Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 190651 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 251 AM EDT Wed Apr 19 2017 .SYNOPSIS...
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A cold front stalled over South Carolina this morning will lift back north as a warm front today into tonight. The Bermuda High will expand west over the region Thursday through Saturday. Another cold front will move through Sunday night with high pressure building in behind it into early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 245 AM Wednesday...Weak front stalled south of the area overnight will try and work its way north during the day. Shortwave moving across the area from the west today will help pull the front north and induce weak cyclogenesis along the boundary. Low clouds and light rain, due to isentropic lift, will remain through the day but the arrival of the wave is likely to add some convective element to precipitation, especially after modest heating leads to a slight increase in surface based instability. Forcing and instability are by no means strong so while scattered day time convection is expected do not think strong storms will be a concern. Do anticipate some thunder but do not expect to see a lot of lightning. CAPE within the charging zone is on the weak side, suggesting what updrafts do form will be weak and will have difficulty creating significant charge differences. Slow storm motion could make flooding a concern but precip coverage will be limited which should keep most areas from having to worry about training storms. Shortwave moves off the coast late today, helping push the weak surface low and the boundary farther off the coast. Light westerly flow sets up late in the period in the wake of the exiting low while post wave subsidence and deep northwest flow aloft bring about a drying trend overnight. Clouds will linger through the period but measurable precip chances will drop below 10% overnight. High will be near normal today, mid 70s, with lows running well above climo tonight, low to mid 60s.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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As of 245 AM Wednesday...Low-end rain chances this period as the trend of mid-level drying is underway, and more in earnest late Thursday as H8-H7 trajectories turn more westerly. Low-level heating accompanied by dewpoints in the middle 60s will allow for a shower or TSTM to pop along any boundary or the afternoon sea breeze front Thursday. This is possible Friday except that more pronounced mid- level drying will suppress convective depth Friday and TSTMS were removed and limited to showers. 80s for maximums both days away from the coast and Friday should be a few degrees warmer than Thursday as warm air advection becomes slightly more of a player. POP values will take a bump upward late Friday as a decaying frontal boundary approaches the area. Minimums remain well above normal for late April elevated into into the lower and middle 60s aided by low-level jets each of the overnight periods. No severe weather signatures appear in the cards this period.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...A streak of very warm weather is expected Friday and Saturday before a significant rain/thunderstorm event accompanies a cold front early next week. A low amplitude upper ridge across the Southeast will support surface high pressure out near Bermuda on Friday and Saturday. Southwesterly low-level flow around this high should provide two warm days with highs easily reaching the upper 80s on Friday. Earlier models had suggested a backdoor cold front may slip southward into the area, but this appears to be a much lesser possibility now. I have increased forecast highs and lows Friday through Saturday by as much as 6 degrees in spots, and feel that I still may be too cool, especially inland on Saturday. Capping aloft with the ridge should keep diurnal thunderstorm activity in the isolated range, mainly inland of each day`s seabreeze front. Our weather pattern changes abruptly by Sunday as an impressive upper level system (especially for late April) dives into the southeastern quarter of the nation. Timing differences between the GFS and ECMWF has narrowed quite a bit with this morning`s 12z model run, and confidence is growing that a wave of thunderstorms will progress from west to east across the area late Sunday ahead of the surface cold front. A non-supercell severe risk may very well develop with this system as models are showing rather strong but unidirectional winds aloft coupled with a favorably positioned jet stream along the Mid-Atlantic and New England coast. As the mid and upper level system slows and almost cuts off along the GA/SC coast on Monday, steadier rains could linger through Monday and perhaps into Monday night along the coast. This is excellent news for especially South Carolina as "abnormally dry" and "moderate drought" designations are expanding on the latest U.S. Drought Monitor summary. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... As of 06Z...Patches of low stratus will continue at all terminals through the remainder of the overnight period. Have high confidence in ceilings generally remaining between 3k and 4k ft with no ceilings under 2k ft expected. Brief patchy 5SM fog could be an issue at any location but IFR visibilities are unlikely. More showers are expected today with the potential for an isolated thunderstorm late morning through the afternoon. Any precipitation should be ending by evening with drying overnight, however lingering low level moisture is likely to produce widespread IFR conditions tonight after midnight. Extended outlook...MVFR/IFR conditions possible in showers and TSTMS Saturday through Sunday night. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 245 AM Wednesday...Northeast flow will gradually decrease this morning into early afternoon as a weak front stalled south of the area lifts north. The front ends up across the waters later today with weak surface wave/low developing along the boundary. The weak low lifts east-northeast later tonight with light and variable winds this evening becoming southwest to west overnight. Seas will run as high as 4 to 5 ft across portions of NC zones through the morning before dropping to 2 to 3 ft across all zones for the remainder of the period. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 245 AM Wednesday...Marine conditions are manageable THU in developing SW flow but will become increasingly hostile THU night and FRI as a low pressure trough inland and high pressure offshore begin to more strongly interact. SW gusts to 25 KT FRI and FRi night may prompt a Small Craft Advisory or an Exercise Caution statement. Spectral plots show 3-4 foot SW waves every 4-5 sec will co-mingle with 2-3 foot E waves every 8-9 sec. An isolated TSTM is possible early THU and again late THU while FRI may be confined to a marine shower at best. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 PM Tuesday...High pressure out near Bermuda will control our area`s weather through the end of the week, maintaining south- southwesterly winds and generally dry conditions. Compared to models a day or two ago, the high is now expected to be stronger and should deflect a backdoor cold front that was earlier believed to make it this far south. Wind speeds should average 15 knots on Friday and 10- 15 knots on Saturday.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...III SHORT TERM...MJC LONG TERM...TRA AVIATION...III

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