Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 200523 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 123 AM EDT Wed Sep 20 2017 .SYNOPSIS... A disturbance aloft will bring isolated showers Wednesday and Thursday. High pressure will build in from the north for the remainder of the week while Jose spins nearly stationary off the Mid-Atlantic coast. Dangerous hurricane Maria approaching Puerto Rico tonight, will bring increasing southeast swell and strengthening rip currents to the Carolinas beginning late week. Maria is expected to move north and offshore of the Carolinas early next week. && .NEAR TERM /THROUGH TODAY/... As of 950 PM Tuesday...Changes not needed at this time to the ongoing forecast aside from minor T and Td tweaks, as evening temperatures have dropped off rapidly. A few sites inland were already reporting upper 60s. The final game day decision was not to include fog overnight, as most guidance and our local fogger tool do not convincingly support its formation. As of 635 PM Tuesday...A delightful evening on tap despite the overwhelming, visual arrest, of Jose in satellite presentations. Meanwhile in the tropics, Maria is bearing down on the Virgin Islands and Puerto Rico, but no sensible weather effects or even SE swell has arrived yet locally from Maria. Visibility can be measured in light years tonight under a clear celestial dome. As Jose`s very outer wind field completely releases its grip on NE SC and SE NC overnight, look for winds to trend from NW to W to WSW by daybreak Wed but speeds light. The downslope wind flow may act as an inhibitor to fog/mist formation but isolated pockets may still form in the protected, cool, or more damp locals. Will use trends in the hours ahead to determine if fog inclusion in the forecasts is warranted. The mostly clear skies overnight will aid cooling and allow minimum temps to dip to 65-68 degrees at daybreak. As of 300 PM Tuesday...Subsidence associated with Jose is still in effect over eastern zones but cu fields show it lessening as one heads south and west. However being mainly fueled by diurnal heating these clouds will thin towards sunset and most of the night should bring generally clear skies. The exception will be some minor coverage of mid cloud that should start to impinge upon NW zones late tonight ahead of diving upper trough/cold pool. This feature will remain over the area into Wednesday and even deepen somewhat. Whereas the mid levels should be cool enough to support some degree of cloud cover the low levels look too dry to support meaningful rain chances. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... As of 3 PM Tuesday...Weak mid-level trough in the wake of Jose will allow for some isolated diurnal convection ongoing at the start of the period. Some of this convection could be extended into the overnight period by an approaching shortwave. It could end up that convection developing west of the area prior to the start of the period moves in from the west during the evening and overnight hours. Similar theme for Thu with weak mid level troughing and heating coupled with some shortwave energy leading to diurnal convection. Think chances a slightly better on Thu with convection once again lingering into the evening and overnight hours. However, the lack of large scale forcing and mid level dry air will limit convection during the period. Temperatures will run above climo through the period. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 245 PM Monday...At onset Friday Jose will be meandering off the New England/Mid-Atlantic coasts while Maria approaches the eastern Bahamas with weak high pressure in place across the Carolinas. Weak high pressure will remain across the Carolinas early next week as Maria moves northward off the Southeast U.S. coast. We will obviously need to keep a very close eye on Maria`s progression, however in the least we expect very hazardous surf conditions as large swells impact the coast. Held onto a small POP for primarily SC areas during Friday, then no POPs thereafter (ultimately dependent on Maria`s track early next week). Favored a blend of MEX/ECE highs/lows through the long term period. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 06Z...Expect VFR conditions through the period. Some regional sites are showing modest fog formation and I did add a tempo group to LBT for MVFR this morning to address. There may also be a few isolated thunderstorms late this afternoon and evening but coverage and confidence is not sufficient to include in the current forecast. Extended Outlook...Mainly VFR conditions through the period are expected with the exception of a few hours of early morning low clouds or fog most mornings through the period. The highest risk of IFR conditions will be in the 0900-1200Z timeframe each morning.
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&& .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 635 PM Tuesday...Plots of wave spectra across the 0-20 NM waters, shows E swell in 12-13 second intervals dominates wave energy with seas 2-3 feet. Flat pressure pattern will result in light winds, which will trend from NW early this evening to WSW into daybreak Wed. No TSTMS expected over the 0-20 NM waters through Wednesday. As of 300 PM Tuesday...Winds slacken and Jose swell energy abates through the period. Flow will tend to veer some to NW as the outer curved isobars of Jose lift out to the NE. Seas will settle into the 2 to 3 ft range. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 3 PM Tuesday...Elongated weak high pressure south and east of the area into Thu will yield to slightly stronger high building down the coast. Light southerly winds Wed night into Thu will become northeast late in the period but speeds should remain under 10 kt through Thu night. Seas will run 2 to 3 ft. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 245 PM Monday...Very hazardous maritime conditions expected during the long term period as large waves emanate outward from Maria. At this time Maria is likely expected to remain offshore as it moves northward from the Bahamas, but all marine interests should closely monitor the progression of this storm given forecast track uncertainty at this time. Winds on Friday will be around 10 knots from the northeast to east with similar conditions Saturday. Speeds will increase during Sunday out of the northeast as the peripheral circulation of Maria begins to come into the picture. Wavewatch III guidance indicates significant swells impacting the coastal waters, especially Sat into Sun. Very steep waves are possible, especially near inlet entrances during the falling tide. && .TIDES/COASTAL FLOODING... As of 300 PM Tuesday...The Cape Fear River will once again reach minor tidal flooding thresholds with this evening`s high tide at 10 PM as the new moon approaches. Coastal Flood Advisory being hoisted for 2 hours either side of low tide for standing water in Battleship Park and downtown Water Street. ET surge data continues to keep ocean/ICW tides below thresholds. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None. NC...None. MARINE...None.
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&& $$ AVIATION...SHK MARINE...REK/RGZ TIDES/COASTAL FLOODING...

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