Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 181747 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 147 PM EDT Fri May 18 2018 .SYNOPSIS... Tropical moisture will continue to stream northward across the Carolinas much of the period, bringing humid conditions and rain chances each day, along with occasional sunshine between daytime showers and storms. && .NEAR TERM /THROUGH TONIGHT/... As of 10 AM Friday...Plume of tropical moisture spreading over the area this morning extends south of Cuba. Latest water vapor imagery shows the tropical moisture feed looking better than it has the last few days. Very few hints of dry air within the stream which suggests an abundance of heavy rain on the way for today and tonight. Precipitable water remains right around 2 inches and the high freezing level coupled with a low LCL show produce showers and isolated thunderstorms with high rainfall efficiencies. Hard to pick out any areas favored for convection given an overall lack of surface or mid-level forcing during the period, but pretty confident most of the area will see a good soaking. Downstream radar and satellite trends suggest SC may be more favored earlier in the period with activity shifting a little farther east this evening and overnight. Abundant cloud cover and moisture will keep highs in the upper 70s to around 80, although breaks of sun could lead to some areas briefly jumping into the mid 80s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 330 AM Friday...Probabilities of precipitation, across the board, will remain elevated through the weekend. Not to say all moments of Saturday and Sunday will be washed out, but outdoor plans should include knowing, that occasional heavy rain with isolated lightning strikes will roam the region, with spots of ponding water on roadways introducing a hydro-planing peril. Jet-max rising north early Saturday may enhance rain- rates and coverage onto the coast and Cape Fear. Tropical infusion and balmy maritime flow will maintain a humid feel as gradually rising SSTs keep dewpoint values lofty. The MUCAPE/MLCAPE trends support isolated thunderstorms through the weekend. Pockets of stronger diabatic heating will shine as a significant player in spurring afternoon convection. It should not come as a shock that weekend FLS or SPS issuances may be needed for training or stronger cells, but wind shear profiles not supporting an organized severe TSTM threat this weekend. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 3 PM Thursday...More of this seemingly ever-persistent tropical airmass will exist much of the extended, although there may at least be breaks in the showers during the long term. Monday into early Tuesday the ridge to the east is still progged to expand to the west followed by some drying in the mid-level which will likely lead to reduced, but still non- zero POP. However, by late Tuesday and through Wednesday the ridge retreats in response to mid-level troughing digging down from the north, allowing for a return/surge of tropical moisture and once again periods of showers/tstms with heavy rainfall. There may finally be an end to this extended period of tropical air however, as this same trough that causes an uptick in rainfall potential, will drive a cold front into the area Thursday which should push through bringing some drier air late in the period. However, it is May, and this front could get hung up across the Carolinas, potentially producing even more convection chances as it serves as a focus in a high PWAT airmass. Will show lowered POP by Thursday, but cannot rule out tropical showers/tstms any day during the period. Temps will be in the low 80s for highs nearly every day, with mins right around 70, as the cloudy and humid airmass prevent large diurnal ranges. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 12Z...Very difficult to time these waves of convection coming ashore, safe to say we will see periods of showers for most of the coast, transitioning inland as we move into the afternoon. Southerly winds will be around 10 kts through the afternoon hours. Ceilings will likely bounce around today, ranging from scattered to near IFR. Tonight some lingering showers. Ceilings are forecast to lower to IFR after midnight at the inland terminals. Another round of nocturnal convection expected along the coast. Saturday, continued tropical flow with scattered convection possible at any time during the day. Extended Outlook...Periods of MVFR/IFR cigs/vsbys associated with tropical type showers and tstorms through the period. Activity will be more numerous along the coast pre-dawn hours thru mid-morning hours each day, then translate to the inland terminals midday-early evening.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 10 AM Friday...Small Craft Advisory remains in effect for all zones. Gradient will maintain 15 to 20 kt southerly flow today and tonight. These winds will keep seas in the 4 to 6 ft range through the period. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 330 AM Friday...Seas will remain in the 4-7 foot range and highest offshore through Saturday evening in blustery S winds. It appears that SCA flags may be allowed to drop by Sunday daybreak, as the low interacting with high pressure offshore, moves off to the north, loosening the pressure gradient along the Carolina coast. Hence Sunday the better marine day in terms of winds and seas, but throughout the weekend mariners should expected scattered showers and TSTMS, and radar updates are recommended. General shower and storm movement this weekend from south to north. Seas this weekend dominated by S-SSE waves every 7-8 seconds mixed with moderate southerly chop. Downpours will reduce local visibility to 1 NM or less on occasion. LONG TERM /MONDAY THROUGH TUESDAY/... As of 300 PM Thursday...Bermuda type high pressure offshore will be the primary feature driving marine conditions into the middle of next week. S/SW winds around this feature will be 10-15 kts with little fluctuation through the period. This persistent SW flow and long fetch around the high will create a 7-8 sec dominant wave period, with amplitudes shrinking slightly into next week. A swell deamplifies, wave heights will as well, becoming 3-5 ft Monday, and 3-4 ft Tuesday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until midnight EDT Saturday night for AMZ250-252-254-256. && $$ NEAR TERM...III SHORT TERM...MJC LONG TERM...JDW AVIATION...43

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