Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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065 FXUS62 KRAH 290058 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 845 PM EDT Sat May 28 2016 .SYNOPSIS...Tropical storm Bonnie off 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 841 PM Saturday... The latest information from the NHC indicated that TS Bonnie had stalled in the last few hours. It is expected to resume the NW movement but less than 10kt this evening as it tracks toward the southern SC coast. There continued to be an impressive plume of deep moisture advecting NW to the east of the center of circulation of Bonnie. At the surface, a surface trough or wind shift line had advanced westward into the Piedmont from the Coastal Plain at mid- evening. Dew points jump into the mid to upper 60s from the upper 50s as the trough moves passes and winds become more easterly off the Atlantic. An initial rain band was rotating NW toward the SE NC coastal region this evening. It appears that it will be late evening before some of this band moves into our southern Coastal Plain. We will ramp up POP in the SE to account for this activity and additional rain later on. Conversely, we will cut POP back for the NW-N zones to a slight chance through 06Z, then as the rain/showers develop and spread NW-W increase POP between 06Z-12Z throughout the region. It appears a surface trough will set up over the region later tonight into Sunday. It should be along this convergence axis that rain/showers become widespread later tonight and Sunday. With dew points rising and skies becoming cloudy, expect lows 65-70 SE and lower to mid 60s NW. && .SHORT TERM /Sunday through Sunday night/... As of 200 PM Saturday... TD#2 is expected to become a low-end tropical storm prior to landfall (or closest approach to the SC coast) around 12Z Sunday morning. The precise evolution of this system (the track in particular) will heavily influence the location/amount of rain that falls across central NC Sunday into Sunday night, as demonstrated by the wide variety of solutions obtained from various convection allowing models. As a result, the location(s) or area(s) that will receive the heaviest rainfall remain difficult to pin-down at this time. Based on the official NHC guidance, one would expect the axis of heaviest rain to become oriented N-S or NNE-SSW in vicinity of Highway 1 or I-95. Locally heavy rainfall amounts of 1-3" will be possible in this area. High temps will depend primarily upon cloud cover and precipitation, which should be pervasive over much of central NC. As such, will indicate highs in the mid/upper 70s, though lower 80s will be possible if/where there are breaks in cloud cover. Expect lows in the mid/upper 60s (possibly near 70F) Sunday night with a tropical airmass in place, southeasterly flow off the Atlantic, lingering cloud cover, and showers. Hazardous Weather: A localized potential for flash flooding will be present Sun/Sun night, primarily in urban areas. Given the anticipated location of TD#2 (expected to stall in southern SC during the day Sun), the best low/mid-level shear (mini-supercell/ tropical tornado potential) is expected to remain south of central NC, along and near the coast from Charleston SC north to Wilmington, NC. -Vincent && .LONG TERM /Monday Through Saturday/... As of 310 pM Saturday... Monday through Wednesday: The low associated with tropical depression two will be captured in a weakness or trough in the upper- level pattern over the southeast U.S. and a 590m ridge over the western Atlantic. This will result in a very slow east to northeast drift of the surface low as the ridge over the Atlantic weakens. The best precipitation chances during the period should be focused across central the eastern half of NC and in our forecast area across the coastal Plain/Sandhills and the eastern Piedmont. This is given the northward advection of deep layer moisture on the backside of the offshore ridge and to the east of the trough axis combined with some modest forcing for ascent east of the trough and low-level convergence resulting from the tropical circulation and frictional convergence in the coastal region. The greatest rain chances during the period will likely be on Monday east of U.S. route 1 where rain coverage and amounts will be greatest. Rain chances decrease somewhat on Tuesday and Wednesday. Rainfall amounts will be rather localized with slow moving bands and clusters of showers/storms driving precipitation amounts. Average amounts through the period will range around an inch to an inch and half from I-95 east, a half inch to an inch between U.S. 1 and I-95 and a half inch or so west of U.S. 1. While these amounts aren`tterribly impressive, we fully expect localized higher amounts during the period. Highs during the period will generally range in the lower 80s on Monday and the lower to mid 80s on Tuesday and Wednesday with morning lows in the mid to upper 60s. Thursday through Saturday: A slow moving trough pushes east across the plains on Thursday and extends from the eastern Great Lakes to the northern Gulf of Mexico on Friday and Saturday. The eastern progression of the trough slows as heights rise off the Southeast coast and the remnants of TD two eventually dissipate off the Northeast coast. The developing southwesterly flow ahead of the approaching upper trough leads to another period of moisture transport with increasing instability. After a modest decrease precipitation chances on Thursday in between systems and with a minimum which should result in a period of unsettled weather for Friday into Saturday with showers and thunderstorms. highs will mainly range in the lower to mid 80s with lows in the 60s. -blaes && .AVIATION /00Z Sunday through Thursday/... As of 8 PM Saturday... 24-Hr TAF Period: A plume of tropical moisture will advect into the area overnight and into the day on Sunday as TS Bonnie moves onshore between Charleston and Beaufort, SC. Ceilings are expected to lower to MVFR/IFR from SE to NW between 06z-12z, with increasing chances for showers and associated sub-VFR visibilities expected at all terminals by mid/late morning. Sub-VFR ceilings and visibilities will persist through the afternoon and evening with numerous heavy rain producing showers across the area, along with a threat for isolated thunderstorms mainly across the eastern terminals. Looking Ahead: Unsettled weather with continue Sunday night through Monday as TS Bonnie and associated tropical moisture plume linger across the area. Significant uncertainty persists whether or not remnants of Bonnie 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. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Badgett SHORT TERM...Vincent LONG TERM...blaes AVIATION...CBL/Vincent

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