Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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887 FXUS62 KRAH 301459 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1050 AM EDT Mon May 30 2016 .SYNOPSIS...Tropical Depression Bonnie, located over the central South Carolina coast, will drift slowly toward 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 /Today through Tonight/... As of 1050 AM Monday... Latest surface analysis shows the remnants of Bonnie centered near Myrtle Beach with an inverted trough extending northeast of the center across the NC Coastal Plain near interstate 95. To the east of this boundary a southeasterly flow is transporting rich moisture with dew points in the lower to mid 70s resulting in an increasingly unstable air mass with mlcape values now exceeding 1000 J/Kg across part of the central Coastal Plain. Regional radar shows isolated showers increasing in coverage and intensity across the Sandhills and Coastal Plain while a region of more widespread showers and storms across northeast NC shifts northward into VA. High resolution guidance pushes the surface trough across the Coastal Plain westward into the eastern Piedmont today. A vorticity maxima noted in WV imagery across southeast NC which is largely driving the larger area of showers in northeast NC will lift north this afternoon. Other than spurious vorticity maximums rotating about the deep cyclonic circulation associated with Bonnie, most of the convection today will be diurnally forced in a very wet, weak to moderately unstable air mass. The greatest convective coverage will be east of U.S. 1 with precipitation chances and amounts significantly diminishing to the west across the western Piedmont and Triad area where the air mass will be more stable and the low level flow is more divergent. Convection today should be efficient rain producers again which combined with slow storm motion will lead to quick accumulations of rain and a localized flooding concern, especially in locations which had significant rain yesterday. While low level shear values are weak and storm organization will be limited, convective cells approaching the surface boundary will need to be monitored for enhanced, albeit short lived rotation. Highs today will be largely a function of the position of the surface boundary and periods of sunshine outside of precipitation. Look for highs today to range in the upper 70s to lower 80s. The convection tonight should diminish in coverage and intensity with the loss of heating with just an isolated shower expected overnight, mainly across the Coastal Plain. Lows will range in the mid to upper 60s with areas of fog and stratus re-developing tonight. -blaes && .SHORT TERM /Tuesday through Tuesday night/... As of 310 AM Monday... The mid level shear axis will weaken further Tue and continue an eastward drift into eastern NC/SE VA, as the center of TD Bonnie drifts NE over the southeast coast of NC. With the shift of both the mid level shear axis and the inverted surface trough eastward into coastal sections, our rain chances Tue should be a bit lower than today with the best coverage shifting into our far eastern sections and at the coast. PW will remain anomalously high, above 1.5" mainly east of Highway 1, so despite the waning dynamic forcing for ascent, it won`t take much to generate scattered showers and perhaps a storm or two especially over the eastern CWA. Will retain cloudy to mostly cloudy skies east, although the western CWA could see some sunshine if the weak mid level low center shifts into eastern NC/SE VA early enough. Highs in the low-mid 80s, coolest east where clouds should be thickest with greater shower coverage. Lows mostly in the mid 60s. -GIH && .LONG TERM /Wednesday through Sunday/... As of 305 AM Monday... Wednesday and Thursday: Tropical Depression Bonnie will continue to churn off the North Carolina coast on Wednesday somewhere between Wilmington and Cape Lookout. With no steering flow in place the forecast remains status quo with the best chances for precipitation in the east but models also hinting at precipitation forming as the result of orographic uplift as northeasterly flow approaches the Appalachians. Therefore will carry chance of showers and thunderstorms everywhere. Hot and humid with highs in the upper to middle 80s and dewpoints in the mid to upper 60s. Lows Wednesday night in the mid 60s. Thursday will see the depression move a bit further northeast and thus central NC may see a bit of a lull in precipitation before the next system approaches from the west. Will carry low chance pops in the forecast but it is possible that precipitation isn`t realized until later in the day as moisture transport ahead of the front increases. By evening expect thunderstorms to become more numerous in the Triad and points west. These will be driven mostly by diurnal heating as any dynamics associated with the fronts parent low will reside well to the north. Highs still in the mid 80s with lows in the mid to upper 60s. Friday through Sunday: Low pressure moving through the Northern Great Lakes and into Ontario and Quebec will move a frontal zone over the east coast and leave it there as it detaches and heads northeast. Back to the southwest an upper level low developing over Texas will help to initiate the development of a broad upper trough that will drape itself over the eastern US for several days. At the surface a couple of waves, most notably on Saturday afternoon, will move along the front and supply extra forcing for showers and thunderstorms over central NC. Expect best chances in the afternoon each day. Temperatures will cool off some during this time starting in the mid to upper 80s on Friday afternoon down to the lower 80s by Sunday afternoon. Lows each night in the mid to upper 60s. && .AVIATION /12Z Monday through Friday/... As of 645 AM Monday... Periods of adverse aviation conditions are expected to dominate over the next 24 hours at Central NC terminals, as very moist air remains in place over the area. At INT/GSO, MVFR cigs are expected to persist through the morning, before gradually lifting to VFR during the early afternoon hours. Scattered showers this afternoon may generate brief MVFR vsbys here, but otherwise VFR vsbys are expected during the daylight hours today. At RDU/RWI/FAY, IFR/LIFR cigs will persist early this morning, especially at RDU/FAY, where IFR vsbys are also likely. Vsbys at these three sites should improve to VFR later this morning, with cigs slower to improve, trending to MVFR during the afternoon. Isolated showers with MVFR vsbys are likely to pass near RDU/RWI/FAY through mid morning, then coverage will increase by afternoon, with numerous showers and a few thunderstorms this afternoon into evening producing brief MVFR to IFR conditions mainly at RDU/RWI/FAY. Shower/storm coverage is expected to slowly decrease this evening with a trend to MVFR to IFR conditions after sunset. Looking beyond 12Z early Tue morning: MVFR to IFR conditions are likely to hold through mid morning Tue, with improvement to MVFR east and to VFR west during Tue afternoon. Nightfall will bring another trend to sub-VFR conditions at all sites Tue night, as the air mass remains moist and unsettled with the center of TD Bonnie tracking slowly toward the NNE along the NC coast. Improvement to VFR is expected Wed lasting into Thu especially at INT/GSO, as Bonnie moves out over the sea, although sub-VFR vsbys in fog are possible late Wed night into early Thu morning with light surface winds. A cold front approaching from the west Thu night may bring sub-VFR conditions in showers/storms on Fri. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...blaes SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield

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