Area Forecast Discussion
Issued by NWS Wilmington, NC

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629 FXUS62 KILM 211409 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1009 AM EDT Mon May 21 2018 .SYNOPSIS... Isolated to scattered showers and thunderstorms will become more numerous mid week as a cold front sags into the area from the north before slowly dissipating Friday. The upcoming holiday weekend looks unsettled as a tropical airmass brings the likelihood for thunderstorms and possibly more heavy rain. && .NEAR TERM /THROUGH TONIGHT/...
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As of 950 AM Monday...Water vapor imagery suggests there is a dense plume of tropical moisture still streaming across the area out of the Caribbean. This is true in the upper levels where the satellite sees, however the 12Z CHS sounding confirmed what the models are showing: drying is occurring below in the 850-500 mb layer with precipitable water values falling below 1.5 inches...well below the 2.0 values we saw over the weekend. While uncapped convective instability should still develop this afternoon and the seabreeze will undoubtedly provide enough lift to fire up some showers and thunderstorms, the dry air should help keep coverage to only 30-40 percent at best. I`ve localized the best chances of afternoon convection to the NC seabreeze zone up through Lumberton and Elizabethtown. Shower chances should diminish after dark, and PoPs have been lowered significantly overnight. No significant changes have been made to temperatures, still expected to range from the mid 80s inland to around 80 on the beaches. Discussion from 300 AM follows... Just a few showers off the coast tonight with mainly mid to high clouds streaming over the Carolinas maintaining a partly to mostly cloudy sky. Lighter winds tonight will drop to near calm inland and expect good chance of patchy fog mainly inland and potential for some stratus as moisture remains concentrated closer to the surface. Temps will hold near 70 most places. Atlantic ridge will build far enough west through today to produce a relatively uneventful weather day. Expect mainly diurnally driven shwrs/tstms associated with convergence around western periphery of high and sea breeze boundary as it pushes inland through this afternoon. The steering flow will be weak once again out of the SW and becoming more southerly into the eve. This could produce some localized ponding of water in any heavier showers in aftn convection inland. Although mid to high clouds will be present through today, expect to see some good periods of sunshine, especially along the coast in the late afternoon as sea breeze marches inland. Pcp water just around 1.6 inches this morning will begin to drop this afternoon as drier air and increased subsidence pushes into the area from S-SE to N-NW. Values along the coast will be down closer to an inch late this aftn and will drop further inland into this eve as ridge builds in. Once afternoon convection drops off as the sun sets and diurnal heating comes to an end, showers will dissipate and expect a fairly quiet, rain free night again Mon night. Increased moisture begins to wrap around the ridge back into the Coastal Carolinas again by Tues morning. Therefore expect the potential for showers to increase once again by Tuesday. Temps will run a few degrees warmer today, into the mid 80s, with increased subsidence and fewer clouds. Overnight lows tonight will be in the mid to upper 60s.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...The eastern Carolinas will be on the western periphery of the Bermuda High which will slowly lose its influence across the area late Wed and Wed night. This will allow a cold front to the N to sag into the FA late Wed night. Precipitable water values will be lower Tue than on Wed and with greater ridging Tue, expect the coverage of showers and thunderstorms will be isolated to scattered. Will show the higher POPs along and W of the seabreeze which should make steady inland progress during the afternoon. The deepening east coast trough along with the approaching cold front should spur scattered to numerous showers and thunderstorms with the greatest coverage expected during the afternoon and through the eve. Did also highlight heavy rain risk as the moisture return is through a deep layer and precipitable water values do surge to near 2 inches. Typical high temps for late May, lower to mid 80s although a few upper 80s are possible inland Wed. Low temps however will be considerably above normal. Normal lows for late May are in the lower 60s. We are forecasting lows in the upper 60s and lower 70s during this period. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 PM Sunday...A brief break in the pattern is forecast Thu into early Fri as a mid-level trough digs into New England driving a surface cold front into the area. Guidance is now insistent that this feature will stall overhead Thu, which seems likely based off the continued southerly flow impeding its southern progress. This front in the vicinity will serve as a focus for convection Thu, which combined with PWATs near 2 inches will likely lead to widespread showers with isolated tstms. On Fri this front will waver/dissipate with another round of convection possible, although coverage should be less than Thu. Thereafter, forecast becomes much more uncertain as a wave of low pressure develops in the tropics. Most extended guidance develops this low, but then tracks it slowly with highly variable solutions. At this point it is far too early to mention any tropical development, but it is likely that tropical moisture pooling near Cuba will again lift north into the Carolinas. This creates what at this point is almost a broken record forecast - increasing rain and thunderstorm chances with heavy rain possible during the Memorial Day weekend. Temps through the extended will feature highs around to slightly above climo, and lows well above normal as diurnal ranges are limited by clouds cover and humidity. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 12Z...IFR early this morning KFLO/KLBT with VFR coastal terminals. VFR expected all terminals 13-14Z. Convergence associated with sea breeze boundary as it pushes inland this morning could produce tempo MVFR cigs along with VCSH coastal terminals until around 16Z. MVFR ceilings along SHRA/TSRA inland terminals 18Z through the afternoon as the sea breeze pushes further inland. For now, showers and storms are covered with VC in TAFs. Convection should wane around 00Z with loss of heating. Fog expected overnight with MVFR coastal terminals and LIFR inland terminals. Extended Outlook...Some MVFR to IFR Fog and stratus possible again Tues morning with sct aftn shwr/tstms to follow. MVFR and possibly IFR conditions will increase late Wednesday into Thursday as a cold front drops across the area and again next weekend as tropical moisture returns. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 950 AM Monday...No significant changes have been made to the forecast, other than enhancing the seabreeze winds this afternoon nearshore a bit. CORMP and NDBC buoys show seas are right in the middle of the forecast range. Discussion from 300 AM follows... Bermuda High will nudge westward through today. This will maintain a southerly flow overall, but the orientation of the high will produce a slight backing of the winds from SW this morning to S-SW by tonight, remaining basically 10 kt or less. Seas 3 to 5 ft this morning will diminish to 2 to 4 ft by this afternoon into tonight. The sea breeze will kick winds up a bit near shore this afternoon. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 300 AM Monday...Bermuda High pressure will gradually lose its influence across the Carolina waters. This will allow a cold front to the N to sag south and into the northern waters late Wed night. S winds Tue will become SW Tue night and Wed. SW winds Wed night will veer to a more westerly direction late and to the NW across portions of the northern waters prior to sunrise Thu. Wind speeds will generally remain in the 10 to 15 kt range. Seas will be 2 to 4 ft, a combination of SE swell and wind energy. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 PM Sunday...A cold front will briefly turn winds to the W/NW Thu before the gradient eases considerably as the front wavers and then dissipates across the area into Fri. This brings a period of light and variable winds Thu before easterly winds develop Fri, becoming south late at 5-10 kt. Wave heights will fall to around 2 ft Thu, and then remain there through the end of the week.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...TRA/RGZ SHORT TERM...RJD LONG TERM...JDW AVIATION...MRR is the U.S. government's official web portal to all federal, state and local government web resources and services.