Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 182235 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 635 PM EDT Wed Oct 18 2017 .SYNOPSIS... Canadian high pressure building into the Mid-Atlantic states will bring several days of cool, dry weather to the Carolinas. Temperatures should begin to warm up this weekend as the high moves off the coast. A cold front will move through on Tuesday with much cooler temperatures to follow. && .NEAR TERM /THROUGH THURSDAY/... As of 300 PM Wednesday...Surface high to the north will become elongated later today into tonight. Southern end of the high will consolidate over eastern TN Thu morning, lingering in the area through the end of the period. Weak shortwave ridge builds over the Southeast tonight in the wake of exiting mid-level trough. Ridging is short lived however as next 5h trough/shortwave moves in from the northwest on Thu. Forecast soundings show a slight increase in moisture around 300 mb ahead of the trough. Although moisture is meager the shortwave could tap into this moisture, producing some high cloud late tonight into Thu morning. Forecast soundings do not show quite as much low level moisture along the coast as this morning, however PVA ahead of the shortwave might be able to generate a small amount of low cloud along the coast. If forecast soundings are to be believed the cloud layer would be little more than a few hundred ft thick. Gradient will start to relax tonight as the high first elongates then breaks off and starts to consolidate farther west. Boundary layer winds will still be sufficient for mixing and significant fog is unlikely. Combination of boundary layer winds, weak warm advection, and possibility of patches of cloud will result in lows 5 to 10 degrees warmer than last night. Thu will be sunny with strong mid-level subsidence keeping a lid on any upward motion. Precipitable water at or below 0.60 inches will keep skies clear in the afternoon. Weak but steady warm advection continues Thu with temps rising into the mid to upper 70s, several degrees above climo. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure centered over the Southern Appalachians Thurs night into Fri will shift slowly east through the period. At the same time the mid to upper ridge shifts east building up from the lower Mississippi Valley up through the southeast following a shortwave which exits off the southeast coast Thurs evening. This will produce strong subsidence with plenty of dry in place through the column. Initially, soundings and moisture profiles show a bit of lingering moisture stuck under subsidence inversion, but a deep northerly flow will reinforce dry air in place with pcp water values dropping from already low values of .6 inches Thurs eve down to less than .4 inches through Fri aftn. Overall, an very dry air mass with no chance of pcp and clear blue skies through Fri. The northerly winds lighten through Fri as gradient relaxes and winds begin to veer to the NE by daybreak Saturday allowing for a slight increase in low level moisture by the very end of the period. Very dry air in place will allow for large diurnal swings in temps. Expect overnight lows to be several degrees cooler Thurs night under ideal radiational cooling conditions and drying column bringing temps between 45 and 50 most places. After a very cool morning, temps will recover to near 80 as ridge builds with h5 height rises and 850 temps increasing up near 14 to 15c. Fri night will see a slight dewpoint recovery but another decent radiational cooling night with overnight low temps between 50 and 55 most places. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Tuesday...A highly amplified H5 pattern will prevail at the onset of the long term period with ridging across the Eastern United States. At the surface, high pressure will also continue to ridge across the forecast area as it departs the Mid-Atlantic Region. As a result, dry weather will continue as temperatures warm a few categories above normal through the weekend into early next week. Eventually the H5 and surface ridges lose control as an upper trough and surface low push eastward. Give this system`s current progression it appears that there will be a good chance of storms during Tuesday with a lowering in temperatures Tuesday night into Wednesday as surface high pressure builds back into the region. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 00Z...Fairly high confidence for VFR through the forecast period. There may be some sunrise very light fog at CRE, otherwise P6SM all other terminals. Some stratocu is possible near the coast, but it should remain scattered. Thursday, continued northeast flow with high pressure dominating. Extended Outlook...Tempo MVFR/showers Mon/Tues. Otherwise VFR. && .MARINE...
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NEAR TERM /THROUGH THURSDAY/... As of 600 PM Wednesday...Given ongoing Small Craft Advisory conditions, extended the advisory til 6 am Thu. Across AMZ254, a Small Craft Should Exercise Caution headline was extended til 6 am thu. Elongated surface high north-northeast of the waters this afternoon into tonight will fragment with a new center consolidating over eastern TN. This will maintain northeast flow through the period, although the gradient will weaken later today through Thu. Speeds around 20 kt this afternoon will drop to 15 to 20 kt overnight and 10 to 15 kt on Thu. Seas across the outer waters will persist near 6 ft. Seas will be trending down to 2 to 4 ft Thu. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure over the southern Appalachians will shift slowly east through the period with a weakening gradient flow. This will help veer the winds from N to NE by daybreak Saturday. Seas will subside from close to 4 to 5 ft off shore Thurs eve down to 2 to 4 ft through the remainder of the period. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...High pressure is expected to shift farther off the Mid-Atlantic coast Saturday and Sunday allowing the flow to veer onshore. Southeast flow will further turn becoming southerly during Monday as an area of low pressure treks from the Gulf Coast to the western Carolinas. Small Craft Advisory conditions may be reached late Monday in the strengthening southerly flow. Seas will be 3-4 ft through much of the period given the duration and size of the onshore fetch around the periphery of the aforementioned high pressure.
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&& .TIDES/COASTAL FLOODING... As of 10 AM Wednesday...Astronomical tides will peak with the new moon on Thursday. High tides and strong northeast winds may combine to push tides above minor coastal flooding thresholds at Wrightsville Beach and the lower Cape Fear River to include downtown Wilmington. Advisories may be needed around the time of high tide through Friday. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...High Rip Current Risk from Thursday morning through Thursday evening for SCZ054-056. NC...High Rip Current Risk from Thursday morning through Thursday evening for NCZ106-108-110. MARINE...Small Craft Advisory until 6 AM EDT Thursday for AMZ250-252- 256.
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&& $$ NEAR TERM...RJD/III SHORT TERM...RGZ LONG TERM...SRP AVIATION...DL TIDES/COASTAL FLOODING...III

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