOMING SYSTEM. LATEST GUIDANCE SHOWS A BIT QUICKER ONSET... WITH PRECIP ARRIVING IN THE NRN/WRN CWA SUN NIGHT... AS WELL AS A SLIGHTLY EARLIER DEPARTURE ON TUE. LONGWAVE TROUGHING WILL CONTINUE TO AMPLIFY ALONG THE MISS VALLEY AS NRN STREAM ENERGY DROPS INTO ITS BASE OVER THE GULF STATES... CULMINATING IN A NARROW DEEP SHORTWAVE TROUGH TAKING ON A POSITIVE TILT AS IT SWINGS ENE INTO THE CAROLINAS. AT THE SURFACE... THE POLAR HIGH SITUATED OVER THE NORTHEAST AND MIDATLANTIC STATES SUN NIGHT CONTINUES TO PUSH STEADILY NORTHEAST AND OFFSHORE 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 WRN NC MON NIGHT/TUE MORNING BEFORE MOVING QUICKLY INTO THE NORTHEAST STATES... WITH A TRAILING FRONT SWEEPING THROUGH CENTRAL/ERN NC BY EARLY TUE AFTERNOON. PRECIPITATION CHANCES: THE INITIAL 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. WILL TREND POPS UP TO LIKELY NW AND RETAIN HIGH CHANCES ACROSS THE SOUTH AND EAST SUN NIGHT INTO MON MORNING... WITH QPF FAIRLY LIGHT... UNDER A QUARTER INCH MAINLY IN THE NW. BUT THIS CHANGES QUICKLY WITH THE ADDITION OF STRONG UPPER DIVERGENCE (DUE TO IDEALLY JUXTAPOSED POLAR AND SUBTROPICAL JETS) AND VIGOROUS LOW LEVEL MOISTURE TRANSPORT EAST OF THE LOW. WILL RAMP UP POPS FURTHER TO CATEGORICAL WEST/LIKELY EAST LATE MON... THEN TO CATEGORICAL EVERYWHERE MON NIGHT THROUGH TUE MORNING... ENDING SW TO NE TUE AFTERNOON. PTYPES: USING THE TOP-DOWN METHODOLOGY WITH CONSIDERATION OF THE INITIALLY VERY COLD/DENSE NATURE OF THE SURFACE AIR MASS... THE INITIAL COLD AIR ALOFT GIVING WAY TO A WARM NOSE... AND THE STRONG LOW LEVEL WARM ADVECTION APT TO DISLODGE THIS SURFACE AIR MASS GRADUALLY FROM SE TO NW MON 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 SLOW STEADY 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. TENTATIVE ACCUMULATIONS ARE UP TO ONE TO TWO HUNDREDTHS OF AN INCH OF ICING (TRACE AMOUNTS) FOR MUCH OF THE CWA... AND SNOW TOTALS OF 1-3" NW QUARTER WITH AN INCH OR LESS ELSEWHERE... ALL OF WHICH SHOULD BE QUICKLY SWEPT AWAY BY MODERATE TO POTENTIALLY HEAVY RAINFALL LATE MON NIGHT INTO TUE MORNING. RAINFALL TOTALS AND STORM POTENTIAL: AT THIS TIME STORM TOTAL LIQUID QPF IS EXPECTED TO BE 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 SEVERAL RIVERS AND CREEKS RUNNING HIGH... A FLOOD WATCH MAY BE NEEDED FOR SOME PORTION OF THE AREA. ALSO... WHILE LAPSE RATES ARE UNLIKELY TO BE VERY IMPRESSIVE... 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 ON TUE. TEMPS: EXPECT LOWS SUN NIGHT OF 22-26. 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 MID 40S SE MON NIGHT... AND PEAKING AT 48-56 TUE PRIOR TO FRONTAL PASSAGE. WED THROUGH FRI: WE MAY SEE A PERTURBATION SWING THROUGH THE LONGWAVE ERN TROUGH BASE ACROSS VA ON WED... BUT MODELS VARY ON THE STRENGTH AND LATITUDE OF ANY SUCH WAVE... AND REGARDLESS THE MOISTURE WILL BE LIMITED YIELDING NO IMPACTS ON CENTRAL NC OTHER THAN SOME CLOUDS ACROSS THE NORTH. OTHERWISE... THIS PERIOD WILL FEATURE A TRANSITION AWAY FROM WRN RIDGE/ERN TROUGH OVER THE CONUS... AS FLAT RIDGING BUILDS OVER THE GULF/SOUTHEAST STATES FROM THE WEST... WITH A NET RESULT OF DRY WEATHER AND NEAR TO SLIGHTLY ABOVE NORMAL TEMPS FOR CENTRAL NC. -GIH && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 1240 AM SATURDAY A LAYER OF SCATTERED-BROKEN STRATOCU WILL LINGER ACROSS THE NORTHERN COUNTIES THROUGH 10Z...THEN GRADUALLY DIMINISH. THE LEADING EDGE OF AN ARCTIC AIRMASS WILL OVERSPREAD CENTRAL NC THROUGH 11Z. SFC WINDS WILL GUSTS BETWEEN 20-25KTS WITH THE PASSAGE OF THE BOUNDARY. AFTER 11Z...EXPECT VFR CONDITIONS WITH FEW-SCATTERED STRATOCU. 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 MORNING. 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. && .CLIMATE...
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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
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...WSS CLIMATE...RAH

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