Area Forecast Discussion
Issued by NWS Wilmington, NC

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342 FXUS62 KILM 071420 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 920 AM EST SUN FEB 7 2016 .SYNOPSIS...
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POWERFUL LOW PRESSURE WILL RAPIDLY INTENSIFY AS IT TRACKS TO THE NORTHEAST OFFSHORE OF THE CAROLINAS TODAY. THIS SYSTEM WILL BRING WINDY AND WET CONDITIONS BEFORE GRADUALLY TAPERING OFF TONIGHT. THE STRONG LOW WILL TRACK FARTHER OUT TO SEA TONIGHT THROUGH MONDAY. WEAK HIGH PRESSURE WILL PREVAIL MONDAY FOLLOWED BY A COLD FRONTAL PASSAGE MONDAY NIGHT. A DRY ARCTIC AIR MASS WILL FOLLOW INTO MID WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 920 AM SUNDAY...NO MOMENTOUS MODIFICATIONS TO THE FORECAST WITH THE MIDDLE MORNING UPDATES. TEMPERATURES REMAIN TOO MILD IN THE LOWER LEVELS TO SUPPORT SNOW. HOURLY TRENDS SHOULD SEE A RISE BY SEVERAL DEGREES NEAR THE SURFACE INTO AFTERNOON. THIS PROCESS WILL BE SLOW DUE TO PRECIPITATION AND EXISTING SEPARATION OF T/TD ALLOWING ONGOING EVAPORATIVE COOLING IN THE LOW SLICES OF THE ATMOSPHERE. PREVIOUS FORECASTER DISCUSSION FOLLOWS. UPPER JET DYNAMICS AND THE POTENT MID-LEVEL S/W TROF WILL COMBINE FORCES TO PRODUCE A MONSTER COASTAL LOW THAT WILL RAPIDLY DEEPEN. AIRMASS IS PROGGED TO REMAIN TOO MILD FOR FROZEN OR FREEZING PCPN FOR THE ILM CWA. COOLING ON THE BACKSIDE OF THE LOW REMAINS SUSPECT...WITH PROGGED 850 TEMPS REMAINING ABOVE 0 AND PARTIAL THICKNESS 1000-850MB ABOVE 1300M... THE THRESHOLD FOR SNOW. THEREFORE...HAVE REMOVED THE THREAT FOR FROZEN/FREEZING PCPN FOR TODAY. THERE ARE SEVERAL ADVISORIES...WATCHES AND WARNINGS ASSOCIATED WITH THIS DEEPENING AND POWERFUL LOW PRESSURE SYSTEM. THE 1ST IS THE FLOOD WATCH FOR THE COASTAL COUNTIES OF THE ILM CWA BI-STATE REGION. STILL LOOKING AT STORM TOTALS OF 1 TO 2 INCHES OF ADDITIONAL RAINFALL FROM THIS SYSTEM ACROSS LOCATIONS THAT EXPERIENCED 2 TO 5 INCHES OF RAINFALL LATE LAST WEEK. THE GROUNDS ACROSS THE WATCH AREA REMAIN SATURATED WITH SOME LOCATIONS STILL EXPERIENCING STANDING WATER. ON A SIDE NOTE...THE FA WILL EXPERIENCE ROUGHLY 12 TO 18 HRS OF STRATIFORM TYPE RAINS TOTALING UP TO 1 TO 2 INCHES. NORMALLY...THESE VALUES FALLING DURING THIS TIME FRAME DO NOT TRIGGER A FLOOD WATCH. THE ANTECEDENT CONDITIONS ACROSS THE FA ARE WHATS DRIVING THIS FLOOD WATCH. AND THE 2ND IS THE WIND ADVISORY FOR THIS MORNING THRU THE MID- EVENING HOURS...FOR THE IMMEDIATE COAST. MODEL MOS GUIDANCE CONTINUES TO PAINT PEAK SUSTAINED WINDS JUST SHY OF 30 KT FOR THE COASTAL LOCATIONS. IN ADDITION...WITH A STORM WARNING IN EFFECT FOR THE ADJACENT COASTAL AND OFFSHORE WATERS...IT WOULD BE PRUDENT TO INCLUDE THE COASTAL COUNTIES WITHIN AT LEAST A WIND ADVISORY. WITH AN OFFSHORE TRAJECTORY...NNE BACKING TO NW...DOMINATING THE WINDS. WIND SPEEDS WILL BE A PERCENTAGE LOWER THAN IF THE DOMINATING DIRECTIONS CONSISTED OF AN ONSHORE COMPONENT. GFS MOS AND NAM MOS GUIDANCE FOR LOCATIONS WITHIN THE COASTAL WATERS... INDICATE 40+ MPH SUSTAINED WINDS. WIND ADV THRESHOLDS ARE 1 HOUR OF SUSTAINED 31 TO 39 MPH OR WIND GUSTS TO 46+ MPH. THE THINKING IS THAT THE IMMEDIATE COAST WILL LIKELY OBSERVE WIND GUSTS THAT SATISFY THE VALIDITY OF THIS WIND ADVISORY. AS FOR TEMPERATURES...TODAYS HIGHS WILL LIKELY RUN IN THE UPPER 30S TO MID 40S...WITH THE MID 40S PUSHING IT. SOME COOLING ON THE BACKSIDE OF THE LOW...WILL PUSH TEMPS TO THE LOWER 30S FOR TONIGHTS LOWS. THESE LOWS WILL OCCUR WELL AFTER WHEN PCPN HAD ENDED. MAY NEED A STATEMENT ON BLACK ICE FOR TONIGHT WITH ROADWAYS HAVING NOT ENOUGH TIME TO DRY PRIOR TO THE ONSET OF FREEZING TEMPS.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 AM SUNDAY...IMPRESSIVE SHORTWAVE DROPPING SOUTH THROUGH THE UPPER MIDWEST SUN INTO MON WILL BRING ANOTHER CHANCE OF WINTRY PRECIP TO THE AREA LATE MON AND MON NIGHT. DYNAMICS WITH THE SHORTWAVE ARE IMPRESSIVE...AS IS THE ABUNDANCE OF THE COLD AIR. THE ONLY LIMITING FACTOR WILL BE THE AMOUNT OF MOISTURE...SPECIFICALLY THE LOW LEVEL MOISTURE. FORECAST SOUNDINGS SHOW STRONG UPWARD MOTION IN THE DENDRITIC GROWTH ZONE WITHIN A LAYER OF INCREASED MOISTURE. HOWEVER...BELOW 5K FT OR SO THE DRY AIR BECOMES AN OBSTACLE. STRONG SHORTWAVES ALWAYS MANAGE TO WRING WHAT LITTLE MOISTURE IS AVAILABLE OUT OF THE ATMOSPHERE BUT IN THIS CASE THE QPF IS GOING TO BE RATHER LOW. SO WHILE THERE IS POTENTIAL FOR RAIN...POSSIBLY WITH SNOW SHOWERS MIXED IN...DO NOT THINK EVENT WILL BE THAT SIGNIFICANT. LATEST SOUNDINGS SUGGEST ALL RAIN FOR THE FORECAST AREA BUT THE COLD AIR IS NOT FAR AWAY AND GIVEN THE STRENGTH OF THE WAVE THERE IS DEFINITELY POTENTIAL FOR DYNAMIC COOLING. WILL KEEP FORECAST ALL RAIN FOR NOW (ESPECIALLY SINCE LOCAL TOP DOWN METHODOLOGIES YIELD ALL RAIN) BUT CANNOT RULE OUT THE ADDITION OF SNOW AS ZERO HOUR APPROACHES. WILL CONTINUE TO CARRY LOW CHC POP WITH MINIMAL QPF. SHORTWAVE HELPS DRIVE THE FIRST OF 2 COLD FRONT ACROSS THE AREA MON NIGHT. NEAR CLIMO TEMPS MON DROP BELOW CLIMO MON NIGHT AS COLD ADVECTION GETS GOING. CONTINUED STRONG COLD ADVECTION TUE AND TUE NIGHT WILL RESULT IN TEMPERATURES BELOW TO WELL BELOW CLIMO FOR THE SECOND HALF OF THE PERIOD. SECOND COLD FRONT CROSSES THE AREA LATER TUE REINFORCING THE ALREADY COLD AIR MASS IN PLACE. THIS COLD FRONT IS BEING DRIVEN BY ANOTHER SHORTWAVE ROTATING AROUND THE BASE OF THE TROUGH. ALTHOUGH LOW LEVEL MOISTURE REMAINS QUITE LIMITED THERE WILL BE ENOUGH MID LEVEL MOISTURE TO SUPPORT AN INCREASE IN CLOUD COVER AND POSSIBLY SOME VIRGA. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 3 AM SUNDAY...REGION WILL BE IN THE GRIP OF AN ARCTIC AIR MASS AS THE PERIOD BEGINS. BROAD 5H TROUGH OVER THE EASTERN CONUS WED INTO THU WILL MAINTAIN TEMPERATURES 10 TO 15 DEGREES BELOW CLIMO. HIGHS EACH DAY WILL STRUGGLE TO REACH MID 40S. LOWS AT NIGHT WILL NOT BE QUITE AS COLD AS ONE WOULD EXPECT GIVEN 850 TEMPS APPROACHING -14C AT TIMES. CENTER OF THE SURFACE HIGH NEVER SETTLES OVER THE AREA WITH THE BITTERLY COLD AIR IN PLACE. SO WHILE THIS MEANS COLD ADVECTION NEVER WANES IT ALSO MEANS BOUNDARY LAYER MIXING NEVER CEASES. LOWS WILL END UP IN THE MID 20S WED NIGHT. RATHER BALMY COMPARED TO WHAT -14C 850 TEMP ON A STRONG RADIATIONAL COOLING NIGHT WOULD YIELD...LOWS APPROACHING SINGLE DIGITS. THE MIXING WILL COME AT A PRICE THOUGH...WIND CHILL VALUES WILL DROP WELL INTO THE TEENS. MID LEVEL PATTERN REMAINS AMPLIFIED THU THOUGH HEIGHTS STARTS BUILDING AS SHORTWAVE EXITS. AIR MASS STARTS TO MODIFY BUT THE SURFACE LAYER WILL REMAIN ISOLATED AND SENSIBLE WARMING IS NOT LIKELY TO BE REALIZED UNTIL THU NIGHT AT THE EARLIEST. BRIEF PERIOD OF RETURN FLOW LATER THU AND THU NIGHT ENDS WITH COLD FRONT CROSSING THE AREA DURING FRI. THIS FRONT IS FOLLOWED BY ANOTHER ROUND OF ARCTIC AIR AS THE PERIOD ENDS. THE BEST...AND REALLY ONLY CHANCE FOR PRECIP WILL BE LATE IN THE PERIOD AHEAD OF THE AFOREMENTIONED COLD FRONT. ALTHOUGH SYSTEM DOES NOT APPEAR TO BE ALL THAT SPECIAL A COLD FRONT/SHORTWAVE COMBO WITH MOISTURE IS USUALLY A RECIPE FOR AT LEAST SOME LIGHT PRECIP. WILL CARRY A SILENT POP LATE IN THE PERIOD FOR NOW. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... AS OF 12Z...A MIXTURE OF VFR/MVFR/IFR EXPECTED THROUGH TONIGHT AS A STRONG COASTAL STORM SYSTEM BRINGS WIDESPREAD RAINFALL...LOW CIGS AND AREAS OF FOG. CONDITIONS IMPROVE TO VFR LATE. A WIND ADVISORY IS IN EFFECT FOR PORTIONS OF THE AREA...WHICH INCLUDE THE COASTAL TERMINALS. LATEST RADAR IMAGERY DEPICTS WIDESPREAD RAINFALL ACROSS THE AREA THIS MORNING...WITH ALL TERMINALS OBSERVING LIGHT TO STEADY RAINFALL ATTM. ALONG WITH LOW CIGS...WILL CONTINUE TO SEE RAINFALL THROUGHOUT THE DAY...WITH REDUCED VISIBILITIES POSSIBLE IN ANY HEAVY DOWNPOURS OR PATCHY AREAS OF FOG. WHILE COULD NOT ENTIRELY RULE OUT THE POSSIBILITY OF SNOW/SLEET MIXED IN THE PRECIPITATION INLAND...CONFIDENCE IS LOW ATTM. AS THE STORM SYSTEM OFFSHORE MOVES UP ALONG THE CAROLINA COAST TODAY...A TIGHTENED SURFACE PRESSURE GRADIENT WILL CREATE GUSTY NORTH WINDS. SUSTAINED WINDS COULD INCREASE TO 20 KTS WITH GUSTS NEAR 40 KTS. INTO TONIGHT...THE RAIN WILL BEGIN TO TAPER OFF AND STRONG WINDS WILL DECREASE AS THE STORM SYSTEM MOVES FURTHER AWAY FROM THE CAROLINAS. AFTER MIDNIGHT SKIES WILL BEGIN TO CLEAR ALLOWING FOR VFR INTO MONDAY MORNING WITH NORTH- NORTHWEST WINDS AROUND 10 KTS. EXTENDED OUTLOOK...A CHANCE OF PRECIPITATION WITH MVFR CONDITIONS POSSIBLE LATE MONDAY INTO TUESDAY. OTHERWISE EXPECT VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 920 AM SUNDAY...THE INTENSE AND WELL TIGHTENED SFC PRESSURE GRADIENT ACROSS THE LOCAL WATERS...WILL RESULT IN 25 TO 40 KT SUSTAINED WINDS WITH GUSTS UP TO 50 KT FROM MID-DAY THRU EARLY THIS EVENING. WITH THE LOW STAYING EAST OF THE LOCAL WATERS...WIND DIRECTIONS WILL START FROM THE NNE THEN BACK TO THE NORTH AS THE LOW PARALLELS THE COASTAL WATERS...AND FINALLY BACK TO THE NW AS IT PULLS AWAY TONIGHT. SIGNIFICANT SEAS WILL QUICKLY BUILD TODAY...PEAKING ROUGHLY IN A 7 TO 11 FOOT RANGE FROM MIDDAY THRU EARLY THIS EVENING. THE WIND DIRECTIONS...NNE BACKING TO NW...WILL RESULT IN A LIMITED FETCH FOR WHICH THE SEAS TO BUILD UPON. NEVERTHELESS...SEAS PEAKING AT 7 TO 11 FT IS NOT BAD FOR BASICALLY A PREDOMINATE OFFSHORE WIND DIRECTION. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 AM SUNDAY...SOUTHWEST FLOW WILL DROP UNDER 20 KT FOR A PERIOD ON MON BUT APPROACH OF STRONG COLD FRONT LATE IN THE DAY WILL PUSH WINDS BACK OVER 20 KT BY LATE AFTERNOON. PASSAGE OF COLD FRONT MON NIGHT IS FOLLOWED BY DEVELOPMENT OF WESTERLY FLOW...ENHANCED BY PINCHED GRADIENT AND STRONG COLD ADVECTION. SPEEDS MON NIGHT WILL APPROACH 30 KT SUSTAINED WITH GUSTS OF 35 TO 40 KT. COLD ADVECTION CONTINUES TUE AND TUE NIGHT WITH WINDS REMAINING IN THE 25 TO 30 KT RANGE THROUGH THE END OF THE PERIOD. SEAS RANGING FROM 3 TO 6 FT MON MORNING START BUILDING IN THE AFTERNOON...PEAKING BETWEEN 4 AND 8 FT MON NIGHT AND STAYING 4 TO 8 FT THROUGH THE END OF THE PERIOD. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 3 AM SUNDAY...STRONG WEST TO NORTHWEST FLOW CONTINUES ON WED THEN STARTS TO WEAKEN THU AS COLD ADVECTION WEAKENS AND GRADIENT RELAXES. OFFSHORE FLOW DURING THE FIRST HALF OF THE PERIOD WILL BE AROUND 25 KT WITH GUSTS APPROACHING GALE FORCE. ELONGATED SURFACE RIDGE STARTS BUILDING IN FROM THE WEST LATE WED NIGHT AND THU. SPEEDS DROP UNDER 20 KT WED NIGHT AND UNDER 15 KT BY THE END OF THU. ALTHOUGH FLOW WILL BE OFFSHORE ELEVATED WIND SPEEDS WILL KEEP SEAS OVER 6 FT THROUGH WED NIGHT. GRADUAL REDUCTION IN WIND SPEEDS LATE WED NIGHT AND THU ALLOWS SEAS TO DROP TO 2 TO 4 FT THU AND THU NIGHT.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH THROUGH THIS EVENING FOR SCZ053>056. WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR SCZ053>056. NC...FLOOD WATCH THROUGH THIS EVENING FOR NCZ099-105>110. WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR NCZ105>110. MARINE...STORM WARNING UNTIL 10 PM EST THIS EVENING FOR AMZ250-252-254- 256. && $$ NEAR TERM...DCH/MJC SHORT TERM...III LONG TERM...III AVIATION...SGL

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