Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 192351 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 640 PM EST FRI DEC 19 2014 .SYNOPSIS...A SHORTWAVE LOW PRESSURE SYSTEM WILL TRACK SOUTH OF THE AREA ON SATURDAY...BRINGING SOME UNSETTLED WEATHER. OTHERWISE... HIGH PRESSURE TO THE NORTH WILL CONTROL THE PATTERN UNTIL A STRONGER LOW MOVES UP THE SOUTHEAST COAST FOR THE BEGINNING OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM FRIDAY... FORECAST REMAINS ON TRACK FOR TODAY WITH MOSTLY CLEAR SKIES ASIDE FROM A FEW HIGH LEVEL CLOUDS MAKING THEIR WAY IN FROM THE WEST. MOSTLY NORTHWESTERLY WINDS IN THE WESTERN HALF OF THE CWA WITH SOME NORTHEASTERLIES ALONG THE COAST AS A SURFACE HIGH OVER THE DELMARVA PENINSULA EXTENDS SOUTHWARD ALONG THE CAROLINA COAST. OVERALL THE TEMPERATURE FORECAST IS LOOKING VERY GOOD WITH MOST LOCATIONS IN THE LOW TO MID 40S AS HEATING BEGINS TO WIND DOWN THIS AFTERNOON. PERHAPS A FEW DEGREES TO WARM WITH FORECASTED MAX TEMPS IN THE EXTREME NORTHEAST AS OBSERVED TEMPS ONLY IN THE MID TO UPPER 40S THERE. FOR TONIGHT EXPECT CLOUD COVER TO GRADUALLY INCREASE WITH SOME CEILINGS FIRST APPEARING ABOVE 15 KFT BUT THEN GRADUALLY MAKING THEIR WAY DOWN TO ABOUT 10 KFT OR JUST BELOW AROUND DAYBREAK ON SATURDAY. DESPITE THE INCREASING CLOUD COVER...ANY PRECIPIATION IS EXPECTED TO HOLD OFF AT LEAST UNTIL SATURDAY MORNING. AS FAR AS TEMPERATURE DISTRIBUTION FOR THE LOW IS CONCERNED...CLOUDS WILL HOLD OFF THE LONGEST IN THE NORTHEAST...AND THUS THE LOWEST TEMPERATURES ARE EXPECT HERE WITH VALUES RIGHT AROUND OR JUST BELOW FREEZING EXPECTED. FURTHER SOUTH AND WEST...TEMPERATURES WILL BOTTOM OUT IN THE MID 30S WITH SOME COLDER POCKETS POSSIBLE IN THE RURAL AREAS. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 300 PM FRIDAY... A SOUTHERN STREAM SHORTWAVE IS EXPECTED TO ARRIVE FROM OUR SOUTHWEST ON SATURDAY MORNING. THE LAST SEVERAL NUMERICAL MODEL RUNS HAVE ALL TRENDED THIS SYSTEM TO BE DRIER...ESPECIALLY IN OUR NORTHERN COUNTIES. BOTH THE GLOBAL AND THE HIGH RESOLUTION MODELS DO THIS AND THEREFORE HAVE TRENDED BACK ON POPS AND QPF FORECASTS FOR SATURDAY WITH MAINLY CHANCES WITH SOME BRIEF LIKELIES ACROSS THE EXTREME SOUTHERN TIER DURING THE LATE MORNING/EARLY AFTERNOON. THIS ALSO SEVERELY HANDICAPS ANY THREAT OF SNOW ACROSS THE TRIAD THAT WAS POTENTIALLY BEING SHOWN BY PRIOR MODEL RUNS. FIRST...THERE MAY NOT EVEN BE PRECIPIATION AT ALL IN THIS AREA. IF PRECIPIATION DOES IN FACT OCCUR HERE...THE BEST OMEGA IS IN THE 700 MB LEVEL AND QUICKLY DIMINISHES ABOVE THAT. THUS CURRENT MODELS...INCLUDING THE NAM WHICH WAS THE MOST BULLISH ON THE SITUATION...NEARLY SATURATES IN THE 800- 600 MB LEVEL BUT LESS SO ABOVE THAT INTO THE SNOW GROWTH ZONE. INCLUDE A WARM BOUNDARY LAYER INTO THE MIX AND CHANCES ARE HIGH THAT ANY FALLING PRECIP WILL BE LIQUID. THE CONCLUDING UPSHOT OF THE DAY WILL BE AN OVERCAST DAY WITH TEMPERATURES IN THE MID 40S WITH BETTER CHANCES OF SOME VERY LIGHT RAIN IN THE SOUTH. THE SYSTEM WILL MOVE OUT TO THE EAST OVERNIGHT AND LOW TEMPERATURES ARE EXPECTED TO DROP IN TO THE LOW TO MID 30S WITH THE COLDEST TEMPS IN THE NORTHWEST PIEDMONT. SUNDAY WILL FEATURE HIGH PRESSURE BUILDING IN FROM THE NORTH AND STARTING TO MOVE INTO POSITION TO EVENTUALLY FORM A CAD WEDGE BUT INITIALLY WILL HELP AID SOME PARTIAL CLEARING EARLY SUNDAY BEFORE INCREASING CLOUDS FROM THE SOUTH TAKE OVER BY AFTERNOON. IT SHOULD BE A WARMER DAY THAN SATURDAY WITH TEMPS IN THE UPPER 40S NW TO LOWER 50S SE. INCREASING MOISTURE FROM APPROACHING SOUTHERN LOW WILL BRING DEWPOINTS UP NEAR 40 DEGREES BY THE END OF THE AFTERNOON BUT THE SURFACE HIGH WILL KEEP ANY PRECIPIATION SOUTH OF THE AREA THROUGH THE AFTERNOON. && .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 /00Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 640 PM FRIDAY... 24 HOUR TAF PERIOD: HIGH PRESSURE WILL RIDGE DOWN THE EAST COAST TONIGHT/SATURDAY. MEANWHILE...A SHORT LIVED OVERRUNNING SCENARIO WILL DEVELOP AS A COASTAL LOW PRESSURE AREA WILL DEVELOP WELL SOUTH OF THE NORTH CAROLINA COAST EARLY SATURDAY. THIS LOW WILL STRENGTHEN A BIT DURING THE DAY AS IT MOVES EAST AND FURTHER OFFSHORE. THE UPSHOT...VFR CONDITIONS ARE EXPECTED AS HIGH CLOUDINESS CONTINUES TO STREAM INTO THE AREA OVERNIGHT. EASTERLY LOW LEVEL FLOW WILL PUSH MOISTURE INTO THE AREA...WITH SOME LOWERING OF THE CLOUDINESS THROUGH THE DAY...WITH CEILINGS BY AFTERNOON IN THE 4-5KFT RANGE. SOME LIGHT RAIN IS EXPECTED ACROSS THE SOUTHERN TIER...AND MAY INDUCE OCCASIONAL MVFR CONDITIONS AT FAY BY MID DAY. ANY RAIN WILL BE ENDING BY THE END OF THE TAF PERIOD WITH DEEP DRYING AS ABOVE- SURFACE FLOW BECOMES WESTERLY. 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.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...ELLIS NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...MLM

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