Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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150 FXUS61 KRNK 270132 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 932 PM EDT Thu Sep 26 2024 .SYNOPSIS... Rounds of scattered showers and thunderstorms will continue across the area tonight and Friday, with moderate to heavy rain associated with Hurricane Helene expected. This will greatly enhance the threat of flooding in the mountains and foothills. Over the weekend the remnants of the tropical system will be trapped over the Tennessee Valley with a lower probability and coverage of showers. && .NEAR TERM /THROUGH FRIDAY NIGHT/... As of 915 PM EDT Thursday... Key Messages: 1) Significant flooding expected; do not try and drive through water covered roads! 2) Heavy rain, landslides, small tornadoes, and very gusty winds are expected to be a threat for much of the area tomorrow. In the last couple of hours Helene has acquired an eye and increased in strength to a category 4 hurricane. The storm will make landfall along the Big Bend of FL in the next couple of hours. Helene is moving relatively fast at 23 mph. Minimum central pressure was 942 mb at 8 PM EDT. After landfall, Helene will travel inland over GA and reach east central TN by 2 pm tomorrow. Affects of Helene are already being felt in the southern Appalachians, as high moisture content interacts with the higher terrain, wringing out moderate to heavy rain. A few tropical spinups have also been noted, mainly in Caswell County, and this threat will continue through the night and into Friday as rainbands from Helene arrive from the south. Repeated rounds of rain and increased forcing for ascent have contributed to rainfall amounts so far ranging from 3 to 7 inches in the last 24 hours from the mountains westward. To the east, amounts have been generally resulted in less than 3 inches. An additional 1 to 3 inches is expected for the lower terrain, with 3 to 7 inches possible for parts of the Blue Ridge and western NC mountains. A Flood Watch remains in place for the entire area, and we have received reports of high water rescues, flooded roads, streams and rivers increasing to bankfull and beyond, and at least one landslide. These problems will only get worse as the storm nears. As a reminder- do not drive across flooded roads, you do not know how deep the water is! Strong sustained winds of 25 to 35 mph with gusts as high as 60 mph are expected for elevated parts of the Blue Ridge, generally above 3500 ft. A Wind Advisory is in place for most of the remainder of the area, with speeds of 15 to 25 mph with gusts to 45 mph possible. As of 415 PM EDT Thursday... Key Messages: - Flood Watch Expanded - High Wind Warning Issued - Wind Advisory Issued Persistent area of moderate to occasionally heavy rain, with prolonged rates of 1 to 2 inches per hour have resulted in flooding southwest of a line from Bluefield WV to Yadkinville North Carolina. As expected the amount of rain needed for flash flooding is under one inch through much of the mountains. Rain was filling in over the foothills and piedmont. As Hurricane Helene moves north the shield of heavier rain will reach the southern Appalachians. The heaviest rainfall amounts expected from this evening through Friday evening is still along the southern Blue Ridge. Bufkit forecast soundings showed the potential for gusts of 40 to 60 mph at the highest elevations of southwest Virginia and northwest North Carolina overnight and into Friday morning. The areas favored to have enhanced wind speeds with strong southeast surface and low level wind in Tazewell to Smyth County also have the potential for damaging wind. These areas area now covered with a High Wind Warning. One change to note is that although winds will diminish in the afternoon, gusty conditions will persist longer into the afternoon. Plus with the saturated ground trees will more easily by blown down. Therefore the Wind Advisory has been issued to cover a large area and until the end of the day Friday. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... As of 200 AM EDT Thursday... Key Messages: 1) Hurricane Helene will quickly weaken and mostly dissipate Friday night into Saturday. 2) Rain chances significantly decrease for Saturday, but increase once again on Sunday. Hurricane Helene will have mostly moved through the area by Friday night, with only scattered showers remaining over the region. However, the airmass will still remain tropical, with dewpoints in the 60s to near 70, especially in the piedmont locations. Despite this, there is increasing confidence that PoPs will be significantly lower on Saturday, due to drier air in the mid-levels. Even some sunshine is expected to return for parts of Saturday afternoon as cloud cover will lessen. The remnant low of Helene will continue to meander through the weekend in the Ohio River Valley, with no significant weather systems expected to pick the storm up and move it. It will then slowly begin to drift back to the east and into the Mid-Atlantic on Sunday, though models differ on how quickly this will occur. Nonetheless, this track to the east will allow showers to develop once again on Sunday. There is moderate confidence that QPF totals for the weekend will generally be under 0.25" for most of the RNK CWA, according to the NBM, with isolated areas possibly seeing up to 0.50" in the heaviest showers. High temperatures on Saturday will be in the 70s to low 80s, due to the break in cloud cover. Sunday will see slightly cooler temperatures, as clouds and showers move back over the region with highs in the 70s. Nighttime lows will be around 60 degrees both days. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 200 AM EDT Thursday... Key Messages: 1) Scattered showers persist for the early week as the remnant low of Helene slowly begins to move east. 2) Drier and quieter weather finally returns for the midweek. As the remnant low of Helene moves back over our area Sunday night and Monday, showers will remain in the forecast as the tropical airmass remains in place. The Ensemble Situational Awareness Table keeps precipitable water amounts around 1.5 inches through Tuesday night. Because of this, PoPs still remain modest for both Monday and Tuesday, though there is uncertainty in the coverage of the rainfall across the CWA. Temperatures will be around normal, with highs in the mid 70s, with 60s for the higher elevations. A cold front begins to approach the area on Tuesday, though confidence remains low on the timing as models disagree on this. Once the front passes, much drier conditions will move into the area, with high pressure building back in place. This will also cause temperatures to fall below normal, with lows possibly in the 40s across most of the CWA for Wednesday night. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... As of 930 PM EDT Thursday... Persistent area of moderate to occasionally heavy rain, with prolonged rates of 1 to 2 inches per hour have resulted in flooding southwest of a line from Bluefield WV to Yadkinville North Carolina. Ceilings will continue to vary from IFR to MVFR until sunset then lower to IFR/LIFR across the region overnight. Visibility will occasionally lower to MVFR in the heavier rain. Catastrophic, life-threatening flooding is possible overnight into Friday, especially along the southern Appalachians. Check your destination before you fly. Bufkit forecast soundings showed the potential for gusts of 40 to 60 mph at the highest elevations of southwest Virginia and northwest North Carolina overnight. By 06Z gusts of 30 to 40 kts from the east are expected at the local TAF sites. Average confidence for wind, ceiling and visibility. EXTENDED AVIATION OUTLOOK... Wind speeds diminish Friday afternoon through Friday night. Flight conditions should improve Saturday through Tuesday. A chance of light showers will continue around the remnants of Helene. && .HYDROLOGY... Affects of Hurricane Helene continue to be felt in the southern Appalachians, as high moisture content interacts with the higher terrain, wringing out moderate to heavy rain. Repeated rounds of rain and increased forcing for ascent have contributed to rainfall amounts so far ranging from 3 to 7 inches in the last 24 hours from the mountains westward. To the east, amounts have been generally resulted in less than 3 inches. An additional 1 to 3 inches is expected for the lower terrain, with 3 to 8 inches possible for parts of the Blue Ridge and western NC mountains. A Flood Watch remains in place for the entire area, and we have received reports of high water rescues, flooded roads, streams and rivers increasing to bankfull and beyond, and a landslide. River flooding is ongoing or expected to begin shortly on the following rivers: Clinch, New, Roanoke, and Dan. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch through Friday evening for VAZ007-009>020-022>024- 032>035-043>047-058-059. High Wind Warning until 8 PM EDT Friday for VAZ007-009-015. Wind Advisory until 8 PM EDT Friday for VAZ010>014-016>020- 022>024-032>035-043>045-058. NC...Flood Watch through Friday evening for NCZ001>006-018>020. High Wind Warning until 8 PM EDT Friday for NCZ001-018. Wind Advisory until 8 PM EDT Friday for NCZ002>006-019-020. WV...Flood Watch through Friday evening for WVZ042>044-507-508. Wind Advisory until 8 PM EDT Friday for WVZ042>044-507-508. && $$ SYNOPSIS...RCS NEAR TERM...AMS/SH SHORT TERM...JCB LONG TERM...JCB/RCS AVIATION...AMS/RCS/SH HYDROLOGY...SH