Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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096 FXUS62 KRAH 291616 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1216 PM EDT Sun May 29 2016 .SYNOPSIS...Tropical cyclone Bonnie will track inland along the South Carolina coast today, then turn northeast and track along the North Carolina coast Sunday through early next week. && .NEAR TERM /Today and Tonight/... As of 1215 PM Sunday... Quick update to the forecast discussion for this morning. As of 1130 am EDT...tropical cyclone Bonnie has tracked inland over southern SC. Shower activity has increased over central NC this morning, with the heaviest activity focused invof an inverted trough/coastal front south and southeast of the Triangle where PWAT values are AOA 2.00" and weak diurnal destabilization has occurred. The primary forecast concern this afternoon will be a potential for isolated flash flooding in areas repeatedly affected by heavy showers, and a low- end potential for an isolated/brief tornado in the far southeast coastal plain (Cumberland/Sampson/Wayne counties) where the latest SPC mesoanalysis indicated a supercell composite parameter of 1-2 and mlcape of ~500 J/kg. With a mean storm motion from the SE (from ~160 degrees), rotating updrafts exhibiting deviant motion will tend to propagate to the N/NNE (from ~190 degrees). A rotating updraft exhibiting deviant motion toward the N/NNE and echo tops approaching 40 KFT has already been observed in Lenoir county late this morning, lending strong support to the notion that a low-end risk for a brief/isolated tornado is present in southeast NC this aft. -Vincent && .SHORT TERM /Monday through Wednesday night/... As of 245 AM Sunday... Mon/Mon night: While this Memorial Day is shaping up to be wetter than a typical spring day especially in the east half, the details unfortunately remain murky. The weak shear axis still sitting over the region will pivot to a more north-south orientation Mon, eventually leading to weak NVA over the western Piedmont by Mon night, as the center of Bonnie continues to sit and spin with a very slow northeastward drift over the central and northern coast of SC. The streak of high-PW air (1.5-2.0") into the eastern half of NC (along an inverted surface trough extending NNE from Bonnie`s center) continues into early Mon, but wanes through the day and night as the band of greatest and deepest moisture flux shifts to our north, while mid level winds to the NE and E of Bonnie veer from SE to more southerly as the shear axis lifts out. So while rain chances should be lower than today, they`ll remain higher than climo, especially east. Pops will range from 30-40% west to 60-70% east on Mon, tapering down to 20% west ranging to 30-40% east Mon night with loss of heating and departure of large scale mechanisms to force ascent. Highs from around 80 to the lower 80s with mostly cloudy to cloudy skies. Lows Mon night in the mid to upper 60s. -GIH Tropical Storm Bonnie and its remnants will be the main weather story during the short term forecast period. With very weak flow aloft there will not be much to steer the storm away from the coastline but it is expected to gradually meander northeastward along the coast and eventually off the Tidewater VA area by Thursday. The question will be just how far inland the precipitation from the storm moves. At this time models don`t have a ton of precipitation over the forecast area with best chances along the I- 95 corridor with only slight chances across the west. Expect diurnal heating to drive thunderstorm chances with the greatest chance each afternoon. Only expecting plus or minus a half of an inch of rainfall...again with heaviest amounts in the east. Hot and humid with highs in the mid 80s and lows in the mid to upper 60s. && .LONG TERM /Thursday Through Saturday/... As of 245 AM Sunday... Focus will shift away from Bonnie on Thursday and will instead concentrate on a frontal system stemming from a low pressure system over the Great Lakes. With the moist tropical airmass still in place...diurnal showers and thunderstorms on Thursday afternoon will be probable as the front approaches. The front will lose forward progress on Friday and stall out over the east coast as an upper low and trough opens up an extended moisture plume from the Gulf of Mexico that will keep conditions wet for several days. Expect best chance for thunderstorms during the afternoon and early evening hours each day. High temperatures in the mid 80s with lows continuing to be in the mid to upper 60s. && .AVIATION /12Z Sunday through Thursday/... As of 615 AM Sunday... FAY has already dropped to IFR in rain, and elsewhere, the current VFR conditions will slowly deteriorate to MVFR or IFR later this morning, although some brief improvement back to VFR may occur this afternoon. The center of Tropical Storm Bonnie, currently located off the SE coast east of SAV (see www.nhc.noaa.gov for the latest), is expected to push slowly to the NW before stalling out near the central SC coast through much of today. A surge of Atlantic moisture to the NE of Bonnie will bring a band of showers toward the NNW through central NC this morning into early afternoon, followed by patchier and more widely scattered showers and perhaps a storm or two during the mid to late afternoon, with the best chance of storms at RDU/FAY/RWI. Within this first band of steady showers, cigs and vsbys should drop to MVFR with cigs potentially IFR at times. Once this main band shifts northward by early afternoon, conditions should vary between MVFR and VFR through early evening. MVFR to IFR fog and stratus are apt to redevelop after sunset, especially at INT/GSO/RDU, with scattered showers persisting areawide. Looking beyond 12z Mon: Unsettled weather will linger with periods of sub-VFR conditions expected through Mon, including a good chance of showers and storms Mon afternoon, especially at RDU/RWI/FAY. IFR fog/stratus is likely to redevelop for Mon night / Tue morning. Numerous sub-VFR showers and storms expected Tue afternoon at RDU/RWI/FAY, with less coverage and mostly VFR conditions at INT/GSO. Chances for sub-VFR showers diminish by Wed/Thu as the TS Bonnie circulation and associated upper level disturbance finally shifts NE away from the forecast area. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Ellis LONG TERM...Ellis AVIATION...Hartfield

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