Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 091706 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1205 PM EST Sat Dec 9 2017 .SYNOPSIS... Low pressure moving away from the area will maintain cloudy and cold conditions today. Sunshine returns for Sunday, but with continued chilly air as Canadian high pressure builds eastward. Another strong cold front will move across the area Tuesday night with Arctic air returning Wednesday. Temperatures will gradually moderate late next week with another cold front possibly moving across the area for the start of next weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1140 AM Saturday...11 AM temperatures are in the upper 30s to around 40, but should not rise more than another couple of degrees in most spots as cold air continues to drain down off the Piedmont region of the Carolinas. Latest HRRR/RAP models continue to show a small potential of measurable rain during the mid afternoon hours near and along the I-95 corridor as the strong upper disturbance moves eastward. The radar depiction of snow associated with this feature is weakening with time, concurrent with model-analyzed drying within the -12C to -18C dendritic growth zone. Areas of drizzle will remain in the forecast for the next few hours with area ASOS/AWOS visibilities implying drizzle is occurring many areas. Discussion from 900 AM follows... Low pressure now east of Hatteras is streaking northeastward away from the North Carolina coast. Dense low clouds will continue throughout the day even as we lose our mid-level moisture. Model soundings show at least 7500 feet of moisture persisting through sunset which should be sufficient for areas of drizzle. Some patchy light rain could even redevelop inland as a strong upper trough approaches from the west this afternoon. There is currently a large area of light to moderate snow falling across the mountains in association with this feature, but mid-level moisture will be thinning with time as the trough moves eastward. Temperatures aren`t going to budge much today. Upstream air temps across the Piedmont are generally in the lower to mid 30s. With virtually no insolation and only a couple degrees of downslope/compressional warming I have adjusted forecast highs slightly downward into the 40-44 range for most areas. For Elizabethtown, Lumberton and Bennettsville highs may not even reach 40 this afternoon. Note: The Florence ASOS reported snow for a few hours before sunrise. This was not snow as there was 10000 feet of above- freezing air in the clouds. The ASOS sensors saw drizzle and cold enough temperatures and made the assumption it was snow. This will be removed for the daily climate report. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...850 mb temps will be warming through the period, from -4 to -7C at the start of the period to +7 to +9C Mon night. Precipitable water values will generally range from a quarter to around a third of an inch and we are expecting sunshine in a deep westerly flow. This sunshine will serve not only to begin to dry us out, but also to moderate the very cold airmass. Highs on Sun will still be well below normal, mainly mid 40s. Highs on Mon will still be below normal, but 10 degrees warmer than on Sun. Light to calm wind will allow for radiational cooling which will drop temps into the mid and upper 20s Sun night with lower 30s at the immediate coast. Low-level SW flow and a slightly tighter pressure gradient Mon night should keep lows from falling below the mid and upper 30s with lower 40s at the coast. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 PM Friday...Period will be dominated by 5h longwave troughing and temperatures below to well below normal. Precip chances will be limited by a pattern where deep west to northwest flow is dominant. Only chances will be with one of several stronger shortwaves dropping into the trough and helping to reinforce the cold air. Looks like there will be three waves with potential to produce at least limited rainfall. The first arrives late Tue, the second late Thu, and the final one arrives Fri night. Forecast soundings keep precipitable water values below half an inch through the period with numbers dropping as low as a tenth of an inch on Wed. Measurable precip seems highly unlikely given the depth and abundance of dry air, but a brief period of increased cloud cover is likely. Temperatures will be below climo to start the period, although only just and will be trending up from Mon into Tue. However, the first shortwave will sweep a strong cold front across the region. The front will be followed by another shot of Arctic air and temperatures will tumble. Highs during the middle of next week will be in the 40s with lows in the 20s. Low level return flow is quick to develop on Thu and temperatures will moderate a little for the end of the period. Temperatures will still end up below climo to end the period, but only by a few degrees. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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As of 17Z...IFR cigs are expected to persist well into the afternoon hours before transitioning to VFR between 00Z and 04Z as westerly winds scour out low clouds and moisture. VFR then expected for the remainder of the TAF period. N to NW winds of 5 to 10 KT today will become W to NW tonight. Extended Outlook...VFR through Thursday.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 900 AM Saturday...Low pressure just east of Cape Hatteras is streaking northeastward into the open Atlantic Ocean. A burst of strong northwesterly winds behind this low gusted up to 30 knots at the Frying Pan Shoals buoy, but it appears these winds are beginning to die away with the latest observations. Breezy and very chilly northwest winds will continue through the day, increasing again this evening as a strong upper level trough moves overhead. This may herald a 3-6 hour period of west winds as strong as 25-30 knots tonight. Rainfall has nearly wrapped up, although some drizzle will continue throughout the day. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...Winds will be diminishing during this period and we should be able to drop the Small Craft Advisory and replace it with a Small Craft Should Exercise Caution headline by/during Sun morning. Wind speeds will lower from 15 to 25 kt near the start of the period to 10 to 15 kt by Sun afternoon. Wind speeds will then remain in this range until Mon night when they will increase to around 20 kt. The direction will back from NW Sun to W Sun night and Mon and then WSW Mon night. Seas will be subsiding from 4 and 5 ft Sun morning to 3 and 4 ft Sun afternoon. Seas of 2 to 3 ft Sun night and Mon will build to 4 and 5 ft Mon night. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Winds will become southwest and increase Tue as a strong cold front approaches from the west. Wind speeds may require a Small Craft Exercise Caution headline by midday Tue, but it seems quite likely that seas will reach 6 ft before winds hit 25 kt. Confidence in a Small Craft Advisory headline is on the high side. Strong offshore flow develops in the wake of the front as cold advection kicks in. Offshore flow of 20 to 25 kt is possible while the offshore component works to drop seas. Offshore flow continues through Wednesday with speeds gradually decreasing as strong cold advection shuts off. && .TIDES/COASTAL FLOODING... As of 1100 AM Saturday...A tremendous positive tidal anomaly has developed along the beaches north of Cape Fear over the past 24 hours, averaging 1.5 to nearly 2.0 feet at the Wrightsville Beach tide gauge! Even though astronomical tides are not particularly impressive, this anomaly should allow today`s noon high tide to create coastal flood thresholds along the beaches north of Cape Fear. An advisory has been issued through 1 PM. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...Coastal Flood Advisory until 1 PM EST this afternoon for NCZ106-108. MARINE...Small Craft Advisory until noon EST Sunday for AMZ250-252- 254-256.
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&& $$ SYNOPSIS...TRA NEAR TERM...TRA SHORT TERM...RJD LONG TERM...III AVIATION...31 TIDES/COASTAL FLOODING...TRA

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