Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211900 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 300 PM EDT Wed Mar 21 2018 .SYNOPSIS... Low pressure will pull away from the East Coast tonight as Canadian high pressure builds in from the west. Well-below normal temperatures will continue for the next several days, with frost or even freezing temperatures possible at night. Low pressure will move across the Carolinas Saturday night and early Sunday bringing rain, followed by below normal temperatures and dry weather again early next week. && .NEAR TERM /THROUGH THURSDAY/... As of 300 PM WEDNESDAY...Broad cyclonic flow continues across the region this afternoon from deep low pressure moving up the east coast. Some residual light rain and drizzle remains but the trend is for decreasing coverage. By 0000 UTC only the extreme northeast zones should be seeing any activity. Skies should clear out later tonight from south to north. For overnight lows, guidance is fairly consistent with the NAM/MET numbers once again cooler. We continue to lean toward the slightly warmer MAV numbers which show mostly middle 30s. An expected mixed boundary layer should keep readings in check as well. For Thursday mostly sunny and cold with highs in the middle to upper 50s. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM WEDNESDAY...`Dry and Cold` captures the essence of this period, as PWAT values take a dip to around a quarter of an inch Thursday night and early Friday, with near freezing conditions likely for pockets of SE NC before daybreak Friday, and again for interior SE NC early on Saturday, as the growing season is underway. The limited geographical extent of forecast Min-Ts below 32 either morning, is not expansive enough to raise a `Freeze Watch`, and confidence level of a widespread freeze across any particular county right now, is low. The deep and arid NW flow will impart 10-15 mph surface winds Friday, and plentiful sunshine minutes will rack up Friday. Clear/chilly into Friday evening, possibly 10-12 kft clouds early Saturday impinging inland zones from the west to east. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM WEDNESDAY...A warm front lying across South Carolina on Saturday should lift northward during the day as surface low pressure moves eastward across Tennessee. This low is being supported aloft by a shortwave rotating southeastward around the longwave trough off the East Coast. Model differences with this shortwave are generally minor, however the ECMWF is stronger and a little slower with the shortwave than the GFS. Although both models show rain developing Saturday night into Sunday, this probably explains the better developed low-level thermal/moisture advection fields shown on the ECMWF. PoPs have been increased to 50-60 percent for this period, and it`s looking more and more likely we`ll see a widespread 0.20 to 0.30 inch rainfall event. The ECMWF shows a stable airmass through the event, while the GFS shows only a tiny region of elevated instability Saturday night, too meager for a significant thunder threat. The surface low should jump the Carolinas Saturday night, redeveloping just off the coast where low-level baroclinicity is significantly greater than inland. Cold northerly winds should punch southward behind the developing low. Sunday`s high temperature forecast is actually quite difficult since it`s tough to know exactly where the front will be located at 7 AM, and temperatures could actually fall throughout the day in the strong low-level cold advection. A model blend gives mid to upper 50s across SE North Carolina and upper 50s to around 60 in South Carolina, however that could easily be 10 degrees lower if faster cold frontal movement (like shown on the GFS) occurs. Light rain should taper off during the afternoon with skies partially clearing Sunday night as moisture thins from north to south. Dry and unseasonably chilly weather is expected Monday and Tuesday as Canadian high pressure builds down the East Coast. Our 850 mb temps should hover in the +1C to +3C range both days, between the 10th and 20th percentile for late March. Of agricultural concern is a possible frost or even freeze event coming up Monday night as surface winds drop off with the incoming high. On Wednesday the surface high should finally move off the East Coast. A westerly component to the low-level flow will finally bring warm advection and temperatures should pop back to seasonal norms. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 18Z...This afternoon VFR at the southern terminals. VFR developing at KLBT and KILM within the next 1-2 hours. Winds will be westerly gusting to 20-25 kt. Gusts subside 23-00Z and skies will become scattered by midnight Z. Thursday VFR/scattered skies with gusty northwest winds to around 20 kt by mid-morning. Extended outlook...VFR. MVFR/IFR/Rain Saturday night and Sunday. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 300 PM WEDNESDAY...Winds and seas remain elevated this afternoon as cold air advection under a deep east coast cyclonic flow continues. Sustained winds are a good 20-25 knots and in some cases higher and will only see a very gradual decline through the overnight hours to the lower end of the range. By Thursday evening winds will be down to a 15-20 knot range. Significant seas will be 5-8 feet overnight and fall to 2-4 feet by tomorrow evening. The small craft advisory for all waters goes through 6 PM Thursday but the latest high resolution wave guidance shows seas falling a little faster and subsequent shifts may be able to end the advisory a little quicker. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM WEDNESDAY...NW gusts to 25 KT offshore may be ongoing Thursday evening, but the overall prospects, will trend to easing wind and subsiding seas, but only a bit, yet enough to put away advisory flags heading into Friday. NW winds 10-15 kt Friday and Friday night, will occasionally gusts to 20 kt. No obstructions to visibility this period, and no TSTMS or precipitation. Seas will be mainly comprised of NW wind-seas, implying fairly nice marine conditions inshore, noticeably bumpier outer waters. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM WEDNESDAY...A warm front will lift north across the area Saturday afternoon as low pressure moves eastward across Tennessee. As often occurs, the low should jump the mountains and redevelop just off our coast, dragging the front southward again as a cold front Sunday morning. Mariners should expect a sudden increase in north-northeasterly winds as the front dives through, with Small Craft Advisory conditions developing and likely persisting through Monday as strong Canadian high pressure builds southward. Our forecast shows 20-25 kt winds Sunday afternoon through Monday, but it`s possible there will be some 30+ knot gusts thrown in there during the period of most rapid thermal advection Sunday afternoon or evening. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until 6 PM EDT Thursday for AMZ250-252- 254-256. && $$ SYNOPSIS...TRA NEAR TERM...SHK SHORT TERM...MJC LONG TERM...TRA AVIATION...MRR is the U.S. government's official web portal to all federal, state and local government web resources and services.