Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 252352 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 752 PM EDT SAT APR 25 2015 .SYNOPSIS... A WARM FRONT WILL APPROACH FROM THE SOUTH AND WILL BE NEAR OR JUST NORTH OF THE AREA SUNDAY MORNING BEFORE GETTING SHOVED SOUTHWARD SUNDAY AFTERNOON AND EVENING. A SMALL RISK FOR STRONG TO SEVERE THUNDERSTORMS WILL REMAIN INTO SUNDAY. DRY HIGH PRESSURE WILL RETURN MONDAY INTO TUESDAY BEFORE A STORM SYSTEM IMPACTS THE AREA DURING THE MIDDLE OF NEXT WEEK. DRY HIGH PRESSURE IS EXPECTED TO RETURN BY FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 530 PM SATURDAY...BASED ON LATEST 88D RADAR MOSAIC TRENDS AND LATEST VIS AND IR SAT IMAGERY TRENDS AND LATEST 18Z VARIOUS MODEL RUNS...HAVE UPDATED EVENING AND OVERNIGHT POPS AND SKY CONDITIONS. BASICALLY LOWERING POPS TRENDS THIS EVENING AND OVERNIGHT TO LOW CHANCE/SLIGHT CHANCE/ISOLATED. IN ADDITION...HAVE SKY CONDITIONS IN THE CLOUDY/MOSTLY CLOUDY/VARIABLY CLOUDY TREND FOR THE EVENING THRU OVERNIGHT. IF SKIES PARTIALLY CLEAR ENOUGH...FOG COULD BECOME AN ISSUE DURING THE PRE-DAWN SUNDAY HOURS. PREVIOUS........................................................ AS OF 300 PM SATURDAY...SEVERE THREAT HAS BECOME REMOTE FOR THE DAYLIGHT HOURS. GUIDANCE AND OBSERVATIONS SHOW A STABLE ATMOSPHERE WITH A SHIELD OF LIGHT AND COOL STRATIFORM RAIN MOVING EAST ACROSS THE FORECAST AREA AND OUT TO SEA. AT THE SURFACE A DIFFUSE QUASI- STATIONARY FRONT IS WAVERING ABOUT WHILE A WARM FRONT MOVES UP FROM THE SOUTH. OVERALL SURFACE PATTERN IS NOT WELL DEFINED AND ALTHOUGH THERE ARE DIFFERENCES AMONG GUIDANCE THE GENERAL TREND IS TOWARDS WEAKER THAN ANTICIPATED CONVECTION AND SPARSER COVERAGE. NAM AND GFS MOS GUIDANCE HAVE SLIGHT CHANCE FOR OVERNIGHT POPS. CONSIDERING OTHER GUIDANCE ON HAND AND GENERAL UNCERTAINTY WILL KEEP IN SLIGHT CHANCE TO CHANCE POPS FOR THE OVERNIGHT PERIOD. BUFKIT AND OTHER DATA SHOW BETTER INSTABILITY SHOWING UP THIS EVENING AND OVERNIGHT SO MAKING CHARACTER OF PRECIP MORE CONVECTIVE IN NATURE AND WILL INCLUDE SLIGHT CHANCE FOR THUNDER. THE HRRR HAS BEEN VERY HELPFUL TODAY IN DEPICTING COVERAGE AND TRENDS SO WILL CONTINUE TO LEAN ON ITS GUIDANCE FOR THE NEAR TERM. THIS MODEL HAS ISOLATED TO SCATTERED SHOWERS FOR THE REMAINDER OF THE AFTERNOON WITH PERHAPS A MORE MODERATE LINE OF CONVECTION MOVING THROUGH AROUND MIDNIGHT. EXTENSIVE CLOUD COVER AND WARM FROPA WILL KEEP TEMPS OVERNIGHT ON THE MODERATE SIDE...IN VARIOUS SHADES OF THE 60S. THIS IS NOT MUCH DIFFERENT THAN TODAYS DAYTIME READINGS. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...A WARM FRONT WILL BE SITUATED VERY NEAR OR JUST N OF THE AREA SUNDAY MORNING. MODEL PROFILES SHOW A DEEP WESTERLY FLOW WITH SIGNIFICANT MOISTURE RELEGATED TO THE LOWEST 3 KFT OR SO IN THE WARM SECTOR. A 50 KT JET WILL BE LOCATED 3-5 KFT AGL SUNDAY. THE GFS SHOWS LITTLE IN THE WAY OF INSTABILITY ON SUN WHILE THE NAM PORTRAYS MIXED LAYER CAPE VALUES UP TO AROUND 1500 J/KG AND THIS SEEMS MUCH MORE REASONABLE. THE INSTABILITY WILL BE SHRINKING SOUTHWARD WITH TIME AS THE LAST OF THE WEAK WAVES OF LOW PRESSURE MOVES OFFSHORE TO CONSOLIDATE AND STRENGTHEN WELL OFF THE NC COAST. MODEL SOUNDINGS ACTUALLY SHOW A STRONG FRONTAL INVERSION DEVELOPING FROM N TO S...LASTLY ACROSS THE SOUTHERN GRAND STRAND AND SOUTH SANTEE RIVER AREAS BY MID AFTERNOON SUN. CONFIDENCE IN TIMING IS NOT HIGH...BUT TRENDS LOOK TO BE ON THE RIGHT TRACK. GIVEN MAGNITUDE OF DRY AIR IN STRONG AND DEEPENING WESTERLY FLOW ALOFT...WOULD EXPECT COVERAGE OF CONVECTION TO BE ISOLATED TO SCATTERED. CAN NOT RULE OUT AN ISOLATED STRONG OR SEVERE THUNDERSTORM TO INCLUDE HAIL AND/OR STRONG TO DAMAGING WIND GUSTS. THE SEVERE WEATHER RISK WILL BE PRIMARILY ACROSS THE SOUTHERN REACHES OF OUR FORECAST AREA...WHERE INSTABILITY WILL BE GREATEST...AS WELL AS PERHAPS WHERE SEABREEZE INTERACTS WITH THE FRONT. ANY SEVERE WEATHER WILL INCLUDE STRONG TO DAMAGING WIND GUSTS WILL SHOW POPS TRENDING LOWER FROM N TO S LATE IN THE AFTERNOON AND THROUGH THE EVE HOURS. A SERIES OF SHORTWAVE TROUGHS ROUNDING A RETROGRADING AN UPPER LOW OFF THE NEW ENGLAND COAST WILL HELP TO REINFORCE THE COOLER AND DRIER AIR ADVECTING INTO THE FORECAST AREA MON AND MON NIGHT. A GOOD DEAL OF SUNSHINE MON WILL BE BATTLING THE COOL NW FLOW WITH 850 MB TEMPS DROPPING TO AROUND 3 DEG C. HIGHS SUN WILL LIKELY VARY FROM N TO S AND DEPENDING ON CLOUD COVER...THERE COULD BE A SIGNIFICANT TEMP GRADIENT ACROSS THE AREA. WILL FORECAST LOWER TO MID 80S ACROSS THE SOUTH SANTEE RIVER AREA WITH MID AND UPPER 70S ELSEWHERE. HOWEVER...THE NORTHERN REACHES OF THE AREA COULD BE STYMIED IN THE LOWER 70S GIVEN THEIR PROXIMITY TO THE BOUNDARY AND GREATER CLOUD COVER. HIGHS ON SUN WILL BE IN THE LOWER 70S FOR THE MOST PART...ONE TO TWO CATEGORIES BELOW NORMAL FOR THE WANING DAYS OF APRIL. AFTERNOON RELATIVE HUMIDITY LEVELS WILL BE FALLING THROUGH THE 40S AND 30S ON MON AS DRY AND COOL HIGH PRESSURE TO THE NW BUILDS INTO THE EASTERN CAROLINAS. THE COOLEST NIGHT...MON NIGHT...WILL BE IN THE MID AND UPPER 40S. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 300 PM SATURDAY....MEDIUM RANGE GUIDANCE CONTINUES TO STRUGGLE WITH THE EVOLUTION OF A MID LEVEL SYSTEM THAT WILL AFFECT THE AREA TO SOME EXTENT FOR MIDWEEK. SEVERAL MODELS KEEP THE TROUGH MORE PROGRESSIVE WHILE OTHERS PHASE THE SYSTEM WITH NORTHERN STREAM ENERGY CREATING A MORE DYNAMIC SYSTEM AND PROLIFIC RAIN MAKER FOR OUR AREA. UNTIL THE MODELS CONVERGE ON A DEPENDABLE SOLUTION...PRUDENCE CALLS FOR KEEPING POPS IN THE FORECAST FROM LATE TUESDAY THROUGH THURSDAY. NO CHANGES TO TEMPERATURE FORECAST WHICH WILL BE A LITTLE BELOW CLIMATOLOGY. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...THE WARM FRONT HAS MOVED TO NEAR A KLBT TO NORTH OF KILM LINE EARLY THIS EVENING. SOME CLEARING OF LOW CLOUDS FROM THE SW-W SUGGESTS MVFR CIGS MAY DECREASE EARLY THIS EVENING LEAVING VFR CONDITIONS. SHOWERS SHOULD BE AT A MINIMUM THIS EVENING AND OVERNIGHT...BUT WILL NEED TO MONITOR SHOWERS AND THUNDERSTORMS MOVING ENE FROM GEORGIA. THUNDERSTORMS SHOULD STAY SOUTH OF THE TERMINALS BUT SOME LIGHT SHOWERS COULD STILL SPREAD ACROSS THE TERMINALS 04-07Z AS THE ACTIVITY DISSIPATES. SKIES CLEAR AND WINDS BECOME LIGHT SW AFTER MIDNIGHT. VSBYS SHOULD BEGIN TO DECREASE WITH IFR VSBYS AND TEMPO IFR CIGS POSSIBLE. CONFIDENCE OF OCCURRENCE IS MODERATE BUT THERE IS VERY LOW CONFIDENCE IN TIMING AND DURATION. A COLD FRONT WILL MOVE THROUGH THE NORTHERN TERMINALS DURING THE EARLY MORNING AND DURING THE AFTERNOON AT THE SOUTHERN TERMINALS WITH WINDS SHIFTING TO THE NW-N. GOOD CHANCE OF IFR CIGS BECOMING MVFR AT KILM/KLBT DURING THE MORNING...WITH MVFR CIGS AT THE REMAINING TERMINALS. SHOWERS POSSIBLE DURING THE DAY WITH ISOLATED THUNDERSTORMS AT THE SOUTHERNMOST TERMINALS. EXTENDED OUTLOOK...VFR MONDAY AND TUESDAY. SHOWERS POSSIBLE WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 530 PM SATURDAY...LATEST MODEL RUNS NOT ALL THAT CONVINCING ENOUGH TO CHANGE THE CURRENT FORECAST WINDS AND SIGNIFICANT SEAS TRENDS FOR THIS EVENING AND OVERNIGHT. WILL HOLD ONTO WHAT IS CURRENTLY ADVERTISED...INCLUDING HOLDING OUT WITH THE ISSUANCE OF A POSSIBLE SCEC. PREVIOUS................................................... AS OF 300 PM SATURDAY...SOUTH WINDS THIS AFTERNOON WILL BECOME SW TONIGHT AS A WARM FRONT MOVES NORTH ACROSS THE WATERS. WINDS WILL STAY IN THE GENERAL 10 TO 15 KT RANGE WITH 2 TO 4 FT OF SEAS FOR MOST OF THE PERIOD. HOWEVER...THERE MAY BE A BRIEF PERIOD OF HIGHER WINDS AND SEAS TONIGHT AS THE WARM FRONT APPROACHES THE WATERS. IF SO...EXERCISE CAUTION HEADLINES MAY BE NEEDED. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...THE WIND DIRECTION WILL BE FROM THE W OR SW SUN MORNING...THEN VEER TO THE NW AND N AS A FRONT SINKS BACK TO THE S THROUGH THE DAY. THE FRONT MAY NOT MOVE S OF THE SOUTHERNMOST WATERS TIL LATE AFTERNOON. THERE WILL BE A MODEST SURGE SUN NIGHT AND THEN A SLIGHTLY STRONGER ONE MON NIGHT AS A SERIES OF SHORTWAVE TROUGHS ROTATE AROUND UPPER LOW RETROGRADING OFF THE NEW ENGLAND COAST. WINDS WILL BE STRONGEST WHEN THE WIND DIRECTION IS FROM THE N OR NNW...UP TO 15 TO 20 KT MON NIGHT. SEAS WILL BE 2 TO 4 FT MOST OF THE TIME. HOWEVER...EXPECT SEAS TO BUILD UP TO 5 FT DURING THE SURGES...WITH THE GREATEST COVERAGE OF 5 FT SEAS MON NIGHT. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 300 PM SATURDAY...DESPITE AN INTERESTING AND POSSIBLY DYNAMIC SYNOPTIC WEATHER SCENARIO AT THE MID LEVELS...THE SURFACE FEATURES DRIVING THE WINDS AND SEAS WILL BE RATHER BENIGN IN COMPARISON. HIGH PRESSURE TO THE NORTH WILL MAINTAIN A NORTH TO NORTHEASTERLY FLOW ACROSS THE WATERS THROUGH WEDNESDAY WITH SPEEDS GENERALLY TEN KNOTS OR LESS. FORECAST CHALLENGE THEN ARISES AS MODELS ARE STILL UNSURE HOW TO HANDLE LOW PRESSURE IN THE GULF OR UP THE EAST COAST BOTH IN A PLACEMENT AND STRENGTH PERSPECTIVE. WILL MAINTAIN THE MODEST OFFSHORE FLOW FOR THURSDAY DUE TO UNCERTAINTY. SIGNIFICANT SEAS WILL BE 2-4 FEET. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...DCH/REK SHORT TERM...JDW LONG TERM...SHK AVIATION...MRR

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