Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 171723 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1223 PM EST WED DEC 17 2014 .SYNOPSIS... HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS THROUGH THE END OF THE WEEK. LOW PRESSURE WILL MOVE NEAR THE AREA ON SATURDAY...BRINGING WIDESPREAD RAIN AND BELOW NORMAL TEMPERATURES THE FIRST HALF OF THE WEEKEND. A DRYING TREND WILL DEVELOP SUNDAY AND INTO EARLY NEXT WEEK...ALONG WITH WARMING TEMPERATURES. ANOTHER LOW PRESSURE SYSTEM MAY APPROACH ON TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1230 PM WEDNESDAY...THE WEAK CYCLONIC FLOW AROUND POTENT LOW PRESSURE MOVING OFF THE CANADIAN MARITIMES WILL WEAKEN THROUGH THE AFTERNOON AS A ZONAL MID LEVEL FLOW PERSISTS. WEAK HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST OVERNIGHT WHICH WILL ONLY SERVE TO DAMPEN TEMPERATURES A BIT THURSDAY. FOR THIS AFTERNOON AND OVERNIGHT...THE ONLY ISSUE IS HIGH CLOUD COVER STREAMING IN FROM THE SOUTHWEST. THE GFS 200MB RH FIELDS CAPTURES THIS FAIRLY WELL. I HAVE INCREASED CLOUD COVER A BIT VERY LATE AS WELL AS ADDING PATCHY FOG AS LIGHT WINDS AND SOME RADIATIONAL COMPONENT WARRANT. WENT WITH THE COOLER NAM/MET NUMBERS FOR LOWS. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...PLEASANT WEATHER FOR MUCH OF THE SHORT TERM AS WE COME TO THE END OF METEOROLOGICAL FALL...BUT RAPID DETERIORATION ANTICIPATED BEGINNING FRIDAY NIGHT. CONFLUENCE ALOFT WILL DRIVE SURFACE HIGH PRESSURE FROM THE OHIO RIVER VALLEY INTO THE CAROLINAS...PRECEDED BY A WEAK AND DRY BACK DOOR COLD FRONT VERY EARLY THURSDAY. THIS WILL LEAVE DRY AND SEASONABLE CONDITIONS ACROSS THE AREA ON THURSDAY WITH PLENTY OF SUNSHINE AND TEMPS IN THE UPPER 50S MOST OF THE AREA. INCREASING CLOUDINESS WILL SOMEWHAT OFFSET RADIATIONAL COOLING THURSDAY NIGHT...BUT WEAK CAA WILL STILL HELP TEMPS DROP TO SLIGHTLY LESS THAN NORMAL VALUES...A DEGREE OR TWO EITHER SIDE OF 35. CHANGES BEGIN ON FRIDAY AS A SOUTHERN STREAM SHORTWAVE EJECTS OUT OF THE DESERT SOUTHWEST AND MOVES ACROSS THE SOUTHERN TIER OF THE NATION. WHILE THE DIRECT IMPACTS OF THIS FEATURE AND ITS SURFACE REFLECTION WILL PRIMARILY OCCUR BEYOND THE SHORT TERM...INCREASING DIFFLUENCE DOWNSTREAM OF THE SHORTWAVE AND SOME ISENTROPIC LIFT AT 300K WILL LEAD TO WIDESPREAD CLOUDS AND SHOWER DEVELOPMENT LATE FRIDAY. WHILE LIFT WILL CAUSE GRADUAL SATURATION OF THE ENTIRE ATMOSPHERIC COLUMN...VERY DRY LOW-LEVEL AIR FRIDAY AFTN/EVE WILL TAKE A WHILE TO MOISTEN AND THUS ONLY VERY LIGHT RAIN IS EXPECTED FRIDAY NIGHT. SREF PROBS FOR 0.01 INCHES REACH ONLY ABOUT 30% BY 7AM SATURDAY...TYPICALLY NOT A SIGNAL FOR A LOT OF RAINFALL...IF ANY AT ALL. THE HIGH RES MODELS ARE LESS AGGRESSIVE WITH QPF ON FRIDAY...AND WPC SHOWS VERY LITTLE DURING THIS TIMEFRAME AS WELL. THUS WILL ACTUALLY LOWER POP VALUES TO CHC/LIKELY FRIDAY NIGHT...HIGHEST IN THE FAR SW ZONES. TEMPS FRIDAY WILL BE COOLER THAN THURSDAY...BUT STILL MAINTAIN NEAR-NORMAL VALUES IN THE MID 50S. LOWS AT NIGHT WILL DROP ONLY TO AROUND 40 AS CLOUDS/RAIN LIMIT COOLING. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 AM WEDNESDAY...A VERY WET AND RAW DAY ON TAP FOR SATURDAY AS A LARGE STORM SYSTEM IMPACTS THE REGION. SOUTHERN STREAM SHORTWAVE WILL MOVE OVERHEAD THE CWA THE FIRST HALF OF SATURDAY...WHILE SURFACE CYCLOGENESIS OCCURS OFFSHORE AND MOVES NORTHEAST THROUGH THE DAY. THIS LEAVES THE REGION ON THE COOL NW SIDE OF THE SURFACE LOW...AND BENEATH SIGNIFICANT ISENTROPIC LIFT AS SW FLOW TOPS THE REMNANT SURFACE WEDGE. THE ENTIRE COLUMN IS SATURATED ON SATURDAY...SO ONE CAN BASICALLY PICK ANY LEVEL BETWEEN 280K AND 305K AND EXPERIENCE MOIST ISENTROPIC LIFT. THIS IS A SIGNAL FOR A WIDESPREAD MDT-TO-HVY RAINFALL EVENT...EASING SLOWLY AFTER DARK THANKS TO DRY ADVECTION SLOWLY OCCURRING FROM THE TOP OF THE COLUMN DOWNWARD. STILL...A SIGNIFICANT QPF EVENT SEEMS LIKELY WITH WIDESPREAD 0.5 TO 1.0 INCHES OF RAINFALL ANTICIPATED. EVEN THOUGH DRYING OCCURS SATURDAY NIGHT AND SUNDAY...THE WEDGE OF HIGH PRESSURE WILL REMAIN IN PLACE AND KEEP LOW CLOUDS/DRIZZLE IN PLACE THROUGH MOST OF THE WKND...AND THUS EXPECT GUIDANCE IS WELL TOO WARM WITH TEMPS. BELIEVE MOST OF THE AREA WILL STRUGGLE ONLY INTO THE LOW 50S SATURDAY AND SUNDAY...WITH UPPER 40S POSSIBLE FAR NW. BRIEF IMPROVEMENT WILL OCCUR MONDAY AS THE COLUMN DRIES AND HIGH PRESSURE BECOMES THE DOMINANT FEATURE LOCALLY...BUT TEMPS WILL REMAIN BELOW SEASONABLE NORMS. GUIDANCE IS SUGGESTING ANOTHER SIGNIFICANT STORM SYSTEM MAY IMPACT THE REGION BEGINNING TUESDAY...BUT THIS IS A NEW SOLUTION AND VARIABILITY IS HIGH. FOR NOW WILL SHOW A RETURN TO SEASONABLE TEMPS WITH SILENT POP. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 18Z...HIGH PRESSURE WILL BUILD IN TODAY BEHIND A FRONT THAT MOVED OFFSHORE OVERNIGHT. THE AIRMASS IS ONLY A FEW DEGREES COOLER THAN THE PREVIOUS. IT WILL NOT TAKE LONG FOR HIGH CLOUDS TO MOVE IN IN ADVANCE OF A WEAK BAROTROPIC LEAF MOVING FAIRLY QUICKLY EAST. IT SHOULD GO BROKEN OR OVERCAST BY LATE AFTERNOON. LIGHT WINDS TONIGHT...HOWEVER MOISTURE PROFILES DO NOT SUPPORT FOG. THURSDAY...CONTINUED VFR WITH LIGHT NORTHERLY WINDS. A WEAK SYSTEM WILL PASS TO THE NORTH OF THE REGION AND WILL NOT AFFECT US. EXTENDED OUTLOOK...VFR THU THROUGH FRIDAY. GOOD CHANCE OF RAIN ON SATURDAY WITH POSSIBLE MVFR/IFR CONDITIONS. A SLIGHT CHANCE OF PRECIP ON SUN AND MON. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1230 PM WEDNESDAY...CONDITIONS WILL BE VERY QUIET OVER THE COASTAL WATERS AS THE PRESSURE GRADIENT...WHAT LITTLE THERE IS OF IT...WEAKENS FURTHER THIS AFTERNOON AND OVERNIGHT. EXPECT A LIGHT NORTHWEST FLOW OF TEN KNOTS OR LESS WITH SEAS OF 1-2 FEET. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...HIGH PRESSURE RIDGING DOWN INTO THE AREA FROM THE MIDWEST WILL KEEP A LIGHT GRADIENT THROUGH MUCH OF THE PERIOD...PERSISTING NORTHERLY WINDS AROUND 10 KTS THURSDAY AND THE FIRST HALF OF FRIDAY. LATE FRIDAY NIGHT LOW PRESSURE WILL BEGIN TO DEVELOP OFFSHORE...WHICH WILL WORK IN TANDEM WITH A DEVELOPING WEDGE OF HIGH PRESSURE INLAND TO CAUSE A SLOWLY TIGHTENING GRADIENT...AND WINDS WILL INCREASE TO 10-15 KTS FROM A MORE NE DIRECTION. WAVE HEIGHTS WILL BE 1-2 FT THURSDAY AND THE FIRST HALF OF FRIDAY THANKS TO THE LIGHT WINDS...BUT WILL BEGIN TO RISE LATE...BECOMING 2-4 FT WITH A N/NE WIND CHOP THE PREDOMINANT WAVE GROUP FRIDAY NIGHT. LONG TERM /SATURDAY THROUGH SUNDAY/... AS OF 300 AM WEDNESDAY...WEDGE OF HIGH PRESSURE INLAND WILL COMBINE WITH A LOW PRESSURE DEVELOPING OFFSHORE TO PRODUCE A PINCHED GRADIENT...AND NE WINDS AROUND 15 KTS ON SATURDAY. AS THIS LOW PRESSURE PULLS AWAY SLOWLY SATURDAY NIGHT AND ON SUNDAY...WINDS WILL BACK TO THE N/NW...BUT AT SIMILAR SPEEDS. SEAS WILL BE HIGHEST SATURDAY ON THE NE FETCH...WITH 3-4 FT SEAS EXPECTED. ALTHOUGH WINDS WILL REMAIN 10-15 KTS SUNDAY...WAVE HEIGHTS WILL DROP ON THE MORE OFFSHORE COMPONENT...BECOMING 2-3 FT...WITH A FEW 4 FTERS PERSISTING ACROSS THE NC WATERS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...SHK NEAR TERM...SHK SHORT TERM...JDW LONG TERM...JDW AVIATION...DL

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