Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 260708 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 308 AM EDT Tue Sep 26 2017 .SYNOPSIS...
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Hazardous beach conditions will continue as hurricane Maria moves slowly north offshore of the Carolinas. Maria will accelerate away from the United States beginning Thursday. A cold front passage late Thursday will bring cooler and drier air into the Carolinas Friday into this weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 3 AM Tuesday...Northward moving Hurricane Maria will slowly pass well east of the area today, moving northeast of the area tonight. Breezy northerly winds will become northwest later today and into tonight. Moisture below 500 mb remains high through the period as Maria`s circulation continues to spread an abundance of tropical moisture over the region. Downward motion due to mid-level subsidence on the periphery of the storm will work to offset what little diurnal instability develops. Low level cloud cover will limit heating today, keeping highs in the upper 70s to lower 80s in most areas. Across inland SC there may be a little less cloud cover, allowing for slightly more insolation (and marginally warmer temps). There will be a little less subsidence across inland SC but also a little less moisture. Cannot rule out an isolated shower but the best shot at measurable rainfall during the period looks to be across southeastern NC. Light showers and/or sprinkles will be possible through early evening with mid to late afternoon favored. By early evening the best low level convergence shifts north and diurnal instability decreases. Do not expect a lot of precipitation both in coverage or amount, but brief showers/sprinkles certainly remain possible. Clouds will linger overnight and, combined with strong boundary layer mixing, will help keep lows well above climo.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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As of 300 PM Monday...By daybreak on Wednesday, Maria will be positioned roughly 150 miles east of Cape Hatteras, meandering there into Thursday, before an acceleration eastward Thursday night. This progression will open the door for cold frontal passage late Thursday night and early Friday, bringing a change in air mass Friday into the weekend. This will result in temps more indicative climate-wise for late September, after an above normal temp regime this week. This will be a dry cold front as moisture aloft remains in limited supply, and subsidence aloft will be formidable in N-NW flow. Downslope flow prior to the cold frontal passage will result in exceptionally warm temps, and while 95 degrees will be a difficult record to break at ILM on Wednesday, the 91 on Thursday set back in 1998 could be closely approached.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...Subsidence in the wake of Maria and pre- frontal warming will lead to one more day of above-average temperatures before a cooling trend commences. A consensus of guidance gives us highs of around 90 on Thursday. A cold front will move offshore later on Thursday, bringing us near to well- below normal temperatures by Friday, with cool weather continuing into the weekend. The cold front will come through dry, although isolated to widely scattered showers are possible along the coast Friday night into Saturday as a strong upper disturbance dips SE across the mid-Atlantic states. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 05Z...Forecast soundings and cross section suggest low stratus deck presently north of the area will gradually sink south overnight. Appears all terminals may have a shot at IFR with best chances at NC sites. IFR ceilings will hang around through mid morning before lifting to MVFR for much of the day, except for FLO which should quickly pop up to VFR. Low chance ILM could see brief shower or drizzle but if this were to happen duration would be very brief. Clearing will start to develop over inland SC prior to sunset and gradually spread east and north overnight. High cloud may linger beyond the end of the period closer to the coast but low stratus seems less likely given forecast moisture profiles. Boundary layer winds should prevent any fog. Winds from the north this morning will gradually back to northwest during the day. Speeds at the coastal terminals could gust to 18 to 22 kt later this morning into late afternoon or early evening before speeds start to drop off. Extended Outlook...MVFR ceilings may linger/redevelop at the coastal terminals Tue night, mainly KILM. Wind gusts at KILM may gust to 15 to 20 kt into Wed. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 3 AM Tuesday...Gusty northerly winds this morning will gradually back to northwest as Hurricane Maria passes well east of the area. SCA headline continues for all zones, mainly due to swells from the storm. In addition, wind speeds across NC waters will remain in the 20-25 kt range through the end of the period. Later today and tonight Maria will be northeast of the area and in the process of moving away from the waters. Despite this, swells above SCA thresholds will likely continue through the end of the period. Nearshore SC waters may start to see seas dropping below 6 ft later tonight but the majority of the waters will remain in the 6 to 10 ft range with potential for up to 15 ft across NC zones near 20 nm. NO TSTMS over the 0-20 NM waters this period but a few brief showers possible Wednesday north of Figure 8 island is possible. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 3 AM Tuesday...SCA in large seas and NW winds 20-25 KT starts Wednesday off rough, but into Thursday vast improvement is expected as Maria not only weakens but begins to accelerate away from the East Coast. Sea height recovery will require an SCA likely all of Wednesday before headlines are likely dropped sometime Thursday. N-NW winds will prevail all of this period although the wave-height trend is a subsiding one. Seas 5-9 feet Wednesday will drop to 3-5 feet during the day Thursday in fading E swell, diminishing NW wind-seas, and easing NE fresh swell or `mature wind-seas`. A myriad of wave trains in the mix but overall heights dropping in each of the partitioned waves. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 3 PM Monday...Expect gradually improving conditions over the waters as Maria moves well northeast into the central Atlantic and a weak pressure gradient takes its place. Do not expect any warnings or advisories during the long term. Highest winds and seas will be on Thursday for our NC coastal waters, with 10 to 15 kt winds and 3 to 5 ft seas. These conditions will improve, with seas in the 2 to 4 ft range and winds of only around 10 kts throughout by evening.
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&& .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...High Rip Current Risk through this evening for SCZ054-056. NC...High Rip Current Risk through this evening for NCZ106-108-110. MARINE...Small Craft Advisory until 8 PM EDT Wednesday for AMZ250-252- 254-256.
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&& $$ SYNOPSIS...8 NEAR TERM...III SHORT TERM...8 LONG TERM...REK AVIATION...III

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