Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211155 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 655 AM EST FRI NOV 21 2014 .SYNOPSIS...BEHIND A COLD FRONT...HIGH PRESSURE BUILDS OVER THE REGION FOR TODAY AND SATURDAY. A STRONG LOW PRESSURE SYSTEM MOVING FROM THE SOUTH PLAINS INTO THE GREAT LAKES SUNDAY SPREADS MOISTURE OVER THE ENTIRE REGION DURING THE DAY SUNDAY. ANOTHER COLD FRONT MOVES EAST ACROSS MUCH OF THE MID-ATLANTIC AND CAROLINAS ON MONDAY. && .NEAR TERM /TODAY THROUGH SATURDAY NIGHT/... AS OF 655 AM FRIDAY... THE LATEST SURFACE ANALYSIS SHOWED THE COLD FRONT ALMOST THROUGH CENTRAL NORTH CAROLINA WITH COOLER...DRIER AIR GRADUALLY MOVING SOUTH. SURFACE OBSERVATIONS ALREADY SHOWED SOME DEW POINTS IN THE NORTHWEST PIEDMONT HAVING FALLEN INTO THE TEENS...AND THESE SHOULD CONTINUE TO MOVE SOUTH AND DRY EVEN MORE WITH SURFACE DEW POINTS FALLING TO AROUND 10F TO THE TEENS DURING THE DAY. THE 00Z 850MB ANALYSIS NOTED NOTICEABLE COOLING TO THE NORTHWEST...FROM 2C AT KGSO AND -2C AT KRNK TO -11C AT KILN. 1000-850MB THICKNESSES WILL RISE LITTLE IF AT ALL TODAY AND THE RESULT IS AROUND 10F OR SO OF COOLING TODAY...DESPITE THE MANY TEMPERATURES IN THE 30S AS OF THIS WRITING. SOME CIRRUS IN THE BASE OF THE BROAD UPPER TROUGH WILL BE NOTICED ESPECIALLY THIS MORNING...BUT THE BUFR SOUNDINGS AND THE CANADIAN CLOUD COVER MODEL SUGGEST ENOUGH DRYING ALOFT ALTHOUGH THE 300MB JET AXIS WILL BE OVERHEAD THAT MUCH OF ANY CIRRUS SHOULD BE ABSENT BY AFTERNOON. THE CIRRUS IS LIKELY DUE...IN PART...TO SOME UPSTREAM ENHANCEMENT ON WATER VAPOR IMAGERY MOVING ACROSS THE OHIO VALLEY COINCIDENT WITH A MID-LEVEL WAVE MOVING OVER THE APPALACHIANS. ONCE THE WAVE PASSES DURING THE FIRST HALF OF THE DAY...THE HIGH CLOUDS SHOULD START TO WANE. THE SURFACE GRADIENT IS A LITTLE TIGHTER THIS MORNING AND BUFR SOUNDINGS ALONG WITH SOUNDINGS FROM THE RAP SUGGEST A FEW GUSTS IN THE MIDDLE AND UPPER TEENS POSSIBLE WITH MIXING BEFORE HIGH PRESSURE MOVING OVERHEAD TONIGHT REALLY LIGHTENS THE WINDS. OVERNIGHT...HIGH-LEVEL RELATIVE HUMIDITY FORECASTS FROM THE NAM AND GFS SUGGESTS THE POTENTIAL FOR SOME THIN CIRRUS AS THE BROAD RIDGE AXIS APPROACHES FROM THE WEST. THE CANADIAN CLOUD COVER MODEL DEPICTS SIMILAR CONDITIONS TO THE MAV AND MET MOS...CLEAR TO FEW CLOUDS WHICH...UNDER A LIGHT WIND AND DRY SURFACE DEW POINTS... SHOULD ALLOW TEMPERATURES TO FALL QUICKLY TONIGHT. MAV AND MET GUIDANCE ARE CLOSE AND TENDED TO STRAY COOLER ESPECIALLY FROM THE TRIANGLE NORTH AND EAST WHERE ANY CIRRUS SHOULD BE EVEN THINNER AND LESS NOTICEABLE. THINK SOME TEENS ARE QUITE POSSIBLE ESPECIALLY IN THE TYPICALLY COOLER LOCATIONS NORTHEAST OF THE TRIANGLE. THE RECORD LOWS AT KGSO AND KFAY APPEAR SAFE FOR SATURDAY...BUT IT WILL BE CLOSE AT THE RELATIVELY WARM RECORD LOW AT KRDU. SATURDAY...AGAIN WITH SOME MOSTLY THIN CIRRUS AROUND...1000-850MB THICKNESSES RISE ABOUT 30M AND HIGHS SHOULD BE 3 TO 5 DEGREES WARMER THAN THOSE HIGHS EXPECTED FOR TODAY. SATURDAY NIGHT...THE 850MB THETA-E GRADIENT IS FORECAST BY THE NAM AND GFS TO JUST BE MOVING INTO THE FAR SOUTHWEST PIEDMONT BY 12Z SUNDAY. K INDICES ARE NEAR 0 OR NEGATIVE ON THE GFS THROUGH SATURDAY NIGHT...AND THE NAM ONLY INCREASES VALUES INTO THE TEENS IN THE FAR SOUTHWEST CLOSE TO 12Z SUNDAY. BUFR SOUNDINGS ARE DRY AND STABLE FOR THE NIGHT...SAVE LATE AND MAINLY ON THE NAM WHERE THE MID-LEVEL MOISTURE IN A SHALLOW VOLUME INCREASES A LITTLE EARLIER SOUTHWEST. QPF IS ESSENTIALLY ZERO IN CENTRAL NORTH CAROLINA ON BOTH THE NAM AND GFS...WITH THE 0.01 LINE ON THE NAM EDGING EVER SO CLOSE TO THE SOUTHWEST PIEDMONT BY 12Z SUNDAY. WILL MAINTAIN A DRY FORECAST OVERNIGHT SATURDAY ALTHOUGH A SPRINKLE IS POSSIBLE VERY LATE SATURDAY NIGHT IN THE FAR SOUTHWEST IF ANY CAN WORK THROUGH WHAT WILL BE A DRY SUB-CLOUD LAYER. OVERNIGHT LOWS WILL PROBABLY BE REACHED EARLY IN THE OVERNIGHT...WITH TEMPERATURES FALLING QUICKLY EARLY AND THEN INCREASING HIGH CLOUDS IN PARTICULAR SLOWING ANY FALL AND WITH POSSIBLY A MINOR RISE IN TEMPERATURES LATE OVER THE WESTERN PIEDMONT. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 235 AM FRIDAY... SOUTHERN STREAM TROUGH AND ATTENDANT DEEPENING SURFACE LOW OVER THE SOUTHERN PLAINS/LOWER MS VALLEY SUNDAY MORNING WILL LIFT NORTHWARD INTO THE UPPER GREAT LAKES SUNDAY NIGHT. WHILE THE BEST TROUGH DYNAMICS REMAINS WEST OF THE MOUNTAINS...STRONG/DEEP GULF MOISTURE TRANSPORT WITHIN THE TRANSIENT EASTWARD PROPAGATING WARM CONVEYOR BELT WILL RESULT IN A WET SUNDAY-SUNDAY EVENING PERIOD ACROSS THE CAROLINAS. AS PWATS INCREASE TO 1.5-1.75"(2 SD ABOVE NORMAL)...LOOK FOR POPS TO QUICKLY RAMP UP SW TO NE LATE SUNDAY MORNING THROUGH THE AFTERNOON VIA SURGE OF ISENTROPIC LIFT/WAA ATTENDANT TO A NORTHWARD LIFTING WARM FRONT...AND FURTHER AUGMENTED BY DPVA AHEAD OF SHORTWAVE DISTURBANCES EJECTING NEWD AHEAD OF THE AFOREMENTIONED PRIMARY TROUGH LIFTING THROUGH THE TN AND OHIO VALLEY. EXPECT WIDESPREAD RAINFALL AMOUNTS OF A 0.50" TO AN 1.0". BULK OF PRECIP LOOKS TO FALL OVER THE AREA BETWEEN 18Z SUNDAY TO 06Z MONDAY WITH LIGHT RAIN...DRIZZLE AND/OR AREAS OF FOG THROUGH MONDAY MORNING AS WE LOSE SATURATION ALOFT. IMPRESSIVE LOW-LEVEL KINEMATIC WIND FIELDS FUELED BY A 60-65KT LOW- LEVEL JET COUPLED WITH ENHANCED NEAR SURFACE HELICITY/SHEAR ALONG A NORTHWARD RETREATING WEDGE FRONT LOOKS TO HAVE LIMITED BUOYANCY TO WORK WITH MODELS KEEPING THE UNSTABLE PORTION OF THE WARM SECTOR NEAR OR OFF THE SE COAST. WILL CONTINUE TO MONITOR FOR ANY INLAND INTRUSION OF UNSTABLE AIR INTO INLAND AREAS...BUT BASED ON RECENT TRENDS WILL KEEP THUNDER OUT OF THE FORECAST. IN-SITU DAMMING FROM THE OFFSHORE HIGH AND WIDESPREAD RAIN WILL RESULT IN A SLOW RISE IN TEMPERATURES DURING THE DAY ON SUNDAY...UNTIL THE WARM FRONT LIFTS NORTH THROUGH THE AREA DURING THE LATE AFTERNOON/EVENING HOURS. DAYTIME HIGHS WILL OCCUR AFTER SUNSET IN MANY LOCATIONS WITH TEMPERATURES HOLDING STEADY OR QUITE POSSIBLY WARM OVERNIGHT. DAYTIME TEMPERATURES HOLDING IN THE 50S ACROSS THE NW PIEDMONT...WITH 60S ACROSS THE SE. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 235 AM FRIDAY... MONDAY AND MONDAY NIGHT: IN THE MIDST OF THE UPSTREAM TROUGH OVER THE CENTRAL US RELOADING...MID-LEVEL DRY AIR INTRUSION FROM THE WEST AND THE LACK OF APPRECIABLE FORCING WILL RESULT IN MOSTLY DRY CONDITIONS DURING THE DAY ON MONDAY. MODELS ARE STILL TRYING TO GENERATE A LITTLE PRECIP UNTIL THE SFC COLD FRONT MOVES THE AREA MONDAY EVENING/NIGHT...BUT RECENT MODEL TRENDS TO KEEP THE BULK OF PRECIP EAST OF THE AREA. WILL HANG ON TO SLIGHT TO SMALL CHANCE POPS WITH HIGHEST CHANCE IN THE EAST. LINGERING LOW-LEVEL MOISTURE TRAPPED UNDERNEATH A STRONG MID-LEVEL CAP WILL RESULT IN CONTINUED CLOUDY CONDITIONS ON MONDAY. EVEN WITH THIS OVERCAST/BROKEN CLOUD DECK...TEMPERATURES IN THE WARM SECTOR WILL WARM INTO THE 60S NW TO 70S SE ON MONDAY. TUESDAY THROUGH THURSDAY: TUESDAY IS SHAPING UP AS A DRY DAY ACROSS THE AREA WITH THE STALLED FRONT EAST OF THE AREA WHILE WEAK HIGH PRESSURE RIDGES IN FROM THE WEST WITH CAA IN THE WAKE OF MONDAY NIGHT FROPA DROPPING TEMPERATURES BACK TO NEAR NORMAL. THERE IS THEN A BIT OF UNCERTAINTY REGARDING THE APPROACH OF THE NEXT BATCH OF SHORTWAVE ENERGY TRAVERSING EASTWARD WITHIN THE BASE OF THE LONGWAVE TROUGH AND ASSOCIATED SFC CYCLOGENESIS ALONG THE OFFSHORE FRONTAL ZONE. THE LATEST GFS AND EC HAVE TRENDED WETTER DURING THE TUESDAY NIGHT-WEDNESDAY PERIOD...WITH PRECIP DEVELOPING INLAND IN THE COOL SECTOR. FOR NOW...WILL ADD A SLIGHT CHANCE POPS TO COASTAL/EASTERN PORTIONS OF THE FORECAST AREA...WITH TEMPERATURES RETURNING TO BELOW NORMAL AS THE UPPER TROUGH MOVES INTO THE EASTERN US. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 655 AM FRIDAY... FOR THE 12Z VALID TAF PERIOD...VFR CONDITIONS CONTINUE WITH MOSTLY FEW-TO-SCATTERED HIGH CLOUDS. THIS MORNING...A BRIEF PERIOD OF BROKEN HIGH CLOUDS IS POSSIBLE BEFORE CLEARING LATER IN THE MORNING. THE SURFACE GRADIENT WILL INCREASE THIS MORNING HOURS SUCH THAT MODEL SOUNDINGS SUGGEST A FEW NORTHERLY GUSTS INTO THE TEENS KNOTS WITH MIXING THIS MORNING. AS THE SURFACE HIGH BUILDS OVERHEAD... WINDS SHOULD BECOME LIGHTER AS THEY VEER LATER IN THE DAY WITH MANY CALM OR VERY LIGHT SURFACE WINDS TAKING PLACE AFTER SUNSET. BEYOND THE 12Z VALID TAF PERIOD...VFR CONDITIONS CONTINUE SATURDAY THROUGH SATURDAY NIGHT. AS MOISTURE AND PRECIPITATION SPREAD NORTHEAST OVER CENTRAL NORTH CAROLINA SUNDAY...CONDITIONS SHOULD DETERIORATE THROUGH MVFR TO IFR IN MOST PLACES AND CONTINUE SUB-VFR AT LEAST THROUGH SUNDAY NIGHT. AREAS OF MVFR CEILINGS ARE POSSIBLE INTO MONDAY WITH GUSTY SOUTHWEST WINDS WHICH COULD REACH 40KT BY 2000FT ALOFT IF THE GFS MODEL VERIFIES. VFR CONDITIONS SHOULD RETURN BY TUESDAY WITH SOME AREAS OF MID-LEVEL CLOUDS OVER A LIGHTER SURFACE WIND VEERING NORTHERLY BEHIND A COLD FRONT THAT MOVES THROUGH LATE MONDAY. THERE IS A CHANCE OF LIGHT RAIN MAINLY TOWARD KFAY AND KRWI LATE TUESDAY ON THE WEST SIDE OF LOW PRESSURE THAT MOVES ALONG THE FRONT WHICH WILL LOCATED THEN JUST OFF THE CAROLINA COAST. && .CLIMATE... RECORD LOW: GSO RDUFAY SAT 11/22 - 13 IN 1914 21 IN 2008 20 IN 2000 && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...DJF SHORT TERM...CBL LONG TERM...CBL AVIATION...DJF CLIMATE...RAH

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