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Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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135 FXUS62 KRAH 180539 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 140 AM EDT Sun Aug 18 2024 .SYNOPSIS... A cold front approaching from the northwest will move gradually eastward through the region today through Monday. A cooler and less humid air mass will settle into the area from Monday night through Friday. && .NEAR TERM /TONIGHT/... As of 940 PM Saturday... Water vapor imagery this evening depicts continued troughing along the eastern seaboard. Several embedded mid-level perturbations continue to generate convection over the Charlotte area southward into central SC. Additional showers and storms associated with a broken MCS continue to track ese over sw VA/central to eastern TN. Thus far this evening, convection has largely developed and quickly collapsed/diminished outside of central NC. With CIN largely encompassing the area at this point, the overnight hours should remain largely dry. The best chance for any showers/isolated storms in the next few hours would be perhaps some of the convection near Charlotte trickling into the far southwest Piedmont. However, even in these locations the POPs remain relatively low. This cluster should move southeast of our area and diminish by ~06Z. Otherwise, isolated showers/storms could develop along the outflow of the aforementioned upstream MCS and maybe trickle into the Triad overnight. Odds of this occurring are low though. Otherwise, the guidance suggest a good potential for stratus to develop overnight which should keep overnight lows warm in the lower 70s. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 230 PM Saturday... ...There is a slight risk (level 2 of 5) for severe storms from Raleigh south and east Sunday afternoon and evening... ...There is also a risk for Isolated Pockets of Heavy Rain and Flash flooding along and east of US 1... An unseasonably strong()~3 S.D. below normal) and amplifying upper- level trough will dig SEWD into the Eastern US Sunday during the period. At the surface, a pre-frontal sfc trough in the lee of the Appalachians will get overtaken by the accompanying cold front that will move east across central NC during the late afternoon and through the overnight hours. As daytime heating commences, moderate destabilization is expected area-wide, maximized across the Sandhills and southern coastal plain. Coincident with the arrival of the cold front and core of the stronger 40-50 meter H5 falls into the area, showers and storms are expected to develop across the western Piedmont between 18-21z, with convection thereafter increasing in coverage and intensity(becoming better organized) as the progresses eastward into the central Piedmont and western Sandhills between 20-00z, and then across eastern Sandhills and coastal plain counties between 23-04z. Deep layer shear of 30-35 kts will likely favor multi-cellular severe threat, with damaging winds the primary threat. Given recent wetness and with area streams and creeks still running high, the convective downpours could also lead to some instances of flash flooding, especially in poor-drainage and urban areas. The severe threat appears greatest between 3 to 10 pm with generally dry conditions after midnight. Highs ranging from mid 80s north to lower 90s south. Lows in the mid/upper 60s to lower 70s south. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 200 PM Saturday... Sat/Sat night: A mid/upper level trough will be positioned over the eastern CONUS with the trough axis extending from southern Quebec trough the Mid-Atlantic and into FL. A leading effective front from prior convection is expected to be situated near the coast with lee- troughing extending through the Piedmont. Surface dew points within and east of the lee-trough should still be in the mid 60s to near 70 and result in 500-1500 J/kg of MLCAPE through daytime heating. A disturbance rotating through the backside of the trough will overlap this weakly unstable airmass and a reinforcing cold front pivoting across central NC to initiate scattered showers/storms during the afternoon/evening hours. The best overlap of synoptic forcing and available instability will be over Northeast Piedmont into the northern/central Coastal Plain. Mid-level flow in the core of the trough will be relatively weak, but some directional shear (20-30kts of 0-6km shear) may lead to some storm organization in this region where clusters organized along a common cold pool will be most probable. DCAPE and theta-e differences will be lower than previous days (around 600 J/kg and 20K, respectively) and lead to a marginal/conditional threat for severe wind gusts. Tues through Sat: The passage of a reinforcing front will mark a pattern change with dropping low-level thicknesses through Tues. High pressure will then shift over the Northeast and ridge down through the Mid-Atlantic through much of the work week. Highs in the upper 70s to mid 80s will become common each afternoon with dew points in the 50s to near 60. Overnight, pockets of calm conditions and clear skies will favor radiational cooling Tues night into Fri morning with lows falling into the mid/upper 50s to near 60. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... As of 137 AM Sunday... Generally VFR conditions with some higher cloudiness can be expected through 18z today. The exception will be between 09z and 13z in which some stratus (IFR) is expected. Scattered thunderstorms are expected this afternoon and evening, with brief IFR conditions possible. Looking beyond 00z Mon, Some lingering storms are expected through 04z/Monday. Otherwise, stratus is possible again around daybreak Monday. Another round of scattered storms is possible at all sites, but mainly RWI/FAY, Monday afternoon. VFR conditions should return Mon night and prevail, with high confidence, through Thu. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Luchetti SHORT TERM...CBL LONG TERM...Swiggett AVIATION...Badgett