Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 090815 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 315 AM EST TUE FEB 9 2016 .SYNOPSIS...
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A CHILLY AIR MASS IN THE REGION TODAY WILL BE REINFORCED BY THE PASSAGE OF A DRY ARCTIC FRONT WEDNESDAY. THE AREA WILL REMAIN DRY WITH BELOW NORMAL TEMPERATURES THROUGH THE WEEK. ANOTHER COLD FRONT WILL CROSS THE AREA FRIDAY NIGHT WITH ARCTIC HIGH PRESSURE MOVING OVER THE CAROLINAS FOR THE WEEKEND AND START OF NEXT WEEK. TEMPERATURES LATE IN THE WEEK COULD BE THE COLDEST OF THE YEAR.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 3 AM TUESDAY...THE CHANGE TO THE LONGWAVE PATTERN HAS NOW BEEN ESTABLISHED...WITH A LARGE AMPLITUDE UPPER TROF AFFECTING ROUGHLY THE EASTERN 1/2 OF THE U.S. AND THE COMPLEMENT LARGE AMPLITUDE UPPER RIDGE AFFECTING THE WESTERN 1/2 OF THE UNITED STATES. THIS WILL PAINT A COLD AND DRY PICTURE FOR THIS PERIOD AND SUBSEQUENT PERIODS...THAT WILL LIKELY CONTINUE THRU THE UPCOMING WEEKEND. THE LONGWAVE UPPER TROF AXIS WILL NEARLY LIE OVERHEAD. IN THIS POSITION...ANY EMBEDDED MID-LEVEL VORTS OR SHEARED VORTICITY WILL NOT BE ABLE TO TAP ANY GULF MOISTURE AND FOR THE MOST PART ATLANTIC MOISTURE WHEN THEY MOVE ACROSS THE ILM CWA. IN ADDITION...THE ILM CWA WILL BE UNDER SYNOPTIC SUBSIDENCE ALOFT DUE TO THE ILM CWA LYING WITHIN THE LEFT REAR QUADRANT OF THE 300MB JET AXIS THAT IS ORIENTED FROM SW TO NE ACROSS THE ADJACENT ATLANTIC WATERS. AS A RESULT...THE EMBEDDED MID-LEVEL S/W TROFS WILL HAVE TO RELY ON MOISTURE THAT ACCOMPANIES THEM...HENCE THE STRATO-CU AND ALTO- CU BKN TO OVC CLOUD DECKS THAT WILL OCCASIONALLY AFFECT THE ILM CWA THIS PERIOD. NO POPS THIS PERIOD...WITH POSSIBLE PCPN REMAINING NORTH OF THE ILM CWA AND ACROSS THE APPALACHIAN MOUNTAINS. ANOTHER REASON TO KEEP A PCPN- FREE FORECAST IS THE DOWNSLOPE TRAJECTORY OFF THE MOUNTAINS THAT WILL ACT TO SCOUR OUT MOISTURE. MODELS INDICATE THE ILM CWA WILL LIE UNDER EXPANSIVE CYCLONIC FLOW SFC AND ALOFT...WITH NO REAL LOCAL INFLUENCES FROM ANY SFC HIGHS OR LOWS. WHAT WILL BE OCCURRING IS A TIGHTENED SFC PG AND CONTINUED CAA...ESPECIALLY AT THE LOWER LEVELS...AS HEIGHTS CONTINUE TO FALL ALOFT DUE TO THE UPPER TROF FURTHER AMPLIFYING. LOOKING AT THE OLD FAITHFUL MODEL CONSENSUS OF THE 1000-500MB THICKNESS FIELD... THICKNESSES DROP FROM 532-536DAM THIS MORNING TO 530-534DAM BY WED DAYBREAK. HOWEVER...CAA AT THE LOWER LEVELS IS MORE PRONOUNCED... TAKE THE 850MB MODEL CONSENSUS TEMP FCST THAT BASICALLY RANGES FROM -3 TO -6 DEGREES CELSIUS THIS MORNING...AND DROPS TO ROUGHLY -9 TO - 11 DEGREES CELSIUS BY DAYBREAK WED. OVERALL...WILL STAY CLOSER TO THE LOWER AVBL MOS GUIDANCE FOR BOTH MAX AND MIN TEMPS THIS PERIOD.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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AS OF 3 AM TUESDAY...ANOMALOUSLY DEEP 5H CUTOFF OVER THE EASTERN CONUS WILL BE IN THE PROCESS OF LIFTING NORTHEAST WED. THIS WILL ALLOW FOR INCREASING HEIGHTS ALOFT DURING THE PERIOD...THOUGH THE LONGWAVE 5H TROUGH WILL REMAIN IN PLACE. DESPITE THE INCREASE IN HEIGHTS THE REGION WILL REMAIN IN THE CLUTCHES OF THE SHALLOW ARCTIC AIR. HIGHS WED AND THU STRUGGLE TO REACH 40...WITH LOW LEVEL PARTIAL THICKNESSES SUGGESTING HIGHS IN THE UPPER 30S. PERIOD WILL BE DRY BUT PASSAGE OF SHORTWAVES THROUGH THE 5H TROUGH COULD LEAD TO BRIEF PERIOD OF INCREASED CLOUD COVER WED AFTERNOON AND AGAIN LATER THU. WIND CHILL VALUES WILL BE A CONCERN WED THROUGH THU GIVEN TEMPERATURES RUNNING 15 DEGREES BELOW CLIMO AND THE ANTICIPATED BREEZY CONDITIONS. WIND CHILLS DURING THE DAY WILL BE IN THE UPPER TEENS TO LOWER 20S WITH VALUES APPROACHING SINGLE DIGITS IN PLACES WED NIGHT. WINDS DO START TO EASE UP LATE THU AFTERNOON AS THE SURFACE HIGH SETTLES IN. ALTHOUGH CONDITIONS WILL NOT BE IDEAL SOME RADIATIONAL COOLING COMPONENT IS EXPECTED THU NIGHT WITH LOWS DIPPING INTO THE LOW TO MID 20S.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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AS OF 3 AM TUESDAY...MID LEVEL TROUGHING WILL BE A FIXTURE THROUGH THE PERIOD WITH ONLY THE AMPLITUDE VARYING. SURFACE HIGH IN THE AREA FRI IS PUSHED SOUTH BY PASSAGE OF STRONG COLD FRONT SAT MORNING...DRIVEN SOUTH BY CLIPPER SYSTEM PASSING WELL NORTH OF THE AREA. FRONT PASSES DRY BUT IS TRAILED BY ANOTHER BLAST OF ARCTIC AIR. LATEST GFS/ECMWF HAVE 850 TEMPS DROPPING BY ALMOST 15C IN A 24 HOUR SPAN FRI NIGHT TO SAT NIGHT. THE COLD ADVECTION CONTINUES THROUGH SAT NIGHT BEFORE EASING ON SUN AS THE CENTER OF THE ARCTIC HIGH SETTLES OVERHEAD. ALTHOUGH CONFIDENCE IS LOW GUIDANCE IS POINTING AT POTENTIAL FOR AN EXTENDED PERIOD OF TIME WITH TEMPERATURES BELOW FREEZING...STARTING LATE SAT AFTERNOON AND LASTING THROUGH MIDDAY MON. DID NOT GO QUITE THAT COLD BUT SOMETHING TO WATCH FOR. CENTER OF SURFACE HIGH OVERHEAD SUN NIGHT WILL ALSO OPEN UP THE POTENTIAL FOR RADIATIONAL COOLING WHICH COULD PRODUCE THE COLDEST TEMPS OF THIS WINTER. SURFACE HIGH MOVES OFF THE COAST DURING MON WITH RETURN FLOW DEVELOPING AHEAD OF A SOUTHERN STREAM SYSTEM. THIS SYSTEM...WHICH WOULD MOVE INTO THE AREA NEAR THE END OF THE PERIOD MAY BE ACCOMPANIED BY SOME RAINFALL BUT CURRENT SOLUTIONS SHOW LIMITED DYNAMICS. THERE ALSO APPEARS TO BE ONLY A BRIEF DURATION OF DEEP MOISTURE RETURN IN THE WAKE OF THE ARCTIC HIGH. SO EVEN IF SOME PRECIP DOES DEVELOP IT WOULD BE LIMITED IN COVERAGE. AS THIS EVENT IS STILL 6 DAYS OUT NOT READY TO GO WITH A HIGH POP BUT WILL INTRODUCE A SILENT 20 FOR MON. ALTHOUGH RETURN FLOW WILL DEVELOP ON MON TEMPERATURES WILL STILL END UP WELL BELOW CLIMO GIVEN THE SLOW RATE AT WHICH ARCTIC AIR MASSES MODIFY AND THE EXPECTED COLD START MON MORNING.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AS OF 06Z...THE COLD FRONT HAS PUSHED OFF THE COAST...WITH ALL TERMINALS EXHIBITING WSW-W WINDS 5 TO 10 KT. LBT TERMINAL MAY BRIEFLY OBSERVE GUSTS ABOVE 15 KT THRU 08Z BUT SHOULD SETTLE BACK TO 10 KT OR LESS THERE-AFTER. A LARGE AMPLITUDE LONGWAVE UPPER TROF IS NOW ENTRENCHED ACROSS THE EASTERN UNITED STATES. SOME SHEARED VORTICITY IN THE MID-LEVELS...AND AVBL MOISTURE IN THE LOW TO MID LEVELS...WILL RESULT IN OCCASIONAL STRATOCU AND ALTOCU CLOUD DECKS THRUOUT THE 06Z TAF ISSUANCE PERIOD. THEIR RESPECTIVE CEILINGS WILL REMAIN IN VFR TERRITORY. THE MAIN CONCERN FOR AVIATORS WILL BE THE GUSTY WSW-W WINDS THAT WILL GET BUSY AN HOUR OR 2 AFTER DAYBREAK TUE. DURING DAYLIGHT TUE...THE CAA WILL COMBINE WITH A WELL TIGHTENED SFC PG AND PRODUCE WESTERLY WINDS SUSTAINED AT 15 TO 20 KT...WITH GUSTS OF 25 TO 30+ KT. THE WINDS WILL SUBSIDE AFTER SUNSET BUT REMAIN ACTIVE IN THE 10 TO 15 KT RANGE THIS EVENING. EXTENDED OUTLOOK...PREDOMINATELY VFR. EXPECT W TO NW WINDS GUSTING TO 20 TO 30+ KT WEDNESDAY INTO EARLY THURSDAY...AND AGAIN LATE SATURDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 3 AM TUESDAY...SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ALL WATERS...THROUGH THE MID-WEEK PERIOD. THIS A RESULT OF A TIGHTENED SFC PG COMBINED WITH CONTINUED CAA SURGES. THIS COLD/ARCTIC AIR WILL BE ADVECTING ACROSS SSTS IN THE 50S WHICH WILL ALLOW STRONGER WINDS AND/OR GUSTS TO MIX DOWN TO THE OCEAN SURFACE. WINDS WILL BASICALLY BE 250-270 DEGREES AT 15 TO 25 KT...AND OCCASIONALLY 20 TO 30 KT THRUOUT THIS PERIOD. THE HIGHER WINDS WILL PRIMARILY OCCUR OVER THE OUTER WATERS WHERE SSTS ARE SLIGHTLY WARMER...ALONG WITH LESS FRICTIONAL EFFECTS FROM LAND. OF NOTE...THE WINDS WILL PRIMARILY BE OFFSHORE WITH THE EXCEPTION OF THE WATERS THAT LIE BETWEEN CAPE FEAR SOUTH TO MURRELLS INLET WHERE THEY ARE PARALLEL TO THE COASTLINE. WITH THIS IN MIND...SIGNIFICANT SEAS WILL BE HIGHER IN THE FOREMENTIONED WATERS DUE TO A SLIGHTLY BETTER FETCH FOR WHICH TO BUILD SEAS UPON. OVERALL...SEAS WILL RUN 3 TO 7 FT...WITH A FEW 8 FOOTERS POSSIBLE ACROSS THE OUTER WATERS OFF CAPE FEAR. SHORT PERIOD WIND DRIVEN WAVES WILL DOMINATE THE SIGNIFICANT SEAS SPECTRUM. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM TUESDAY...STRONG COLD ADVECTION WED WILL KEEP WESTERLY FLOW AROUND 25 KT THROUGH WED NIGHT. ADVECTION STARTS TO WEAKEN ON THU WHICH ALLOWS FOR A SLOW BUT STEADY DECREASE IN WEST TO NORTHWEST WINDS THU AND THU NIGHT. LATE IN THE PERIOD HIGH BUILDING IN FROM THE WEST WILL RESULT IN WINDS VEERING TO NORTHEAST AND DROPPING TO 10 KT OR LESS. SEAS 4 TO 7 FT ON WED WILL GRADUALLY START DECREASING LATE WED NIGHT AND CONTINUE FALLING THROUGH THU AND THU NIGHT. BY THE END OF THE PERIOD SEAS WILL BE 2 FT OR LESS. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 3 AM TUESDAY...HIGH PRESSURE IN THE AREA FRI IS PUSHED TO THE SOUTH LATE FRI NIGHT BY COLD FRONT SWEEPING ACROSS THE WATERS SAT MORNING. SOUTHWEST FLOW FRI WILL INCREASE A LITTLE DURING THE DAY AS THE FRONT APPROACHES BUT SIGNIFICANT WINDS ARE NOT EXPECTED UNTIL LATER SAT. STRONG COLD ADVECTION WILL DEVELOP AROUND MIDDAY SAT WITH NORTHWEST FLOW EXCEEDING 20 KT SAT AND 25 KT SAT NIGHT. GUSTS LATE SAT NIGHT MAY APPROACH GALE FORCE. SEAS 2 TO 3 FT FRI INTO SAT START BUILDING ON SAT...PEAKING IN THE 3 TO 6 FT RANGE LATE SAT NIGHT.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR AMZ250-252- 254-256. && $$ NEAR TERM...DCH SHORT TERM...III LONG TERM...III AVIATION...DCH

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