Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 251823 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 123 PM EST Sat Feb 25 2017 .SYNOPSIS... Warm air will prevail across the Carolinas today. A cold front approaching from the west will move off the coast this evening. Cooler and drier air high pressure will spread into the area tonight and persist through Monday. Shower chances will increase Monday night and early Tuesday as a warm front lifts north across the area. Much warmer temperatures will follow the front Tuesday and Wednesday before the next cold front moves offshore Thursday. Temperatures will drop to near to slightly below normal Friday as a cooler and drier air mass builds over the area. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1230 PM Saturday...Unfortunately, fog issues are not behind us. The low level winds complements of a sea breeze with winds from the S to SSW helping to push the sea fog partially onshore the local beaches during this aftn. Extending from Holden Beach south across Myrtle Beach and Murrells Inlet to the mouth of Winyah Bay. The low level flow will become more SW and eventually WSW this aftn helping to punch in some lower sfc dewpoints off the coast basically detouring the onshore movement of the sea fog. It may take a little longer for the Brunswick County Beaches due to the parallel flow and coastline configuration but in the end the lowering sfc dewpoints moving off the mainland will help demise the sea fog. No changes needed for aftn max temps. Previous...................................................... As of 915 AM Saturday...All fog issues should be behind us now. Latest sat imagery via IR and Vis channels indicate generally mostly sunny skies with any leftover thin low stratus burning off rather quickly. Clouds ahead and associated with the eastward moving cold front will begin pushing into the area by mid-day and progressing across the FA this afternoon and off the Carolina Coasts early this evening. Limited moisture avbl for low level cu/sc and mid level altocu. Latest model trends indicate this limited moisture to scour out even more-so as it progresses east in association with the cold front. Latest HRRR indicates even a drier scenario and thus as a result will keep a dry fcst with POPs below 15 percent. Not a true downslope trajectory within the atm column today, however with a late Feb sun equivalent to a mid to late October sun, should see widespread 80+ degree readings away from the immediate coast. Model 1000-500mb thicknesses in the low 560s and 850mb temps at + 10 to 12 degrees C and a good dose of insolation, all aiding these warm Spring-like max temps in late Feb. A return back to reality to occur this evening with the passage of the cold front off the Carolina coasts this evening. Sfc pg tightens with SW winds veering to WSW-W and becoming gusty as the cold front pushes closer this aftn. After the CFP, CAA will be in full force later this evening and overnight under active NW winds, gusty for several hours immediately after the CFP itself. Previous.................................................... As of 430 AM Saturday...Surface observations and 11-3.9 micron difference satellite imagery suggest the area of dense fog across eastern South Carolina is expanding and may be here to stay for several hours. A dense fog advisory has been issued for Georgetown, Horry, and Williamsburg counties until 9 AM. One final day of unseasonably warm temperatures is expected before a cold front brings us back to reality tomorrow. Today`s highs are expected to reach the lower 80s inland, with 70s closer to the ocean due to cool nearshore water temperatures. Southwesterly winds will increase today ahead of the front, likely gusting to over 25 mph this afternoon. Record highs today, February 25... Wilmington 81 set in 1930 Florence 78 set in 1977 North Myrtle Beach 77 set in 1949 Precipitation potential is low today owing to shallow moisture depth, a capping inversion between 7000-10000 feet AGL, and virtually all of the upper dynamics shearing out far to the north. I do expect there will be plenty of cumulus and even towering cumulus around late this morning into this afternoon, however the lid of warm air around 7000 feet should stop these updrafts from becoming taller. The latest several HRRR runs look very reasonable showing a line of sprinkles racing eastward across the eastern Carolinas this afternoon between 1-4 PM. Relatively shallow convective cloud depths and fast forward movement should keep precip totals in the trace category for most locations. Better precip potential will exist across the northern half of North Carolina where moisture depth will be greater and the warm air cap will be less prevalent, allowing for greater convective depth. Behind the cold front this evening, winds will shift northwesterly as much colder and drier air moves in. By morning lows should reach the lower to middle 40s, with some upper 30s possible west of I-95.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...High pressure centered over east Tennessee on Sunday morning will move over the area Sunday afternoon, then offshore Sunday night. Even with full sunshine highs will only barely reach 60 degrees on Sunday, slightly below normal and the coolest we`ve been since February 16th. Good radiational cooling conditions with the high just offshore Sunday night should allow temperatures to fall into the 30s away from the beaches. It`s not impossible some of the normally colder interior locations could see some patchy frost. Southeasterly return flow behind the departing high will strengthen Monday. An approaching positively-tiled upper disturbance will encounter the low-level warm advection across the Carolinas Monday night, leading to cloudy skies and an increasing potential for showers. PoPs have been increased to 50-60 percent for what should be a fairly light precipitation event. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 AM Saturday...Warm front in the vicinity Tue morning will lift north of the area, taking the bulk of the showers ongoing at the start of the period with it. Weak mid level ridging expands north Tue and Wed as Bermuda High builds back west. Although mid level subsidence and dry air aloft will be present, a warm and moist boundary layer may allow for at least a few afternoon showers each day, especially along the sea breeze. Temperatures will be well above normal with highs approaching 80 and lows around 60. Strong cold front is driven across the area late Wed night/early Thu, accompanied by showers and isolated thunderstorms. Morning timing of fropa will limit available instability but the front will have plenty of forcing associated with it. Moisture return ahead of the front is limited which will affect storm coverage and rainfall totals. Strong cold advection follows the front with temperatures dropping in the afternoon Thu. Winds at the top of the mixed layer will be around 30 kt with RH aloft dropping into the single digits. Mixing could lead dry and breezy conditions Thu afternoon. Canadian high continues to build in from the northwest Fri with temperatures dipping a little below normal for the end of the period. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 12Z...Fog/stratus will persist til 13Z, and should dissipate pretty quickly between 13-14Z. Southwest flow is expected ahead of a dry but moderately potent cold front. Winds will become more westerly and gusty immediately ahead of the front late this afternoon, with fropa expected this evening. Moderate northwest flow tonight with cold air advection. Extended Outlook...VFR. VSBY and ceilings lowered to MVFR/IFR with pcp Mon night into Tues and again with SHWRs on Wed. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 1245 PM Saturday...Well the sea fog issues have re- appeared. Given sat imagery and local obs, have issued an update to the CWF as well as issuing a MWS for patchy sea fog. The local sea breeze along the immediate coast has been aiding the sea fog development and partial onshore movement. With time, the low low level winds will become more SW and WSW this aftn keeping any sea fog off the coast with the exception of Brunswick County. Lower dewpoints will begin pushing off the mainland this aftn and especially tonight after the CFP. Will see the sea fog diminish in coverage later this aftn, especially nearshore, and the remainder of the waters this evening. Previous................................................... As of 1000 Am Saturday...The fog issues earlier this morning along the immediate coast have faded away. Sfc dewpoints may increase into the 60s across the local waters. However SSTS have rebounded into the low 60s, well above the climo norm. Thus, the difference between the 2 temps are not conducive for sea fog to develop today. The fog earlier was land-based that affected the immediate coast, inlets and the Intra Coastal Waterway. The sfc pg will tighten ahead of the approaching cold front and yield increasing SW to WSW winds to SCA values across the ILM NC waters, and SCEC thresholds for the ILM SC Waters. Winds will veer to the NW after the CFP this evening and persist thru the remainder of the night. The CAA surge will combine with the tightened gradient to produce SCEC thresholds for the SC Waters with 15 to 20 kt with gusts up to 25 kt. For the NC Waters, winds will increase to 20 to 25 kt and hold thru the night. Significant seas will run a healthy 3 to 5 ft SC Waters and 3 to 6 ft NC Waters. The ESE 11 second period ground swell has peaked earlier this morning, however it will remain a dominant force today and may equal out with locally produced wind driven waves tonight and beyond. Previous................................................ As of 430 AM Saturday...NWS Charleston relayed a report from the Charleston pilot boat around 230 AM indicating visibility was around 1 mile at a distance of 10 miles offshore. This region of marine fog appears to be crawling northward along the South Carolina coast according to 11-3.9 micron difference satellite imagery. Low visibilities inland at Georgetown and Conway, SC also imply the area of dense fog is expanding. A marine dense fog advisory has been issued for our South Carolina coastal waters until 9 AM. Southwesterly winds should be increasing by then, hopefully pushing the fog farther out to sea. The Carolina coastal waters are in a region of very light winds between two regions of low pressure: one several hundred miles east of the Outer Banks, and the pressure trough surrounding a cold front over Tennessee. As the front approaches the region later today, southwesterly winds will increase to 15-20 kt. The front should move offshore and across the coastal waters this evening, followed by gusty northwest winds overnight as colder air builds in. Buoys are still showing a significant easterly swell affecting the waters. Seas at Frying Pan Shoals are nearly 7 feet, entirely in a 9- second easterly swell. This swell will diminish only slowly today, but increasing short period wind chop may make boating conditions rather unpleasant. The Small Craft Advisory has been extended for the NC waters through tonight, and an exercise caution headline will be posted for the SC waters as soon as the advisory expires there. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...High pressure centered over Tennessee on Sunday morning will move overhead Sunday afternoon, then offshore Sunday night. Veering winds Monday into Monday night will develop as the high moves farther offshore. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 AM Saturday...Warm front in the area Tue morning lifts north as Bermuda High expands west. Southwest flow will persist through the forecast period with speeds 10 to 15 kt on Tue. Gradient tightens up Wed, ahead of approaching cold front, with speeds increasing to 15 to 20 kt by midday Wed. Seas 2 to 4 ft Tue into Wed build to 3 to 5 ft later Wed.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 6 AM EST Sunday for AMZ250-252. && $$ SYNOPSIS...III NEAR TERM...DCH/TRA SHORT TERM...TRA LONG TERM...III AVIATION...DL MARINE...

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