Area Forecast Discussion
Issued by NWS Blacksburg, VA

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031 FXUS61 KRNK 292322 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 722 PM EDT SUN MAY 29 2016 .SYNOPSIS... Tropical Depression Bonnie has weakened. It is centered over eastern South Carolina but will influence our weather over the next several days as it slowly moves northeast along the coast. && .NEAR TERM /THROUGH MONDAY NIGHT/... As of 330 PM EDT Sunday... clouds and scattered showers will remain over the forecast area through Memorial Day as Tropical Depression Bonnie meanders over northeast South Carolina. Abundant cloud cover and tropical moisture extend north through the Carolinas associated with Tropical Depression Bonnie. This tropical system is forecast to move very little through Monday, resulting in considerable cloudiness throughout the Mid Atlantic Region along with scattered to numerous showers and thunderstorms. PWATs east of the Blue Ridge are in excess of 1.50 inches, thus any deep convection will be rain efficient, heavy downpours potentially leading to poor drainage flooding. Coverage attm has not justified the need for a flood watch. Main area of concern within our CWA this evening and overnight will be Southside VA into the Piedmont of NC where convergence axis will exist on the north side of the tropical system, but even so, the deepest moisture will remain confined farther south closer to the circulation center. For Monday and Monday night the circulation center is expected to move very little...the Tropical Prediction Center showing a slight jog to the north. Unlike today were there was abundant mid/upper level moisture, models on Monday are suggesting some drying in the mid levels allowing for some breaks in the overcast and subjecting the forecast area to surface heating. This increase in solar insolation is expected to increase the CAPE, allowing for diurnally driven deep convection. Since airmass is of tropical origin, anything that develops will contain heavy downpours. Temperatures through Memorial Day will remain mild, elevated dewpoints keeping the overnight lows above normal. The daytime high is advertised in the 70s, but could easily eclipse 80 with a few hours of sun. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 400 PM EDT Sunday... Little change through mid week. TD Bonnie is forecast to slowly move northeast just inland of the coast. Heaviest rain is forecast to be aligned with the I-95 corridor, however our forecast area will be subject to a daily threat of diurnally driven deep convection aligned with the mountain ridges. Steering currents are forecast to be weak, and with PWATs running AOA 1.5 inches, expect scattered slow moving showers/storms with heavy downpours. With more breaks in the cloud cover, temperatures will be warmer than normal with 80s for highs. Lows generally in the 60s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 400 PM EDT Sunday... Thursday 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 late Thursday into Friday. This boundary will result in an increased threat for showers/storms...its passage bringing a less humid airmass to the region for the weekend. Until the frontal passage at the end of the week, temperatures, especially the overnight lows, will favor above normal readings. After the frontal passage, lower dewpoints and clearing skies will support lower nightime lows. Daytime highs are advertised to be close to normal. && .AVIATION /00Z SUNDAY THROUGH FRIDAY/...
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As of 722 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 more stable environment that resides over the TAF sites. Fully expect some degree of shower activity to linger on the radar east of the Blue Ridge through the overnight hours but the overall trend will be for decreasing coverage tonight. Guidance is very keen to develop low cigs and fog at all sites toward daybreak. The atmospheric column is indeed quite moist but there are is a non trivial amount of dryness shown in model soundings especially in the boundary layer. While confidence is not high still believe the degree and extent of vsby restrictions are overdone in the west as mid/upper cloud cover looks sufficient to significantly restrict radiational cooling and this should 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/IFR conditions there. However as stated earlier this is not a high confidence situation so will monitor closely to see if trends deviate from the expected forecast. 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 NEAR TERM...PM SHORT TERM...PM LONG TERM...PM AVIATION...MBS/WP

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