Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 150334 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1034 PM EST Sun Jan 14 2018 .SYNOPSIS... Cold and dry high pressure will hold into Tuesday. An area of low pressure will develop off the coast mid-week, bringing a period of light wintry precipitation Wednesday and Wednesday night. Arctic air will reach the area late Wednesday and Thursday. Temperatures will begin to climb Friday, rising into the 60s next weekend. && .NEAR TERM /THROUGH MONDAY/...
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As of 1034 PM Sunday...No significant changes made in the late evening updates, the trend to partly cloudy looks okay for the SE NC coast. The leading edge of these clouds can be seen thinning upon encountering the drier continental air near-shore, with land dewpoints in the teens along the coastal interior. As of 728 PM Sunday...Clear skies prevailed this evening with unlimited visibility, and below normal temperatures, already below freezing in many locals. 15 kft clouds moving at 55-60 kt across north GA and western SC, will have minimal impact on sensible weather or hourly temperature curves across NE SC and SE NC overnight. Looking offshore, the western edge of a 3 kft strato-cumulus deck, was making landward progress. Current forecast appears to account for the moisture intrusion, and little edits were needed, as portions of the north coast and Cape Fear region become impacted by the encroaching clouds. This in turn may slow cooling several degrees in these coastal zones, and the current forecast minimums reflect this horizontal temp gradient. Wind chills will range between 10-15 deg at daybreak, although winds will be 10 mph or less generally, air temps will be a couple degrees either side of 20. As of 300 PM Sunday...Arctic high will shift from the OH Valley to New England later today and tonight as it continues to extend down the east coast. Skies will remain mostly clear overnight, although forecast soundings are suggesting there could be some low cloud. This appears similar to what forecast soundings were showing last week when no cloud developed. Thus will not go for any low cloud but soundings also suggest there could be some patches of thin cirrus at times overnight. Although the gradient steadily weakens overnight do not think the boundary layer will completely decouple. A few sheltered areas and cold spots could, but winds under 5 mph will not be the norm. Still, northerly flow will be a good bit lighter than it was last night and with mostly clear skies lows will end up well below climo. Some areas will dip into the upper teens with most of the area in the lower 20s. Northerly flow continues on Mon but with the elongated ridge axis just west of the area north to northwest flow will be lighter. Lack of any advection and an abundance of sunshine allows for some airmass modification, but with temps starting out close to 10 degrees cooler than this morning highs will remain well below climo, peaking in the mid 40s at the warmest locations. Airmass remains very dry with precipitable water at or below 0.30" Mon and relative humidity will once again dip under 30% in the afternoon.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...High pressure stretched from north to south over the Carolinas, will weaken as a potent mid to upper level trough pushes a cold front east, into the Carolinas Tues night into Wed. Overall, the air mass will modify through the period with increasing moisture toward Wed morning. Temps Mon night will drop into the mid 20 most places under decent radiational cooling conditions as the sky remains mainly clear and winds near calm. Warm and moist advection through Tues will help to bring temps up around 50 most places and give a boost to dewpoint temps bringing them up near 30 by the end of the day. Moisture will increase in the mid to upper levels as digging H5 trough pushes eastward. This will throw some mid to high clouds across the western portions of the area Tues night. Sounding profiles show moisture increasing through the column above 13k ft mainly west of I-95. The GFS is a bit faster with system and shows a greater increase in cloud cover. Overall expect some increase in clouds Tues night, mainly after midnight but any pcp holding off until later on Wed. Therefore, may see temps drop out with better radiational cooling conditions to start the night allowing temps to fall to 30 to 35 most places, but may see a slight rise in temps once clouds arrive. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 300 PM Sunday...A brief Arctic blast and light wintry precipitation Wed-Thu and then a warm up as more dry weather returns. The risk for rain showers will return at the tail end and just beyond this forecast period. The latest NAM has bolstered the latest European solution with precipitation developing ahead of a vigorous upper low and associated shortwave energy. The upper trough is expected to swing across the FA late day Wed and Wed night. The upper low will move off the Mid-Atlantic coast Thu morning. In the wake of this system, 850 mb temps will drop to minus 8 to minus 12C Wed night as Arctic air briefly builds across the eastern Carolinas. The Euro has latched back on to the solution of a coastal low and the NAM depicts a coastal low as well. However, the NAM is weaker and further off the coast with its depiction than is the Euro model. If the Euro does verify, then more precipitation may clip the coast Wed morning and this bears watching. Otherwise precipitation should be increasing from W to E as lift associated with the upper trough increases. Isentropic upglide may also allow precipitation to break out across the eastern Carolinas. The column is supportive of frozen precipitation early on Wed and then again late Wed and Wed eve. At this time, the brunt of the precipitation is slated to fall Wed afternoon to early eve. QPF is forecast to be a tenth of an inch or less. Factor in mix and changeover to rain and slow column moistening and this looks like a very light to no snow accumulation event. At this time, we do show some accumulation of snow, a tenth of an inch or two, across portions of our NW zones and NE zones where ice in the cloud and low level thermal structure may line up best for brief accumulating snow. Wind chill values overnight Wed and Thu morning will be in the single numbers and a Wind Chill Advisory may be issued for at least portions of the area with later forecast packages. Arctic high pressure will build strongly across the region Thu with its center passing to our S Fri and then offshore Sat and Sun. Southerly return flow will bring gradually higher temps and humidity levels during this time. A cold front will approach Sun night and may bring some showers, but otherwise it will be dry Thu through Sun. Highs will be in the upper 30s to lower 40s Wed and around 40 Thu. High temps should rebound into the 50s Fri and Sat and 60s Sun. Lows will be mainly in the teens Wed night to around 20 along the coast with strong cold air advection. It will likely not be quite as cold Thu night, but some locations could again sneak down into the teens with strong radiational cooling. Lows will then trend from upper 20s and lower 30s Fri night to 40s by Sun night. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... As of 00Z...VFR conditions expected through the period. A bank of stratus is lingering offshore but is expected to make little westward progress. Extended Outlook...Rain/MVFR/IFR/with a slight chance for wintry precipitation late Wed, otherwise VFR. && .MARINE...
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NEAR TERM /THROUGH MONDAY/... As of 1034 PM Sunday...SCA replaced with an `Exercise Caution` headline, for 15-20 KT winds and 4-5 foot seas offshore for the overnight period. No other changes at this time. As of 728 PM Sunday...Advisory conditions prevail with N wind gusts to 25 KT and 6 foot seas offshore, so will allow the SCA in place, to continue on this evening. As winds back to NW overnight, sea heights should drop 1 - 1.5 ft, allowing the SCA to expire later tonight. As of 300 PM Sunday...High pressure remains north of the area, building down the coast tonight and Mon. Northeast flow this afternoon and overnight will gradually weaken as the surface pressure gradient relaxes. Speeds currently around 20 kt will drop to 15 to 20 kt overnight and the winds will back to a more northerly direction. The combination of the wind shift and the decrease in speeds should bring about an end to the already marginal small craft advisory. In fact AMZ254 will probably drop below advisory conditions prior to the current end time of midnight. Elongated ridge axis remains west of the waters Mon with northerly flow continuing to decrease and possibly becoming northwest as the period ends. Seas 4 to 6 ft into the evening drop to 3 to 5 ft overnight and will run 2 to 4 ft Mon. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...High pressure extending down into the Carolinas will maintain a light northerly flow through much of the period. Models have been showing a possible area of low pressure developing to the east of the waters late Tues into early Wed which may sharpen the gradient and enhance the northerly flow, but for now, will maintain northerly flow 10 kt or less becoming more variable late Tues into Tues night as high pressure weakens. Seas will remain 2 to 4 ft. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM Sunday...Small Craft Advisory conditions likely to develop late Wed into Thu. Still unclear as to the exact location and strength of developing coastal low. However, magnitude of cold and dry advection will result in a period of higher winds and seas through the first half of the period. Wind speeds will likely peak in the 20 to 25 kt range with higher gusts Wed night. The direction will be NW Wed and then slightly veer to NNW Wed night into Thu morning. Seas will peak in the 5 to 9 ft range Wed night and Thu morning. Winds will decrease to 10 to 15 kt by Thu afternoon and then hold around 10 kt Thu night and Fri. The direction will back to NW during Thu, W Fri morning and to SW Fri afternoon. Seas will subside to 4 to 5 ft Thu afternoon with 2 to 4 ft seas generally expected Thu night and Fri.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...None. MARINE...None.
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&& $$ SYNOPSIS...8 NEAR TERM...III/8 SHORT TERM...RGZ LONG TERM...RJD AVIATION...SHK

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