Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 190007 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 707 PM EST Sun Feb 18 2018 .SYNOPSIS... A front stalled south of the area overnight will return north as a warm front Monday. Bermuda High pressure will bring temperatures well above normal beginning Monday with possible record warmth for the middle of the week. A cold front will approach from the north on Friday, but may end up stalled before reaching the area. The Bermuda High will expand over the region for the weekend. A cold front will approach from the northwest Sunday night. && .NEAR TERM /THROUGH MONDAY/... As of 3 PM Sunday...A front stalled just south of Savannah, GA will begin to lift northward late tonight as high pressure over the Delmarva Peninsula moves offshore. Mid-level cloudiness is already thickening south of Florence and Myrtle Beach, and a few showers have even showed up on radar recently. This little pulse of lift should dissipate over the next couple of hours, but isentropic upglide over the frontal surface should redevelop by late evening with more scattered showers expected overnight into Monday. PoPs around 30 percent are forecast with QPF only around a few hundredths of an inch expected. The warm front should slowly move northward tomorrow, but models are not unified with their depiction of how quickly the front moves farther north through North Carolina. The GFS and ECMWF push it through Lumberton and Florence during the afternoon while the NAM and the ARW/NMM variants of the WRF aren`t quite as fast. Given a deep bank of low clouds expected ahead of the front and relatively weak southerly winds to drive the front northward, I`ve lowered high temperature forecasts northwest of I-95 for Monday mainly into the 60s, with 70s across most of the remainder of the area inland from the beaches. If the NAM is completely correct, that gradient in temperatures Monday afternoon could be even more extreme with temps hung in the mid 50s near and west of I-95! One more possible forecast issue to keep in mind is sea fog. Sea surface temperatures are coldest in the shallow water near the Grand Strand, and this is where high dewpoints behind the warm front will have the best potential to create sea fog during the day Monday. Some of this fog could slip onshore at times mainly affecting areas within a mile of the beaches. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 3 PM Sunday...Bermuda surface high pressure and 595dam ridge at 500mb both off the coast through the period. This will catapult temperatures well above climatology with nighttime lows higher than seasonable norms as well as offer near record afternoon warmth. Something that will also be out of the norm will be the level of humidity in the air as dewpoints surge into the low to maybe mid 60s. While sea fog (see marine section) is not a certainty quite the different situation over land however where saturation and fog look quite attainable. This idea very supported by SREF probs both nights. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 3 PM Sunday...Main theme for the extended will be strong surface and mid-level ridging sitting off the coast. Strong mid- level subsidence and deep southerly flow will contribute to an extended period of temperatures well above climo. While there is high confidence in a warm and mostly dry period, there area a few times within the forecast with much lower confidence. The first concerns a backdoor cold front Thu night into Fri. Previous solutions had this feature moving into the area late Thu night and lingering for much of Fri before returning north as a warm front. However, recent guidance has shifted away from this scenario, the both the GFS and ECMWF being quicker to move the 1040 high across the Great Lakes and into the Northeast. Given the propensity for ridging to hold on longer than the guidance expects, am leaning in favor of a warmer, drier solution Thu night and Fri. Other area of uncertainty concerns potential cold front late in the period. GFS/ECMWF currently bring this feature into the area later Sun but not confident it will arrive that early, which would contribute to warmer temps Sun night. Temperatures, as previously mentioned, will be significantly above normal for much if not all of the period. Medium range guidance continues to depict heights at level not seen before during the last week of Feb. At the same time 850 temps will flirt with 15C. Away from the coast highs will run in the upper 70s to lower 80s through the period with the possible exception of Fri. Unfortunately, closer to the coast the combination of water temps in the mid 50s and onshore flow will keep highs much cooler. The large temperature gradient will also create rather windy conditions on the cool side of what should be a strong sea breeze. Lows will range from upper 50s to mid 60s through the period. Average daily temperatures could run 20-25 degrees above normal each day. Another way of putting it would be that the departure from normal next week will be equal to what the area experience during the first week of January 2018, just in the opposite direction. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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As of 00Z...A warm front will lift towards the area tonight and then across the terminals during Monday. Increasing moisture associated with this feature will bring isolated showers and gradually lowering cigs. VFR presently is expected to become MVFR during the next several hours, followed by IFR late during the overnight into Monday morning. Have included VCSH and IFR at all terminals, but the cigs will be the more significant impact to aviation. The present gusty east winds will gradually weaken overnight and remain E/NE before becoming S/SE Monday as the front lifts northward. There is still some uncertainty into the timing of actual FROPA, so cigs may linger at IFR longer than current forecast suggests. However, have optimistically raised cigs to MVFR inland, VFR at the coast, by the end of this valid period. Some light showers are possible during Monday as well, but coverage is expected to be too isolated for even a VCSH mention attm. Extended Outlook...VFR with periods of MVFR through Fri. Good chance of extended periods of IFR/LIFR in sea fog coastal terminals Tues-Fri.
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&& .MARINE... NEAR TERM /THROUGH MONDAY/... As of 3 PM Sunday...A cold front pushed south across the area early this morning and has stalled out just south of Savannah. 1031 mb high pressure over the Delmarva Peninsula will move off the Mid- Atlantic coast overnight, with return flow behind the high gradually starting to lift the front back to the north on Monday. Northeasterly winds behind the front will continue to increase in speed through this evening, and we`re issuing a Small Craft Advisory for the NC waters through midnight for winds up to 25 kt and 6 foot seas inside 20 miles of shore. An `exercise caution` headline will continue for the SC waters where conditions should not become quite as severe. Winds and waves should diminish overnight. On Monday the front, now a warm front, will lift northward across the area during the morning hours. Winds shifting to the south will bring much more moisture across the area, and this will create the potential for sea fog mainly over the South Carolina coastal waters. SREF probabilities for visibility less than 1 mile are over 70 percent just off Murrells Inlet Monday afternoon, and it`s possible we`ll need a marine Dense Fog Advisory. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 3 PM Sunday...Quite the summer-like pattern in store for the short term. High pressure well off the coast to bring a light southerly wind (whereas a closer to shore Bermuda high usually brings SW winds). Wave spectral bulletins show that light seas will generally be in the wind-wave period, with a weak swell component not really materializing locally until later in the week. A point of uncertainty will be the development of sea fog given these dewpoints. We`ve already had a few setups this season and some have panned out while other have not. The short term seems more like the latter where dewpoints are not quite elevated sufficiently and the airmass grows so warm that saturation becomes difficult.The SREF probabilities disagree to an extent, especially over SC waters where SSTs are a tad cooler. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 3 PM Sunday...Bermuda High will extend across the waters through the period, maintaining south to southwest flow with speeds 10 kt or less. Weak backdoor cold front will try to drop in from the north early Fri, but it is starting to look like the front will stall before reaching the area. Flow may become a little more easterly during Fri, depending where the front ends up, but speeds would drop closer to 5 kt. Seas will run 2 to 3 ft through the period with occasional 4 ft possible near Frying Pan Shoals later Thu and Thu night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until midnight EST tonight for AMZ250-252. && $$ SYNOPSIS... NEAR TERM...TRA SHORT TERM...MBB LONG TERM...III AVIATION...JDW MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.