Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 200651 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 251 AM EDT Thu Apr 20 2017 .SYNOPSIS...
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The Bermuda High will expand west over the region through Saturday. A cold front will sag south toward the area during the weekend. Low pressure will move slowly through the Carolinas late Sunday through Monday night, possibly bringing strong to severe thunderstorms. Low pressure may linger off the coast into the middle or later portions of next week as a ridge builds across the Southeast states.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 AM Thursday...Weak front in the area will dissipate during the next few hours while surface high to the east expands back west. Abundant low level moisture combined with the weak to nonexistent boundary layer flow has resulted in widespread fog and a few areas of low stratus with inland areas being favored. Low clouds and fog will mix out fairly quickly if forecast soundings are correct in showing a nearly saturated boundary layer between 500-700 ft thick. Today the Bermuda High will be the main surface feature while aloft a flat 5h ridge sits over much of the Southeast. Lack of any surface gradient combined with temperatures above climo will result in sea breeze development by midday. Sea breeze should work its way inland but is likely to do so at a slower rate based on westerly flow of 8 to 10 kt working against it. Surface based instability will be on the order of 1500-2000 j/kg which in the presence of the sea breeze should be good for some scattered afternoon convection. There is a lack of deep moisture above 18k ft or so which will limit coverage and keep best chances aligned with the sea breeze. Any convection will rapidly diminish with the loss of surface heating this evening. High pressure remains the dominant feature overnight but cold front slowly approaching from the northwest will start affecting the gradient and boundary layer flow is likely to be strong enough to prevent much, if any fog development. Temperatures today and tonight will be well above climo with highs generally in the low to mid 80s and lows in the mid 60s.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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As of 300 AM Thursday...A warm ridge of high pressure will be offshore at the start of the period. A cold front to our N will be strung out W to E. This front is expected to sag southward and should be in close proximity to our northern zones late Sat and Sat night. At this time, we are keeping the front north of the forecast area, but it is possible it does sneak a little further south than our current forecast indicates during the weekend. It will feel like summer with 850 mb temps climbing to 14 deg C. Widespread upper 80s are expected for high temps inland on Fri and Sat. Along the coast, the seabreeze will be strong and will push inland, first across Brunswick and southern New Hanover counties and then progressively inland from there. The arrival of the seabreeze will keep the beaches in the 70s with again the south facing beaches being the coolest. Confidence in a dry forecast for Fri is high. The front to our N may provide enough lift to produce a shower or thunderstorm across our northernmost counties Fri night, but the prospects are rather remote. The column does moisten, mainly in the lower levels Sat and Sat night, as precipitable water values climb to just over an inch. We may see a shower or thunderstorm develop along the front and possibly along the inland propagating seabreeze Sat afternoon. Will carry small POPs for this risk. There will be a much higher risk for thunderstorms late in the weekend as low pressure approaches from the W and this is when rainfall amounts will be more widespread and substantial.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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As of 300 PM Wednesday...Sun should start off dry with increasing clouds through late Sun as cold front approaches from the west. Best chc of showers and thunderstorms will come late Sun west zones and into Sun night for coast, but should be fairly widespread coverage with strong to possible severe storms in a very warm and moist air mass ahead of front. Cooler northerly flow will advect drier air into the area on the back end of the low, but the low will linger right off the coast with clouds and pcp remaining on Mon and possibly into Tue. The greatest chc for pcp will be closer to the coast especially as the low pulls slowly away late Mon into Tue. Drier high pressure will build in behind the departing low Tue into Wed. Temps will reach into the 80s except right along the coast Sun, but Mon will cool down to near 70. Slight warming will follow bringing near normal temps.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 06Z...MVFR to LIFR fog expected across the region this morning along with patches of low stratus. Densest fog will be found at inland sites but expect at least tempo IFR fog along the coast as the night wears on. Although low level moisture is abundant, boundary layer RH will approach 100% overnight, the moisture is rather shallow. This should lead to rapidly increasing ceilings/visibilities shortly after sunrise. Remainder of the day will be VFR with the exception of isolated sea breeze convection that could affect any of the coastal terminals for a short period of time in the afternoon. Based on expected strength and orientation of sea breeze would think best chances would be at ILM. Any convection that develops this afternoon will rapidly dissipate with loss of heating as the sun sets this evening. Boundary layer winds are expected to be stronger late in the period and fog development is not anticipated. Extended outlook...MVFR/IFR conditions possible in showers and TSTMS Saturday through Sunday night. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 AM Thursday...Remains of front lingering in the area will dissipate in the next few hours with Bermuda High expanding west and becoming the dominant feature. Southerly flow will be 10 to 15 kt today, highest along the coast once the sea breeze develops. Winds remain 10 to 15 kt overnight, but increasing to the high end of the range late in the period. Slow moving cold front approaching from the northwest late tonight will have some affect on the gradient, bringing about the gradual increase in speeds. Seas 2 to 3 ft today will transition to more widespread 3 ft seas overnight. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...A ridge of high pressure will be offshore at the start of the period. A cold front to our N will be strung out W to E. This front is expected to sag southward and should be in close proximity to our northern waters late in the period. At this time, will keep the wind direction SW with the direction backing to SSW across the near shore waters both afternoons due to a strong seabreeze circulation. Sustained wind speeds will be 15 to 20 kt for much of the period. Wind gusts will be strongest across the near shore waters each afternoon and eve. Seas will build slightly in persistent SW flow and an increasing easterly swell due to a distant subtropical depression, from 3 to 4 ft at the start of the period to 3 to 5 ft at the end of the period. LONG TERM /SUNDAY THROUGH MONDAY/... As of 300 PM Thursday...South to southwesterly flow will persist around Bermuda High into Sun. This southerly push will drive seas up to 3 to 5 ft Sun. Wind speeds should be about 10 to 15 knots with a slight uptick and backing of winds Sun afternoon due to the seabreeze. Low pressure and associated cold front will approach late Sun into Sun night. Winds will shift to the north behind the front and may increase up to 20 kt or so on the back end of this low as it lingers and begins to slowly depart Mon night. This northerly surge may produce Small Craft Advisory conditions by late Mon.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...III SHORT TERM...RJD LONG TERM...RGZ/RJD AVIATION...III

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