Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 212313 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 613 PM EST Mon Jan 21 2019 .SYNOPSIS... Chilly and dry high pressure will slowly modify as it shifts off the coast late Tuesday into Wednesday. Warming will take place through mid week with increasing chance of showers ahead of next cold front Wednesday night into Thursday. Cool and dry High pressure will build in Friday through the weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 630 PM Monday...The Arctic High will remain well to our north tonight, dropping as far south as central Virginia by daybreak. While clear skies and bone-dry air will promote efficient radiational cooling, boundary layer winds are not going to become calm. In fact, most models actually show an increase in winds just above the surface after midnight as the low-level flow veers more northeasterly. Raw model output shows lows in the mid to upper 20s tonight. This seems unreasonably warm given that we`re already near freezing here at 6 pm. GFS, NAM, and ECWMF MOS guidance shows lows in the 15-19 range overnight, and that seems unreasonably cold given still-warm soils and inferred boundary layer turbulence from the 15 knot wind expected to persist just 500 feet above ground level. The National Blend Guidance set shows generally lower 20s across the area -- a couple degrees cooler near Lumberton and Burgaw, and a bit warmer along the SC beaches. This seems to be a good compromise and is the basis for our forecast this evening. Assuming our forecast lows work out, tonight will have the coldest temperatures since the middle of of January 2018. -TRA Discussion from 300 PM follows... High pressure sliding into the Carolinas has brought strong northwest winds and cold air advection to the region today. Temperatures across the region as of the early afternoon were between the mid to upper 30s, which was about 20 degrees colder than this time yesterday. Winds were gusting between 15 and 20 mph, which was a bit lower than earlier windspeeds this morning. Skies across the forecast area were clear under the dry Canadian air mass. Winds will continue to decrease tonight as the center of high pressure moves into the coastal plain, with lows in the upper teens to lower 20s, which is about 10 to 15 degrees below average low temperatures for this time of year. As high pressure shifts eastward offshore Tuesday, surface winds will shift to the east and tap into some warmer air and increase highs in to the low to mid 40s, which is still about 10 to 15 degrees below normal high temperatures for January. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...Transition from cold to warm through this period. High pressure reaching down the eastern seaboard will be centered just to our north at the start of the period, before shifting further off the Outer Banks on Wednesday. This will allow winds to shift around, becoming on shore Tues night and then southerly on Wed. The very light flow and lack of clouds Tues eve should produce decent radiational cooling allowing temps to drop out, but as the night progresses, isentropic lift will increase slightly as coastal trough/warm front pushes on shore. Overnight lows should occur Tues night before midnight, down into the 30s most places. Expect some low clouds and light pcp possible into Wed morning with temps warming into the 40s fairly rapidly. On Wednesday, deep S to SW flow will produce plenty of WAA with temps increasing a good 30 degrees into the mid 60s. By late Wed into Wed night, increasing southerly flow may produce some sea fog before showers with moderate to heavy rain spread across the area from west to east ahead of a cold front. the heaviest rain should reach the I-95 corridor by Thurs morning. Temps will remain well above normal Wed night, between 55 and 60 under cloudy skies and increasing showers. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 PM Monday...Period will start out wet, as cold front progresses east across the area moving rapidly off shore by Thurs eve. Increasing LLJ combined with deep moisture and deep mid to upper trough will provide some decent support for showers with moderate to heavy rain and gusty winds. Although, overall instability is lacking, temps and dewpoints will reach into the 60s. Drying through the mid levels will occur from west to east through Thurs aftn with skies clearing and temps dropping through Thurs night. Cold and dry high pressure will build in with temps on the cool side Friday through the weekend. Next storm system should begin to affect the area Sun night into Mon, although there is quite a spread in the guidance solutions with this system. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 00Z...Clear skies and VFR throughout the forecast period. Northerly winds calming to around 5 knots at the coast and a little lighter inland this evening. Very cold and very dry; no fog with dew points near 0. Winds stay light and become northeasterly on Tuesday as an area of high pressure moves southeastward and centers itself over Delmarva by Tuesday evening. No aviation concerns other than a few high clouds near the end of the period. Extended Outlook...VFR becoming MVFR Wednesday morning as a warm front approaches continuing into Thursday. VFR Friday into Saturday. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 630 PM Sunday...Winds reported by area buoys and piers were a couple knots stronger across the board than forecast. A blend of the latest GFS, NAM, and ARW-NMM model were used for forecast wind speeds overnight, which may reach 15-20 knots late as the arctic high drops into northern Virginia and our wind directions veer northeasterly. This should also lead to an increase in seas, approaching 4 feet after midnight in a short 5-second wind chop. Discussion from 300 PM follows... Conditions are improving offshore as winds and significant wave heights decrease. Some locations may see elevated winds and waves into this evening, especially further offshore beyond 20 NM. As high pressure continues to move offshore tomorrow, winds will shift from offshore to more of an onshore direction Tuesday. Otherwise, expect waves 2 to 4 feet Tuesday at 5 to 6 second periods with northeast winds 10 to 15 kts. Astronomical low tides and offshore winds will result in abnormally low-water levels overnight along the coastline. Boaters should use extra caution if navigating inlets tonight watching for sand bars and increased shoaling potential. Water levels should rise after 2 AM Tuesday. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...High pressure north of the waters will shift further off the Outer Banks Tues night into Wed. This will shift winds around, becoming on shore Tues night as a coastal trough/warm front pushes on shore. Seas will 2 to 4 ft until Wed morning. Winds will increase out of the south through Wed into Wed night as a cold front approaches from the west. This increasing southerly push will drive seas up through Wed, reaching above SCA thresholds by Wed eve. Seas should peak right ahead of the cold front early Thurs morning, possibly reaching up to 8 to 10 ft. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 300 PM Monday...Winds and seas will be peaking Thurs morning up to 20 to 30 kts out of the south, before veering to the west behind cold front by Thurs aftn. Seas up to 8 to 10 ft Thurs morning will begin to diminish through late Thurs and should drop below advisory thresholds by Fri morning in diminishing off shore flow. Winds will become northerly on Fri as high pressure builds in. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...TRA/MCK SHORT TERM...RGZ LONG TERM...RGZ AVIATION...21

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