Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 041712 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1215 AM EST THU FEB 4 2016 .SYNOPSIS... SEVERAL WAVES OF LOW PRESSURE WILL CAUSE A COLD FRONT TO DRIFT SLOWLY ACROSS THE EASTERN CAROLINAS AND OFFSHORE. THE LAST OF THESE WAVES WILL INTENSIFY OFF THE NORTH CAROLINA COAST OVERNIGHT. COOL HIGH PRESSURE WILL ARRIVE FRIDAY AND PERSIST THROUGH SATURDAY. LOW PRESSURE WILL DEVELOP OFFSHORE LATE SATURDAY AND QUICKLY MOVE OFF TO THE NORTHEAST. THIS SYSTEM WILL BRING A QUICK BOUT OF RAIN WITH JUST A SMALL CHANCE OF SNOW MIXING IN. ARCTIC AIR WILL ARRIVE FOR THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1130 AM THURSDAY...AFTER REVIEWING THE NEW 12Z GFS MODEL I HAVE RAISED A FLOOD WATCH FOR THE COASTAL COUNTIES FROM GEORGETOWN NORTHWARD...PLUS BLADEN AND COLUMBUS COUNTIES IN INTERIOR EASTERN NC. DEEP LIFT IS EXPECTED TO INCREASE BETWEEN 6 PM AND MIDNIGHT RESULTING IN HEAVY RAIN DEVELOPING OVER THE WATCH AREA. IN ADDITION TO THE RAIN THAT HAS ALREADY FALLEN... ANOTHER 1-3 INCHES IS EXPECTED WHICH SHOULD EXCEED LATEST 24 HOUR FLOOD GUIDANCE ESTIMATES FROM THE ATLANTA RIVER FORECAST CENTER. OTHER UPDATES MADE TO THE FORECAST INCLUDE TWEAKS TO HOURLY TEMPERATURE BASED ON AN EVEN SLOWER MOVEMENT OF THE COLD FRONT EASTWARD TOWARD THE COAST. DISCUSSION FROM 930 AM FOLLOWS... A VERY SLOW MOVING COLD FRONT CURRENTLY BISECTS OUR FORECAST AREA...EXTENDING ROUGHLY FROM BENNETTSVILLE SOUTHWARD THROUGH FLORENCE TO JUST EAST OF KINGSTREE. WIND DIRECTIONS ARE GENERALLY SW AHEAD OF THE FRONT AND WESTERLY BEHIND...ALTHOUGH TEMPERATURE IS ALSO A GOOD CLUE TO THE FRONTAL POSITION GIVEN THE 8-10 DEGREE DIFFERENT NOTED. THIS BOUNDARY IS ONLY SLOW PUSHING EAST AND SHOULD TAKE THE REST OF THE MORNING TO MAKE IT TO THE GRAND STRAND. WILMINGTON MAY NOT SEE A WIND SHIFT UNTIL EARLY TO MID AFTERNOON! AN IMPRESSIVE BELT OF MOISTURE EXTENDS ALONG THIS FRONT SOUTHWARD INTO FLORIDA AND THE GULF OF MEXICO. ALTHOUGH ISENTROPIC LIFT (NOTED ALONG MANY LEVELS BUT MOST PROMINENT AT 305K THETA) IS MODERATE IN INTENSITY NOW...MODELS SUGGEST THAT AS A STRONG UPPER TROUGH APPROACHES FROM THE WEST THIS EVENING LIFT WILL BECOME MUCH STRONGER ALONG THE COAST. THIS COULD LEAD TO A 3-6 HOUR WINDOW OF HEAVY RAINFALL AND POSSIBLE FLOODING ALONG THE SC COAST AND ALSO OVER SE NORTH CAROLINA BEGINNING AROUND SUNSET. SOILS ARE FAIRLY SATURATED AFTER THE 1.5 TO 2.5 INCH RAINFALL TOTALS OF THE PAST 24 HOURS...AND IF AN ADDITIONAL 2-3 INCHES WERE TO FALL I WOULD NOT BE SURPRISED TO SEE FLOODING DEVELOP. THERE HAS BEEN SOME DISCUSSION OF THIS ALREADY WITH SURROUNDING NWS OFFICES...BUT I WOULD LIKE TO REVIEW THE 12Z GFS BEFORE RAISING A WATCH IN AN ATTEMPT TO LOCALIZE THE AREA POTENTIALLY AFFECTED. TEMPERATURES ALONG THE COAST ARE PRACTICALLY AT HIGHS NOW AND SHOULD BEGIN TO SLIP AS THE COLD FRONT ARRIVES OVER THE NEXT 2-4 HOURS. INLAND TEMPERATURES SHOULD REMAIN ESSENTIALLY UNCHANGED THIS AFTERNOON IN THE UPPER 50S AFTER HIGHS IN THE MID 60S A FEW HOURS AGO. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 AM THURSDAY...MID LEVEL TROUGHING EARLY FRIDAY WILL QUICKLY GIVE WAY TO A MORE ZONAL FLOW BRIEFLY. THIS WILL PERSIST THROUGH SATURDAY. AT THE SURFACE HIGH PRESSURE BUILDS ACROSS THE APPALACHIANS. EXPECT CLEARING SKIES FRIDAY AND PARTLY TO MOSTLY SUNNY SKIES SATURDAY. TEMPERATURES WILL BE SOMEWHAT BELOW NORMAL WITH HIGHS IN THE LOWER 50S BOTH DAYS AND LOWS IN THE LOWER 30S SATURDAY MORNING. THE FOCUS THEN SHIFTS TO A FAST MOVING TROUGH DIVING OUT OF THE ROCKIES INTO THE SOUTHEAST WHICH WILL SPARK LOW PRESSURE OFF THE COAST. THE NAM AND GFS HAVE SHIFTED A BIT FURTHER OFFSHORE WITH THE SURFACE LOW AS THE MID LEVEL CLOSED LOW DEVELOPS ACROSS SOUTH CAROLINA. THE ECMWF HAS A SOMEWHAT SIMILAR SCENARIO AND HAS BEEN THE MOST CONSISTENT. ISENTROPIC LIFT AND DYNAMIC LIFT SHOULD DEVELOP PRECIPITATION ACROSS THE EASTERN TWO THIRDS OF THE CWA LATE SATURDAY EVENING INTO SUNDAY MORNING. THERMAL PROFILES CONTINUE TO SHOW MOSTLY RAIN. WITH HIGHS IN THE LOWER 50S SATURDAY AND SURFACE DEWPOINTS RISING TO ABOUT 30...IT APPEARS THERE WILL JUST BE TOO MUCH COOLING NECESSARY FOR ANY FROZEN PRECIPITATION TO REACH THE GROUND. NOT THAT THERE WON`T BE DIABATIC COOLING OF THE PROFILE WITH THE RAIN FALLING AND DYNAMIC COOLING AS WELL WITH THE FRONTOGENESIS...ITS CLEARLY NOTED ON BUFKIT SOUNDINGS AND IN THE 850MB PLAN VIEW OF THE GFS WITH THE COLD POCKETS DEVELOPING. AS STATED BEFORE THE ANTECEDENT THERMAL PROFILES AND THE RELATIVELY LIGHT RAINFALL RATES WILL BE DIFFICULT TO OVERCOME TO PRODUCE SNOW. SO THAT BEING SAID...THE CHANCES OF FROZEN PRECIP HAVE JOGGED A LITTLE LOWER BUT WE WILL CONTINUE TO WATCH THIS CLOSELY. ONE POSITIVE IS THAT A LIGHTER QPF EVENT MAY PRECLUDE FLOODING CONCERNS COMING OFF THE CURRENT EVENT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 300 AM THURSDAY...MID LEVEL LOW PRESSURE AND ASSOCIATED SURFACE FEATURES WILL GET KICKED OUT QUICKLY TO THE NORTHEAST LATER SUNDAY. ANY LINGERING PRECIPITATION SHOULD COME TO A QUICK END. THIS SETS THE STAGE FOR DEEP EAST COAST TROUGHING TO DEVELOP MONDAY AND TUESDAY. 850MB TEMPERATURES DROP TO ABOUT MINUS TWELVE C WEDNESDAY. IT APPEARS THE COLDEST AXIS REMAINS TO THE WEST AND MODIFIES SLIGHTLY AS IT MOVES EAST. THIS IS PROBABLY...ALONG WITH THE CLIMATOLOGY FACTOR THE REASON MEX GUIDANCE ISN`T TOO COLD RELATIVELY SPEAKING AT THIS POINT. OVERALL FEW CHANGES WITH A COLD FORECAST AND THE LINGERING POSSIBILITY OF A FEW SPRINKLES OR FLAKES FROM TIME TO TIME. TIMING IS DIFFICULT ON THE BEST CHANCE BUT IT WOULD APPEAR A LITTLE DAYTIME HEATING WITH VERY STEEP LAPSE RATES MAY FAVOR THE PM HOURS. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 18Z...A FRONTAL BOUNDARY AND A SHORTWAVE FROM THE WEST MOVING ACROSS THE REGION LATER THIS AFTERNOON AND OVERNIGHT WILL COMBINE TO PRODUCE A DEVELOPING SURFACE LOW OFF THE COAST. THE COASTAL TAF SITES WILL BE BOUNCING BETWEEN MVFR AND IFR EARLY THEN IFR FOR BOTH CEILINGS AND VISIBILITIES OVERNIGHT. THE SITES ARE EXPECTED TO LIFT TO MVFR BY LATE MORNING ON FRIDAY. AT KFLO AND KLBT WITH THE DEVELOPING LOW FARTHER TO THE EAST...THESE SITES SHOULD SEE MORE MVFR THROUGH THE PERIOD BUT IFR IS EXPECTED AS RAIN...LOW CEILINGS PERSIST UNTIL THE MID-OVERNIGHT PERIOD. IF THE LOW DEVELOPS AS EXPECTED MAY SEE VFR CONDITIONS AT THE KFLO AND KLBT JUST AFTER 12UTC. STRONG NORTHWEST LOW-LEVEL WINDS ARE EXPECTED TO DEVELOP AFTER 00 UTC AND GUST WINDS WILL FOLLOW THROUGH THE LATE OVERNIGHT INTO FRIDAY. EXTENDED OUTLOOK...BECOMING VFR FRIDAY AND SATURDAY. RAIN POSSIBLE SUNDAY WITH MVFR. VFR MONDAY INTO TUESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1130 AM THURSDAY...A VERY SLOW MOVING COLD FRONT IS STILL INLAND ACROSS EASTERN NORTH AND SOUTH CAROLINA AND SHOULD REACH THE SC BEACHES NOON-1PM AND THE COAST OF SE NORTH CAROLINA BY MID AFTERNOON. WIND SPEEDS HAVE REALLY DIMINISHED NEAR THIS FRONT WITH SPEEDS GENERALLY UNDER 15 KT EVEN OFFSHORE. THE BIG CHANGE IN WEATHER CONDITIONS SHOULD OCCUR NOT WITH THE FRONTAL PASSAGE ITSELF...BUT INSTEAD LATE THIS EVENING AS LOW PRESSURE QUICKLY DEVELOPS AND STRENGTHENS ALONG THE FRONT OFFSHORE. A QUICKLY TIGHTENING PRESSURE GRADIENT ON THE BACK SIDE OF THIS FRONT WILL CAUSE INCREASING OFFSHORE WINDS. THIS WILL DRAG COLD AIR OFF THE COAST...WITH SUBSTANTIAL GUSTINESS OCCURRING AS THIS COLD AIR MOVES OUT ACROSS THE RELATIVELY WARM OCEAN SURFACE. A GALE WATCH REMAINS IN EFFECT FOR THE POTENTIAL OF 35 KNOT WINDS LATE TONIGHT INTO FRIDAY MORNING. RADAR SHOWS RAIN EXTENDING ALL THE WAY BACK TO THE FLORIDA PANHANDLE. RAIN SHOULD CONTINUE THROUGH TODAY AND MOST OF TONIGHT. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 600 AM THURSDAY...BRIEF STRONG COLD AIR ADVECTION AND DEPARTING LOW PRESSURE TO THE NORTHEAST WILL PRODUCE VERY STRONG NORTHWEST WINDS INITIALLY...ON THE ORDER OF 25-30 KNOTS FOR A COUPLE OF HOURS. THE GRADIENT RELAXES QUICKLY BY LATE MORNING/EARLY AFTERNOON TO 15- 20 KNOTS. HIGH PRESSURE WILL BE CENTERED OVER THE TENNESSEE VALLEY SATURDAY PRODUCING A NORTHEAST FLOW OF 15-20 KNOTS. THE SPEEDS MAY INCREASE LATE SATURDAY EVENING INTO EARLY SUNDAY AS LOW PRESSURE DEVELOPS OFF THE SOUTHEAST COAST. RUGGED SEAS WILL BE IN PLACE EARLY AND CONTINUE INTO SMALL CRAFT CRITERIA UNTIL ABOUT MIDNIGHT FRIDAY. EXPECT A MORE MODEST RANGE OF 2-4 FEET SATURDAY. A GALE WATCH HAS BEEN POSTED FOR THE POSSIBILITY OF GALE CONDITIONS FOR THE FIRST PART OF FRI. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 300 AM THURSDAY...EXPECT A FAIRLY STRONG NORTHWEST FLOW SUNDAY AS VERTICALLY STACKED LOW PRESSURE RACES OFF TO THE NORTHEAST. SPEEDS 20-25 KNOTS AND MAYBE A LITTLE HIGHER LATE VIA STRONG COLD AIR ADVECTION. A BRIEF RESPITE MONDAY WITH A SOUTHWEST FLOW AHEAD OF AN ARCTIC FRONT WHICH WILL BRING RUGGED CONDITIONS TO THE WATERS FOR THE MIDDLE PART OF NEXT WEEK. HIGH SEAS SUNDAY ESPECIALLY OFFSHORE VIA THE FLOW DROPPING A BIT MONDAY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH THROUGH LATE TONIGHT FOR SCZ053>056. NC...FLOOD WATCH THROUGH LATE TONIGHT FOR NCZ096-099-105>110. MARINE...GALE WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON FOR AMZ250-252-254-256. && $$ NEAR TERM...TRA SHORT TERM...SHK LONG TERM...SHK AVIATION...HAWKINS

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