Area Forecast Discussion
Issued by NWS Wilmington, NC

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339 FXUS62 KILM 250529 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 129 AM EDT Tue Jul 25 2017 .SYNOPSIS... Scattered showers and thunderstorms will raise the risk for heavy rainfall and possible localized flooding into mid week. A cold front will approach from the north and should slip into the area later Tuesday night and on Wednesday before stalling and then dissipating by Thursday. After a brief hot and dry period Thurs day into Friday. the arrival of a stronger cold front this weekend will bring numerous thunderstorms back into the eastern Carolinas. && .NEAR TERM /THROUGH TODAY/... As of 730 PM Monday...Updated POPs across much of the ILM CWA to account for current mosaic radar trends and sat imagery for cloudiness. Added the tstrm attribute "Some thunderstorms may produce heavy rainfall" to the convection mainly over the southern portions of the ILM CWA for mainly this evening. Hourly temps/dewpts adjusted to account for pcpn. Min temps for tonight adjusted by a degree or so upwards due to clouds and the threat of pcpn closer to the immediate coast. Previous..................................................... AS OF 230 PM Monday...Low cloud deck has played havoc with high temperatures today and delayed destabilization. The area of clouds will become increasingly scattered finally allowing parts of the forecast area to warm up. Dewpoints remain in the mid to upper 70s and the precipitable water is above 2 inches. SPC mesoanalysis shows CAPE above 3000 j/kg but lifting mechanisms remain weak/limited associated with the sea breeze front and inland trough. Will maintain chance POPs through the afternoon and into the evening. Scattered showers and thunderstorms possible again during Tuesday with weak trough aloft and sea breeze inland trough providing lift. Storm motion will be weaker tomorrow and the risk for localized flooding in a high precipitable water air-mass will increase as a result. Followed a blend of MAV/MET temperatures for tonight and with highs in the lower 90s and dewpoints in the mid 70s the heat index will be around 100 to 103 during Tuesday. Lastly, not expecting water levels to exceed minor coastal flood thresholds at downtown Wilmington tonight. Latest ETSS takes the gauge to just below Coastal Flood Advisory criteria. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...Mid to upper trough and frontal boundary remain strung out and become nearly stationary across the Southeast through the period as high pressure reaches down from the north behind it. This will leave a gradient of very moist air to the south running most likely right through our forecast area from SC east to northeast into the Atlantic. Pcp water values will be greater than 2 inches to south of this boundary and less than 1.5 inches to the north. The GFS is less bullish and maintains a wetter more unsettled forecast for Wed, as compared to other models showing boundary farther south and a drier forecast. Overall, would expect a greater chc of stronger storms to the south and east over the waters, but will maintain higher PoPs across most of NE SC up to the Cape Fear coast with gradient of lower PoPs as you head N to NW. The drier air may reach into most of NC to produce a sunnier forecast with lower end pops, but overall expect potential for shwrs/tstms but confidence is low as to exactly where this boundary will be located. Models also showing potential for low pressure to develop along this boundary on Wed which could also push pcp farther south into local forecast area. If this occurs, QPF could be on the higher side. For now will show a trend to lower end pcp and brighter skies end of day Wed but will show potential for convective development through Wed aftn. The weaker steering flow will also point toward greater potential for slow moving storms and therefore higher end QPF which could lead to localized flooding issues. It could end up with two different atmospheric conditions with one to the NW and N being drier mid levels with threat of gusty winds in storms while to the south, expect mainly heavier rain. Temps will be in the mid 70s Tues night and up toward 90 on Wed. As drier air moves in late Wed into early Thurs, dewpoint temps will drop a few degrees allowing for overnight lows to drop to the lower to mid 70s on Wed night. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 PM Monday...Longwave trough which has affected the eastern CONUS for what seems like most of the summer will re-intensify this weekend after a brief period of warm and dry weather on Friday. Front will dissipate across the area Thursday with warm westerly flow developing aloft. This will dry the column out on Thursday, and while isolated tstms will be likely, coverage will be less than earlier in the week and highs will climb towards 90. On Friday, WAA drives 850mb temps towards 20C, and convective coverage will be even more limited despite highs climbing into the 90s with heat index values once again rising towards 105. Eastern trough re-loads beginning Saturday driving another cold front into the eastern Carolinas. This front will become aligned parallel to the flow through the wknd and into early next week as an anomalous cutoff digs towards GA. Deep moist advection, upper diffluence, and PWATs over 2 inches all suggest periods of heavy rain and tstms Saturday through Monday as more unsettled weather plagues the region. The benefit to the forecasted rainfall is that temps will remain at or below climo, mid to upr 80s, the latter half of the extended. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 06Z...Convective debris clouds linger over the area this morning but should gradually decrease in coverage prior to daybreak. This may allow for patchy MVFR fog development at inland terminals while along the coast slightly higher boundary layer winds will prevent any fog development. May see some marine stratus spread onshore at coastal sites through sunrise or so but do not think ceilings drop below MVFR. Another day with afternoon and evening showers and thunderstorms expected. Storms will develop along the sea breeze and the Piedmont trough with a gradual southeastward drift. Storm motion will be slow so any storms affecting a terminal could do so for an extended period of time. What storms do develop will dissipate shortly after sunset with debris cloud lingering overnight. Weak cold front will drop in from the north overnight which may introduce some IFR ceilings and/or visibilities at LBT and FLO, something to keep an eye on. Extended Outlook...MVFR/IFR conditions are likely in showers and thunderstorms today thru Wednesday. Less chance of convection by Thursday. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 730 PM Monday...Short term SCEC raised for the local waters between Surf City and Murrell Inlet. Latest Buoy and OMR wind and seas trends indicate the need for the SCEC thru 3 am Tuesday. The sfc pg should relax some during the pre-dawn Tue hrs with resulting winds diminishing-some. Significant seas will be initialized at 3 to 5 ft and have indicated a subsiding trend to 2 to 4 ft by daybreak Tue. Dominating periods will run 5 to 7 seconds. Previous.................................................... As of 230 PM Monday...Trough across the inland Carolinas with Bermuda High pressure will maintain a southwesterly fetch across the waters tonight into Tuesday. However, the fetch will weaken as the inland trough shifts eastward with a weaker pressure gradient expected over the adjacent coastal waters. In the meantime winds of 15-20 knots will prevail, especially away from the coast tonight with seas in the 3 to 5 ft range. Plan on continuing the Small Craft Should Exercise Caution headline through the afternoon. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...A front will drop south and should reach into the waters by Wed morning. This boundary will remain in the vicinity producing light and variable winds through much of the period, although initially the winds will be SW up to 10 to 15 kts ahead of the front into early Tues night. Once the front drops south overnight Tues into Wed the winds will turn around to the NE and should back to the E through Wed, but this is all dependent on where the boundary ends up. Either way, expect seas to diminish through Wed with seas up to 3 to 4 ft Tues eve and down less than 3 ft Wed aftn into Wed eve. This front will produce an increased chc of shwrs/tstms through much of the period. LONG TERM /THURSDAY THROUGH SATURDAY/... As of 300 PM Monday...High pressure offshore will intensify through Friday before weakening again in response to a cold front dropping down from the north. SW winds around this surface high will slowly increase to around 15 kts during Friday before weakening and then shifting to the W/NW late on Saturday as the front encroaches on the waters. Seas will be formed by a SE swell as well as an amplifying SW wind wave through Friday, with significant seas building from 2 ft Thursday to 3-4 ft late Friday into Saturday. Seas will fall slowly late in the period as the winds ease and shift offshore. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...RGZ NEAR TERM...DCH/SRP SHORT TERM...RGZ LONG TERM...JDW AVIATION...III

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