Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191904 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 205 PM EST FRI DEC 19 2014 .SYNOPSIS...HIGH PRESSURE CENTERED OVER THE GREAT LAKES REGION WILL BUILD SLOWLY INTO OUR REGION THROUGH SATURDAY... AS LOW PRESSURE TRACKS JUST TO OUR SOUTH. THIS HIGH WILL SHIFT EAST OVER THE CANADIAN MARITIMES THROUGH SUNDAY... WHILE EXTENDING SOUTHWARD INTO NORTH CAROLINA. AN UPPER LEVEL DISTURBANCE WILL PASS OVERHEAD ON MONDAY... WHILE A STRONG STORM SYSTEM STARTS TO TAKE SHAPE OVER THE GULF COAST REGION. THIS SYSTEM WILL APPROACH OUR AREA FROM THE SOUTHWEST LATE TUESDAY INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 943 AM FRIDAY... TODAY...AS EXPECTED...EARLIER CLOUDINESS HAS DISSIPATED AND SKIES HAVE CLEARED OUT NICELY OVER CENTRAL NC. EXPECT THIS TO CONTINUE FOR THE NEXT SEVERAL HOURS BEFORE SOME HIGHER CLOUDS COULD BEGIN TO CREEP IN LATER THIS AFTERNOON. PLUS OR MINUS 5 KT WINDS THIS MORNING GENERALLY OUT OF THE NORTH NORTHWEST. THESE COULD VEER AROUND TO NORTH OR NORTH NORTHEASTERLY AS THE MORNING PROGRESSES. OTHERWISE COOL AIRMASS IN PLACE WILL KEEP TEMPERATURES DOWN A BIT BELOW NORMAL WITH MAX TEMPS IN THE LOWER 50S NORTH TO MID 50S SOUTH. -ELLIS TONIGHT...A S/W LIFTING E-NE FROM THE SOUTHERN PLAINS WILL ADVANCE EAST ACROSS THE LOWER MS VALLEY TONIGHT. WARM AIR ADVECTION AHEAD OF THIS SYSTEM WILL INCREASE MOISTURE ACROSS OUR REGION...RESULTING IN THICKENING CLOUD COVERAGE FROM THE WEST-SW. MODEST ISENTROPIC UPGLIDE MAY CAUSE PATCHES OF LIGHT RAIN TO DEVELOP OVER THE FAR WESTERN-SOUTHERN PIEDMONT PRIOR TO DAYBREAK. MIN TEMPS GENERALLY IN THE LOW-MID 30S THOUGH SOME PLACES IN THE WEST AND SOUTHWEST WILL SEE MIN TEMPS OCCUR SHORTLY AFTER MIDNIGHT...WITH TEMPS HOLDING STEADY THEREAFTER DUE TO THE THICKENING CLOUDS. -WSS && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 315 AM FRIDAY... S/W CROSSING THE DEEP SOUTH EARLY SATURDAY WILL SPREAD MOISTURE INTO CENTRAL NC. BEST LIFT THROUGH THE COLUMN ASSOCIATED WITH SPEED CONVERGENCE AT 700MB AND MODEST HEIGHT FALLS IN THE MID LEVELS. THE MODEL GUIDANCE HAS BEEN TRENDING DRIER COMPARED TO 48-72 HOURS AGO WITH SOME NEAR TERM MODELS NOW SUGGESTING LITTLE IF ANY MEASURABLE PRECIP OVER THE NORTHERN PIEDMONT. WILL NEED TO MONITOR THE DEVELOPING RAIN SHIELD OVER THE LOWER MS VALLEY TODAY...AND THE TN VALLEY/DEEP SOUTH TONIGHT. PER LATEST MOISTURE PROFILES AND LIFT...FELL THAT A FEW HUNDREDTHS PROBABLE ACROSS THE PIEDMONT SATURDAY MORNING. THUS HAVE ADJUSTED POPS BACK INTO THE LIKELY CATEGORY OVER THE NW PIEDMONT AND MAINTAINED A LIKELY POPS IN THE SOUTH. FOR AREAS NORTH AND EAST OF RDU..CONTINUED CHANCE POPS. AGAIN...WHAT PRECIP THAT OCCURS WILL BE LIGHT WITH AMOUNTS VARYING BETWEEN A TRACE TO LESS THAN A TENTH OF AN INCH. NAM AND GFS BUFKIT SOUNDINGS SUGGEST A BRIEF OPPORTUNITY FOR MIXED PRECIP IN THE NW PIEDMONT AROUND DAYBREAK...COINCIDING WITH THE BEST LIFT. THE GFS AND NAM HAVE TRENDED SLIGHTLY COOLER WITH PARTIAL THICKNESSES SUGGESTING A RAIN/SNOW MIX POSSIBLE IN THE TRIAD AND POSSIBLY THE ROXBORO AREAS...MAINLY WHEN HEAVIER PRECIP INTENSITY IS OCCURRING. WHILE BULK OF PRECIP WILL BE LIQUID...CANNOT RULE OUT THE POSSIBILITY OF SOME SNOW MIXED IN AT TIMES NORTH OF TEH I-85/40 CORRIDOR IN THE TRIAD. HIGH TEMPS SATURDAY DEPENDENT UPON EXTENT OF PRECIP SATURDAY AND WHETHER PRECIP DOES DIMINISH SATURDAY AFTERNOON. HAVE ADJUSTED MAX TEMPS UP A DEGREE OR TWO. HAVE LEANED TOWARD A DRIER FORECAST FOR SATURDAY NIGHT AS SUBSIDENCE IN THE WAKE OF THE DEPARTING S/W SHOULD END THE THREAT OF PRECIP ACROSS THE REGION BY LATE SATURDAY...AND MORE SO SATURDAY EVENING WITH SOME DECREASE IN CLOUDS POSSIBLE AFTER SUNSET. IF ENOUGH CLEARING OCCURS...MAY SEE POCKETS OF FOG DEVELOP AFTER MIDNIGHT. IN ANTICIPATION OF SOME PARTIAL CLEARING...HAVE LOWERED MIN TEMPS A FEW DEGREES FROM THE PREVIOUS FORECAST (LOW-MID 30S). SUNDAY: SURFACE HIGH PRESSURE WILL CONTINUE TO EXTEND SOUTHWARD INTO THE AREA FROM NEW ENGLAND ON SUNDAY... WHILE BRIEF MID LEVEL S/W RIDGING BUILDS ACROSS CENTRAL NC. HOWEVER... THE NEXT SOUTHERN STREAM S/W DISTURBANCE WILL BEGIN TO SPREAD CLOUD COVER NORTHEASTWARD FROM THE GULF OF MEXICO AND INTO OUR REGION. THIS WILL YIELD PARTLY SUNNY SKIES DURING THE MID MORNING BECOMING MOSTLY CLOUDY BY LATE DAY INTO THE EVENING. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO BE NEAR NORMAL. THUS... GIVEN WE SHOULD SEE SOME SUN ON SUNDAY EXPECT HIGH TEMPS WILL BE NEAR NORMAL... FROM AROUND 50 N TO LOWER 50S SOUTH. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... AS OF 205 PM FRIDAY... FOR SUN NIGHT THROUGH MON NIGHT: COOL SURFACE HIGH PRESSURE CENTERED OVER FAR SERN CANADA WILL CONTINUE TO WEDGE SSW THROUGH CENTRAL NC SUN NIGHT/MON. THE MID LEVEL WAVE NOW OFF THE PACIFIC COAST WILL TRACK EAST AND DIG THROUGH THE SRN PLAINS SUN... THEN KICK NORTHEAST THROUGH THE LOWER MISS VALLEY TOWARD THE OH VALLEY/MIDSOUTH/SRN APP REGION... DAMPENING IN THE PROCESS AS NRN STREAM ENERGY BEGINS TO DIG AND PHASE WITH A SRN STREAM WAVE OVER THE CENTRAL CONUS. THE APPROACH OF THE INITIAL WEAKENING WAVE AND RESULTANT HEIGHT FALLS HELP SATURATE THE MID-UPPER LEVELS FIRST SUN NIGHT... THEN AS THE 700-850 MB WARM FRONTAL ZONE APPROACHES FROM THE SOUTH WITH STRENGTHENING LOW LEVEL MOIST ISENTROPIC UPGLIDE AROUND 290K-295K... EXPECT PRECIP TO SPREAD INTO OUR AREA FROM THE SSW AS THE COLUMN SATURATES. MODEL TIMING AND THEIR RECENT SLOWING TRENDS SUGGEST A MID EVENING ONSET TIME IN THE SW... SPREADING NNE OVERNIGHT. EXPECT THE BEST COVERAGE AND HIGHEST AMOUNTS WILL BE ALONG THE MORE STEEPLY SLOPED PORTION OF THE COLD DOME SURFACE OVER THE PIEDMONT... AND WILL RAISE POPS HERE TO LIKELY... AND IF TRENDS CONTINUE... CATEGORICAL POPS MAY BE NEEDED STARTING OVERNIGHT SUN NIGHT. HIGH COVERAGE (70-80%) OF RAIN SHOULD CONTINUE TO PUSH NORTHEAST THROUGH CENTRAL NC MON MORNING... AND INTO NE NC IN THE AFTERNOON... WITH PRECIP THEN TAPERING DOWN TO PATCHY DRIZZLE OR LESS OVER CENTRAL NC FROM SW TO NE MON AFTERNOON AS THE DRY SLOT ARRIVES FROM THE SW BEHIND THE RETREATING MID LEVEL WARM FRONTAL ZONE... RESULTING IN TOP-DOWN DRYING. THIS IS VERY CLOSE TO THE PREVIOUS FORECAST TRENDS. THE LOW LEVELS WILL REMAIN COOL/MOIST AND STABLE... AS THE DAMMING WEDGE SHOULD HOLD FIRM... REINFORCED BY NE FLOW AROUND SURFACE LOW PRESSURE OVER THE OUTER BANKS OR SOUNDS LATE MON. WILL RETAIN OVERCAST SKIES (LOW CLOUDS PLUS SOME HIGH CLOUDINESS AS THE DIGGING CENTRAL CONUS TROUGH YIELDS INCREASING SW MID LEVEL FLOW INTO NC) AND LOW CHANCE POPS MON NIGHT WITH THE POTENTIAL FOR SOME DRIZZLE IN THIS REGIME. THICKNESSES AND BUFR SOUNDINGS INDICATE ALL-LIQUID PRECIP WITH THIS EVENT ACROSS CENTRAL NC. THE GFS/ECMWF HINT AT SOME INLAND PROGRESSION OF THE ASSOCIATED WEDGE WARM FRONT INTO CENTRAL NC... HOWEVER THIS LOOKS UNLIKELY TO MAKE MUCH HEADWAY GIVEN AN EXPECTED STRONG COLD DOME... AND WILL NOT INDICATE A DRASTIC WARMUP IN THE COASTAL PLAIN MON NIGHT... ALTHOUGH TEMPS ARE LIKELY TO BUDGE LITTLE FROM MON TO MON NIGHT GIVEN THE WARMING ALOFT. LOWS SUN NIGHT IN THE UPPER 30S TO MID 40S... AND HIGHS MON IN THE LOW 40S TO LOWER 50S (ALTHOUGH THIS DIURNAL RISE IN TEMPS MAY BE TOO LARGE IF WE SEE STEADY PRECIP INTO THE WEDGE ALL DAY LONG). LOWS MON NIGHT FROM AROUND 40 NW TO UPPER 40S SE. FOR TUESDAY THROUGH FRIDAY: STILL LOOKS LIKE A STORMY PATTERN FOR MID WEEK... ALTHOUGH SOME IMPROVEMENT TO QUIETER WEATHER APPEARS PROBABLE FOR CHRISTMAS DAY AND FRIDAY. WE`LL START THIS PERIOD WITH THE PARENT SURFACE HIGH OVER THE CANADIAN MARITIMES SHIFTING EASTWARD YET STILL EXTENDING SE DOWN THROUGH WRN/CENTRAL NC... WHILE THE COASTAL/WEDGE FRONTAL ZONE SITS OVER COASTAL NC EXTENDING BACK THROUGH NRN GA TO A SURFACE LOW OVER THE MIDWEST. MID LEVEL LOW PRESSURE CONTINUES TO DEEPEN OVER THE CENTRAL CONUS TUE... THEN DRIFT NE AS ITS LONGWAVE TROUGH PIVOTS EASTWARD INTO THE EASTERN STATES WED. THE GFS/ECMWF BRING THE WEDGE FRONT WELL INLAND TUE EVENING/NIGHT... AS THE PRIMARY SURFACE LOW MOVES OVER LAKE MICHIGAN AND A TRIPLE POINT LOW PUSHES INTO SW NC (MORE PROMINENT ON THE ECMWF THAN THE GFS). TRYING TO TRACK THE PROGRESSION OF WEDGE FRONTS ASSOCIATED WITH LATTER-STAGE DAMMING EVENTS IS ALWAYS DIFFICULT... GIVEN THAT THE PARENT HIGH WILL BE PUSHING OVER AND JUST OFF THE MARITIMES BUT MAINTAINING A CENTRAL STRENGTH NEAR 1030 MB. WILL FOLLOW THE CLIMATOLOGICAL LEANINGS OF SUCH EVENTS AND KEEP A COOL STABLE REGIME IN THE NW PIEDMONT... AS IS TYPICAL WITH THESE EVENTS. WE SHOULD SEE THE RELATIVE LULL IN PRECIP EXTEND INTO TUE... CONTINUED CLOUDY SKIES AND A CHANCE OF LIGHT RAIN AS THE COLUMN REMAINS FAIRLY MOIST BUT WITH MARGINAL/WEAK FORCING FEATURES. STRENGTHENING AND DEEPENING MOISTURE INFLUX AT MULTIPLE LEVELS WILL OCCUR TUE NIGHT INTO WED... INCLUDING STRENGTHENING LOW LEVEL MOIST ISENTROPIC UPGLIDE AND INCREASING UPPER DIVERGENCE AS MID-UPPER LEVEL WINDS INCREASE JUST TO OUR SW. WILL STICK WITH POPS INCREASING TO LIKELY FOR NOW. THE GFS/ECMWF STILL INDICATE THE OCCLUDED/COLD FRONT SWEEPING ENE THROUGH THE REGION SOMETIME WED (WITH THE ECMWF SLIGHTLY FASTER THAN THE GFS)... AND DEPENDING ON THE LOCATION/TRACK OF VORTICITY CENTERS AND THE TRIPLE POINT LOW... WE MAY STILL SEE A THREAT OF A FEW STRONG STORMS LATE TUE NIGHT INTO WED IF WE ARE ABLE TO ACHIEVE ANY INSTABILITY... AND WE WILL CONTINUE TO MONITOR FOR THIS POTENTIAL AS THIS TIME FRAME APPROACHES. IMPROVING CONDITIONS ARE EXPECTED THE EVENING OF CHRISTMAS EVE AS THE COLUMN DRIES OUT... ALTHOUGH WE SHOULD KEEP SOME CLOUDS WITH THE TROUGH AXIS SWINGING THROUGH THE REGION. TEMPS TUE/WED ARE TRICKY AND DON`T HAVE A LOT OF CONFIDENCE... AS A MINOR SWING ONE WAY OR THE OTHER WITH THE WEDGE FRONT OR LOW TRACKS WILL GREATLY ALTER TEMPS. WITH EXPECTATIONS OF SOME DAMMING AIR MASS HOLDING IN THE NW CWA... EXPECT HIGHS TUE FROM 49 NW TO 61 SE. MINIMAL DROP TUE NIGHT WITH STRENGTHENING LOW LEVEL WINDS AND POSSIBLE ERODING WEDGE AIR MASS OVER MOST OF THE CWA... AND WILL GO WITH LOWS OF 44-52. HIGHS 52 NW TO 61 SE WED WITH ALL BUT POSSIBLY THE NW CWA IN THE WARM SECTOR. TEMPS SHOULD THEN FALL OFF WED EVENING/NIGHT WITH RAPIDLY CLEARING AND COOL AIR ADVECTION... TO LOWS OF 33-38. CHRISTMAS DAY AND FRI APPEAR FAIR WITH A WARMING TREND AS SOUTHERN-STREAM HIGH PRESSURE BUILDS OVER THE GULF AND SOUTHEAST STATES WITH DECREASING AMPLITUDE OF THE MID LEVEL FLOW. HIGHS IN THE LOW 50S CHRISTMAS DAY (NEAR NORMAL) AND MID TO UPPER 50S FRI. LOWS IN THE 30S. -GIH && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 100 PM FRIDAY... 24 HOUR TAF PERIOD: FAIRLY HIGH CONFIDENCE IN VFR CONDITIONS PERSISTING THROUGH THE TAF PERIOD. SKIES CONTINUE TO REMAIN MOSTLY CLEAR THIS AFTERNOON WITH VARYING COMPONENTS OF NORTHERLY WIND AT ROUGHLY 5 KTS. HIGH CLOUDS ARE EXPECTED TO FILTER IN OVERNIGHT TONIGHT WITH CEILINGS STARTING OUT IN THE 10-15 KFT RANGE. NEAR DAYBREAK THESE CEILINGS WILL BEGIN TO COME DOWN...MOST LIKELY INTO THE 3-5 KFT RANGE BY EARLY AFTERNOON AS A SHORTWAVE PASSES TO OUR SOUTH. WINDS WILL REMAIN LIGHT AND OUT OF THE NORTHEAST WITH LITTLE GUSTING. THERE IS A CHANCE OF SOME LIGHT RAIN IN THE SOUTH...MAINLY AT KFAY BEGINNING LATE MORNING/EARLY AFTERNOON AND LASTING INTO THE EARLY EVENING. ACCUMULATIONS SHOULD BE LIGHT AND VISIBILITIES SHOULD NOT BE AFFECTED BY ANY PRECIPITATION. IF HEAVIER PRECIPITATION MOVES IN WITH THE WAVE...CEILINGS COULD POTENTIALLY LOWER TO MVFR LEVELS BUT THIS IS UNCERTAIN AT THIS TIME. LONG TERM: BEYOND THE POTENTIAL RAIN ON SATURDAY INTO SATURDAY EVENING...THE NEXT CHANCE FOR ADVERSE CONDITIONS WILL BE ON MONDAY WITH A COASTAL LOW AND SOME POTENTIAL COLD AIR DAMMING. AFTER THAT THE PATTERN REMAINS UNSETTLED THROUGH MIDWEEK BEFORE CLEARING OUT FOR CHRISTMAS EVE NIGHT AND INTO CHRISTMAS DAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...ELLIS/WSS SHORT TERM...WSS/BSD LONG TERM...HARTFIELD AVIATION...ELLIS

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