Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210607 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 105 AM EST SUN DEC 21 2014 .SYNOPSIS...WEAK LOW PRESSURE WILL MOVE OFF THE SOUTHEAST COAST TONIGHT...AS HIGH PRESSURE REMAINS OVER THE AREA THROUGH SUNDAY. ANOTHER LOW PRESSURE SYSTEM WILL MOVE ALONG THE CAROLINA COAST MONDAY. && .NEAR TERM /THROUGH SUNDAY NIGHT/... AS OF 1030 PM SATURDAY... TONIGHT: SATELLITE TRENDS AND NEAR TERM NWP GUIDANCE SUGGEST MULTI- LAYERED CLOUDS BETWEEN 2500-7000 FT WILL BE MOST PERVASIVE...AVERAGING MOSTLY CLOUDY...OVER THE PIEDMONT...WHILE PERIODS OF CLEAR TO PARTLY CLOUDY SKIES PREVAIL OVER THE COASTAL PLAIN. WITH A LIGHTLY MOISTENED SOIL FROM EARLIER LIGHT PRECIPITATION AND LIGHT WINDS WITHIN A SURFACE RIDGE AXIS OVER THE AREA...AREAS OF FOG WILL BE POSSIBLE IN AREAS OF RELATIVE CLEARING (IE. MOST LIKELY OVER THE COASTAL PLAIN). WITH THE AFOREMENTIONED CLOUDINESS OVERHEAD... TEMPERATURES WILL MOVE LITTLE - INTO THE LOWER TO MIDDLE 30S FOR MOST - THOUGH SOME UPPER 20S WILL LIKELY OCCUR IN AREAS OF CLEARING PER 12Z-PROJECTED LOW LEVEL THICKNESS VALUES AROUND 1310 METERS. AS OF 245 PM SATURDAY... SUNDAY AND SUNDAY NIGHT: TEMPERATURES WILL QUICKLY REBOUND AND THE SURFACE LAYER SHOULD DRY OUT AFTER 14Z OR SO. THE ATTENTION THEN WILL TURN TO THE EVOLVING PATTERN FOR SUNDAY WHICH WILL BE THE DEVELOPMENT OF TWO FEATURES...ONE BEING A COASTAL LOW ALONG THE SOUTHEAST COAST AND THE SECOND BEING THE DEVELOPMENT OF A CAD WEDGE ASSOCIATED WITH A HIGH PRESSURE OVER THE NORTHEAST. MOST OF THE MOISTURE ASSOCIATED WITH THE LOW WILL REMAIN SOUTH OF THE AREA...SO SUNDAY SHOULD BE DRY BUT WE WILL SEE SOME CLOUD COVER ENCROACHING FROM THE SOUTHWEST...WHICH WILL INCREASE THROUGH SUNDAY AFTERNOON. HIGHS ON SUNDAY WILL BE IN THE UPPER 40S NORTH TO LOW 50S SOUTH. ON SUNDAY NIGHT THE ISENTROPIC LIFT WILL INCREASE SIGNIFICANTLY AS THE LOW GETS CLOSER TO THE AREA AND THE WEDGE FRONT SHARPENS UP. PRECIPITATION CHANCES WILL STEADILY INCREASE OVERNIGHT FROM SLIGHT CHANCE EARLY ON TO NEAR DEFINITE BY MONDAY MORNING. SOUTHWESTERN AREAS WILL SEE THE MOST QPF BEFORE DAYBREAK...MOST LIKELY BETWEEN 0.1-0.2 INCHES. BECAUSE OF THE CLOUD COVER...LOWS WILL MODERATE A LITTLE...MID 30S TO LOWER 40S NORTHEAST TO SOUTHWEST. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 310 PM SATURDAY... HIGH PRESSURE OVER THE CANADIAN MARITIMES WILL EXTEND SOUTHWARD INTO THE MID ATLANTIC...AND WILL WEDGE SOUTH INTO THE CAROLINAS ON MONDAY. MINOR SHORTWAVE IMPULSES IN ADVANCE OF THE AMPLIFYING UPSTREAM TROUGH OVER THE CENTRAL US COUPLED WITH ANOTHER ENSUING SFC WAVE DEVELOPMENT ALONG THE STALLED OFFSHORE FRONTAL ZONE WILL SPUR ANOTHER WEAK ISENTROPICALLY DRIVEN PRECIP EVENT ACROSS CENTRAL NC ON MONDAY. A MORE PRONOUNCED WARM NOSE WILL PRECLUDE ANY P-TYPE ISSUES...WITH LIKELY TO CATEGORICAL RAIN AND QPF AMOUNTS IN THE 0.25-0.50 RANGE...WITH THE HIGHEST AMOUNTS INLAND OVER THE MORE STEEPLY SLOPED PORTION OF THE COLD DOME SURFACE OVER THE PIEDMONT. MEASURABLE RAIN CHANCES REALLY DECREASE BY MONDAY EVENING AS WE LOSE SATURATION ALOFT...BUT LIGHT...DRIZZLE AND/OR AT THE VERY LEAST FOG WILL PERSIST OVERNIGHT AMIDST CONTINUED WEAK SOUTHERLY UPGLIDE. LITTLE DIURNAL VARIATION THROUGH MONDAY NIGHT. HIGHS IN THE UPPER 30 NW TO MID/UPPER 40S SE. LOWS IN THE MID 30S NW TO NEAR-LOWER 40S SE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 308 PM SATURDAY... TUESDAY: ALTHOUGH THE PARENT HIGH WILL BE WELL REMOVED(OVER OF JUST OFF THE CANADIAN MARITIMES)...INITIALLY WEAK SOUTHERLY UPGLIDE DOWNSTREAM OF THE AMPLIFYING TROUGH WILL KEEP THE WEDGE OF COLD AIR LOCKED FIRMLY IN PLACE ACROSS THE PIEDMONT UNDERNEATH A SHROUD OF LOW CLOUDS AND POSSIBLY DRIZZLE...WITH A RETURN OF MEASURABLE RAIN CHANCES BY THE LATE AFTERNOON/EVENING WITH THE RESURGENCE OF LOW- LEVEL CONVERGENCE ALONG THE RETREATING WEDGE FRONT. MADE MINOR ADJUSTMENTS TO INHERITED GRID FORECAST WHICH MAINTAINS A CLASSIC CAD CLIMATOLOGY...BUT CONFIDENCE IS BELOW AVERAGE...ESPECIALLY ON THE SOUTHERN/EASTERN FRINGES OF COLD DOME. HIGHS RANGING FROM MID 40S NW TO NEAR 60 SOUTHEAST. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT: MODELS ARE IN VERY GOOD AGREEMENT REGARDING EVOLUTION OF A HIGH-AMPLITUDE UPPER TROUGH THAT IS FORECAST TO ADVANCE SLOWLY EASTWARD ...LIKELY ASSUMING A NEGATIVE TILT AS IT CROSSES THE SOUTHERN/CENTRAL APPALACHIANS ON WEDNESDAY. EXPECT WET CONDITIONS TUESDAY NIGHT WITH THE PASSAGE OF THE WARM FRONT THROUGH THE AREA...FOLLOWED BY WET...WINDY AND POSSIBLY STORMY CONDITIONS DURING THE DAY CHRISTMAS EVE AS THE OCCLUDED FRONT PUSHES THROUGH THE AREA. MODELS HAVE BACKED OFF FROM THE TRIPLE POINT LOW ACROSS THE CAROLINAS BUT REGARDLESS...DEEP LAYER SHEAR OF 50-60KTS WILL BE MORE THAN SUFFICIENT TO SUPPORT STRONG TO SEVERE CONVECTION. THE BIGGEST QUESTION AT THIS POINT WILL BE THE AVAILABILITY/PRESENCE OF WEAK INSTABILITY...WHICH MODELS CURRENTLY INDICATE MUCAPE 100-200 J/KG WITH WEAK LAPSE RATES ALOFT OF 5.0-5.5 C/KM. FOR NOW WILL ADD AN ISOLATED CHANCE TO FAVORED CLIMO REGION OF THE SANDHILLS AND COASTAL PLAIN. TEMPERATURES VERY CHALLENGING...WARMING TUESDAY NIGHT WITH PASSAGE OF THE WEDGE FRONT INITIALLY AND THEN THE WARM FRONT DURING THE PREDAWN HOURS. WARM SECTOR SHOULD EXTEND WELL INTO THE PIEDMONT ON WEDNESDAY WITH MUCH OF THE AREA WARMING INTO THE 60S...WITH THE EXCEPTION OF THE NW PIEDMONT WHERE THEY MAY HOLD IN THE 50S. RAPIDLY CLEARING AND COOL AIR ADVECTION WILL COMMENCE CHRISTMAS EVE EVENING/NIGHT WITH LOWS CHRISTMAS MORNING IN THE 30S. DEEPENING SURFACE LOW OVER THE GREAT LAKES WILL RESULT IN BREEZY CONDITIONS ON CHRISTMAS DAY. OTHERWISE DRY WITH SEASONABLE TEMPERATURES CONTINUING INTO FRIDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTHERN GULF. NEXT SYSTEM WILL APPROACH THE AREA LATE SATURDAY/SATURDAY NIGHT. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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AS OF 105 AM SUNDAY... WIDESPREAD MVFR/LOW END VFR CEILINGS WILL PERSIST THROUGH DAYBREAK ACROSS MUCH OF THE PIEDMONT. OVER THE COASTAL PLAIN AND THE SANDHILLS INCLUDING THE KFAY AND KRWI TERMINALS...PARTIAL CLEARING WILL ALLOW AREAS OF FOG AND LOW CLOUDS TO DEVELOP. THIS MAY LEAD TO AREAS OF MVFR/IFR CONDITIONS BETWEEN 08Z-12Z. AFTER 12Z...IMPROVING CONDITIONS ANTICIPATED AS DRIER AIR ALOFT SHOULD MIX DOWN TOWARD TEH SURFACE...HELPING TO SCOUR OUT THE LOW LEVEL MOISTURE. RESPITE FROM THE ADVERSE AVIATION CONDITIONS WILL BE BRIEF AS A DEVELOPING LOW PRESSURE SYSTEM OVER THE NORTHERN GULF WILL BEGIN TO LIFT NE ALONG THE GA-SC COAST TONIGHT. THIS WEATHER SYSTEM WILL SPREAD ADDITIONAL MOISTURE LEADING TO WIDESPREAD MVFR/IFR CEILINGS ALONG WITH WIDESPREAD RAIN. THE ADVERSE AVIATION WEATHER CONDITIONS WILL PERSISTS INTO MONDAY MORNING. THE RAIN WILL DIMINISH MONDAY AFTERNOON-MONDAY NIGHT THOUGH EXTENSIVE CLOUDINESS EXPECTED TO PERSIST. ANOTHER LOW PRESSURE SYSTEM WILL AFFECT CENTRAL NC LATE TUESDAY INTO WEDNESDAY...BRINGING A ROUND OF HEAVY SHOWERS AND POSSIBLY A FEW THUNDERSTORMS. SFC WINDS WILL BECOME WEDNESDAY THROUGH CHRISTMAS DAY WITH WIND GUSTS 30-35KTS PROBABLE.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...MWS/ELLIS SHORT TERM...CBL LONG TERM...CBL AVIATION...WSS

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