Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 300617 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 215 AM EDT Sun Apr 30 2017 .SYNOPSIS... High pressure will extend across the area from offshore through early Monday with warm and humid conditions continuing. A cold front will bring a likelihood of showers and thunderstorms late Monday into early Tuesday. High pressure will follow for the mid-week period. A Low pressure system will impact the region Thursday into Friday amd may bring widespread showers and thunderstorms and heavy rain. && .NEAR TERM /THROUGH SUNDAY/... As of 1000 PM Saturday...Short-term guidance is converging on the idea of fewer low clouds developing overnight. This may be due to dewpoints, while still running exceptionally high for this time of year, are just not high enough relative to the warmth of the airmass to ensure a good saturated layer develops. Latest HRRR and GFS-LAMP guidance still shows 1000-2000 foot stratus inland, but only for a few hours late tonight. I have trimmed back this potential in the latest sky cover forecast and tweaked a few temperatures with somewhat more clear skies anticipated. Discussion from 730 PM follows... Very few changes were needed to the previous forecast. An exceptionally humid and warm airmass for this early in the season will continue to spread onshore tonight. Temperatures should run a solid 15 degrees above normal with low temps around 70 degrees. Dewpoints will remain in the 60s and lower 70s. Much like we saw last night, low stratocumulus clouds should develop and persist through daybreak Sunday. We`re already seeing some cloudiness develop now in the Cape Fear area, probably an early sign of what will come. Between 10 PM and 1 AM expect skies to become cloudy to mostly cloudy area-wide except perhaps right on the beaches as these clouds will be the result of humid air lifted up over the shallow nocturnal inversion near the coast. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 315 PM Saturday...Strong mid level ridging which has been responsible for the summer like conditions of the past few days will give way to a dampening cyclone moving from the Central U.S. to the Great Lakes region through the period. At the surface, Bermuda High pressure will be displaced by a cold front moving across the area late Monday into early Tuesday. The timing of the front is becoming more consistent within the guidance suite and there should be a broken to almost solid line of showers and thunderstorms moving west to east across the area from about 0 to 6z Tuesday. Severe potential doesn`t look overly impressive with 850mb winds only 45-50 knots with the higher values to the north. Still, the timing could make things a bit interesting over the western zones early in the evening. Warm temperatures continue with highs in the 80s monday following another night with lows in the 60s Monday morning. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 315 PM Saturday...Broad high pressure behind Monday night`s cold front will expand across the Southeast Tuesday creating dry and seasonable weather with highs and lows right around climo. This high will remain in place Wednesday with slightly warmer temperatures but continued dry weather before it shifts offshore Thursday. This occurs in response to a deep mid-level trough digging into the middle of the country and then evolving across the eastern CONUS into the weekend. There exist two distinct camps in the guidance: the GFS has this low cutting off and dropping southeast through the end of the period. The CMC/ECM have a similar pattern initially to the GFS, but the upper low drifts north before cutting off overhead the Northeast. The biggest difference between the guidance appears to be the evolution of the ridge across the middle of the country. The CMC/ECM keep the ridge axis aligned N/S, while the GFS produces a more tilted NE/SW ridge which suppresses the upper low. The agreement between the ECM/CMC tends to favor that solution a bit more, despite the fact that the GFS has been consistent and we had a similar setup just last week so there is precedent. The evolution of this upper pattern is critical because, while all scenarios support showers and thunderstorms late Thursday and Friday, the CMC/ECM would dry things out for the weekend, while the GFS would maintain unsettled and possibly very wet weather for several days. Without a clear solution at this time range, will hedge with a WPC favored blend of guidance but with a bit more weight on the drier ECM by the weekend. This would also bring much cooler temperatures to the region Fri/Sat with highs and lows falling below climo. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... As of 06z...Although there is a decent low status deck across many TAF sites south and west of local area, confidence is lower tonight for prevailing IFR/LIFR ceilings. Soundings and moisture profile continue to lock in moisture right below 1000 ft in this unseasonably humid air mass over the area. Have included a tempo group between 06z and 10z at all TAF sites for LIFR stratus deck lifting after sunrise, through the morning and maintaining some MVFR stratocu and also some cirrus through the aftn. Southerly winds are slightly lower overnight into early this morning and therefore may see some MVFR fog but have not included in TAFs for now as winds were remaining up near 4 to 5 kts. Ridge slips east through this aftn and allows for convection to develop a bit closer to inland TAF sites but have held it to the west and therefore did not include any shwrs. Soundings and guidance hint at another night of low clouds for Sunday night and therefore put some SCT lower ceilings at the end of TAF period. Extended outlook...Periods of IFR/MVFR conditions are possible in showers and thunderstorms late Monday into early Tuesday. && .MARINE... NEAR TERM /THROUGH SUNDAY/... As of 1000 PM Saturday...High pressure well offshore will maintain a southerly wind tonight around 10 knots. Stronger winds this afternoon along the coast were the result of the seabreeze, which produced gusts over 20 knots at times. Seas around 3 feet should continue overnight in a mix of 5-second wind waves and 8 second SE swell. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 315 PM Saturday...A southerly flow will be in place most of the period with wind speeds increasing Monday as a cold front approaches from the west. Initial speeds of 10-15 knots will increase to a respectable 20-25 knots late Monday and persist into the evening hours. The front will move across with a modest westerly flow setting up by early Tuesday. Small craft conditions are likely for Monday. Significant seas will ramp up as well increasing from 2-4 feet early to 5-8 feet late. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 315 PM Saturday...Broad high pressure builds across the waters behind a cold front Tuesday. Residual gusty W/NW winds of 15 kts and 4-6 ft seas will fall quickly during Tuesday as winds back to the SW at 10-15 kts late Tuesday before a secondary surge flips winds around to the NW by Wednesday at less than 10 kts. As the high shifts offshore into Thursday, southerly winds will ramp up quickly becoming 15-25 kts, driving seas back to 4-7 ft after being just 2-3 ft much of Wednesday. An SCA will likely be needed beginning late in the extended. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...Coastal Flood Advisory until 3 AM EDT Sunday for NCZ107. MARINE...None. && $$ SYNOPSIS...SHK NEAR TERM...TRA SHORT TERM...SHK LONG TERM...JDW AVIATION...RGZ

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