FXUS62 KILM 191713 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 113 PM EDT Thu Sep 19 2024 .SYNOPSIS... A weak cold front and low pressure aloft will result in a chance for showers and isolated thunderstorm today. Slightly cooler and drier weather will accompany persistent north- northeasterly winds from Friday through the weekend as high pressure builds in from the north. && .UPDATE... No big changes necessary from the previous forecast with this update. && .NEAR TERM /THROUGH TONIGHT/... Mid-level trough axis lingering over the region today and an abundance of deep moisture will lead to another round of diurnal showers and thunderstorms. The location of the trough axis suggest NC portion of the forecast area will see more of the action, but the typical subsidence/dry air in the wake of a 5h trough never seems to materialize. Mid-level lapse rates in forecast soundings are nothing to write home about and there is no shortwave energy. On the flip side there is nothing preventing deeper convection from developing once surface based instability increases, especially if a weak sea breeze can develop in the afternoon. Coverage on Wed was aided by shortwave enhancement, which will be lacking today. Despite this, still think coverage under the trough axis will be similar to yesterday. High chance to likely along the southeast NC coast with pop gradually decreasing south and east, ending up low chance to slight chance across inland SC. Temperatures will near to slightly above climo, but lingering cloud cover has the potential to disrupt the temp forecast. Lows above climo tonight, but debris cloud will determine how much above. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... A mid-level trough axis should be over or near the coastal areas at the start of the period and will continue slowly shifting into the western Atlantic as the upper high centered over the Rio Grande evolves into an elongated ridge with its axis nosing into the southeastern US. Meanwhile, a weak cutoff low off the upper Mid-Atlantic coast is expected to keep the troughing over the western Atlantic from shifting away. The end result will be abundant dry air in the mid-upper atmosphere with subsidence largely keeping showers at bay through the weekend. Nevertheless, daytime heating combined with pwats around 1.5-1.6" and relatively weak subsidence could permit a few brief, shallow showers to develop on Friday with little or no rainfall accumulation. In addition, northwesterly flow aloft may start to bring in impulses that could lead to shower activity grazing northern portions of the CWA on Sunday, so this will need to be monitored. Temperatures should hold right around normal each day with highs in the middle 80s and lows in the low-mid 60s. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... The mid-level ridge axis looks to gradually shift overhead early next week and then confidence in what happens thereafter drops off significantly. A general trend appears to be the approach of a trough and associated cold front, but differences on the timing, magnitude, and southern extent of the trough are driving low confidence. In addition, guidance continues to suggest that some tropical system brewing in the Caribbean may have some influence on the weather just beyond the end of the period. This will need to be monitored closely in the coming days as run-to- run consistency in the timing and location of this potential system has been very poor both within any given model and across models. Otherwise, another high pressure wedge looks to bring a breath of cooler air on Monday with temperatures dropping 2-4 degrees for both highs (low 80s) and lows (low 60s) compared to over the weekend. Temperatures should then slowly rise through midweek as the ridge axis shifts overhead. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... Mainly VFR to start off the 18Z TAF period. Scattered showers are starting to form across the areas, and could lead to occasional MVFR/IFR for the remainder of the day. Low cigs and/or vsbys then likely, at least inland, late tonight into Thursday morning especially over areas that received rainfall today. Boundary layer winds are more favorable for low stratus, but with with today's rain and lighter wind in spots, fog cannot be ruled out. Conditions improve to VFR everyday into the day Thursday with dry weather. Extended Outlook...Mainly dry with VFR conditions, but early morning MVFR/IFR cannot be ruled out at times. && .MARINE... Through Tonight... North to northeast flow develops today as surface high starts to expand east. Weak enough gradient and possibly enough heating that weak, but atypical east-northeast sea breeze is possible in the afternoon. Gradient becomes a little more defined tonight with northeast flow increasing from around 5 kt for much of the day to 10- 15 kt late tonight. Seas around 2 ft with the exception of 2 ft with occasional 3 ft north and east of Frying Pan Shoals today. Seas north and east of Frying Pan Shoals start to build late tonight with 3 ft becoming more widespread. Remainder of the waters will remain around 2 ft. The easterly swell will continue to be the only noticeable wave today. However, tonight a northeast wind wave will start to develop, although the easterly swell will remain dominant. Thursday Night through Monday... A general northerly to northeasterly flow will dominate through the period on the backside of slow-moving low pressure located well to our northeast which will then be replaced by a high pressure wedge as the low moves further out to sea on Monday. Speeds will generally favor 10 kts or so. Wave heights look to stay in the 2-3 ft range with 4 foot waves possible in the outer portions of the 20nm coastal zones, especially for the NC waters over Friday night into Saturday and again on Monday. Easterly 10 sec swells will remain a key component of the wave spectrum with generally 1-2 ft wind waves also contributing. && .TIDES/COASTAL FLOODING... High astronomical tides will once again lead to coastal flooding with this morning's high tide. Water levels will rise above the minor flooding category for the beaches or downtown Wilmington. Another round of advisories is expected with this evening's high tide. && .ILM WATCHES/WARNINGS/ADVISORIES... NC...Coastal Flood Advisory until 3 PM EDT this afternoon for NCZ107. SC...None. MARINE...None. && $$ SYNOPSIS...ILM UPDATE...MAS NEAR TERM...III SHORT TERM...ABW LONG TERM...ABW AVIATION...MAS MARINE...III/ABW TIDES/COASTAL FLOODING...