Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210600 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 200 AM EDT Sat Apr 21 2018 .SYNOPSIS... Canadian high pressure will build into the Carolinas through the weekend, bringing dry weather with chilly temperatures. Slow-moving low pressure will cross the Southeastern U.S. Monday through Wednesday, bringing widespread rainfall with continued below-normal temperatures. Another system may affect the Carolinas Thursday into Friday. && .NEAR TERM /THROUGH TODAY/... As of 945 PM Friday...Dewpoints rising quicker than forecast, and under clear skies and light wind, this will only help the prospects for fog overnight, and will expand this potential in the overnight forecasts. No other significant changes. As of 630 PM Friday...Radar wind profiler showing an easing and backing wind column early this evening, now, 10 knots or less in the lowest 5000 feet. GOES-East visible data showing a cloudless sky over all of the Carolinas. Hourly temperatures will fall through 5 AM before gradually rising, while dewpoints climb slowly through the night, into the low 40s by daybreak. 10 meter winds should hold at 3-6 mph overnight. These factors will lead to patchy fog along the coastal interior where slightly higher dewpoints will reside, and away from the higher coastal winds. The combination of low-levels near saturation into the predawn, and chilly pockets of middle to upper 30s, results in patches of frost over portions of Pender, central Brunswick, and Robeson counties at first light. As of 300 PM Friday...A 500 mb ridge over the Southern Plains will move into Georgia and the southern Appalachians by late Saturday. Dry northwesterly mid and upper level flow ahead of this ridge will continue. At the surface, Canadian high pressure covering most of the Great Lakes region will develop a secondary center along the Virginia coast Saturday afternoon. Light winds and clear skies tonight should promote very good radiation cooling. My forecast lows are at the very bottom end of guidance, ranging from the upper 30s to around 40 inland with a sliver of mid 40s on the beaches. I`ve got mid 30s forecast across the normally colder locations across SE North Carolina and have added patchy frost to the forecast here as well. Blueberry growers, whose farms are often located on the nocturnally cold peat soils, may have some concern tonight. Sunny skies are expected Saturday, Another weak seabreeze along the coast should keep the beaches 5-10 degrees cooler than inland areas. Forecast highs range from the lower 70s across the Pee Dee region to the mid 60s near the coast. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...High pressure slides east of the area Saturday night, passing by well to our north. Temperatures will be held a bit below climatology in the NE flow with a mainly clear sky brought by the downsloping mid level flow. Wit the high progressing further off the MidAtlantic coast on Sunday the door will open up to moisture influx. Cloud cover will increase from SW to NE. Some of the guidance that has been suggesting that rain could start breaking out soon thereafter has been discounted as being too fast. This will eventually start to change heading into Sunday night as the moistening deepens in response to approaching upper troughiness tilting flow to the southwest. POPS will increase though rainfall amounts expected to remain light and generally confined to SC zones Sunday night. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Cutoff low will continue to move east along the Gulf Coast states Mon into Tues spreading clouds and rain across the area from south to north. Increasing moist on shore flow will push pcp water values up to near 1.5 inches late Mon into Tues. The center of the low should reach the SC coast Tues night and then track up along the Carolina Coast lifting off to the northeast late Wed. The best moisture and lift should come together to produce the greatest QPF Mon night through Tues with fairly widespread amounts between a half inch and an inch with locally higher amounts. Some dry air should wrap in with westerly flow on the back end of the system on Wed, but lingering upper level energy could keep some lingering clouds and showers around. By Thurs, another cutoff low will track across the Appalachian Mtns, with increased potential for clouds and pcp late Thurs into Fri. Overall a damp week ahead with a good amount of clouds and pcp through the week. Temps running on the cooler side on Mon will return toward normal Tues into Wed. Overall temps will remain near or just below climo through much of the week. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 06Z...Although a period of MVFR or IFR fog is possible at the coastal sites during the next few hours, especially at KCRE, these restrictions are unlikely to last for any length of time. As such have carried VFR for all sites through the entire forecast period. Northeast winds this morning become more easterly later this morning and eventually east to southeast by afternoon. Extended outlook...VFR. Mon periods of MVFR/RA. Tue periods of IFR/RA becoming MVFR. Wed VFR.
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&& .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 630 PM Friday...Spectral plots show wave frequencies centered near 7 seconds, from the E. Chop is decreasing and will be light overnight. Inshore SSTs have leveled off at 62-64 deg. The atmosphere is starved of moisture aloft, so no TSTMS or marine showers. All in all, very manageable marine conditions through tonight, tides are running normally, and little hazard expected in the near term. As of 300 PM Friday...Sprawling Canadian high pressure over the Great Lakes will develop a secondary center along the Virginia coast Saturday afternoon. This should maintain northeasterly winds along our portion of the Carolina coast, with a weak seabreeze expected to turn nearshore wind directions more directly onshore Saturday afternoon. All models are in excellent agreement and there is high confidence in this scenario. Residual strong northeasterly winds most of this morning maintained a hybrid 6-7 second northeasterly swell. Now that this wind is diminishing, look for waves to quickly subside this evening. By 8 or 9 PM seas within 20 miles of shore should be only 1-2 feet! The `exercise caution` headline will be allowed to expire at 3 PM, and no advisories are needed for the next 24 hours. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...High pressure progressing eastward and staying well north of the area all period. This will turn flow onshore Saturday night with wind and seas remaining quite light/small. This will hold true most of Sunday as well save for a gradual increase in wind speed. Things then ramp up with the approach of low pressure from the west Sunday night. Expect conditions to deteriorate to near Advisory levels, though the flags will likely go up this period to incorporate further deterioration later on/early in the long term. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Low pressure system will move east across the Gulf Coast States to the coast of SC by Tues night and then will track NE parallel to the Carolina coast. A strong on shore flow will persist Mon into Tues in a tightened gradient flow between this low pressure system and high pressure moving slowly off the Northeast coast. Winds will diminish as they back from E-SE to N-NE Tues night as the center of the low tracks northeast becoming elongated just off the Carolina coast. Eventually an off shore W-SW flow will develop late Wed as the low exits off to the northeast. Overall, expect this onshore push of easterly winds up to 25 to 30 kts to push seas up through Mon into Tues, from near 6 ft Mon morning up to possibly 10 to 12 ft by Tues morning and then subsiding slowly as winds back around further becoming off shore Wed. Expect SCA conditions through much of the period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...TRA SHORT TERM...MBB LONG TERM...RGZ AVIATION...III

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