Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 081416 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 916 AM EST Fri Dec 8 2017 .SYNOPSIS... Periods of cold rain will continue through Saturday morning, before drying begins to settle in Saturday afternoon and night. Sunshine will return Sunday, but temperatures will remain below normal through Monday. Another strong cold front Tuesday, will bring more cold air to the Carolinas into the upcoming week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 915 AM Friday...Based on the latest model data and progression of events anticipate no changes to the forecast thinking as outlined below. 100 POPs still looks good for the whole area as a cold rain/drizzle event continues through the day/nighttime hours. There will be periods of relief here and there, but in all cases the rain will make a return appearance. Previous discussion from early this morning follows: The pattern remains relatively unchanged from the past few days, but even cooler and wetter conditions are forecast today. WV imagery across the CONUS this morning shows the deep longwave trough amplifying across the eastern CONUS, with weak ridging downstream of this feature identified by a moisture tap from the tropical Pacific Ocean, across Texas, and into the Carolinas. At the surface, broad high pressure across the MS VLY extends to the East Coast with a stalled cold front lingering offshore. These features will all act in concert to produce an unsettled and anomalously cold day across the eastern Carolinas. Surface high pressure centered to the west will maintain northerly surface winds today, while flow above 850mb will persist from the SW downstream of the aforementioned trough. This is driving continued isentropic lift, maximizing near the 300K surface, and guidance suggests this will only increase through today and especially tonight. This increase in lift is due in part to increasing speeds aloft ahead of a sharp shortwave currently digging through TX which will approach from the west. This trough will also help to spawn weak cyclogenesis along the stalled boundary offshore, which will move up the coast tonight. While this occurs, the eastern Carolinas will enter the RRQ of a jet swinging into New England, and while much of the Fgen forcing will be displaced west of the area, warming 850mb temps ahead of the low will drive subtly increasing temperature gradients and weak Fgen between 850 and 750 mb to further enhance lift. This all occurs in a fully saturated column with PWATs near 1.5 inches, and while no part of the ILM CWA will experience any wintry precip, light rain all day transitioning to moderate or at times heavy rain tonight, will produce widespread 1-2 inches of rainfall, and have categorical POP through the period. The widespread clouds, showers, and cool surface flow will keep temps even cooler than what occurred on Thursday, with highs likely struggling to 40-43 most places, some mid 40s possible well south. A very narrow diurnal range is also expected as mins tonight fall only to 37-42, warmest again south. Despite the cool temps tonight, and the potential for accumulating snow well inland in the Carolinas, a clear warm nose will preclude anything other than rain across our area for this system.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 350 AM Friday...Main headline this period, `Cold and Wet Then Cold and Dry`, as the weekend offers a return to sunshine if not by late Saturday then fully on Sunday. Water vapor loops reveal very nicely the impulse that will bring this dramatic weekend transition, presently diving south out of Nunavut into northern Manitoba. At the surface, deepening low pressure will be pulling off the Outer Banks daybreak Saturday, allowing cold high pressure to build in late Saturday and Sunday. Minimum temperatures of upper 20s and low 30s will greet daybreak on Sunday, and a few degrees colder early Monday, as winds ease up. Despite two completely different sensible weather days Saturday and Sunday, maximums temperatures will be similar, upper 40s. Winds will remain primarily offshore this period. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 3 PM Thursday...Extended forecast offers few changes this afternoon. A deep mid level trough will be in place across the eastern U.S. for the foreseeable future. This leads to a mostly dry and cold forecast. The only pops in the forecast have been with a potent shortwave diving down in the mid level flow late Tuesday into Wednesday. Guidance has backed off light dynamically induced precipitation which was a stretch to begin with as has the official forecast. As for temperatures, not a whole lot of change here either. Temperatures will be well below normal throughout, with the coldest mornings (widespread mid 20s) both on Monday and Thursday mornings. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... As of 12Z...A cold front stalled west of the terminals will dissipate today as a bubble of high pressure expands locally. This will cause a lowering inversion. With widespread rainfall continuing cigs will eventually lower at all terminals. Thus, high confidence of reduced flight conditions this TAF valid period with widespread light to moderate rain with embedded heavy showers. IFR cigs with MVFR/tempo IFR vsbys will develop south to north across the terminals through 16Z. The best chance of LIFR would be 400 foot cigs KMYR- KFLO this morning, but confidence is low. Once cigs lower expect cigs to persist through the end of the valid period. Rain could end around 00Z, but a wave of low pressure is expected to develop along a stalled boundary offshore. This will cause increasing northerly winds reaching 10-15 kts. This cool wind will lower the inversion even further, and with widespread rainfall heavy at times re-developing tonight, LIFR cigs are possible. Extended Outlook...MVFR Sat/showers ending. VFR Sun through Tue. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 915 AM Friday...Hazardous boating conditions continue across the waters this morning with northerly winds gusting close to 30 kts in places and seas of 3 to 6 ft. Seas near shore are closer to 2 ft due to offshore fetch, but ongoing cold rain and otherwise bumpy conditions will make for an unpleasant day at sea. Forecast good to go with no major changes anticipated. Small Craft Advisory continues as before for all waters. Previous discussion from early this morning follows: Stalled boundary just offshore will serve as the focus for developing wave of low pressure tonight, while high pressure continues to push east towards the waters from the MS VLY. This drives slowly increasing N to NE winds, reaching 20-25 kts at times. This has prompted the ongoing SCA, and while seas are not forecast to reach 4-6 ft until late this aftn, the hazard will remain unchanged and is in effect now for all waters. In addition to the seas becoming amplified, the spectrum will remain confused as an 11-12 sec E/SE swell persists, albeit in a weakening state, while the northerly wind chop grows through the period, becoming dominant this evening and tonight. The waters will also experience periods of moderate to heavy rainfall as well, especially tonight, causing reduced visibility in addition to the poor wind/wave conditions. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 350 AM Friday...A difficult marine period this weekend as deepening low pressure pulls offshore of the Outer Banks and and cold, strong high pressure builds from the west. The cold air surge will likely produce gusts of 25 KT and higher much of this period on the 0-20 NM waters. Additionally, rain will also reduce visibility to below 1 NM at times through Saturday before drying sets in Saturday night. Latest wave guidance continues to forecast 6-7 foot seas offshore Saturday before a subsiding trend Sunday. As a result, a Small Craft Advisory will be needed much of this weekend, perhaps dropping sometime on Sunday. Steep and short period N-NE waves will dominate the spectrum with an offshore chop, and an underlying 2 foot SSE swell every 8-9 seconds. Isolated TSTMS possible Saturday offshore, especially in the morning. LONG TERM /MONDAY THROUGH TUESDAY/... As of 300 PM Thursday...Monday into early Tuesday westerly winds of 10-15 knots. Another surge of cold air arrives later Tuesday with winds increasing once again to 15-20 knots. Seas should stay below flag criteria with the possible exception of late Tuesday when some six footers may develop across the outer waters.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until noon EST Sunday for AMZ254-256. Small Craft Advisory until 6 PM EST Sunday for AMZ250-252. && $$ SYNOPSIS...99 NEAR TERM...REK/JDW SHORT TERM...MJC LONG TERM...SHK AVIATION...MRR MARINE...MJC/REK/JDW/SHK

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