Area Forecast Discussion
Issued by NWS Wilmington, NC

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533 FXUS62 KILM 211957 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 357 PM EDT Mon Aug 21 2017 .SYNOPSIS...
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High pressure will expand across the area from the western Atlantic through Wednesday, allowing the heat and high humidity to continue. A cold front will track across the Eastern Carolinas from the northwest late Wednesday night thru Thursday. Canadian high pressure will build in behind the front bringing drier and breezier weather with slightly below normal temperatures for the weekend.
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&& .NEAR TERM /THROUGH TUESDAY/...
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As of 300 PM Monday...Although the area is primarily under the influence of mid level ridging, there is a slight deformation zone and surface troughing residing offshore that is sparking convection. This will continue through the afternoon hours and subside this evening. There may be another diurnal increase over the waters. The same elements will be in play Tuesday although with moisture profiles a little drier, the coverage should be less. No surprises in temperatures with another night of lower to middle 70s and highs Tuesday from the upper 80s along the coast to lower 90s inland.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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As of 300 PM Monday...Mid to upper level ridge will be sprawled south and east of forecast area Tues night into Wed. A bit of shortwave energy riding up around the ridge from the south will act to enhance localized convection along Piedmont trough and sea breeze front into Tues eve. The westerly steering flow will push any debris clouds or storms toward the coast in the evening. Expect a lull through the night into early Wed, but a cold front will reach into the Carolinas on Wed and expect trough to push east and any convection once again to move toward the coast in a westerly push. Convective activity ahead of the front will increase into Wed evening as mid to upper trough digs down from the north pushing the front east. Plenty of warm air and moisture ahead of the front combined with dynamics aloft could lead to stronger storms into late Wed and Wed night as front marches east. Expect boundary to be right near I-95 corridor by Thurs at daybreak. Temps will be in the 70s overnight and 90 to 94 most places Wed aftn. Head index values will reach around 100 degrees in a continued hot and humid air mass.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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As of 300 PM Monday...The extended period is initiated with a frontal boundary along the coast, pushed offshore by Canadian high pressure by Thursday night. The seasonably strong Canadian anticyclone will continue to press SSE into the area through the weekend, offering a dose of a very early fall feel here with slight cooling and drying. As the strong high interacts with low pressure development off Florida, a stiff NE flow should prevail much of this period into early next week. This will keep maximums moderated, and notably milder minimums at and near the coast compared to the interior. Highest POp values is the very beginning of the extended on Thursday, while low temperatures this weekend dip into the 60s in many locations inland. Because of upper winds, any tropical formation off Florida this weekend should remain east and offshore of the Carolinas through early next week.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 18Z...Expect mostly VFR conditions for the afternoon and evening hours. There is some convection around and coverage may increase for a few hours but not enough confidence to put in other than VCTS. Guidance is showing a good signal for fog area wide Tuesday morning. I addressed with prevailing MVFR for this cycle but some IFR could be in play as well. Extended Outlook...Diurnal showers/tstms expected Wednesday afternoon, becoming more numerous Wednesday night and Thursday with fropa. Convective potential will decrease Friday as the front moves south of the area. && .MARINE...
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NEAR TERM /THROUGH TUESDAY/...Conditions will remain quiet across the coastal waters with very little in the way of forcing for the wind fields. Expect an east to southeast flow of ten knots or less tonight through Tuesday. There are some indications of slightly stronger winds (10-15 knots) late in the period. Significant seas will continue to hover around two feet. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...Winds will increase into Tues eve up 10 to 15 kts as gradient tightens between high pressure to the east and trough to the west. Winds will lighten toward daybreak Wed but will increase again with an approach of a cold front Wed night into early Thurs. Expect seas to reach up near 4 ft in outer waters Tues eve with a slight drop Wed morning and rise again Wed night. Overall expect 2 to 4 ft seas with a longer period, up to 10 sec, SE swell mixing with the shorter period wind waves. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 300 PM Monday...This period will become fraught with challenges for marine activities as a seasonably strong Canadian high forces a cold front across the coast Thursday. Aside from TSTMS Thursday on the 0-20 NM waters, NE winds will begin to increase Thursday night and Friday as the Canadian high presses SSE over the waters, and a Small Craft Advisory may be needed for 25 KT gusts and 6 foot seas offshore. The strong onshore flow will likely persist into Saturday, as the high interacts with deepening low pressure off Florida, and thus maintaining rough conditions into the weekend.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...SHK SHORT TERM...RGZ LONG TERM...MJC AVIATION...SHK

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