Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 290706 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 305 AM EDT Sun May 29 2016 .SYNOPSIS...Tropical Storm Bonnie will approach the South Carolina coast this morning, and then track slowly northeastward along the South Carolina and North Carolina coastline through the middle of the week. && .NEAR TERM /through Monday night/...
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As of 305 AM Sunday... For today: Thickening clouds and rising rain chances are on the horizon for central NC today. The center of TS Bonnie is now located a couple hundred miles south of MYR and is on pace to reach the central SC coast near CHS later today, before essentially stalling out. Convection with Bonnie remains disorganized and has frequently been focused well away from its center, and this should remain the case today despite expected minor strengthening. Water vapor imagery reveals the stream of deep moisture east and north of Bonnie, extending from NE of the Bahamas to the NW across NC. Low level mass convergence occurring now along the southern NC and NE SC coast is supporting a broad band of steady showers, and this should continue to track to the NW through central NC this morning. The mid level shear axis which has extended across SC and SW NC over the last day or two will pivot slowly to the ENE through tonight, leading to increasing DPVA in central/eastern NC. One vorticity center in particular over central/SE SC will streak NNW then N into our area later today into tonight, while a second potent mid level vorticity max now located well east of SAV and east of the Bonnie center sheared to the NNW over eastern NC late tonight. Both of these features combined with the influx of deep moisture (PW nearing 2.0") and added lift from weak upper divergence will support likely to categorical pops today, slipping gradually after nightfall to likely areawide mid-late evening, then to chance west / likely east late tonight with decreasing coverage / intensity as the weak yet vertically juxtaposed lift mechanisms start to shift into eastern NC/SE VA. Forecast instability is modest, peaking near 1000 J/kg mainly east of the Triad, with marginal deep layer shear barely reaching 20 kts, so will restrict a mention of isolated thunder to the afternoon and early evening hours in eastern sections, mainly east of Highway 1, where surface dewpoints at or above 70 will contribute to the instability potential. Temps are tough today as any break in the clouds and subsequent heating (a likely bet in the eastern CWA) will cause temps to soar. Conversely, the lighter but more expansive rain now over the western Piedmont (supported by moist upglide at 300K-315K) in tandem with the NW movement of the coastal rainband inland should keep lots of clouds and good rain chances there, hindering heating. Thus, expect highs from the lower 70s far NW to the lower 80s over the Coastal Plain. Despite the steady slow decrease in pops from west to east tonight, chances will remain higher than climo, especially in our eastern half, and clouds will be abundant and at multiple levels, cutting down on nocturnal cooling. Total rainfall through tonight is expected to range from a half to one inch, although certainly there will be locally heavier totals, given the slow MBE movement. lows from 64 west to around 70 east. 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
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&& .SHORT TERM /Tuesday through Wednesday night/... As of 245 AM Sunday... 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 /06Z Sunday through Thursday/... As of 135 AM Sunday... Details are tough to pin down but the most likely scenario consists of current VFR conditions at all sites slow deteriorating to MVFR later this morning, and wavering between MVFR and VFR through much of today. As low level moisture increases further, pockets of MVFR vsbys in fog are expected areawide between 07z and 12z this morning. The center of Tropical Storm Bonnie, currently located off the SE coast ESE of SAV, 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 is expected to bring a band of showers toward the NNW through central NC from mid morning through 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 06z Mon: Unsettled weather will persist with periods of sub-VFR conditions expected through Mon, including a good chance of showers and storms Mon afternoon. IFR fog/stratus 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...Hartfield NEAR TERM...Hartfield SHORT TERM...Ellis LONG TERM...Ellis AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.