Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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683 FXUS62 KRAH 310707 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 307 AM EDT Tue May 31 2016 .SYNOPSIS...Post Tropical Cyclone Bonnie over northeast South Carolina will drift slowly to the northeast along the North Carolina coast through mid week, before moving offshore. A cold front will approach from the west late in the week. && .NEAR TERM /through Wednesday night/... As of 240 AM Tuesday... Today/tonight: With little change in the overall pattern today, persistence will be the rule. The center of Post-Tropical Cyclone Bonnie, located along the SC coast NE of CHS, will continue a slow northeastward drift today along and just off the northern SC coast, as a weak inverted trough lingers over coastal NC. Only isolated patchy showers remain over northern NC, a function of weak low level mass convergence and the continued presence of the weak mid level shear axis that has been drifting ENE over the region over the last few days. Plentiful low level moisture, decreasing clouds early this morning, and very light surface winds will foster formation of fog and stratus this morning, particularly over the piedmont. The column remains quite moist over central/eastern NC with PW values holding at 140-180% of normal, and models agree on low level moisture transport ramping up starting this morning, so despite the lack of strong mechanisms to force ascent, it won`t take much to kick off showers especially along/east of Highway 1. Will maintain a trend to chance pops west and likely pops east this afternoon. Cell motion should again be fairly slow, facilitating locally higher rainfall totals which could prompt localized street flooding again today, and urban and small stream flood advisories may once again be needed. Instability is projected to be marginal (peaking near 1000 J/kg in the far east only) with very weak deep layer shear, so thunder should remain isolated. Thicknesses are expected to be close to normal but with considerable cloudiness, highs should hold in the lower to mid 80s. Will trend shower coverage down to low chances tonight with loss of heating, and more fog and stratus looks like a good bet for later tonight with continued elevated low level moisture transport over the region. Lows in the mid to upper 60s. Wed/Wed night: More of the same, although the better rain chances should shift slightly more eastward. The center of Bonnie is expected to continue a northeastward drift off the southern coast of NC, as the weak mid level shear axis maintains its very slow eastward drift. PW is forecast to remain above normal, in the 1.5- 2.0" range over central and especially eastern NC, and models are projecting perhaps a bit more instability (MUCAPE topping out at 750- 1500 J/kg), which should ensure at least scattered coverage. Will again trend pops up to chance west and likely east Wed afternoon, before trending them back down to isolated at most Wed night. With similar thicknesses and similar cloud cover anticipated as compared to today, will again have highs in the lower to mid 80s. Lows Wed night in the mid-upper 60s with fair skies early and areas of stratus once again forming overnight. -GIH && .SHORT TERM /Thursday through Friday night/...
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As of 305 AM Tuesday... Post-tropical storm Bonnie will continue to spin along the North Carolina coast on Thursday with most of the precipitation occurring east of I-95. Back to the west, a frontal system will move towards the Appalachians and into western NC. For central NC this could mean a lull in the soggy weather and perhaps a mostly dry day for much of the area. Still expect partly to mostly cloudy skies however and still a tropical air mass in place with highs in the mid 80s and dewpoints in the upper 60s. Any showers and thunderstorms that do occur could produce some locally heavy rain but otherwise not much QPF expected. Lows Thursday night only dropping down into the upper 60s. On Friday, the remnants of Bonnie will finally move offshore to our northeast and attention will turn to the frontal system moving in from the west. Any dynamics with this system will be well to the north of our area. A few waves moving along the front from the south to north will provide some vorticity in the mid to upper levels. The main forecast problem surrounds how far south the front will be able to push. At this time...the GFS solution has a big stronger of a surface high over the Ohio Valley that helps to push the front further south by Friday afternoon. This scenario suggest plenty of showers and thunderstorms for the entire forecast area on Friday, whereas the ECMWF solution has rain only in the north and western portions of the CWA. With the lack of forcing the ECMWF solution seems more likely at this time. This will also keep temperatures and dwpoints up in the mid 80s and upper 60s respectively as there will not be any air mass change on Friday. Lows Friday night in the upper 60s to near 70 degrees.
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&& .LONG TERM /Saturday through Monday/...
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As of 305 AM Tuesday... The evolution of the front in both models is fairly similar for Saturday as a tropical upper ridge helps to stall the front out over the area making another wet weekend the most likely scenario for central NC. Looking back to the west, a new and more organized low pressure system moves into the western Great Lakes on Saturday with a frontal system extending down the Mississippi Valley with an upper trough to support it. This system will eventually take the stalled front back to the north as a warm front as the cold front approaches from the west later on Saturday and into Sunday. Pre-frontal precipitation, supported by several strong waves from the southwest will affect the area on Sunday. The current GFS scenario is very wet on Sunday night into Monday and the ECMWF is much more subdued. This leads to a very low confidence forecast for day 7 but will carry pops through Monday. Continued low to mid 80s for highs with lows in the mid to upper 60s.
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&& .AVIATION /06Z Tuesday through Saturday/... As of 100 AM Tuesday... Persistence will be the rule today, with aviation weather likely to follow a pattern similar to yesterday, meaning a high chance of predominant adverse aviation conditions through this morning and again as we head through tonight. Patchy showers over north central NC should continue to slowly diminish as the low levels stabilize. Decreasing clouds early this morning should lead to stratus and fog development this morning (best chances at GSO/RDU/RWI but possible at all sites) with IFR conditions expected. The IFR fog/stratus will slowly lift to MVFR by mid morning (by 12z-14z) and to VFR by midday (14z-16z). Scattered showers with MVFR vsbys and brief MVFR cigs are possible this afternoon and evening mainly at RDU/RWI/FAY, and isolated storms are also possible. These showers should slowly weaken and dissipate toward the end of the TAF valid period. Winds will remain light, mainly under 10 kts, from the NE today. Looking beyond 06z early Wed morning: Another round of IFR fog and stratus is expected late tonight into Wed morning, improving to VFR by late morning. More scattered afternoon showers and isolated storms will affect central NC TAF sites Wed with brief MVFR conditions. More IFR stratus/fog is then expected late Wed night into Thu morning. The risk of showers/storms appears to be less on Thu afternoon than in recent days, so VFR conditions should dominate. An approaching cold front will bring a return to mostly afternoon showers and storms Fri/Sat. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Ellis LONG TERM...Ellis AVIATION...Hartfield

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