Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210301 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1001 PM EST Tue Feb 20 2018 .SYNOPSIS... Bermuda high pressure off the coast will continue to push an unseasonably warm and humid airmass across the Carolinas through the weekend. Temperatures should run 20 degrees above normal through Sunday. A cold front will bring a chance of showers Sunday night or Monday, with temperatures cooling back toward normal by Tuesday. && .NEAR TERM /THROUGH WEDNESDAY/... As of 1000 PM Tuesday...Quiet pressure pattern more typical of summer than February remains in place as Bermuda High is anchored offshore and a large ridge extends overhead the Southeast. This will persist overnight with the weak gradient keeping light warm S/SE winds across the area. Full decoupling is not expected, further echoed by LTX VWP now showing 30-35 kts at 1kft, indicating of an environment unlikely to feature calm winds. This is important because the primary forecast challenge tonight is the potential for fog/stratus. The aforementioned 35 kts of wind would likely preclude fog, although latest forecast soundings have the LLJ decreasing to around 20 kts, especially inland. With moist advection from the Atlantic continuing, any decrease in wind could produce fog, especially where cloud cover is not robust. However, latest UPS fog tool produces just some areas of fog, and NBM MOS has visibility dropping only inland. Will continue with patchy fog inland and areas closer to the coast, but would not be surprised if stratus becomes the primary weather feature overnight. Temps will remain warm, dropping only to around 60 degrees. Have removed any mention of showers along the coast as guidance has backed off, and moisture in forecast profiles appears to be too shallow for any mentionable precip. Similar pattern for Wednesday as Bermuda ridge remains dominant. Another very warm day expected with highs approaching record values. Records for Wednesday 2/21 include, ILM 78 in 2014, FLO 81 in 1997, and CRE 76 in 1953. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...Little change in the synoptic pattern for the short term period. Strong mid level ridging will remain entrenched over the Western Atlantic as will surface high pressure. With good low level moisture fog is a good possibility both Thursday and Friday mornings as well as sea fog. No rainfall is expected. Regarding temperatures the NAM is off to an abysmal start with the airmass and will follow the MAV numbers for the most part. Lows will be in the upper 50s to lower 60s both mornings although guidance is just a tad lower for Friday. Thursday`s highs will be in the middle 70s along the coast to near 80 inland. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...An exceptional upper level ridge will remain anchored off the East Coast through this weekend. Model consensus 500 mb heights peak on Wednesday at 593 dam along the coast, nearly 3 standard deviations above normal, and among the highest values ever measured this early in the year. By Friday heights should drop by about 40 meters to 589 dam, a typical mid-August value. Nestled beneath this upper ridge will be the Bermuda high at the surface. This summerlike feature will maintain a south-southwesterly wind across the Carolinas and very warm conditions continuing. For the past several days models have been showing a backdoor front dropping into eastern NC Friday morning. The latest model consensus is the front should remain far enough north to have no impact locally. Record high temperatures could occur on Sunday ahead of a cold front, with highs all weekend ranging from the upper 70s to lower 80s away from the cooler beaches. A strong subsidence inversion on Friday and Saturday should keep the area dry despite what should be plenty of cumulus around. By Sunday an upper trough shearing northward as it moves into the ridge may punch a large enough hole in the inversion to allow some deeper convection to develop. As the cold front moves through the area early Monday, the GFS and Canadian models suggest more showers could develop in a brief period of overrunning behind the front, however the ECMWF is dry. All models show the front should be far enough south by Tuesday for drier weather to develop with temperatures falling much closer to normal. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... As of 00Z...Currently VFR at the terminals. VFR is expected to continue this evening through 06Z, highest confidence inland terminals. Lowest confidence would be at the coastal terminals if sea fog develops more than anticipated. IFR would not be out of the question. 07-09Z fog will develop across the terminals although it may not be as widespread and dense as last night due to cloud cover and a bit higher winds above the low level inversion. IFR is expected to develop at all terminals with periods of LIFR mainly after 09Z. Shortly after sunrise LIFR fog will lift, but broken clouds at 5k could hinder improvement. IFR/MVFR cigs/vsbys will improve to VFR by mid morning at the coastal terminals and by 18Z at the inland terminals. Extended Outlook...VFR. Morning IFR/BR possible through Thur am. Sea fog possible through Thu but confidence is low. && .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 1000 PM Tuesday...Bermuda high pressure will remain the dominant feature overnight maintaining a weak gradient and S/SE winds 10 kts or less. A 3 ft/6sec wave remains predominant in the spectrum, but an increasing easterly swell is forecast to develop overnight as winds remain light. This will keep seas in the 2-3 ft range. Sea fog will again be possible tonight, however wind trajectories more from the SE are not ideal, and water temps did increase at least slightly today. Still, setup appears at least favorable for patchy sea fog and SREF probs are high, so have included patchy sea fog all coastal waters overnight. Relevant portion of previous discussion below: As of 300 PM Tuesday...With high pressure to hold offshore, a steady 9-12 kt S wind is expected, with gustiness to 16 kt in the afternoon, due to the sea breeze. SE waves around 2 feet every 6 seconds will dominate the wave spectrum, with moderate afternoon chop inshore Wed afternoon. No TSTMS, but isolated showers should be expected early Wednesday morning over the 0-20 NM zones. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...Essentially a summer like setup for the coastal waters outside of the sea fog that may develop at any time through the period. With surface high pressure remaining offshore, south winds around ten knots will remain over the waters. Significant seas will remain steady-state as well with 2-3 feet with maybe a few four footers into the mix across the outer waters late. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...High pressure will remain anchored off the East Coast between Cape Fear and Bermuda through the weekend. This should maintain a south-southwesterly wind direction through the period. Models for the past several days have shown a backdoor cold front making its way down into eastern North Carolina on Friday morning. The latest model consensus is that the boundary could make it Cape Lookout Friday morning, but will almost immediately lift back to the north with no impact this far south. As a cold front crosses the southern Appalachians Sunday our pressure gradient will tighten substantially. Relatively gentle winds Friday and Saturday should increase to around 20 knots on Sunday with seas building to a very choppy 5-6 feet. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...MJC/JDW SHORT TERM...SHK LONG TERM...TRA AVIATION...MRR MARINE...

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