Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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457 FXUS62 KRAH 051954 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 254 PM EST FRI FEB 5 2016 .SYNOPSIS... IN THE WAKE OF A LOW PRESSURE SYSTEM DEPARTING THE MID- ATLANTIC COAST...COOL HIGH PRESSURE WILL BUILD IN FROM THE WEST THROUGH THE WEEKEND. A SURFACE LOW WILL PASS BY THE CAROLINA COAST ON SUNDAY...FOLLOWED BY AN ARCTIC COLD FRONT THAT WILL ARRIVE EARLY NEXT WEEK. && .NEAR TERM /TODAY THROUGH TONIGHT/... AS OF 1015 AM FRIDAY... THE EARLY MORNING RAIN/SNOW MIX HAS FIZZLED AS DRIER AIR WORKS IN FROM THE WEST IN THE WAKE OF THE DEPARTING LOW...WHICH IS NOW SOUTH OF LONG ISLAND. LINGERING MOISTURE AROUND 4000K FT IN THE COASTAL PLAIN AND SOME VERY SHALLOW INSTABILITY...PER RAP SOUNDINGS...COULD STILL RESULT IN A FEW RAIN DROPS EAST OF THE I-95 CORRIDOR THROUGH NOON. HOWEVER...WITH THE MOISTURE STEADILY ERODING AND STRENGTHENING SUBSIDENCE INVERSION ALOFT...HAVE REMOVED REMAIN POPS. COLD ADVECTION AT 850MB IS PROGGED TO CONTINUE THROUGH THIS AFTERNOON AND DRY ADIABATIC MIXING TO BETWEEN 925MB AND 850NMB SUPPORTS HIGHS IN THE MID 40S...A DEGREE OR TWO BELOW STATISTICAL GUIDANCE. -SMITH 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 NIGHT THROUGH FRIDAY/... AS OF 250 PM FRIDAY... SHORTWAVE ENERGY MOVING ONSHORE BRITISH COLUMBIA TONIGHT WILL RESULT IN RAPID AMPLIFICATION OF A LONGWAVE TROUGH OVER THE EASTERN US SUN NIGHT/MONDAY AS IT DIGS SOUTHEAST THROUGH THE UPPER MIDWEST INTO THE OH VALLEY AS AN UPPER LOW...ON THE HEELS OF A NEGATIVELY TILTED SHORTWAVE PROGRESSING OFFSHORE THE SOUTHEAST COAST. THE RESULTING LONGWAVE TROUGH IS EXPECTED TO PERSIST OVER THE EASTERN CONUS THROUGH MID-WEEK...OR UNTIL UNIDIRECTIONAL FLOW ALOFT BECOMES ESTABLISHED THU/FRI. LIGHT PRECIP IS EXPECTED TO OCCUR IN ASSOC/W POTENT SHORTWAVE ENERGY ROUNDING THE SOUTHEAST PERIPHERY OF THE AFOREMENTIONED UPPER LOW MONDAY AFT/EVE. GIVEN SOUTHWEST FLOW THROUGHOUT THE COLUMN AND THE PRESENCE OF LOW-LEVEL WARM ADVECTION...NO PTYPE CONCERNS ARE ANTICIPATED. EXPECT BELOW NORMAL TEMPERATURES TUE/WED IN ASSOCIATION WITH STRONG/PERSISTENT COLD ADVECTION AS THE LONGWAVE TROUGH SHIFTS EAST INTO THE MID- ATLANTIC/CAROLINAS. FROM A PATTERN RECOGNITION STANDPOINT...I.E. UPPER TROUGH AXIS NEAR/OVER THE REGION AND WESTERLY FLOW THROUGHOUT THE LOW/MID LEVELS...DRY CONDITIONS ARE GENERALLY EXPECTED TO PREVAIL. ONE EXCEPTION WILL BE A POTENTIAL FOR ISOLD/SCT DIURNAL CONVECTION TUE AFTERNOON GIVEN STEEP LAPSE RATES/VERY COLD TEMPS ALOFT AND OCCASIONAL DPVA ASSOC/W SHORTWAVE ENERGY ROUNDING THE BASE OF THE TROUGH /UPPER LOW/ OVER THE MID-ATLANTIC. WHETHER OR NOT CONVECTION DEVELOPS WILL HIGHLY DEPEND ON THE TIMING/MAGNITUDE OF DPVA...AND EVEN IF CONVECTION WERE TO DEVELOP...A VERY DRY SUB-CLOUD LAYER WOULD HAVE TO BE OVERCOME...THUS CONFIDENCE REMAINS LOW. IF CONVECTION WERE TO DEVELOP...A SHALLOW ABOVE FREEZING LAYER IN THE LOWEST 500-1000 FT AGL WOULD SUGGEST RAIN SHOWERS...THOUGH SOME POTENTIAL FOR A RATE-DRIVEN CHANGEOVER TO SNOW SHOWERS WOULD BE PRESENT. -VINCENT && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 1245 PM FRIDAY... NORTH-NORTHWESTERLY WINDS WILL CONTINUE TO GUST INTO THE 20-25KT RANGE THIS AFTERNOON...WITH VFR CONDITIONS OTHERWISE PREVAILING. THE PRESSURE GRADIENT WILL WEAKEN QUICKLY TONIGHT AS HIGH PRESSURE BUILDS IN FROM THE WEST...ALLOWING WINDS TO BECOME NEARLY CALM. VFR WILL CONTINUE. LOOKING BEYOND 18Z SATURDAY...VFR CONDITIONS WILL PREVAIL ON SATURDAY. A SURFACE LOW PASSING BY THE CAROLINA COAST ON SUNDAY MAY BRING LIGHT PRECIP AND A PERIOD SUB-VFR CONDITIONS FROM KFAY TO KRWI. AN UPPER LEVEL DISTURBANCE WILL BRING ANOTHER CHANCE OF SUB- VFR CONDITIONS AND PATCHY PRECIP TO ALL SITES MON AFTERNOON INTO TUE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD/SMITH SHORT TERM...HARTFIELD LONG TERM...VINCENT AVIATION...SMITH

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