Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270817 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 314 AM EST THU NOV 27 2014 .SYNOPSIS...AN UPPER LEVEL DISTURBANCE AND ASSOCIATED LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS THE REGION EARLY THIS MORNING. HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE WEST THIS AFTERNOON AND TONIGHT THEN SETTLE OVER THE CAROLINAS ON FRIDAY AND SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 305 AM THURSDAY... HAPPY THANKSGIVING! TODAY...A PAIR OF S/W...A WELL-DEFINED FEATURE CROSSING THE SMOKEY MOUNTAINS AT 07Z...AND THE OTHER LESS DEFINED FEATURE OVER THE LOWER OH VALLEY...WILL BRING A PERIOD OF UNSETTLED WEATHER TO CENTRAL NC THIS MORNING WITH GRADUALLY IMPROVING CONDITIONS ANTICIPATED THIS AFTERNOON. THE LEAD S/W WILL BRING AN AREA OF SHOWERS TO MAINLY THE NORTHERN PIEDMONT EARLY THIS MORNING (THROUGH 12Z-13Z) THOUGH A STRAY SHOWER OR TWO MAY TRACK ACROSS THE SOUTHERN PIEDMONT-SANDHILLS BY DAYBREAK. THE SECOND S/W WILL FOLLOW QUICKLY ON THE HEELS OF THE INITIAL S/W AND CROSS THE PIEDMONT MID DAY-EARLY AFTERNOON. SUBSIDENCE BEHIND THE LEAD S/W MAY DRY OUT THE ATMOSPHERE ENOUGH TO CAUSE A DECREASE IN SHOWER ACTIVITY WITH THE SECOND S/W. THUS PLAN TO HAVE SOLID CHANCE/LOW END LIKELY POPS EARLY THIS MORNING ACROSS THE FAR NORTHERN POP...TRENDING TO SLIGHT CHANCE OVER THE SOUTHERN PIEDMONT. AFTER 18Z...WILL CONFINE POPS TO THE FAR NORTH-NE WITH THE SECOND S/W...TRENDING POPS TO LESS THAN 15 PERCENT BY 21Z AS THIS FEATURE EXITS THE REGION. LOW LEVEL FLOW WILL BECOME WEST-NW THIS AFTERNOON IN THE WAKE OF THE DEPARTING S/WS. DUE TO PRESENCE OF FAIRLY STEEP LAPSE RATES ALOFT CAUSED BY THE POCKET OF COLD AIR ASSOCIATED WITH THE MID LEVEL S/WS (-30 DEG C AT NASHVILLE AT 00Z...AND -32 AT CENTRAL IL)...EXPECT BLUSTERY CONDITIONS TO DEVELOP AROUND LATE MORNING IN THE SOUTH..AND THIS AFTERNOON ACROSS THE NORTH. WIND GUSTS IN THE 25-30 MPH WILL BE COMMON. MAX TEMPS MID-UPPER 40S ACROSS THE FAR NORTH WHERE SHOWERS AND CLOUDS WILL BE MORE PREVALENT...TO THE MID 50S ACROSS THE FAR SOUTH. TONIGHT...SKIES WILL CLEAR OFF FAIRLY QUICKLY WEST-TO EAST LATE THIS AFTERNOON EARLY EVENING AS DRIER AIR OVERSPREADS THE REGION. COLD AIR ADVECTION WILL KEEP THE NEAR SURFACE ATMOSPHERE WELL MIXED UNTIL JUST PRIOR TO DAYBREAK. THE CAA WILL SEND TEMPS INTO THE MID-UPPER 20S BY EARLY FRIDAY. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 305 AM THURSDAY... FRIDAY...CHILLY HIGH PRESSURE WILL BUILD INTO AND SETTLES OVERHEAD. LOW LEVEL THICKNESSES AVERAGE 45M BELOW NORMAL...SUGGESTIVE OF MAX TEMPS 10-14 DEGREES BELOW NORMAL. THIS YIELDS MAX TEMPS IN THE LOW- MID 40S. SKIES WILL REMAIN MOSTLY CLEAR ASIDE FROM A FEW PASSING CIRRUS IN THE AFTERNOON. -WSS FRIDAY NIGHT: SURFACE HIGH PRESSURE WILL SETTLE OVER THE REGION ON FRIDAY NIGHT. MEANWHILE... MID LEVEL FLOW WILL REMAIN OUT OF THE WNW WITH THE POTENTIAL FOR A FEW WEAK DISTURBANCES TO MOVE ACROSS THE MID ATLANTIC REGION. HOWEVER... WE WILL REMAIN DRY WITH ONLY AN INCREASE IN SOME HIGH CLOUDS ON SATURDAY MORNING. STILL THINK THE CLOUDS WILL BE THIN ENOUGH NOT TO HAVE A SIGNIFICANT IMPACT ON LOW TEMPS. GIVEN THIS... THINK WE SHOULD SEE TEMPS PLUMMET INTO THE 20S ACROSS THE ENTIRE AREA... WITH LOWS IN THE MID TO UPPER 20S (MAYBE EVEN A FEW LOWER 20S IN THE USUAL RURAL COLD SPOTS DEPENDING ON THE CLOUD COVER). -BSD && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 310 AM THURSDAY... HIGH PRESSURE WILL SHIFT TO THE SOUTH AND EAST OF CENTRAL NC THIS WEEKEND ALLOWING FOR A WARMING TREND. HIGH TEMPS ARE EXPECTED TO BE IN THE LOWER TO MID 50S FOR SATURDAY AND LOWER TO MID 60S FOR SUNDAY. MID LEVEL RIDGING IS FORECAST TO BUILD NORTHWARD DURING THIS TIME FRAME AND NUDGE INTO OUR AREA. HOWEVER... AS A NORTHERN STEAM TROUGH IS FORECAST TO TRACK NEAR THE U.S./CANADIAN (EAST COAST THAT IS) BORDER DURING THIS TIME FRAME A TRAILING COLD FRONT WILL DROP SOUTHWARD AND INTO CENTRAL NC EARLY NEXT WEEK. MODEL GUIDANCE HAS TRENDED TOWARDS THE SURFACE FRONT MOVING INTO THE AREA ON MONDAY NIGHT INTO EARLY TUESDAY MORNING... PUSHED BY A 1035-1040 MB SURFACE HIGH TO THE NORTH/NORTHWEST. THIS SHOULD ALLOW FOR ONE LAST WARM DAY ON MONDAY... WITH HIGHS IN THE 60S TO LOWER 70S SOUTH. GIVEN THE LAST SEVERAL DAYS MEDIUM RANGE MODELS HAVE TRENDED WETTER WITH THE AFOREMENTIONED FRONT AND THE POTENTIAL FOR AT LEAST SOME HYBRID COLD AIR DAMMING FOR MONDAY NIGHT INTO TUESDAY. HOWEVER... WPC STILL PREFERS TO KEEP POPS LOW WITH THE ARRIVAL OF THE FRONT GIVEN THE APPARENT SPREAD IN GUIDANCE/ENSEMBLES GUIDANCE OVER THE PAST FEW DAYS AND DIFFERENCES WITH THE OPERATIONAL MODELS VS THEIR ENSEMBLES. THUS... FOR NOW PREFER TO KEEP POPS AT SLIGHT CHANCE FOR MONDAY NIGHT INTO TUESDAY AND TREND TEMPS DOWNWARD. FOR WEDNESDAY... WE MAY HAVE SOME FORM OF LINGERING CAD ACROSS THE AREA. HOWEVER... THE PARENT SURFACE HIGH SHOULD BE WELL OFF THE NORTHEAST U.S. COAST BY THIS TIME. THE NEXT SYSTEM WILL QUICKLY APPROACH FROM THE NORTHWEST. HOWEVER... THERE IS A LARGE SPREAD AMONG THE GUIDANCE IN TIMING OF THE FRONT. WPC HOLDS THE FRONT TO OUR NORTH DURING THIS TIME FRAME... GOING WITH A LESS AMPLIFIED PATTERN. GIVEN THE LOWER CONFIDENCE WILL KEEP TEMPS WITHIN A COUPLE CATEGORIES OF NORMAL AT WORST... GIVEN THE LARGE POSSIBLE SPREAD IN TEMPS. THIS YIELDS HIGHS ON TUESDAY IN THE UPPER 40S TO 50S... WITH HIGHS ON WEDNESDAY IN THE 50S TO SOME 60S... AND LOWS IN THE 30S AND 40S. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 100 AM THURSDAY... A STRONG UPPER LEVEL DISTURBANCE WILL CROSS CENTRAL NC EARLY THIS MORNING...EXITING OUR REGION BY THIS AFTERNOON. PROCEEDING THIS SYSTEM...THERE WILL BE A PERIOD OF MVFR/LOW END VFR CEILINGS ALONG WITH PATCHES OF LIGHT RAIN. THESE CEILINGS AND PRECIP WILL BE MOST PROMINENT ACROSS THE NORTHERN TERMINALS AND LESS LIKELY AT KFAY. AFTER 14Z...WEST TO NW SFC WINDS WILL BE BLUSTERY WITH GUSTS 18-23 KTS LIKELY. THE GUSTS WILL BECOME LESS LIKELY AFTER 22Z...THOUGH A STEADY NW WIND AROUND 10KTS EXPECTED WELL INTO TONIGHT. HIGH PRESSURE WILL BUILD INTO CENTRAL NC TONIGHT AND SETTLE OVERHEAD FRIDAY THROUGH SATURDAY...PROVIDING A PERIOD OF VFR CONDITIONS WITH SFC WINDS LESS THAN 10KTS. THE HIGH WILL SHIFT OFFSHORE SUNDAY. THE RESULTING SOUTH-SOUTHWEST LOW LEVEL FLOW WILL ADVECT MOISTURE INTO OUR REGION BY LATE SUNDAY- SUNDAY NIGHT LEADING TO THE POTENTIAL FOR AREAS OF MVFR FOG OR IFR CEILINGS IN STRATUS BY EARLY MONDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS/BSD LONG TERM...BSD AVIATION...WSS

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