Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 041152 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 652 AM EST Sun Dec 4 2016 .SYNOPSIS... A weak wave of low pressure moving along the coast will bring increasing rain chances through tonight. A more significant and complex low pressure system will move in the vicinity late Monday and Tuesday accompanied by periods of heavy rain. Two to three inches of rainfall is forecast through Tuesday. Seasonable weather will follow for mid-week before an Arctic front brings very cold temperatures Friday and into the weekend. && .NEAR TERM /THROUGH TONIGHT/...
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As of 600 AM Sunday...Patchy very light rain continues to move across the area with more upstream headed in this direction. Chilly high pressure centered to our N, will be moving offshore tonight. A front will extend from low pressure along the Gulf Coast eastward and will develop to our S and offshore along the Carolina coast tonight. A wave of low pressure is expected to develop along the front to our S and move NE along the Carolina coast. This will allow precipitable water values to increase through the day with the lowest levels of the column becoming saturated by/during this evening. The best isentropic lift arrives late tonight and this is when we expect the highest rainfall rates. We will show POPs increasing through the day with widespread rain expected tonight. Light rain today will turn moderate to briefly heavy late tonight. Cloudy skies through the period will minimize the diurnal range with highs in the upper 40s to lower 50s and mid 50s along portions of the immediate coast. Lows will be mainly in the mid and upper 40s with upper 40s to around 50 near the coast.
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&& .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 300 AM Sunday...Rain should be temporarily tapering off from W to E, in both coverage and intensity on Monday. A frontal boundary will be draped to our S Monday and extend up the Carolina coast across the coastal waters. A wave of low pressure will be positioned on this front. The low is expected to be along the Carolina coast in the morning, lifting away from the area and shoving the front further S and E during the day. As this occurs, upward vertical motion will greatly diminish as will the depth and magnitude of moisture. We do not think the warm sector will bleed onto land Monday morning, thus any thunderstorms will be kept offshore. The main area of low pressure along the western Gulf Coast Monday will lift NE across the mid south Monday night and up the Ohio Valley Tuesday. This low pressure will actually fill/weaken late Tuesday and Tuesday night as the upper support wanes and energy is transfered to developing low pressure along the coast of North Carolina and Virginia. The primary low early Wednesday morning will be off the Del-Mar-Va. The front to our S is expected to advance N as a warm front Monday night and Tuesday as a 50 to 60 kt low level jet impinges on the area. Moisture depth increases dramatically and precipitable water values climb to near 2 inches. Strong isentropic upglide will increase rainfall rates and we expect periods of heavy rain late Monday night into Tuesday. Also, we have added mention of thunderstorms for portions of the area, especially near the coast and southern portions of the forecast area where instability increases with the arrival of the warm sector. Current timing would suggest the first half of Tuesday will be wetter than the second half. The risk for rain will end by/during Tuesday night as low pressure and its associated frontal system moves away from the area, allowing drier air in make inroads. Storm total rainfall is expected to be in the 2 to 3 inch range. A good soaking and given the time of year, we should expect low-lying areas to experience ponding despite several weeks of mainly dry weather. && .LONG TERM /TUESDAY THROUGH SATURDAY/...
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As of 300 AM Sunday...Big story this period will be a true Arctic front progged to cross the Carolinas during Thursday. Ahead of this feature, dry and seasonable weather is expected as a diffuse pressure gradient sets up behind Tuesday`s cold front. Highs Wed/Thu will be in the 60s, but these will crash down with the arctic front late Thursday. 850mb temps are forecast to fall as low as -10C across this area by Friday morning, indicative of the coldest air mass we have seen since last winter. Moist advection ahead of this front is weak, but a few showers cannot be ruled out late Thursday along the front. These will all be of the liquid variety however, no snow showers this time around despite soundings forecasting dendritic saturation, as any snowflakes will sublimate into the very dry air below 700mb. Highs behind this front will drop to 15 degrees below climo Fri/Sat with lows in the 20s by Saturday morning.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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As of 12Z...Expect conditions to gradually deteriorate today as a weak wave of low pressure brings increasing coverage of rainfall along with low cigs and fog to the area. VFR prevails across the area this morning with light northeast winds and scattered light showers as seen from latest radar imagery. A gradual deterioration of conditions is expected this morning into the afternoon hours as rainfall coverage becomes more widespread and lower cigs infiltrate into the area. As a result, a mixture of MVFR/IFR is expected today with winds becoming east-northeasterly, 5 to 10 kts. Into tonight, IFR is expected to prevail with low cigs and areas of fog as rainfall continues well into the morning hours on Monday. A veering of the winds will continue to the southeast and then south towards morning, with sustained winds remaining around 10 kts. Extended Outlook...Periods of IFR likely through Tuesday night due to rainfall and low cigs/reduced visibilities. MVFR developing on Wednesday, with VFR returning on Thursday.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 600 AM Sunday...High pressure centered to our N will be moving offshore tonight. A front is expected to develop to our S and up along the offshore waters of the Carolinas tonight. A wave of low pressure will develop to our S tonight and then move up along the offshore front overnight and into Monday morning. This may bring a brief period of Small Craft Advisory conditions late tonight into Monday morning, especially across the northern waters where the pressure gradient should be tightest. A Small Craft Should Exercise Caution headline is most probable across the southern waters. Wind directions will be quite varied over the course of the next 48 hours or so. Mariners should consider this as well as the deteriorating conditions before venturing out. NE winds today will veer to E and SE tonight and then S and SW overnight in response to a developing front and wave of low pressure. Wind speeds will be 10 to 15 kt this morning, increasing to 15 to 20 kt by/during this eve and up to 20 to 25 kt overnight. Seas will respond, building from 2 to 3 ft this morning to 3 to 4 ft this afternoon and up to 5 to 6 ft late tonight. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 400 AM Sunday...A complex storm system will bring poor marine conditions along with changeable wind directions. One area of low pressure will be departing to the NE during Monday, taking a front further offshore. Then another area of low pressure will move from the Gulf Coast through the mid south and up the Ohio Valley. This low will transfer its energy to developing low pressure off the North Carolina and Virginia coast late Tuesday and Tuesday night. SW winds Monday morning should veer back to the N and NE Monday afternoon and night. Winds should then veer to E and SE overnight Monday and S and SW Tuesday as a warm front reaches the area. As the low lifts away from the area and the front moves offshore, the wind direction will veer to W and then NW Tuesday night. The strongest winds this period should be late Monday night and on Tuesday although winds Monday morning will be nearly equivalent. Seas will be as high as 5 to 6 ft Monday morning and then again later Tuesday into Tuesday night. Small Craft Advisory conditions will be possible Monday morning and then again Tuesday into Tuesday night. Mariners should expect widespread rain and some thunderstorms. The highest risk for thunderstorms will be late Monday night and during Tuesday. LONG TERM /WEDNESDAY THROUGH THURSDAY/... As of 300 AM Sunday...Cold front offshore Wednesday morning will leave winds of 10-15 kts from the NW across the waters. These winds will gradually ease through Wednesday as the gradient relaxes, and begin to back to the west into Thursday morning ahead of an arctic front. Seas Wednesday of 3-5 ft very early will fall to 2-3 ft through the day. A very strong arctic front will then cross the waters on Thursday, causing winds to veer again to the NW and increase to 15-25 kts late, pushing seas back to 2-4 ft, lowest near- shore. Attm forecast conditions are just below any cautionary thresholds, but a SCEC or SCA may be needed late Thursday if winds increase a bit more than current forecasts suggest.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...RJD SHORT TERM...RJD LONG TERM...JDW AVIATION...SGL

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