Area Forecast Discussion
Issued by NWS Wilmington, NC

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423 FXUS62 KILM 061007 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 507 AM EST SAT FEB 6 2016 .SYNOPSIS...
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HIGH PRESSURE WILL MOVE OFF THE VA CAPES TODAY. LOW PRESSURE WILL DEVELOP OFFSHORE AND EAST OF THE FLORIDA COAST TONIGHT AND QUICKLY INTENSIFY AS IT MOVES NORTHEAST. THE DEEPENING LOW WILL PASS THE AREA WATERS DURING SUNDAY...AND PULL AWAY FROM THE REGION SUN NIGHT. LOOKING AT LIGHT TO MODERATE RAIN WITH THIS SYSTEM... WITH A CHANCE OF SNOW MIXING IN MAINLY WELL INLAND LATE TONIGHT INTO SUNDAY. AN ARCTIC AIRMASS WILL ARRIVE MONDAY NIGHT BEHIND A COLD FRONTAL PASSAGE...AND WILL REMAIN OVER THE AREA THROUGH THE MID TO LATE WEEK PERIOD.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM SATURDAY...DIFFICULT FORECAST IN RELATION TO PCPN TYPE AND AMOUNTS FROM THE DEVELOPING COASTAL LOW LATE IN THIS FORECAST PERIOD. MODELS AGREE THAT A POTENT MID-LEVEL S/W TROF WILL RAPIDLY MOVE EAST SOUTHEAST FROM THE LOWER MISSISSIPPI VALLEY TO NORTHERN FLORIDA BY SUNRISE SUNDAY. AT THIS POINT IT REMAINS POSITIVELY TILTED...HOWEVER A FEW MODELS TRY TO CLOSE IT OFF. THIS WOULD SLOW THIS SYSTEMS PROGRESS IF THE LATTER IS THE CASE. FOR THE TIME BEING...STAYED A BIT CLOSER TO THE NAM/GFS MODEL SOLUTION WHICH IS MORE GENEROUS WITH THE MOISTURE AND PCPN AMOUNTS. THE EUROPEAN IS SOMEWHAT DRIER WITH LESS OF AN INLAND PUSH OF PCPN. THE MID- LEVEL TROF WILL TAP THE GULF OF MEXICO MOISTURE AND ALONG WITH ATLANTIC MOISTURE...HAVE OVERRUNNING/ISENTROPIC TYPE PCPN STARTING OUT LATER THIS EVENING ACROSS THE SOUTHERN PORTIONS OF THE ILM CWA. IT SHOULD OVERSPREAD THE ILM CWA DURING THE PRE-DAWN SUNDAY HOURS. HAVE IDENTIFIED THE THREAT FOR A MIXTURE OF LIGHT SNOW WITH THE RAIN FOR THE FAR NW PORTIONS OF THE ILM CWA...RUNNING FROM NORTHERN BLADEN... ROBESON AND DILLON COUNTIES AND MUCH OF MARLBORO AND DARLINGTON COUNTIES. THIS WILL OCCUR DURING THE PRE- DAWN SUNDAY HOURS. 850MB TEMPS ARE RIGHT AT 0 ACROSS THE MENTIONED AREA...WITH 1000-850MB THICKNESS RANGING FROM 1305-1310M WHICH IS STILL HIGHER THAN THE RECOMMENDED 1300M FOR SNOW. EARLIER IN THE DAY...THE 1000-850MB THICKNESS ACROSS THIS REGION WAS BETWEEN 1295 AND 1300M...FAVORABLE FOR SNOW. ENOUGH WAA IN THE LOWER LEVELS FROM OFF THE ATLANTIC WILL KEEP THIS SYSTEM RAIN OVERNIGHT...AND WILL ADVERTISE SNOW MIXING IN ACROSS THE FAR NW PORTIONS...ALONG WITH A TRACE FOR ACCUMULATIONS THRU DAYBREAK SUN. TONIGHTS TEMPS TO REMAIN SLIGHTLY ABOVE FREEZING...EXCEPT THE NW PORTIONS WHERE IT COULD DROP TO AROUND 32. WITH MAX TEMPERATURES TODAY EXPECTED TO REACH THE UPPER 40S TO LOW 50S...PLENTY OF COOLING IS NEEDED FOR THAT SNOW MIXTURE TO BE REALIZED LATE TONIGHT. THE DYNAMICS FROM THE DEVELOPING SYSTEM WILL LIKELY SUPPLY SOME OF THE COLD AIR BUT WILL IT BE ENOUGH FOR SNOW TO OCCUR. ONE TENTH TO ONE HALF INCH OF RAINFALL IS EXPECTED WEST OF THE I-95 CORRIDOR. ALONG AND EAST OF THE I-95 CORRIDOR TO THE COAST... ONE HALF TO 1.25 INCHES ARE EXPECTED. THE HIER END OF THIS RANGE WILL OCCUR ACROSS THE IMMEDIATE COASTAL COUNTIES. THE RAIN WILL FALL IN A 12 TO 18 HR PERIOD AND THEREFORE DO NOT ANTICIPATE ANY FLOOD WATCHES. TEMPORARY NUISANCE TYPE FLOODING MAY OCCUR ACROSS THOSE AREAS THAT RECEIVED 2 TO 5 INCHES OF RAIN SEVERAL DAYS AGO. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY...ALL EYES REMAIN ON THE SYSTEM THAT WILL ALREADY BE AFFECTING THE FORECAST AREA AS THE PERIOD BEINGS. SOUTHERN STREAM SHORTWAVE OVER THE EASTERN GOMEX WILL INDUCE SURFACE LOW DEVELOPMENT OFF THE FL COAST LATE TONIGHT. THE LOW WILL THEN TRACK NORTHEAST...PASSING OFF THE CAROLINA COAST SUN INTO SUN NIGHT. THERE WILL BE AN ABUNDANCE OF DEEP MOISTURE DURING THE FIRST HALF OF THE PERIOD AND STRONG UPPER LEVEL JETTING WILL HELP DEEPEN THE LOW AND PROVIDE DYNAMICS. THIS SHOULD RESULT IN PRECIP FALLING ACROSS MUCH OF THE AREA. HAVE HIGH CONFIDENCE IN PRECIP FALLING SUN INTO SUN NIGHT BUT CONFIDENCE DROPS WITH RESPECT TO THE TYPE OF PRECIP EXPECTED DURING THE EVENT. CURRENTLY ALL BUT THE COLDEST OF THE GUIDANCE IS POINTING TO A RAIN/SNOW EVENT FOR THE AREA WITH POTENTIAL FOR ALL SNOW AS IT ENDS ACROSS INLAND LOCATIONS. THIS HOWEVER DOES NOT TAKE INTO ACCOUNT DYNAMICAL PROCESSES THAT CAN CONTRIBUTE A SIGNIFICANT AMOUNT OF COOLING AS A LOW RAPIDLY DEEPENS. THERE WILL BE PLENTY OF ICE IN THE CLOUD AS STRONG UPWARD MOTION WITH THE DENDRITIC GROWTH ZONE WILL BE PRESENT AND FORECAST SOUNDINGS SHOW THE COLUMN BELOW FREEZING ABOVE ROUGHLY THE 850MB LEVEL (AGAIN DISCOUNTING THE COLDEST OUTLIER). GIVEN THE HIGH LEVEL OF UNCERTAINTY AND THE SENSITIVITY OF THE P TYPE FORECAST TO MINOR ADJUSTMENTS IN THE LOWS TRACK DO NOT PLAN TO ALTER THE INHERITED FORECAST SIGNIFICANTLY. AFTER DISCUSSION WITH NEIGHBORING OFFICES DECIDED ON A RAIN/SNOW MIX FOR INLAND AREAS SUN MORNING TURNING TO ALL RAIN IN THE AFTERNOON. HOWEVER IT MUST AGAIN BE MENTIONED THAT CONFIDENCE REMAINS EXTREMELY LOW AND CHANGES TO THE FORECAST WILL LIKELY BE REQUIRED. SECOND HALF OF THE FORECAST PERIOD IS NO LESS OF A CHALLENGE. BRIEF PERIOD OF DRYING LATE SUN NIGHT AND EARLY MON COMES TO AN END AS SHORTWAVE/COLD FRONT COMBO APPROACH FROM THE NORTHWEST. THIS FEATURE ALSO HAS PLENTY OF LIFT AND MOISTURE WITHIN THE DENDRITIC GROWTH ZONE. COLD AIR WILL AGAIN BE THE ISSUE BUT LATEST GUIDANCE IS SHOWING TEMPS A BIT COOLER AND THE SYSTEM WILL HAVE STRONG DYNAMICS. THE LIMITING FACTOR WILL BE A FAIR AMOUNT OF DRY AIR BELOW 850 MB. SO WHILE THERE IS ARGUABLY A BETTER CHANCE AT GETTING SNOW TO FALL WITH THE SECOND SYSTEM THE LOW LEVEL MOISTURE REMAINS A LIMITING FACTOR. HAVE MAINTAINED INHERITED CHC POP FOR LATE MON AND MON NIGHT BUT WHETHER PRECIP ENDS UP RAIN...RAIN/SNOW MIX...OR EVEN ALL SNOW THE QUANTITY THAT REACHES THE SURFACE WILL BE LITTLE MORE THAN A TRACE FOR MOST AREAS. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 3 AM SATURDAY...IMPRESSIVE LONGWAVE 5H TROUGH OVER THE EASTERN CONUS TUE WILL USHER IN ARCTIC AIR FOR MID WEEK. FIRST SHOT OF COLD AIR ARRIVES EARLY TUE AS COLD FRONT MOVES ACROSS THE AREA WITH A REINFORCING SHOT EXPECTED ON WED. INITIAL ROUND TUE DROPS 850 TEMPS TO AROUND -8C IN THE AFTERNOON WITH POTENTIAL FOR 850 TEMPS APPROACHING -13C ON WED. BY THU THE MID LEVEL TROUGH STARTS LIFTING NORTH WITH AN INCREASE IN BOTH 850 TEMPS AND 1000-500 HEIGHTS IN STORE. UNFORTUNATELY LITTLE OF THIS WARMING TRANSLATES TO THE SURFACE WHERE PARTIAL THICKNESSES SUGGEST ARCTIC AIR WILL HOLD ON THROUGH THU BEFORE AIR MASS STARTS TO MODIFY FRI AND TEMPS APPROACH NORMAL. TEMPERATURES FOR MUCH OF THE PERIOD WILL BE BELOW CLIMO WITH WED AND THU HAVING TEMPS 10 TO 15 DEGREES BELOW. PRESENCE OF COLD ADVECTION THROUGHOUT THE EVENT IS A DOUBLE EDGED SWORD. IT WILL HELP PREVENT STRONG RADIATIONAL COOLING...WHICH WOULD YIELD LOWS IN THE TEENS...BUT IT WILL LEAD TO WIND CHILL VALUES WHICH WILL MAKE IT FEEL LIKE IT IS IN THE TEENS TUE AND WED NIGHTS. ANY PRECIP CHANCES DURING THE PERIOD WOULD BE LINKED TO SHORTWAVES ROUNDING THE BASE OF THE 5H TROUGH. THERE APPEARS TO BE ONLY 1 WITH ANY SHOT AT SQUEEZING OUT PRECIP AND THIS IS CURRENTLY TIMED TO PASS TUE AFTERNOON AND EVENING. FORECAST SOUNDINGS DO NOT SHOW A LOT OF MOISTURE TO WORK WITH...PWATS REMAIN WELL BELOW HALF AN INCH...BUT STRONGER SHORTWAVES ALWAYS SEEM TO SQUEEZE OUT WHAT LITTLE MOISTURE IS AVAILABLE. AT BEST IT WOULD BE SOME PATCHY LIGHT FLURRIES AND DOES NOT CURRENTLY WARRANT A POP OVER 5%. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... AS OF 06Z...FAIRLY HIGH CONFIDENCE FOR VFR CONDITIONS EARLY THIS MORNING THROUGH DAYTIME SATURDAY AND INTO THE EARLY EVENING. HIGH PRESSURE NEARLY OVERHEAD THROUGH THE PRE-DAWN HOURS WITH WINDS EITHER CALM OR NE AT 3 KT OR LESS UNDER SCT CIRRUS CLOUDS. FOR DAYTIME SATURDAY...EXPECT NORTHEAST WINDS 5 TO 10 KT WITH A DECK OF CI/CS AT 250K FT WITH A SCT/BKN DECK OF AC AT 100K TO 120K FT IN THE AFTN AND EVENING. EARLY THIS EVENING... LOW PRESSURE WILL DEVELOP OFF THE FLORIDA EAST COAST...THEN DEEPEN RAPIDLY AS IT TRACKS NE JUST OFFSHORE AND PARALLEL TO THE SE U.S. COAST TONIGHT THRU SUNDAY. FOR SUNDAY EVENING...LOW LEVEL CLOUDS IN THE 2500 TO 5000 FT LEVEL WILL DEVELOP AS WELL AS STREAM NORTHWARD OVER THE REGION FROM THIS DEVELOPING LOW. BY THE END OF THE FORECAST PERIOD...RAIN IS EXPECTED TO HAVE COMMENCED...ESPECIALLY ACROSS THE COASTAL TERMINALS. POSSIBLE MVFR CONDITIONS ALONG THE IMMEDIATE COAST AT THE END OF THE 06Z TAF ISSUANCE PERIOD. THE SFC PG WILL TIGHTEN SATURDAY EVENING RESULTING WITH INCREASING N TO NNE WINDS...BECOMING GUSTY AT THE COAST. EXTENDED OUTLOOK...RAIN AND OR POSSIBLE SNOW SUNDAY WITH IFR CONDITIONS POSSIBLE. BECOMING VFR LATE SUN NIGHT INTO MON. CLOUDINESS AND A CHANCE OF PRECIPITATION WITH MVFR CONDITIONS POSSIBLE LATE MONDAY INTO TUESDAY. PREDOMINATELY VFR WEDNESDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 415 AM SATURDAY...GALE WARNING HAS BEEN RAISED FOR ALL WATERS...COMMENCING AT 600 AM SUNDAY...RIGHT AT THE END OF THE NEAR TERM PERIOD. A POTENT MID-LEVEL S/W TROF WILL CROSS NORTHERN FLORIDA LATE TONIGHT...AND AID IN THE DEVELOPMENT OF A SFC LOW JUST OFFSHORE FROM THE FLORIDA EAST COAST BY DAYBREAK SUN. A MODESTLY TIGHTENED SFC PG ACROSS THE LOCAL WATERS...WILL FURTHER TIGHTEN LATER TONIGHT ONCE THE SFC LOW COMMENCES OFF THE FLORIDA COAST. THE 1003-1005MB LOW WILL AT SUNRISE WILL RAPIDLY DEEPEN TO 995MB SUNDAY MORNING...AND DEEPER YET 986-990MB SUN AFTN. THIS WILL RESULT IN A SMALL PERIOD OF SCA CONDITIONS DEVELOPING LATER TONIGHT...AND RAPIDLY TRANSITION TO GALE CONDITIONS BY SUNRISE SUNDAY AND THERE-AFTER. FOR TODAY...NE 15 TO 20 KT BACKING TO N TO NNE 15 TO 25 KT WITH GUSTS TO 30 KT TONIGHT. SIGNIFICANT SEAS WILL BE GOVERNED BY WIND DRIVEN WAVES AT 5 TO 7 SECOND PERIODS. LOOKING AT 2 TO 5 FT SEAS TODAY...BUILDING TO 3 TO 6 FT TONIGHT. THE N TO NNE WINDS WILL RESULT IN A LOWER FETCH FOR WHICH SIGNIFICANT SEAS TO BUILD UPON...AND HENCE THE RATHER LARGE RANGE OF SEAS BEING FORECASTED. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SATURDAY...GALE CONDITIONS THROUGH SUN EVENING RELENT SUN NIGHT AND EARLY MON AS LOW EXITS AND WEAK SURFACE RIDGE BUILDS IN.THE REPRIEVE IS SHORT LIVED AND SOUTHWEST TO WEST FLOW EXCEEDING 25KT IS EXPECTED TO DEVELOP LATE MON AFTERNOON AND CONTINUE THROUGH THE END OF THE PERIOD. SEAS FOLLOW A SIMILAR PATH WITH HIGHEST VALUES ON SUN BEFORE DROPPING UNDER 6 FT LATE SUN NIGHT AND EARLY MON. HOWEVER BY MON EVENING SEAS WILL BE AT OR ABOVE 6 FT AND WILL CONTINUE TO BUILD MON NIGHT. LONG TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 3 AM SATURDAY...ANTICIPATE CONTINUATION OF HEADLINES FOR MUCH OF THE PERIOD DUE TO STRONG COLD ADVECTION AND OFFSHORE FLOW. WEST TO NORTHWEST FLOW WILL REMAIN IN THE 20 TO 25 KT RANGE FROM THE START OF THE PERIOD THROUGH WED EVENING WITH SEAS RUNNING 4 TO 7 FT FOR ALL BUT THE VERY END OF THE PERIOD. COLD ADVECTION AND WINDS START TO WEAKEN WED EVENING WITH SPEEDS DROPPING TO NEAR 15 KT BY THE END OF THE PERIOD.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...GALE WARNING FROM 6 AM TO 10 PM EST SUNDAY FOR AMZ250-252-254- 256. && $$ SYNOPSIS...III NEAR TERM...DCH SHORT TERM...III LONG TERM...III AVIATION...DCH

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