Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281516 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1116 AM EDT Sat May 28 2016 .SYNOPSIS...A tropical depression offshore the Southeast coast will track northwest to the South Carolina coast tonight, stall along the South Carolina coast on Sunday, then track slowly northeast along or just offshore the North Carolina coast through mid-week. && .NEAR TERM /Through Tonight/... As of 1100 AM Saturday... As TD#2 tracks NW toward the Southeast coast this afternoon, an increasingly moist/tropical airmass will advect inland from the Atlantic, aiding in marginal diurnal destabilization (~100-250 J/kg mlcape) this afternoon across portions of the southeast coastal plain. Though shallow diurnal convection is unlikely to develop directly over portions of the coastal plain today given little forcing and very weak instability, the airmass in place by late afternoon should be sufficient to maintain upstream showers (on the seabreeze or moving onshore the Carolina coast) as activity advects inland via 15-20 kt E/ESE steering flow. Will indicate an increasing chance for showers late this afternoon and evening from the SE coastal plain west to the sandhills and north to the Hwy 64 corridor. Expect highs in the mid 80s, warmest over the northern piedmont /Triangle/ and northeast coastal plain. -Vincent && .SHORT TERM /Sunday through Sunday night/... As of 325 AM Saturday... This is shaping up to be a very wet day, potentially lasting into the night, with locally heavy downpours likely over a portion of the Carolinas, although the details of who precisely will get the heaviest precip and exactly how much will fall remain somewhat uncertain. The center of TD2/TS Bonnie is expected to approach CHS Sun morning before turning right and then tracking NE just off the central and NE SC coastline through Sun night. Moderate upper divergence in the right entrance region of the southerly Great Lakes / E Ontario jet will persist, and as the weak shear axis edges slightly to the NE and overhead, we`ll see increasing DPVA as well. This lift will be acting on a very moist column featuring PW of 1.5- 2.0" (highest east) and a deep LCL-to-0C layer nearing 4 km, favoring efficient warm rain processes. The weak mid level winds will also mean slow cell movement and possibly prolonged moderate to heavy rainfall. The risk of heavy rain appears to be best over the Coastal Plain, where the juxtapositioning of the greatest moisture and lift is best, but there are enough differences among the models regarding timing and placement to preclude issuing any sort of flood watch at this time. Additionally, the Coastal Plain`s sandier soil can typically hold more water, raising the threshold for flooding in this area. Will monitor this threat closely today. Will carry tonight`s likely pops through Sun, trending down to chance pops Sun night west to east with loss of heating and passage of vorticity lobes just to our east leading to reduced DPVA and lower dynamic forcing in general. Highs Sun 76-82 and lows Sun night 63-68, all under cloudy skies. -GIH && .LONG TERM /Monday Through Friday/... As of 300 AM Saturday... Monday and Tuesday: Tropical Depression Two will continue to spin along the Carolina coast on Monday somewhere in the vicinity of Myrtle Beach and heading northeastward towards the NC/SC border by Monday night. The storm should be in a weakening mode possibly moving from tropical storm strength back down to tropical depression strength sometime during the day on Monday. Regardless of the strength...models point to a large amount of moisture across the eastern half of the state. Will keep pops in the high chance to likely range with slight chance of thunder Monday afternoon. The depression will shift slightly eastward on Tuesday as surface high pressure builds in over the Ohio Valley. This will quickly move northward though and weaken and is unclear how much of an effect it will have on precipitation. Therefore expect lower chances Tuesday but still a good chance for wet weather east of I-95. Highs during this period in the low 80s with lows in the mid 60s. Models diverge on Wednesday as the handling of Tropical Depression Two becomes more uncertain. The ECMWF keeps the storm lingering off of the coast while the GFS breaks it down. Either way a low pressure system over the northern plains with a frontal system extending down the Mississippi Valley will start to work eastward but will be very slow in doing so. This will leave a very moist and warm airmass in place, but a stagnant one without much forcing. Therefore expect diurnal chances for rain and possibly thunder as well Wednesday and Thursday. Highs and lows remain steady in the mid 80s and mid 60s respectively. There is very good agreement in the models regarding the frontal system finally making it to the area on Friday as an upper trough digs out of the Great Lakes. This will increase the chances for precipitation on Friday closer to 50 percent and may cool temperatures a few degrees into the lower 80s, at least across the NW Piedmont. && .AVIATION /18Z Saturday through Thursday/... As of 1100 AM Saturday... 24-Hr TAF Period: Aside from a small potential for isolated showers at the FAY terminal late this afternoon, VFR conditions will prevail through this evening. Between 06-12Z Sunday, expect an increasing potential for MVFR/IFR ceilings and visbys associated with showers at all terminals as TD#2 progresses toward Charleston, SC overnight. Sub-VFR ceilings and showers/isolated thundestorms are likely at all terminals during the day Sunday. Looking Ahead: Significant uncertainty persists with regard to the evolution of TD#2, i.e. whether or not it stalls along the Carolina coast through mid to late week. At this time, a chance for diurnally driven convection and morning stratus are expected to be the primary aviation hazards. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Vincent

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