Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201738 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 138 PM EDT Sun May 20 2018 .SYNOPSIS... A southerly flow will continue to push warm and humid air into our region today and tonight. Scattered showers and thunderstorms will develop this afternoon and become more numerous for Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 945 AM EDT Sunday... Drew back the PoPs significantly for the next several hours as short range guidance such as the HRRR and Conshort are much more bearish than previously forecast. Will hold on to the more widespread PoP after 21Z to wait and see how convection plays out this afternoon. This also mandated a change to forecast weather and QPF grids. Otherwise, minor adjustments made to match current temp trends. Nothing else significant enough to note. As of 420 AM EDT Sunday... An upper level disturbance rotating east across the region this morning creating a few lingering showers and isolated thunderstorms. This convection will dissipate as the shortwave shifts farther to the north and away from the area. Southerly flow will continue to advect warm, moist and unstable air into our region. Scattered showers and thunderstorms will develop this afternoon. The HRRR and NAM showed limited coverage, while HiResw-ARW-East indicated better coverage with convection starting along the southern Blue Ridge initially after 18z, then increasing coverage by 00z. The ECMWF and GFS had s scattered storms by 00z. The Day One Convective Outlook placed our forecast area in general thunderstorms with a marginal threat of severe to our west. With a saturated ground and rich moisture, there remains the potential for flooding. However, the coverage will be less than recent days and more localized. Please continue to monitor for river flood warnings and localized flooding problems and heed remaining road closures. High temperatures this afternoon will range from the lower 70s in the northwest mountains to the mid 80s in the Piedmont. Any convection should move east this evening. It will turn out partly to mostly cloudy and mild tonight. Low temperatures tonight will vary from the upper 50s in the mountains to the upper 60s in the Piedmont. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... As of 600 AM EDT Sunday... Continued wet and unsettled through much of the period. A Bermuda ridge will remain in place to our southeast keeping a steady, warm, moist flow of Gulf air into the region while a weak upper-level disturbance approaches from the Ohio Valley. This disturbance will push yet another weak front into the area that will stall Monday into Tuesday near the NC/VA border. A convective complex tracking across the Ohio Valley Sunday night will drift into the far western portions of the CWA early Monday before dissipating, but leave outflow boundaries along with the front draped across the area Monday afternoon to result in scattered to numerous showers and thunderstorms once again. Locally heavy rainfall and renewed flooding would be the main concern. Cannot rule out an isolated strong to severe thunderstorms, but with limited dynamics, not expecting anything organized and SPC has pulled the marginal outlook back to the west out of our area with the latest update. The boundary or baroclinic zone will linger across the area Tuesday, most likely near the NC/VA border and continue to serve as a focusing mechanism for convective development. Weak upper-level disturbances in the westerlies will drive the time frames over the more widespread convective coverage, along with diurnal heating. There is also evidence of yet another weak disturbance tracking north from the eastern Gulf of Mexico into the southeast and southern Appalachians that will serve to keep deep tropical moisture across the region and as noted above the main concern through the period of heavy rainfall and possible renewed flooding. Additional Flash Flood Watches may be needed if these forecast trends continue given that most of the forecast area is completely saturated from this past week of heavy rainfall. Little change in temperature is expected through the period with maximum temperatures just above normal in the mid 70s to lower 80s and minimum temperatures well above normal in the 60s. && .LONG TERM /THURSDAY THROUGH SATURDAY/... As of 630 AM EDT Sunday... Global models point to the later part of the week being a bit drier than the first half of the week as upper troughing drifts to the northeast of the area and an upper ridge builds over the southeast U.S. Initially this will bring a drier northwest flow aloft to the area and a large surface high drifting across OH/PA and the northern Mid-Atlantic region. This should confine the best chances for precipitation across the southern parts of the CWA. This should hold until the weekend when there is some potential for a tropical disturbance/system to move north from the eastern Gulf of Mexico renewing the threat for rain across our region. Temperatures will be a bit cooler, yet very close to normal, at the start of the period thanks to the Canadian high pressure drifting across the Ohio Valley and northern Mid-Atlantic region. By the weekend conditions should return to slightly warmer and more humid conditions once again. && .AVIATION /17Z SUNDAY THROUGH THURSDAY/...
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As of 140 PM EDT Sunday... VFR conditions to start the period as weak high pressure builds into the region. This afternoon into the evening, diurnally driven, isolated showers and possibly a rumble of thunder will be possible, mainly near and along the Blue Ridge but will move east into the lower elevations. Based on persistence, fog will be possible again overnight and could be especially dense in areas that receive rain today. Guidance suggests that while LWB will not likely see rain, fog will be particularly heavy at this TAF location. Fog should dissipate shortly after sunrise. Toward the end of the TAF period, guidance suggests MVFR ceilings will begin to drift over DAN ahead of convective activity developing to the south of the region. Winds are expected to be light and mainly from the south and west during the forecast period. Medium confidence in ceilings and visibilities. .Extended Aviation Discussion... Another weak cold front will bring increasing coverage of showers and thunderstorms again on Monday. Scattered MVFR showers and thunderstorms are possible Monday night into Tuesday with another round likely Wednesday. Conditions are expected to improve later in the week.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...JR/KK SHORT TERM...RAB LONG TERM...AL/RAB AVIATION...JR/KK

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