Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
634 FOUS30 KWBC 270836 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 436 AM EDT Fri Sep 27 2024 Day 1 Valid 12Z Fri Sep 27 2024 - 12Z Sat Sep 28 2024 ...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR THE BLUE RIDGE OF NORTH CAROLINA... ...CATASTROPHIC FLASH FLOODING WILL LIKELY BE ONGOING FRIDAY MORNING... ...Southern Appalachians... As the dissipating circulation center of Helene continues to move northward today bands of heavy rain will overspread the Southern Appalachians focusing some of the highest amounts along the Blue Ridge of North Carolina. With likely well over 12 inches of rain having fallen in this area prior to the start of the period at 12Z/8am Friday, this quick hit of as much as 6 inches of additional rain in 6 hours will likely push any flooding rivers, streams and creeks into major/catastrophic flooding stage. Te High Risk is exclusively for Friday morning with the last of Helene`s rainfall...albeit again some of the heaviest in terms of intensity. Once the circulation center passes (and largely dissipates as it moves into the mountains), all of the significant rainfall associated with Helene will finally be over in this region. A broad rain shield will linger over Virginia and West Virginia as Helene pivots northward. This part of the region will continue to be sensitive to the additional rain and flooding. Despite slightly lower amounts of total rain expected, numerous instances of flash flooding are expected. The Moderate Risk was maintained for far northwest South Carolina, western North Carolina, and portions of eastern Tennessee, West Virginia and Virginia. ...Ohio, Tennessee, & Mid-Mississippi Valleys... The westward portion of Helene`s circulation will interact with a strong upper level low whose nearly stationary movement has been partially responsible for the northward surge of tropical moisture associated with the PRE as well as Helene`s northward movement. Once the circulation center nears Atlanta Friday morning, it will turn more northwestward into central Tennessee, then stall out there for an extended period of time, maybe even 2 days. A fair amount of the tropical moisture will advect westward into the Ohio, Tennessee and Mid-Mississippi Valley to help support locally heavy rain across Kentucky and Tennessee. The latest model guidance and CAMs are depicting a swath of 2 to 4+ inches over urban or flood prone areas thus a Moderate Risk was upgraded for this period for western and central Tennessee. Campbell/Wegman Day 2 Valid 12Z Sat Sep 28 2024 - 12Z Sun Sep 29 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDDLE TO LOWER OHIO RIVER VALLEY... Lingering rain associated with the combined upper low and Helene will continue mainly across the Ohio Valley into Saturday morning. Any flooding impacts may be realized to their greatest extent along this portion of the Ohio River on Saturday. A Slight Risk remains in effect for portions of the Ohio River Valley although with an eastward and southward adjustment to reflect the latest trends and observations. Additionally, southern portions of the Northeast/northern Mid-Atlantic were trimmed out of the Marginal Risk area due to drier antecedent conditions and not as much rainfall from Helene and the frontal system as once expected. Campbell Day 3 Valid 12Z Sun Sep 29 2024 - 12Z Mon Sep 30 2024 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE EASTERN Tennessee VALLEY/SOUTHERN Appalachians AND MID- ATLANTIC REGION... Remnant energy and moisture from Helene will still be present over the region with lingering rain over extra sensitive soils. Some locations will likely have ongoing riverine flooding and additional rain amounts may aggravate the situation. A Marginal Risk for excessive rainfall remains in effect from Tennessee and Kentucky to points east to Maryland. Campbell Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt