Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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073 FXUS61 KRNK 261545 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1145 AM EDT Thu Sep 26 2024 .SYNOPSIS... Rounds of scattered showers and thunderstorms will continue across the area through today with the rainfall resulting in increasingly saturated soils. Then tonight and Friday moderate to heavy rain around Hurricane Helene 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 TONIGHT/... As of 1145 AM EDT Thursday... Key Messages: 1) Flood Watch Expanded Band of moderate rain over the mountains will continue along the same axis for the remainder of the day. Flash flood guidance is exceptionally low across much of the New River basin. Rain will also fill in along the east side of this band. Therefore the flood watch has been expanded. No other changes to the forecast at this time. Previous Discussion: An upper level low will wobble in the vicinity of Memphis TN while an upper level ridge sits off the southeast coast. These two systems will help guide Hurricane Helene as it enters the Gulf of Mexico. Hurricane Helene is expected to intensify and become a major hurricane as it moves over the warm waters of the eastern Gulf of Mexico today. Helene is expected to move inland around the Big Bend area of Florida this evening, then turns northward towards the southern tip of the Appalachian mountains (NW GA) tonight. Shortwaves coming around the upper level low will keep the chance for showers and a few thunderstorms over the area through this evening. The chances for moderate to heavy rain will be over the Mountain Empire of SW Virginia, the Grayson Highlands and NW North Carolina mountains and foothills. This area is currently under a Flash Flood Watch through this evening. Rain bands from Helene will enter the current Flash Flood Watch area and spread across the rest of the area overnight into Friday. Rainfall amounts of 1 to 3 inches fell across the area last night. An additional 1 to 2 inches are possible for most of the area and another 2 to 6 inches are likely over the current Watch area tonight into Friday. A new Flood Watch with respects to Helene`s rainfall covering the entire RNK`s forecast area is a good possibility. Winds from Helene will range between 15 to 30 MPH with gusts as high as 45 MPH late Thursday night into Friday morning. The higher end of the range will primarily be across the NW North Carolina High County, the Grayson Highlands and the Mountains Empire of SW Virginia between midnight and noon Friday. Even though winds speeds will not reach advisory criteria, trees could topple as ground will be saturated. High temperatures today will range from the mid 60s to lower 70s across the mountains and in the mid to upper 70s over the foothills and piedmont. Humidities will remain high with a tropical airmass over the region. && .SHORT TERM /FRIDAY 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 WEDNESDAY/... 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 /15Z THURSDAY THROUGH MONDAY/... As of 140 AM EDT Thursday... Showers and isolated thunderstorms will continue for locations along the western slopes (KBLF/KLWB) through 10Z, then light spotty showers for the rest of the morning. IFR to MVFR ceiling and visibilities expected through this morning. For the rest of the area, light spotty showers with MVFR ceilings and visibilities into this morning. Another round of rain enters this afternoon, then rain bands from Hurricane Helene enter the forecast area overnight. IFR to MVFR ceilings and visibilities this afternoon, becoming LIFR to IFR tonight. Light easterly flow through this afternoon, increasing to 10-15kts with gusts up to 25kts across the mountains. Stronger winds possible over the KTNB area. EXTENDED AVIATION OUTLOOK... Widespread moderate to heavy showers and isolated thunderstorms will cover the mountains and foothills with light rainfall amounts in the piedmont tonight and Friday. Wind speeds will increase in the mountains. Gusts of 25 to 40 kts are likely at the higher elevations. Wind gusts at local TAF sites will remain at or below 40 knots. Moderate in flight conditions and diminishing winds are expected Saturday through Tuesday. A chance of light showers will continue around the remnants of Helene. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch through Friday evening for VAZ007-009>020-022>024- 032>035-043>045. NC...Flood Watch through Friday evening for NCZ001>004-018>020. WV...Flood Watch through Friday evening for WVZ042>044-507-508. && $$ SYNOPSIS...RCS NEAR TERM...AMS/RCS SHORT TERM...JCB LONG TERM...JCB/RCS AVIATION...AMS/RCS