Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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349 FXUS62 KRAH 051103 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 605 AM EST FRI FEB 5 2016 .SYNOPSIS... A STRONG UPPER LEVEL DISTURBANCE WILL CROSS THE AREA THIS MORNING. COOL HIGH PRESSURE WILL BUILD IN FROM THE WEST THIS AFTERNOON INTO THE WEEKEND. AN ARCTIC COLD FRONT WILL ARRIVE EARLY NEXT WEEK. && .NEAR TERM /TODAY THROUGH TONIGHT/... AS OF 145 AM FRIDAY... THE PRIMARY WEATHER CONCERN WILL TAKE PLACE FROM NOW THROUGH THIS MORNING... AS A POWERFUL SHORTWAVE TROUGH SWINGS ENE THROUGH THE REGION. CURRENTLY... WIDESPREAD RAIN PERSISTS OVER ERN NC INCLUDING THE ERN COASTAL PLAIN... AHEAD OF THE 700 MB TROUGH... WEST OF THE SURFACE FRONTAL ZONE NEAR THE COAST... ALONG WHICH A LOW PRESSURE CENTER NOW JUST EAST OF ILM WILL TRACK TODAY. THE LOW AND MID LEVELS WILL STEADILY COOL THIS MORNING AHEAD OF AN APPROACHING MID LEVEL TROUGH AND POWERFUL VORTICITY MAXIMUM... AND WITH CONTINUED DEEP MOISTURE BELOW 15 000 FT... PRECIP WILL CONTINUE TO DEVELOP AND FILL IN OVER THE PIEDMONT EARLY THIS MORNING BEFORE SHIFTING EASTWARD THROUGH MID MORNING. THE STRENGTHENING FORCING FOR ASCENT FROM DPVA IS LIKELY TO LIFT THIS SATURATION INTO THE -12C TO -20C LAYER... ENSURING A HIGH PROBABILITY OF ICE IN THE CLOUDS... AND RESULTING IN A BAND OF WHAT SHOULD BE MOSTLY LIGHT SNOW... MIXED WITH A LITTLE LIGHT RAIN ESPECIALLY ALONG/SOUTH OF HIGHWAY 64. THE INITIAL SURFACE WET BULB TEMPS ARE ABOVE FREEZING OVER THE AREA BUT WILL BE DROPPING FROM THE NW OVER THE NEXT FEW HOURS. THE DURATION OF THIS BAND OF SNOW/RAIN MIX SHOULD BE BRIEF... AND THIS FACTOR PLUS THE BORDERLINE WET BULB TEMPS AND THE WARM GROUND TEMPS WILL LIMIT ANY ACCUMULATION TO JUST A LIGHT SLUSHY COAT. THE BEST SHOT AT SUCH A SLUSHY COAT WILL BE IN AREAS NORTH AND EAST OF THE TRIANGLE... INCLUDING THE I- 95 CORRIDOR NORTH OF WILSON... WHERE THE BEST JUXTAPOSITIONING OF THE GREATEST LIFT AND DEEPEST MOISTURE WILL OCCUR. IMPACTS OF THIS SHOULD BE MINOR... HOWEVER EVEN A THIN ACCUMULATION OF WET SNOW MAY CAUSE SOME SLICK SPOTS IN SOME AREAS SUCH AS BRIDGES AND OVERPASSES. AMOUNTS ARE UNLIKELY TO BE ENOUGH FOR AN ADVISORY... HOWEVER WE WILL CLOSELY MONITOR THE SITUATION THROUGH THIS MORNING AND ASSESS ANY TRENDS AND IMPACTS. BOTH MODELS AND EXTRAPOLATION SUGGEST THAT PRECIP WILL BE EXITING THE NE CWA BEFORE 16Z... AFTER WHICH TIME SKIES WILL BE CLEARING OUT WITHIN DEEP POST-SHORTWAVE SUBSIDENCE. THE COASTAL LOW AND RESULTING TIGHT MSLP GRADIENT WILL KEEP NNW WINDS ELEVATED AT 12-18 MPH WITH FREQUENT GUSTS TO AROUND 25-30 MPH THROUGH THIS MORNING WITH GOOD LOW LEVEL MIXING... TRENDING DOWN TOWARD MIDDAY AS THE GRADIENT RELAXES. EXPECT HIGHS OF 45-50.... REFLECTING THICKNESSES DROPPING TO AROUND 20 M BELOW NORMAL. WINDS DIMINISH LATE THIS AFTERNOON THROUGH TONIGHT UNDER CLEAR SKIES... AS THE SURFACE HIGH BUILDING IN FROM THE WEST SHIFTS OVERHEAD. LOWS 23- 29... COLDEST IN THE RURAL PIEDMONT AND WRN SANDHILLS. -GIH && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 245 AM FRIDAY... THE WEEKEND WILL START OUT QUIET... ALTHOUGH CLOUD COVER WILL BE ON THE RISE... WITH PATCHY LIGHT PRECIP POSSIBLE LATE SAT NIGHT IN THE FAR SE. INITIALLY DRY AND STABLE AIR OVER CENTRAL NC WILL LEAD TO CONSIDERABLE SUNSHINE TO START SAT. THE SURFACE RIDGE EXTENDING SW TO NE ACROSS NC EARLY SAT WILL NARROW FURTHER AND BE OVERTAKEN BY LOW PRESSURE FORMING OVER THE BAHAMAS ALONG THE OFFSHORE FRONTAL ZONE... IN RESPONSE TO HEIGHT FALLS WITH THE APPROACH OF A POTENT SHORTWAVE TROUGH NOW DIVING DOWN THROUGH ERN CO/NM. AS THIS AMPLIFYING WAVE CROSSES THE GULF STATES/NRN GULF AND SOUTHEAST SAT/SAT NIGHT... THE SURFACE LOW IS EXPECTED TO DEEPEN QUICKLY AND TRACK TO THE NE... STAYING FAR ENOUGH OFFSHORE TO BE OF LITTLE CONSEQUENCE FOR CENTRAL NC. HOWEVER... A FEW MODELS SUGGEST THAT THERE WILL BE ENOUGH ATLANTIC MOISTURE WRAPPING AROUND THE LOW TO SPREAD LIGHT PRECIP INTO OUR FAR SE CWA OVERNIGHT. THE LOW LEVELS ARE EXPECTED TO REMAIN SOMEWHAT DRY BELOW 5 000 FT... WHICH WOULD MAKE ANY PRECIP VERY LIGHT WITH ONLY TRACE AMOUNTS. PARTIAL THICKNESSES SUPPORT THIS PRECIP BEING MOSTLY LIGHT SNOW... AND THIS IS ALSO WHAT IS INDICATED BY THE TOP-DOWN METHODOLOGY... AS FORECAST SOUNDINGS SHOW GOOD SATURATION UP TO AND ABOVE -20C WITH A COLD COLUMN. WILL BRING IN SMALL POPS IN OUR SOUTHEAST SAT NIGHT BUT WITH MINIMAL QPF AND NO NOTABLE IMPACT EXPECTED AT THIS TIME. HIGHS SAT IN THE MID 40S TO LOWER 50S WITH SOME RECOVERY IN THICKNESSES. LOWS FROM THE UPPER 20S NW TO LOWER 30S SE. -GIH && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 245 AM FRIDAY... SUNDAYS PROMINENT WEATHER FEATURE WILL BE A DEEPENING LOW PRESSURE SYSTEM WITH AN UPPER LOW OVER THE CAROLINAS AND THE SURFACE LOW OFF THE CAROLINA COAST. WHILE MUCH OF THE SYSTEM WILL REMAIN OFF OF THE COAST...THERE IS SOME POTENTIAL FOR PRECIPITATION TO CREEP INTO THE EASTERN THIRD OF OUR CWA ON THE NORTHWEST SIDE OF THE STORM. AT THIS TIME MOST OF THE PRECIPITATION IS EXPECTED TO BE RAIN WITH POTENTIALLY SOME WET SNOW MIXED IN PER NOMOGRAM THICKNESSES. DRY LOW LEVELS MAY KEEP SOME OF THE PRECIPITATION FROM REACHING THE GROUND FOR A WHILE. ANY PRECIPITATION THAT DOES OCCUR SHOULD EXIT TO THE EAST BY SUNDAY EVENING AT THE LATEST. NO IMPACTS ARE EXPECTED WITH THIS STORM AT THIS TIME. WE WILL CONTINUE TO MONITOR FOR ANY SHIFT IN THE GUIDANCE. HIGHS ON SUNDAY WILL BE AROUND 50 DEGREES WITH AN UNUSUAL TEMPERATURE DISTRIBUTION OF WARMEST TEMPERATURES IN THE WEST AND COLDEST IN THE SOUTHEAST DUE TO GREATER CLOUD COVER AND COLD AIR ADVECTION AROUND THE NORTHWEST SIDE OF THE STORM. LOWS MONDAY MORNING NEAR FREEZING IN MOST LOCATIONS. MONDAY WILL BEGIN WITH A LULL BETWEEN THE EXITING COASTAL SYSTEM AND THE NEXT LARGE UNORGANIZED SYSTEM OVER THE GREAT LAKES WHICH WILL USHER IN ARCTIC AIR FROM CANADA. TIMING OF THE WEAK FRONT THAT WILL SIGNAL THE ARRIVAL OF THIS COLDER AIRMASS WILL BE LATER IN THE DAY SO TEMPERATURES IN THE SOUTH WILL STILL MAKE IT TO THE LOW 50S WITH MID 40S IN THE TRIAD. AS THIS IS A CONTINENTAL AIRMASS...THERE IS NOT MUCH MOISTURE WITH THE SYSTEM AT ALL AND PW VALUES REMAIN BELOW A HALF OF AN INCH. THAT BEING SAID...THERE WILL STILL BE SOME PRECIPITATION WITH THIS SYSTEM...BEGINNING MOST LIKELY AFTER 15Z ON MONDAY AS RAIN. ANYTHING THAT FALLS SHOULD REMAIN RAIN UNTIL LATER IN THE EVENING WHEN A RAIN/SNOW MIX WILL EVENTUALLY TURN TO ALL SNOW AFTER 3Z TUESDAY AS NOMOGRAM THICKNESSES TANK. BY THIS TIME HOWEVER...MOST OF THE MOISTURE WILL BE THROUGH THE AREA AND ANY SNOW SHOWERS ARE NOT EXPECTED TO ACCUMULATE AT THIS TIME. LOWS MONDAY NIGHT IN THE UPPER 20S NW TO LOW 30S SE. SOME INTERMITTENT LIGHT SNOW SHOWERS WILL STILL BE POSSIBLE ON TUESDAY BUT OF LITTLE CONSEQUENCE AS QPF VALUES REMAIN VERY LOW. EVENTUALLY THE VERY DRY AIR WILL TAKE OVER AND THE COLD TEMPERATURES WILL BECOME THE MAIN STORY AS HIGHS TUESDAY ONLY MAKE THE LOW TO MID 40S AND LOWS TUESDAY NIGHT DIVE INTO THE MID 20S. WEDNESDAY WILL BE THE COLDEST DAY...WITH HIGHS IN THE MID 30S TO NEAR 40 DEGREES AND WIND CHILLS IN THE 20S FOR MOST OF THE DAY. LOWS IN THE LOWER TO MID 20S BY THURSDAY MORNING WITH WIND CHILLS IN THE TEENS. DESPITE THE COLD...DRY CONDITIONS WILL PREVAIL. ON THURSDAY THE UPPER TROUGH BEGINS TO FINALLY LIFT OUT AND TEMPS WILL REBOUND INTO THE MID 40S. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 605 AM FRIDAY... VFR CONDITIONS ARE LIKELY TO HOLD AT INT/GSO THROUGH THE NEXT 24 HOURS... HOWEVER MVFR CONDITIONS WILL HOLD OVER ERN TAFS THROUGH 13Z... WITH IMPROVEMENT TO VFR AT THESE SITES BY 15Z. A FRONTAL ZONE NOW SITS NEAR THE NC COAST... AND LOW PRESSURE NOW JUST EAST OF ILM WILL STRENGTHEN AS IT TRACKS NE ALONG THE FRONT. PATCHY LIGHT RAIN MIXED WITH LIGHT SNOW AT TIMES WILL AFFECT ERN TERMINALS (RDU/RWI/FAY) BETWEEN 12Z AND 15Z... AS A POWERFUL DISTURBANCE ALOFT CROSSES THE REGION. THIS IS EXPECTED TO BRING A QUICK SHOT OF LIGHT PRECIP LASTING JUST AN HOUR OR TWO... MAINLY IN THE FORM OF LIGHT SNOW MIXED WITH LIGHT RAIN. AFTER ABOUT 15Z... VFR CONDITIONS WILL DOMINATE AT ALL SITES FROM LATE MORNING THROUGH THE AFTERNOON AND TONIGHT. SURFACE WINDS FROM THE N AND NW WILL BE 10-15 KTS WITH GUSTS UP TO 18-23 KTS POSSIBLE THROUGH EARLY AFTERNOON... AFTER WHICH TIME SURFACE WINDS WILL DECREASE AND BECOME LIGHT FROM THE NORTH FOR THIS EVENING AND TONIGHT... WITH VFR CONDITIONS PERSISTING. LOOKING BEYOND 12Z SAT MORNING... VFR CONDITIONS SHOULD DOMINATE THROUGH THE WEEKEND... ALTHOUGH A LOW TRACKING OFF THE CAROLINA COAST MAY BRING A LITTLE LIGHT PRECIP TO FAY EARLY SUN MORNING. THE CHANCE OF SUB-VFR CONDITIONS WITH THIS WILL BE LOW. AN UPPER LEVEL DISTURBANCE WILL BRING ANOTHER CHANCE OF SUB-VFR CONDITIONS AND PATCHY PRECIP TO ALL SITES MON AFTERNOON INTO TUE. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...ELLIS AVIATION...HARTFIELD

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