Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240723 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 222 AM EST SAT JAN 24 2015 .SYNOPSIS...
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A STRONG STORM SYSTEM WILL MOVE NORTHEASTWARD THROUGH THE REGION THROUGH TODAY. A HIGH PRESSURE RIDGE WILL BUILD BRIEFLY ACROSS THE REGION TONIGHT THROUGH SUNDAY... THEN A CLIPPER LOW WILL TRACK ACROSS THE AREA SUNDAY NIGHT THROUGH MONDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 948 PM FRIDAY... OVER THE PAST FEW HOURS...A LARGE HOLE HAS DEVELOPED ALONG THE WESTERN EDGE OF THE PRECIP SHIELD...LIKELY A PRODUCT OF THE DEEP CONVECTION THAT SWEPT EAST ACROSS THE NORTHEAST EARLIER THIS AFTERNOON/EVENING THAT PER LATEST WV IMAGERY HAS SHUNTED THE DEEP MOIST PLUME EASTWARD...PRIMARILY OFFSHORE. SIGNIFICANT CONCERNS HAVE ARISEN AS TO WHETHER OR NOT PRECIP WILL FILL BACK OVERNIGHT AS THE AREA OF LOW PRESSURE OVER THE SE US TRACK NEWD ACROSS EASTERN NC BETWEEN 06 TO 12Z. MODEL GUIDANCE IS NOT HANDLING CURRENT RADAR TRENDS WELL AT ALL...BUT ITS STARTING TO LOOK LIKE QPF AMOUNTS WILL BE SIGNIFICANTLY LESS THAN EARLIER ANTICIPATED...WITH THE MODERATE AND HEAVY RAINFALL REMAINING SOUTH AND EAST OF THE AREA. WHILE INFLUX OF ATLANTIC MOISTURE AHEAD AND ALONG THE LOW PRESSURE TRACK COULD RESULT IN A SLIGHT UPTICK IN INTENSITY ACROSS THE FAR SE ZONES...INLAND/PIEDMONT AREAS WILL LIKELY SEE INTERMITTENT LIGHT RAIN AND DRIZZLE FOR THE REMAINDER OF THE NIGHT. HAVE REDUCED QPF BY HALF...WITH STORM TOTAL QPF 0.50 TO 1.0" EXPECTED ACROSS THE AREA. TEMPERATURES OVERNIGHT WILL HOLD NEARLY STEADY IN THE MID TO UPPER 30S ACROSS THE PIEDMONT...WELL WITHIN THE CAD AIRMASS. A LITTLE DIFFERENT STORY ACROSS THE SOUTHERN COASTAL PLAIN ZONES WHERE TEMPS WILL WARM INTO THE 50S THROUGH 09Z WITH THE APPROACH OF THE LOW AND ASSOCIATED SOUTHERLY FLOW...THEN DROP BACK DOWN INTO THE 40S IN THE WAKE OF THE LOW LIFTING OFF TO THE NORTH AS WINDS BECOMING NORTHERLY. && .SHORT TERM /SUNDAY THROUGH MONDAY/...
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AS OF 210 AM SATURDAY... SUN: EXPECT PLENTY OF SUNSHINE FOR MOST OF SUNDAY... AS THE SURFACE RIDGE EXTENDS WEAKLY AND BRIEFLY INTO NC FROM THE SW WITH DRY AIR IN PLACE THROUGH THE COLUMN. HIGH CLOUDS WILL INCREASE AND THICKEN FROM MID AFTERNOON ONWARD AHEAD OF THE STRONG CLIPPER LOW TRACKING FROM THE UPPER MIDWEST INTO THE OH VALLEY. THICKNESSES ARE EXPECTED TO START THE DAY CLOSE TO NORMAL AND RISE DECENTLY THROUGH THE DAY... EQUATING TO HIGHS A COUPLE DEGREES ABOVE NORMAL... SUN NIGHT/MON/MON NIGHT: THE POTENT CLIPPER SURFACE LOW WILL MOVE FROM AROUND CINCINNATI EARLY SUN EVENING (THE 00Z GFS IS A TAD SLOWER THAN THE NAM WHILE THE ECMWF IS THE FASTEST BY NEARLY 6 HRS) ACROSS SW VA AND NORTH-CENTRAL/NE NC THROUGH MON MORNING. THE GFS HAS BEEN TRENDING DEEPER AND A TAD FASTER WHILE THE ECWMF HAS EXHIBITED MORE RUN-TO-RUN CONSISTENCY... SO FAVOR A GFS/ECMWF COMPROMISE WITH A LEAN TOWARD THE FASTER ECMWF. THE MID LEVEL SHORTWAVE TROUGH PIVOTS OVER NC EARLY MON MORNING BUT SHEARED VORTICITY DIVING IN JUST BEHIND THE TROUGH WILL KEEP A THREAT OF FORCING FOR ASCENT OVER NC FROM MID-LATE SUN EVENING (SLIGHTLY SLOWER ONSET GIVEN THE INITIALLY HIGH CLOUD BASES AND DRY SUBCLOUD LAYER) WELL INTO MON... WITH LINGERING LIGHT PRECIP CHANCES PARTICULARLY OVER THE NRN AND ERN CWA INTO LATE AFTERNOON OR EARLY MON EVENING. THERE ISN`T A GREAT DEAL OF MOISTURE RETURN WITH THIS SYSTEM... WITH PW EXPECTED TO REACH JUST SLIGHTLY ABOVE NORMAL... AND DESPITE IT BEING A PRETTY ROBUST TROUGH AND SURFACE LOW... THE OVERALL LIFT IS NOT TERRIBLY STRONG AS THE GREATEST UPPER DIVERGENCE WILL BE FOCUSED TO OUR SE. THESE TWO FACTORS SHOULD NOT ONLY RESULT IN FAIRLY LIGHT QPF BUT MAY ALSO HELP DETERMINE PTYPE. FORECAST THICKNESSES INDICATE A PTYPE TRENDING FROM LIGHT RAIN TOWARD INDETERMINANT (LIKELY MEANING LITTLE TO NO PRECIP EXPECTED) BEFORE TRENDING TOWARD A SNOW SOUNDING LATE MON. BUT THE MARGINAL LIFT AND MOISTURE ABOVE THE -12C LEVEL SUGGESTS THAT THIS IS LIKELY TO BE A PRIMARILY LIGHT-RAIN EVENT... ALTHOUGH THIS COULD EASILY BE MIXED WITH OR CHANGE TO WET FLAKES IF POCKETS OF SUFFICIENT LIFT CAN BE ACHIEVED TO SATURATE THE ICE NUCLEATION ZONE ALOFT. THIS OCCURRENCE IS FAR FROM CERTAIN HOWEVER (ALTHOUGH THE CHANCES APPEAR BETTER NEAR THE VA/NC BORDER)... SO WILL CONTINUE TO FOCUS ON A MOSTLY RAIN EVENT WITH A SMALLER CHANCE OF INCONSEQUENTIAL WET SNOWFLAKES AS THE TROUGH SHIFTS TO OUR EAST MON AFTERNOON INTO THE EVENING. WE MAY ACTUALLY SEE A LULL IN ANY PRECIP MON AFTERNOON THEN RENEWED LIFT MON EVENING AS THE STRONG NRN STREAM JET ACCELERATES TO THE SE WITH A RESULTING UPTICK OF UPPER DIVERGENCE OVER NC. WILL BRING IN CHANCE POPS ACROSS THE NORTH AND NE STARTING LATE SUN EVENING... WITH SMALLER CHANCES SOUTH... CONTINUING THROUGH MON BEFORE TAPERING DOWN MON NIGHT. EXPECT OVERALL AMOUNTS TO BE A TENTH OF AN INCH OR LESS... AS INDICATED BY OPERATIONAL MODELS AND SREF MEMBERS. RAIN CHANCES AND CLOUDS WILL HOLD TEMPS DOWN MON... AND THICKNESSES AND GUIDANCE SUPPORT HIGHS FROM THE MID 40S NORTH TO LOWER 50S SOUTH... AFTER MORNING LOWS IN THE MID-UPPER 30S. AS THE SURFACE LOW INTENSIFIES MON NIGHT EAST OF NJ/SE OF CAPE COD... COLD AIR ADVECTION WILL COMMENCE INTO NC... AND EXPECT LOWS IN THE UPPER 20S TO AROUND 30. -GIH
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/...
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AS OF 220 AM SATURDAY... TUE: ADDITIONAL WEAK SHEARED VORTICITY WILL DIVE SE THROUGH THE CAROLINAS TUE WITH THE GFS/ECMWF INDICATING A WEAK ATTENDING SURFACE LOW. THE GFS AND ITS FURTHER-NORTH VORTICITY TRACK GENERATES PATCHY LIGHT PRECIP OVER CENTRAL NC TUE... BUT IT`S UNCLEAR IF WE`LL GET ENOUGH RECOVERY OF LOW LEVEL MOISTURE FOR ANYTHING MEASURABLE AT THE SURFACE. WILL KEEP THE FORECAST DRY FOR NOW WITH THE CHANCE FOR MEASURABLE PRECIP UNDER 15%. WE SHOULD SEE PLENTY OF CLOUDS HOWEVER... AND THICKNESSES WITH STRONG LOW LEVEL COLD AIR ADVECTION INDICATE HIGHS IN THE UPPER 30S TO MID 40S. WED-FRI: SHOULD BE FAIRLY QUIET. THE LONGWAVE TROUGH AXIS FINALLY SHIFTS EAST OFF THE COAST WED... FOLLOWED BY EITHER FLAT WNW FLOW OR WEAK SHORTWAVE RIDGING. SURFACE HIGH PRESSURE WILL SHIFT OVERHEAD THEN TO OUR EAST... SO EXPECT A MODIFICATION OF TEMPS BY LATE WEEK AS WE GET INTO SOUTHWESTERLY RETURN FLOW. ANOTHER NORTHERN STREAM CLIPPER WAVE SHIFTS BY TO OUR NORTH THU NIGHT/FRI... ACROSS IL/IN/OH AND THE CENTRAL APPALACHIANS TO THE MIDATLANTIC COAST... WITH A CORRESPONDING FRONTAL PASSAGE THROUGH CENTRAL NC FRI... POTENTIALLY KNOCKING TEMPS BACK DOWN BELOW NORMAL AS WE HEAD INTO THE WEEKEND. -GIH
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&& .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 1240 AM SATURDAY... 24 HOUR TAF PERIOD: HEAVIEST PRECIPITATION THIS MORNING REMAINING SOUTH AND EAST OF THE AREA. WE WILL BE ENTERING A LULL IN THE PRECIPITATION FOR THE NEXT SEVERAL HOURS WHERE DRIZZLE OR VERY LIGHT RAIN WILL BE THE PREDOMINANT MODE OF PRECIPITATION. HIGH RESOLUTION MODELS SHOW SOME PRECIPITATION FILLING BACK IN AFTER 9Z FROM RALEIGH EASTWARD TO THE COAST WITH DRIZZLE TO LIGHT RAIN STILL POSSIBLE IN THE WEST. MODELS HOLD ON TO PRECIPITATION THROUGH 18Z ALTHOUGH IT MAY PULL OUT TO THE NORTHEAST EARLIER THAN THAT. ONCE IT MOVES OUT. THE REMAINDER OF THE TAF PERIOD IS EXPECTED TO BE DRY. CEILINGS WILL MOST LIKELY REMAIN IFR/LIFR THROUGH MID MORNING OR SO BEFORE STEADILY IMPROVING BACK TO VFR. SKIES WILL EVENTUALLY CLEAR BY LATE AFTERNOON. VISIBILITIES MEANWHILE SHOULD REMAIN IN THE IFR/MVFR RANGES THROUGH A SIMILAR TIME PERIOD BEFORE RETURNING TO VFR. WITH PRECIPITATION AND WINDS STAYING UP A LITTLE OVERNIGHT...DO NOT EXPECT MUCH OF A DENSE FOG THREAT. WINDS WILL VARY FROM CALM TO 10 KTS THROUGH THE MORNING WITH SOME VARYING DIRECTION AS WELL BUT WITH SOME NORTHERLY COMPONENT. BY AFTERNOON WINDS WILL BACK AROUND TO WESTERLY WITH SUSTAINED WINDS NEAR 10 KTS GUSTING TO 20 KTS. GUSTS WILL SUBSIDE AFTER SUNSET WITH WINDS OUT OF THE WEST AT 5-10 KTS. LONG TERM: MAINLY VFR CONDITIONS FOR THE LONG TERM AFTER THE CURRENT SYSTEM MOVES OFF. THE EXCEPTION TO THIS COULD BE WITH A CLIPPER SYSTEM ON MONDAY THROUGH MONDAY NIGHT WHICH COULD PRESENT A FEW PERIODS OF SUB VFR CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...CBL SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...ELLIS

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