Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 270545 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 145 AM EDT Fri Apr 27 2018 .SYNOPSIS... Low pressure will pass across northern North Carolina late tonight bringing a good chance of showers. A pair of cold fronts will push offshore late Friday and Saturday night, bringing unseasonably cool temperatures for Sunday and Monday. Canadian high pressure will push offshore late Monday, and temperatures should warm rapidly Tuesday and Wednesday, with dry weather continuing. && .NEAR TERM /THROUGH TODAY/... As of 900 PM Thursday...Have re-adjusted overnight POPS, Skycover thru 15Z Fri, using the latest 88D trends, HRRR and 18Z Superblend models respectively. All of this to take into account the latest band of mainly showers with embedded thunderstorms associated with the upper low that will affect the ILM CWA late this evening thru the overnight and exiting NE-E of the area by daytime mid-morning. QPF was also updated using the latest WPC guidance. Some tweaking of temps/dewpts using current trends applied to 18Z Superblend model guidance. Previous...................................................... As of 300 PM Thursday...Combination water vapor imagery and regional radar mosaic show a large spin across northern AL into GA representative of both a closed upper low and surface reflection. These will slowly eject to the NE tonight to become over VA on Friday. As this occurs, 500mb diffluence increases as the flow spreads out ahead of the mid-level low, in conjunction with 300mb divergence in the RRQ of an exiting upper jet. At the same time, moist advection peaks in the warm sector ahead of the associated weak cold front, and this combination of moisture and lift suggest precip chances will increase from west to east and this is echoed by all available high res guidance. However, despite mins expected to remain around 60 tonight, diurnal instability will wane significantly and this will limit both coverage and intensity of showers overnight. Have maintained high CHC showers with SCHC tstms since elevated instability is progged to remain 300-500 J/kg which could support a few lightning strikes in any stronger updrafts, aided additionally by a robust 30-40 kt LLJ. Most of this activity will occur after midnight, moving from SW to NE and leaving the area by daybreak on Friday. Another very nice day forecast Friday with a ridge of high pressure building in from the west while yet another weak cold front pushes down from the NW. This front is driven by another spoke of vorticity moving through the longwave eastern CONUS trough, and will exit offshore just beyond this period. Despite temps climbing into the mid 70s once again, do not anticipate convection Friday even with the added lift of the FROPA thanks to very dry air aloft keeping PWATs around 0.75 inches. There should be rather extensive diurnal Cu Friday however as soundings saturate at the LCL beneath a pronounced subsidence inversion. && .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/... As of 300 PM Thursday...Quiet, rain-free, and seasonable weather expected through the short term period. The area will find itself between two cold fronts and under a broad mid level trough. The second cold front will come through Saturday night with far too dry an antecedent airmass to bring any weather. It will mark the turn to slightly cooler weather. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 300 PM Thursday...Model differences are very small through the extended portion of the forecast and have only minor impacts on sensible weather. Confidence is rather high. The tail-end of an upper trough will pass over the Carolinas Sunday as high pressure, centered over the Midwest, builds southeastward toward the area. Chilly air beneath the upper trough (850 mb temps only +2C to +3C Sunday) should give us another unseasonably cool day despite nearly full sunshine: highs only 69-72. The upper trough pushes offshore Monday,but a lobe of that chilly low-level air remains behind with highs not expected to be warm much from Sunday. Nighttime lows early in the week should be quite chilly for this late in the year. Diminishing winds and clear skies Sunday night should allow lows to fall into the low-mid 40s, and it wouldn`t surprise me if a few of the typical cold spots get into the upper 30s. We`re not expecting a freeze, but it`s interesting that the latest freeze on record in Elizabethtown, NC was May 2, 1963, and for Lumberton was May 10, 1980. By Tuesday, the surface high should push offshore with upper level ridging building across the Carolinas. Our high and low temperatures should quickly warm as 850 mb temps rise to +12C Tuesday and +14C Wednesday and Thursday. The orientation of the mid and upper level ridge should prevent any inflow of moisture, and skies should remain very clear through the extended forecast period. Dewpoints dipping into the 30s Sunday and perhaps Monday should moderate through the week, finally reaching 55-60 by Thursday which may develop the first flat cumulus we will have seen all week! && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... As of 06Z...A mid-level wave moving northeast this morning is spreading showers across the area. Thus far ceilings have not dropped into the MVFR category, but this will be possible closer to daybreak. At this time IFR ceilings seem unlikely. The wave will help pull a cold front across the area later this morning, leading to a drying trend during today. Winds from the west-southwest around 20 kt at 4k ft will mix to the surface from late morning through early afternoon. Scattered afternoon clouds are expected but skies will clear out in the evening with widespread VFR expected overnight. Extended outlook...VFR. && .MARINE... NEAR TERM /THROUGH FRIDAY/... As of 900 PM Thursday...Winds likely at their lowest for the night, 5 kt or less. Should see an increasing trend as well as a veering trend during tonight. And by daybreak, winds should be from the SSW-SW at 10 to possibly 15 kt. Significant seas will continue to be governed by the ESE ground swell at 9 second periods. Along with a noteworthy increase in wind chop by morning. Could see vsby briefly reduced to 1 to 3 nm from showers associated with the rotating band of pcpn extending out from the upper low and associated with the cold front. Previous...................................................... As of 300 PM Thursday...Light S/SE winds this eve will veer gradually to the SW as a weak cold front moves across the waters. Wind speeds will generally increase to 10-15 kts tonight, and then slightly higher towards 15-20 kts Friday as the gradient becomes more pinched ahead of another weak cold front which will approach late on Friday. Seas this even will remain 2-3 ft, but a gradual amplification to 3-5 ft is expected as the winds increase to drive a growing 6 sec wind wave, which will combine with the 8-9 sec SE swell. SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 300 PM Thursday...West to southwest flow to dominate through the period as the area spends most of the time in between two cold fronts. The second boundary is slated for passage near the end of the period, and it may bring a sharp turn to the north towards daybreak. Swell energy will be quite minimal, seas will be comprised of a series of fairly diminutive wind waves. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 300 PM Thursday...High pressure will build southeastward behind Saturday night`s cold front, finally reaching the eastern Carolinas Monday afternoon or evening. Northerly winds as strong as 15-20 kt at daybreak Sunday should subside to around 10 kt Sunday afternoon. An upper level disturbance passing just to our north late Sunday night should bump winds back up toward 15 knots, but winds should diminish again as the high pressure area approaches later Monday. Westerly winds behind the high Monday night will turn more southerly along the beaches Tuesday afternoon with the daily seabreeze circulation. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...DCH/JDW SHORT TERM...MBB LONG TERM...TRA AVIATION...III

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