Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 291803 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 203 PM EDT SUN MAY 29 2016 .SYNOPSIS... Tropical Storm Bonnie will weaken today as it moves to the South Carolina coast. This system is expected to move very slowly northward along the coast the next several days causing unsettled weather across the mid atlantic region through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of Noon EDT Sunday... Lot`s of cloud cover across the forecast area, but not a lot of rain. Main focus for rain has been along and east of Highway 29. Morning RNK sounding indicated a dry layer around 800 mb...so any rain that is falling west of the blue ridge is occurring in an environment that is not quite saturated...PWAT 1.17. The GSO sounding on the other hand was near saturation with a PWAT of 1.73. Latest meso analysis continued to indicate dry sub cloud layer in the west with near saturation south and east of danville. As such expect the most persistent, and heaviest rain this afternoon to be mainly confined to our southeastern CWA. Tropical Depression Bonnie has moved onshore vicinity of Charleston SC, the heaviest of the rain occurring over south central South Carolina. Scattered to numerous showers extend northward from the system into our forecast area. For our forecast area, unless the showers become more organized the probability of a flooding sort of rainfall appears low attm. Latest guidance from WPC continues to focus the heaviest rain and potential for excessive run-off along the I-95 corridor. The thunderstorm threat this afternoon appears minimal, clouds and occasional tropical precip inhibiting instability. That said, will maintain isolated thunderstorm threat with heavy rain over Southside Virginia into the NC Piedmont where CAPE will increase from breaks in the overcast over central/eastern NC. Tonight, the remnants of Bonnie will stay along or just inland of the South Carolina coast. Setup continues to favor showers over the east during the night but usually at night tropical systems with respect to rainfall tighten up, such that areas along and west of the Blue Ridge appear to dry out after midnight or have limited coverage. Still confidence is not high to go completely dry as the 00z NAM and ECMWF are hitting an area over the Triad of NC into portions of Southside VA around Martinsville and Danville with a heavy band of rain. As for temperatures, the clouds and showers should be keeping highs lower today but expect muggy conditions with temps reaching the 70s most areas. Tonight stays muggy with lows in the upper 50s mountains to mid 60s east. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... As of 210 am Sunday... Tropical Storm Bonnie, lingering around the Carolina coast, will be the focus through mid week. High humidity and showers will be in the forecast as long as it remains with highest pops along and east of the Blue Ridge, and lowest in the west. Even if the deeper moisture hugs the coast, any increase in sunshine across our area will result in increasing instability with diurnally driven showers and scattered thunderstorms. With more breaks in the cloud cover, temperatures will be warmer than normal with 80s for highs. Lows generally in the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 350 PM EDT Saturday... The air mass will remain warm and humid, with a continuation of diurnally driven deep convection. A cold front is forecast to approach the forecast area from the west Friday. If by chance the tropical low is still around, this front should give it a boot out to sea. If there is a threat for stronger sort of storms for this upcoming week, it would come with Friday`s frontal passage. Temperatures, especially the overnight lows, will favor above normal readings through the end of the week. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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As of 150 PM EDT Sunday... High confidence in light winds but below average confidence in cigs/vsbys during this taf period. The circulation of Bonnie continues to spin over South Carolina. This is pushing moisture in our direction from the southeast but we are lacking a good focusing mechanism to realize significant precipitation. Orographic affects are being minimized since the low level flow is not favorable for upslope along most of the Blue Ridge so we are seeing showers move in our direction and lose a lot of vigor as they enter the cloudy more stable environment that resides over the TAF sites. Believe the trend will be for showers to be on the decrease through early this evening as diurnal heating affects wane but still expect some showers to be floating around east of the Ridge through at least early tonight. Guidance is very keen to develop low cigs and fog at all sites toward daybreak. Believe there will be too much mid/upper cloud cover west to allow for good radiational cooling and this should severely limit the changes for sub VFR conditions at KBLF and KLWB. The chances for lower cigs and vsbys are better further east where low level moisture will be higher so will introduce some MVFR conditions further east. However as stated earlier this is not a high confidence situation so keep a close eye on satellite/radar trends and observations. EXTENDED DISCUSSION... Low confidence on flight category for Monday-Thursday. Models indicate low pressure will stall over the eastern mid-atlantic and linger through mid week. Our forecast area will be on the western periphery of this feature which suggests best flight conditions will be over and west of the Blue Ridge. MVFR or lower ceilings are possible at KLYH and KDAN Monday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM/WP NEAR TERM...PM/WP SHORT TERM...RCS LONG TERM...PM AVIATION...MBS/WP

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