Area Forecast Discussion
Issued by NWS Wilmington, NC

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244 FXUS62 KILM 061121 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 621 AM EST Tue Dec 6 2016 .SYNOPSIS... A strong storm system will bring periods of heavy rainfall through today. Dry and seasonable weather will follow for mid- week ahead of an arctic front which will cross offshore late Thursday. Very cold temperatures will follow for Friday and Saturday. A warming trend will begin Sunday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 620 AM Tuesday...Miller type B storm system to affect the area today. At the sfc, currently a rather strong wedge has developed across the Carolinas with the offshore frontal system now slowly backing to the north. What once was a closed mid- level low over TX last night, has opened up into a s/w mid- level trof now over LA and MS early this morning. Modest Sfc low is basically underneath this upper s/w trof. The dynamics aloft will track to the NE today, staying west and north of the ILM CWA this morning and afternoon. The sfc low underneath is progged to weaken and fill in while off the southeast NC coast a new low will develop early this afternoon on a frontal system that has been back and forth across the coastal and adjacent offshore waters the past couple days. Models bring this frontal system to the coast and just like the previous scenario, the front may temporarily push just inland from the coast by midday thru this afternoon. This will play havoc with temperatures, with 40s and 50s west and north of this front and 60s to around 70 south and east of the coastal front. In addition, the frontal position will become the focus of isolated thunderstorms due to enough instability either sfc based or elevated for convection to key off of. West and north of this front, expect overrunning ie. isentropic lift, light to moderate rains with embedded heavier showers. The low will slowly intensify as it moves northeast along the coastal front this afternoon, reaching off the Outer Banks early this evening. The pcpn will come to an end from southwest to northeast during the mid to late afternoon hours. QPF from this storm system will observe a nice uniform 1 to 1.5 inches of rainfall. Tonight, will see a drying trend with residual low cloudiness possible given various models rh time height displays. Lows will drop back into the 40s. Northwest winds during this evening with diminish enough for possible patchy fog.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 400 AM Tuesday...Looking at benign weather Wednesday thru Thursday afternoon as weak high pressure prevails with basically the FA under a rather low amplitude longwave trof aloft that affects much of the U.S. with Pacific origins. The trof aloft amplifies-some during Thu into Fri enabling a piece of a 1050+ mb Arctic High to break and push toward the area late Thu night. The cold or arctic front ahead of it is progged to push across Thu afternoon and early evening. A thin band of moisture along this front may be enough to squeeze out a few hundredths of an inch of rain. With no tapping of any moisture, this front may end up being a dry passage. The sfc pg tightens after its passage Thu night and combined with excellent CAA as evidenced with a nice packing of the various thickness fields dropping across the FA, especially in the low levels when looking at the 1000-850mb thicknesses. Have basically stayed with a blend of model guidance for max/min temps this period with temps running at or slightly higher than the 30 year normals. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 AM Tuesday...Very cold temperatures greet the extended as an arctic front will be well offshore Friday morning. Highs and lows Fri/Sat will be 10-15 degrees below climo, peaking in the upper 40s both aftns, and dropping into the low 20s by Saturday morning. This will be the coldest air since last winter, and gusty winds Friday will create an even more significant "bite" to the air despite full sunshine. The cold Canadian high pressure responsible for this chill will push offshore quickly by Sunday thanks to broad cyclonic flow aloft, setting up a warming trend back to seasonable values Sunday and into early next week. As this high moves offshore, return flow develops, and a weak coastal trough may develop offshore, advecting warm and moist air into the region for Monday ahead of a rapidly approaching cold front for Monday night. This will allow Monday to warm to above seasonable temps, but at the same time rain chances will increase ahead of the front late on Monday. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... As of 06Z...High confidence in IFR overnight, and persisting through much of this valid period. Low pressure consolidating near Florida will ride up a stalled front just offshore through this period, creating widespread rain, heavy at times. IFR cigs are slowly advancing NE tonight, and will envelop all terminals in the next few hours. Once this occurs, cigs will slowly lower, and LIFR is forecast much of Tuesday. VSBYS will fluctuate considerably during periods of heavier rainfall, but MVFR is forecast to be predominant. Winds will increase from the NE overnight to 10-15 kts, but will then back to the NW as the low pulls away during Tuesday, driving the front offshore. This wind shift will create subtle dry advection, and cigs will gradually improve late Tuesday, with VFR possibly developing inland by the end of this valid period. Extended Outlook...Fog possible Tuesday and Wednesday nights. VFR conditions expected to prevail late week through this weekend. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 620 AM Tuesday...Small Craft Advisory raised for all waters due to effects from this Miller Type B storm system. Modest to strong wedge in place across the Carolinas with the frontal system offshore now returning north and west toward the coasts later this morning. The positioning of this frontal boundary will make wind direction forecasts across the local waters rather difficult. Models indicate this front will temporarily progress onshore but just if and how far inland and how long it meanders across the local waters. For now will go with the scenario of temporarily pushing 5 to possibly 10 miles inland around midday. Low pressure will develop off Cape Fear, on the front by midday and intensify as it tracks northeast away from the local waters this afternoon. This will pull the front as a cold front back off the coast and offshore this afternoon and evening. The sfc pg tightens enough to produce 15 to 25 kt wind speeds, with gusts on the warm side of the front 30+ kt. Significant seas will peak in the 5 to 8 foot range this aftn and mainly dominated by wind driven waves at 4 to 6 second periods. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 415 AM Tuesday...Leftover SCA or SCEC conditions possible Wed morning. Overall, winds and seas will diminish and subside respectively Wed thru Thu as weak high pressure prevails. By late Wed afternoon thru early Thu, winds will have become variable in direction at 10 kt or less. In lieu of forecasting variable, will indicate a predominate direction. A cold or arctic front is progged to push off the coast late Thu afternoon and across the local waters and well offshore during Thu evening. After the CFP, the sfc pg will tighten dramatically and excellent CAA will prevail across the area waters Thu night. Guidance indicates NW winds increasing to 15 to 25 kt with gusts over 30 kt possible as the core of the cold air begins pushing across the local waters during the pre-dawn Fri hours. Significant seas having mellowed to around 2 ft early Thu, will rapidly build Thu night. With a NW wind direction, an offshore trajectory, will indicate a range of seas building. Could see 1 to 3 ft near shore and 3 to 6 ft across the outer waters from 10 to 20 nm out. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 AM Tuesday...SCA conditions possible to greet Friday morning as an arctic front will be positioned well offshore. In the wake of this front early Friday, NW winds of 20-25 kts will push seas up to 4-6 ft, and an SCA may be required. These winds and elevated seas will fall through Friday however as high pressure builds eastward. As this surface high moves eastward and offshore the Mid-Atlantic region during the wknd, winds will weaken to around 10 kts by late Saturday, with a slow veering to the NW. Seas fall quickly late Friday and on Saturday as well, from 3-5 ft Friday aftn to just 1-2 ft at the end of the period.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until noon EST Wednesday for AMZ250-252- 254-256. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...DCH LONG TERM...JDW AVIATION...SGL

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