Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 150232 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1032 PM EDT MON APR 14 2014 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS THE AREA TUESDAY...WITH INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND TUESDAY. HIGH PRESSURE WILL MOVE INTO THE AREA WEDNESDAY AND CONTROL AREA WEATHER INTO FRIDAY BEFORE CONDITIONS DETERIORATE IN ADVANCE OF A COLD FRONT THAT WILL MOVE INTO THE AREA AND STALL INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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AS OF 1015 PM MONDAY...THE REMAINDER OF THE EVENING POPS WILL CONTINUE TO TAKE INTO ACCOUNT THE CURRENT PCPN PAINTED BY MOSAIC RADARS...ALONG WITH ITS IMMEDIATE FUTURE MOVEMENT. FOR POPS AFTER MIDNIGHT THROUGH DAYBREAK...HAVE FOLLOWED MORE CLOSELY TO THE HRRR OUTPUT THAT MIMICS PROGGED REFLECTIVITY ACROSS THE ILM CWA. IN ADDITION...FOLLOWED THE LATEST SREF OVERNIGHT PROBABILITIES FOR MEASURABLE RAIN. IN ESSENCE...THE BEST SYNOPTIC/MESOSCALE UVVS ARE PROGGED TO OCCUR AND REMAIN WEST AND NORTH OF THE ILM CWA DURING THE PRE-DAWN TUE HOURS. AND AS A RESULT...HAVE ALIGNED THE HIER POPS ACROSS THE NORTHERN AND WESTERN PORTIONS OF THE ILM CWA. FOR THE EASTERN AND SOUTHERN PORTIONS OF THE ILM CWA...YOU WILL FIND MUCH LOWER CHANCE POPS. THIS PLAN OF ACTION ALIGNS UP NICELY WITH OUR NEIGHBORING CWAS. LATEST LIGHTNING OBSERVING NETWORK CONTINUES TO INDICATE A LACK OF ANY STRIKES ACROSS THE FA UP TO THIS POINT IN TIME. ONLY A FEW SELECT UPSTREAM TSTORMS HAVE EXHIBITING LIGHTNING. WILL THEREFORE CONTINUE TO INDICATE NO THUNDER FOR THE REMAINDER OF THIS EVENING. HOWEVER...DID ILLUSTRATE ISOLATED THUNDER DURING THE PRE-DAWN TUE HRS...AND CONTINUED THAT INTO THE DAYLIGHT TUE MORNING HRS. PROGGED OVERNIGHT TSTORM PARAMETERS RATHER WEAK BUT NEVERTHELESS PRESENT ENUF TO INCLUDE ISOLATED THUNDER. CAE`S LONE SVR ISSUED THIS EVENING CONFIRMS THE POSSIBILITY OF THUNDER BUT LATER TONIGHT ACROSS THE ILM CWA. LATEST OBSERVED TEMPS/DEWPOINTS HAVE BEEN TWEAKED TO ACCOUNT FOR LATEST READINGS AND TRENDS. WHAT MAKES IT DIFFICULT FOR THE OVERNIGHT MIN TEMP FORECAST IS THAT ANY PCPN THAT OCCURS ACROSS THE FA...MAY LOWER TEMPS TO AT OR BELOW THE CURRENT MIN TEMP FORECAST FOR THAT AREA. OVERALL...TEMPS ACROSS THE FA MAY LOWER A FEW MORE DEGREES AND THEN BASICALLY REMAIN STEADY FOR THE REMAINDER OF THE OVERNIGHT PERIOD. PREVIOUS DISCUSSION............................................... AS OF 300 PM MONDAY...SCATTERED SHOWERS HAVE DEVELOPED ACROSS THE AREA AS EXPECTED...THANKS TO MOIST ADVECTION ON S/SE WINDS AROUND A SURFACE HIGH PRESSURE CENTERED WELL OFFSHORE. SHOWERS HAVE DEVELOPED ALONG CONVERGENT BOUNDARIES...SINCE MORE WIDESPREAD ACTIVITY IS LIMITED BY A DECENT INVERSION ABOVE 800MB...AND PERSISTENT VERY DRY AIR IN THE MID-LEVELS. THIS INVERSION IS PROGGED TO SLOWLY ERODE THROUGH THE REMAINDER OF THE AFTN INTO THIS EVENING...AS MID-LEVEL THICKNESSES DECREASE IN ADVANCE OF AN APPROACHING UPPER LOW AND COLD FRONT. AT THE SAME TIME...MID-LEVELS WILL MOISTEN TONIGHT...AND THUS PRECIPITATION WILL HAVE THE POTENTIAL TO BECOME MORE WIDESPREAD THROUGH TONIGHT. HOWEVER...THE NATURE OF THE SHOWERS HAS BEEN PRIMARILY CONVECTIVE...ALBEIT OF SHALLOW NATURE. THUS WITH LOSS OF DIURNAL HEATING...THERE IS LIKELY TO BE A PERIOD OF REDUCED COVERAGE/ACTIVITY AFTER DARK BEFORE PRECIP RAMPS BACK UP AGAIN TOWARDS DAYBREAK. HAVE SHOWN THIS IN POP GRIDS...THE EXCEPTION BEING OVER THE WATERS WHERE ACTIVITY MAY BLOSSOM OVER THE GULF STREAM AND ADVECT INTO THE COASTAL WATERS (POSSIBLY ONSHORE AS WELL)...BUT THE MOST SIGNIFICANT RAINFALL WILL HOLD OFF UNTIL AFTER THIS PERIOD. TEMPS TONIGHT WILL REMAIN QUITE WARM AS SOUTHERLY WINDS INCREASE OVERNIGHT AS THE PRESSURE GRADIENT TIGHTENS. HAVE SHOWN A NON-TYPICAL DIURNAL CURVE...WITH MINS BEING REACHED A FEW HOURS AFTER MIDNIGHT...AND THEN RISING TOWARDS DAWN. LOWS WILL BE IN THE MID/UPR 60S...SUPPORTING VERY LITTLE DIURNAL CHANGE OVERNIGHT.
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&& .SHORT TERM /6 AM TUESDAY THROUGH 6 AM TUESDAY/... AS OF 300 PM MONDAY...A STRONG COLD FRONT WILL MOVE MOVE THROUGH THE AREA TUESDAY BRINGING SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. WINDS AT H8 ARE FORECAST TO BE IN THE 50 TO 55 KT RANGE WITH 0-3 KM SRH VALUES IN EXCESS OF 300 DURING THE AFTERNOON WHEN A SQUALL LINE IS EXPECTED TO MOVE THROUGH. MAX TEMPERATURES IN THE MID TO UPPER 70S WILL YIELD CAPE VALUES BELOW 1000 J/KG BUT THERE STILL IS SOME POTENTIAL FOR TEMPERATURES IN THE LOWER 80S WHICH WOULD YIELD CAPES AROUND 2000 J/KG AND ENHANCE SEVERE WEATHER POTENTIAL. SHOWERS AND STORMS END RAPIDLY BY ABOUT 03Z WEDNESDAY WITH FROPA FOLLOWED BY STRONG CAA RESULTING IN TEMPERATURES FALLING TO THE MID 30S TO AROUND 40. GUIDANCE HAS TRENDED COLDER TUESDAY NIGHT AND THERE IS SOME POTENTIAL FOR NEAR FREEZING TEMPERATURES NW BUT WILL WAIT TO SEE LATER MODEL RUNS TO SEE IF THE TREND CONTINUES. MAINLY CLEAR SKIES ARE EXPECTED WEDNESDAY WITH CAA CONTINUING ON N TO NE FLOW WHICH SHOULD YIELD MAX TEMPERATURES IN THE UPPER 50S TO LOWER 60S. AT THIS TIME...CONTINUED LIGHT WINDS AND A SLIGHT INCREASE IN CLOUDS...ESPECIALLY NE...SHOULD PRECLUDE A FREEZE BUT SOME FROST IS NOT OUT OF THE REALM OF POSSIBILITY...ESPECIALLY WESTERN AREAS. MINS WILL BE IN THE MID TO UPPER 30S. && .LONG TERM /TUESDAY THROUGH MONDAY/... AS OF 300 PM MONDAY...STRONG HIGH PRESSURE CENTERED ACROSS NEW ENGLAND AND THE CANADIAN MARITIMES WILL REMAIN IN PLACE...AND MAY PERSIST INTO FRI...ALTHOUGH THE PRESSURES WILL BE LOWERING WITH TIME...AN INDICATION THAT THE WEDGE WILL BE WEAKENING WITH TIME. LATEST MODEL DATA INDICATES THE ORIENTATION OF THE WEDGE AND ITS EASTWARD EXTENSION DOES NOT SUPPORT THE DEVELOPMENT OF A COASTAL TROUGH NEAR THE COAST. THE DEVELOPING AND PRONOUNCED TROUGH INITIALLY OFFSHORE DOES MIGRATE CLOSER TO THE COAST BY THE WEEKEND AS THE UPSTREAM TROUGH STRUGGLES TO GAIN PROXIMITY AS THE UPPER SUPPORT REMAINS WELL AWAY FROM THE SOUTHEAST AND IS LIFTING NE AND FURTHER AWAY. THE CLOSER THE TROUGH IS TO THE COAST...THE GREATER THE ISENTROPIC LIFT POTENTIAL AND THE HIGHER THE RISK FOR RAINFALL. THE GFS AND EUROPEAN MODELS ARE SHOWING VERY DIVERSE SOLUTIONS THIS WEEKEND AND EARLY NEXT WEEK. THE EURO IS POINTING TO A WET FRI NIGHT AND SAT AS LOW PRESSURE MOVES OUT OF THE GULF OF MEXICO AND UP THE SOUTHEAST COAST. THE GFS KEEPS PRECIPITATION OFFSHORE DURING THIS TIME...BUT DOES BRING A WAVE OF LOW PRESSURE AND A SLUG OF DEEPER MOISTURE ACROSS THE FORECAST AREA LATE IN THE WEEKEND AND ON MON WITH A FRONTAL BOUNDARY STALLED NEAR IF NOT OVER THE FORECAST AREA. THE EURO ON THE OTHER HAND DOES NOT BRING THIS WAVE ACROSS THE AREA UNTIL MON NIGHT. THUS...THE WEEKEND AND EARLY NEXT WEEK FORECAST IS VERY MUCH A LOW CONFIDENCE FORECAST AND WILL BENEFIT FROM MODEL CONSISTENCY IF NOT A MORE UNIFIED SOLUTION WITH LATER RENDITIONS. TEMPERATURES WILL STILL BE COOL AND WELL BELOW NORMAL ON THU...WITH A SLOW MODERATING TREND THROUGH MON. HIGHS THU ARE NOT EXPECTED TO EXCEED THE LOWER TO PERHAPS MID 60S. WE WILL ADD ABOUT 5 DEGREES TO THAT ON FRI WITH TEMPS BACK TO NORMAL FOR THE WEEKEND AND MON... LOWER TO MID 70S. LOWS WILL BE CHILLY LATE WEEK...AROUND 40 THU NIGHT...NO FREEZE IS EXPECTED. MINIMUMS WILL BE ON THE UPSWING INTO EARLY NEXT WEEK...RETURNING TO NEAR NORMAL FRI NIGHT AND THEN ABOVE NORMAL SAT NIGHT AND SUN NIGHT. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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AS OF 00Z...A MIX OF MVFR/IFR WITH POSSIBLE BRIEF PERIODS VFR EXPECTED THROUGH THE OVERNIGHT HOURS AS LOWERED CIGS AND ISOLATED SHOWERS MOVE THROUGH. LOWERED RESTRICTIONS CONTINUE INTO TUESDAY WITH INCREASING CHANCES FOR WIDESPREAD RAINFALL AND ISOLATED TO SCATTERED THUNDERSTORMS...SOME SEVERE. VFR/MVFR/IFR CONDITIONS ARE CURRENTLY AFFECTING THE AREA TAF SITES THIS EVENING AS VARYING CEILING HEIGHTS AND ISOLATED SHOWERS MOVE ACROSS THE AREA...WHICH IS EXPECTED TO PREVAIL THROUGH THE OVERNIGHT HOURS. SOUTH-SOUTHWEST WINDS WILL CONTINUE AOB 10 KTS WITH OCCASIONAL GUSTS AROUND 15-20 KTS POSSIBLE. ON TUESDAY CONFIDENCE REMAINS LOWERED REGARDING FLIGHT RESTRICTIONS GIVEN VARYING CLOUD HEIGHTS AND SHOWERS...OVERALL THOUGH ANTICIPATE MVFR/IFR AGAIN WITH INTERMITTENT IMPROVEMENTS TO VFR POSSIBLE. CHANCES INCREASE THROUGHOUT THE DAY FOR THUNDERSTORMS...WITH THE POSSIBILITY OF SOME BEING SEVERE...THOUGH CONFIDENCE IS LOW IF THE ANTICIPATED LINE OF CONVECTION WILL MAKE IT TO THE COAST. PRIMARY THREAT WITH POSSIBLE SEVERE WEATHER WILL BE DAMAGING WINDS. SOUTH- SOUTHWEST WINDS WILL CONTINUE ON TUESDAY AOB 10-15 KTS WITH HIGHER GUSTS POSSIBLE...ESPECIALLY IN STRONGER STORMS. EXTENDED OUTLOOK...BECOMING LATE VFR TUESDAY NIGHT...CONTINUING THROUGH THURSDAY. POSSIBLE FOG/STRATUS FRIDAY AND SATURDAY...LOW CONFIDENCE.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM MONDAY...WIND SPEEDS STILL SLOW TO INCREASE ACROSS THE COASTAL WATERS DUE TO THE STABLE LOW LEVEL MARINE LAYER INDUCED BY THE COOL SHELF WATERS WITH READINGS IN THE LOW TO MID 60S. LATEST 41013 BUOY JUST OUTSIDE THE COASTAL WATERS...HAS FINALLY SHOWN AN INCREASE IN THE SOUTHERLY WINDS. AS THE SFC PG TIGHTENS OVERNIGHT...WIND SPEEDS WILL FOLLOW SUIT. COULD SEE WIND GUSTS UP TO 25 KT LATE TONIGHT AS THE LOW LEVEL STABLE MARINE LAYER DECREASES IN DEPTH...ALLOWING SOME OF THOSE HIER WINDS JUST OFF THE DECK TO DROP DOWN TO THE OCEAN SFC. THE SFC PRESSURE PATTERN WILL CONTINUE TO PRODUCE A SOUTHERLY WIND DIRECTION THROUGH DAYBREAK TUE. BUILDING SIGNIFICANT SEAS WILL HIGHLIGHT THE OVERNIGHT PERIOD ...AND CONTINUE INTO DAYLIGHT TUE. CURRENTLY...THE MAJORITY OF THE SIGNIFICANT SEAS MAKE-UP COMES FROM A SE-S...7 TO 8 SECOND PERIOD...PSEUDO SWELL FROM THE OFFSHORE WATERS. THIS A RESULT OF THE STRONGER WINDS FURTHER OFFSHORE HAVING A DECENT FETCH TO BUILD UPON. WIND DRIVEN WAVES WILL BECOME THE DOMINANT CONTRIBUTOR TO SIGNIFICANT SEAS BY DAYBREAK TUE...WITH AVERAGE PERIODS AT 5 TO 6 SECONDS. PREVIOUS DISCUSSION............................................... AS OF 300 PM MONDAY...HIGH PRESSURE WELL OFFSHORE WILL SLOWLY RETREAT TO THE EAST THROUGH TONIGHT...AS A COLD FRONT APPROACHES FROM THE WEST. THIS WILL DRIVE THE CURRENT 10 KT S/SE WINDS UPWARD THROUGH THE PERIOD...BECOMING 15-20 KTS TONIGHT WITH A SLIGHT VEERING TO THE SOUTH. THESE STRONGER WINDS AND CONTINUED LONG DURATION FETCH AROUND THE HIGH PRESSURE WILL FORCE WAVE HEIGHTS TO AMPLIFY TONIGHT. EXPECT WAVE HEIGHTS TO GROW TO 4-6 FT OVERNIGHT...AND THE SMALL CRAFT ADVISORY HAS BEEN EXTENDED TO BEGIN AT 8PM TONIGHT FOR ALL THE COASTAL WATERS. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED THROUGH MUCH OF THE PERIOD WITH S TO SW WINDS OF 20 TO 25 KT TUESDAY WHICH WILL SHIFT TO N TO NE AFTER THE FROPA TUESDAY NIGHT AND INCREASE TO 25 TO 30 KT. N TO NE WINDS WILL CONTINUE THROUGH WED NIGHT AS THEY GRADUALLY DIMINISH TO 15 TO 20 KT. SEAS WILL BUILD TO 6 TO 8 FT ON THE OPEN WATERS TUESDAY...MAY RELAX A LITTLE AS THE FRONT GOES THROUGH...THEN BUILD AS HIGH AS 9 FT TUESDAY NIGHT. SEAS WILL SLOWLY SUBSIDE WEDNESDAY AND WEDNESDAY NIGHT BUT RESIDUAL 6 FOOTERS ARE POSSIBLE AT 20 NM AROUND DAYBREAK THURSDAY. FOR NOW SCA HAS BEEN EXTENDED THROUGH 2 AM THURSDAY BUT MAY NEED TO BE EXTENDED FURTHER IN TIME IN LATER FORECASTS. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM MONDAY...A PROLONGED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS...ASSOCIATED WITH A COOL WEDGE OF HIGH PRESSURE AND ITS ASSOCIATED TIGHT PRESSURE GRADIENT...IS EXPECTED TO DROP BELOW THRESHOLDS THU NIGHT OR FRI. SEAS OF 6 FT ACROSS PORTIONS OF THE OUTER WATERS WILL BE THE LAST TO DROP BELOW THRESHOLD. THE JUXTAPOSITION OF A DEVELOPING COASTAL TROUGH MAY COMPLICATE THE WIND FORECAST FRI THROUGH SAT. AT THIS TIME...WILL KEEP NE WINDS THROUGHOUT THE PERIOD...HIGHEST THU AND THU NIGHT...UP TO 20 TO 25 KT. SEAS WILL BE HIGHEST DURING THIS TIME AS WELL...UP TO 5 TO 7 FT.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR AMZ250-252- 254-256. && $$ SYNOPSIS...RAN NEAR TERM...DCH/JDW SHORT TERM...RAN LONG TERM...RJD AVIATION...SGL

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