Area Forecast Discussion
Issued by NWS Wilmington, NC

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519 FXUS62 KILM 261722 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 121 PM EDT Wed Apr 26 2017 .SYNOPSIS... High pressure offshore will bring a warming and drying trend into the weekend. A weakening and lingering cold front will bring a chance of showers or a thunderstorm late Thursday and Friday, with temperatures remaining warm. A stronger frontal system will bring a chance of rain early next week. Inland areas may see temperatures of 90 degrees or higher Friday and Saturday afternoon. && .NEAR TERM /THROUGH TONIGHT/... As of 1124 AM Wednesday...W-WNW winds are pushing a stubborn patch of strato-cumulus 7000 feet off the ground over SE NC toward the ocean. As these clouds become less stratified and sail to sea, developing diurnal cumulus should pop up at around 5000 feet across the land forecast area, although with little vertical extend as a short-wave upper ridge presses dry air downward on their tops. The snap-back thickness values within with the upper ridge will also boost afternoon maximums into the 80s away from the coast this afternoon. This will fuel a sea breeze circulation bringing a bit of gustiness at the beaches and a slight backing in wind direction there. Transition to a synoptic return flow will commence later this afternoon and a low-level jet overnight from the SW, bringing 25 KT winds as low as 500 feet off the surface, will likely inhibit fog and mist formation overnight despite damp grounds and clear skies. This will also result in a mild night in the 60s, and winds near the coast will support minimums elevated into the upper 60s at the beaches as SSTs hold in a 69-72 degree range. The dry air aloft will prevent precipiation through tonight. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 330 AM Wednesday...Low amplitude ridging aloft to affect the FA Thu, complements to the northeast moving upper closed low. The associated ridge axis, overhead at the start of this period, will slide east and off the Carolina coasts by Thu evening. An expansive and rather amplified upper trof will become established across much of the CONUS with it`s trof axis nearly mimicking the continental divide. At the sfc, weak high pressure centered well offshore from Florida, will ridge back across the southern portions of the FA Thu. An eastward moving and weak frontal boundary, well displaced from it`s parent sfc low near Hudson Bay, will approach from the west before stalling across the far western Carolinas and Virginia Friday morning. Moisture accompanying the front remains limited, and will eventually push well ahead of the stalled front by Friday morning. Just enough dynamics and weak instability to aid isolated to widely scattered showers late Thu night thru Midday Friday along with a possible rumble of thunder. Upper level ridging will spring back up across the southeast States and the Atlantic waters. 5H Heights rise to 590+ dam. Strengthening Bermuda high pressure will ridge back to the west and extend inland in the vicinity of Cape Romain by daybreak Sat. Subsidence aloft, ie. NVA, will become more dominant late Fri aftn and night, essentially putting a lid on any convection that tries to develop. The pre-dawn hours of Thu, and Fri and Sat will each feature a SW low level jet. The stronger jets will occur Fri and Sat mornings. This will aid in keeping SW winds active at the sfc and in turn likely preventing any radiational fog development each night. As for daily max and min temps for the 2 days, you may be looking at the warmest temps of the Spring season so far. Model Mos Guidance shows widespread 80s both days with 90 degree readings possible inland locations on Fri. In essence, will be looking at max/min temps running up to 15 degrees above climo. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Surface and mid level ridging will be the dominant features through the weekend. The 5h ridge axis is just offshore and a slow but steady increase in moisture as flow aloft becomes more southwesterly opens up the possibility of sea breeze/diurnal convection, especially Sun afternoon and evening. Temperatures will be above to well above climo with potential for 90 degree readings inland. Next system winds up over the central CONUS early next week, lifting from the plains on Sun to the Great Lakes on Mon. Warm advection ahead of the front will maintain temps above climo through Mon. Cold front trailing the low moves into the area later Mon preceded by convection. Best dynamics pass well north of the area but there will be a narrow band of deeper moisture along with low level convergence and a strengthening low level jet. Also potential for some PVA depending on timing of any shortwave rotating around the base of the trough. Surface high and broad troughing aloft Tue contribute to deep westerly flow, drying the region out but with a cooler air mass building in temps will be slightly below climo as the period ends. && .AVIATION /18Z WEDNESDAY THROUGH SUNDAY/... As of 1720Z...VFR conditions expected this TAF cycle. SCT-BKN050 this afternoon until 00z-01z as loss of heating allows cumulus dissipation. Tonight and overnight a low-level jet, SW at 25-30 KT, as low as 500 feet agl, will help prevent fog and mist formation overnight into Thursday morning. Surface winds partially decoupled will range from SSW to SW at 5-9 KT for the overnight period. Aft 15Z on THU, SSW gusts up to 20 KT at terminals. SKC-SCT015 overnight, with relative humidity values of such that do not support widespread stratus development. Extended outlook...VFR expected from Thursday afternoon through Sunday. Isolated MVFR from spotty showers THU night and early FRI. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1124 AM Wednesday...Light winds much of the day will allow SE swell to remain the dominant wave energy although its intensity will wane today. By late day and overnight, increasing SW winds will bring moderate choppiness to the waters with 4-5 second wave periods becoming more dominant along with a little inshore gustiness this afternoon with the sea breeze winds. No showers or TSTMS however are expected through the overnight period. Increasing synoptic winds may approach cautionary levels tonight as the pressure gradient tightens and a low level jet develops. As of 330 AM Wednesday...The system moving into the Northeast will no longer be the main wind-making feature today. In its wake the high over the Atlantic will bring a S to SW flow. An approaching cold front will also slightly contribute. With the coast between the two winds will be quite light. Seas will setting into a general 2 to 3 or 4 ft range. Some larger waves outside of 20nm have swell energy from the departing storm as evidenced by the 10 sec dominant period. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 330 AM Wednesday...Thursday will feature weak ridging from offshore high pressure east of Florida, extending inland just south of the area waters. Thursday will see SSW to SW flow at 10 to 15 kt with an 8 to 9 second period ESE ground swell dominating the significant seas. By late Friday thru Friday night, strengthening ridging sfc and aloft, will affect the area waters. The sfc pg will tighten-some, resulting with SW 10 to 20 kt winds. An ESE ground swell will remain present but increasing short period wind waves will eventually dominate the significant seas. In addition, a SW low level jet will affect the local waters during the pre-dawn hrs of THu, Fri and Sat. The strongest low level jet will occur Fri morning and may just be strong enough to produce SCEC and/or SCA conditions. Will monitor. The aftn/evening sea breeze each day will also provide additional choppiness to the overall seas. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 PM Tuesday...High pressure will be the dominant feature through the period with south to southwest flow in place. Speeds will be on the low end of the 10 to 15 kt range early in the period but increase to a solid 15 kt Sun as gradient becomes a little more defined. Seas mostly 2 to 3 ft early in the period will experience an upward trend late in response to increasing southwest flow. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...MJC SHORT TERM...DCH LONG TERM...III AVIATION...MJC MARINE...MBB/DCH/8

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