Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 PM EDT Wed Sep 25 2024 Valid 00Z Thu Sep 26 2024 - 00Z Sat Sep 28 2024 ...Helene is forecast to rapidly intensify to a major hurricane in the Gulf and bring life-threatening impacts to Florida and the Southeast through Friday... ...A rare High Risk of Excessive Rainfall is in place for the southern Appalachians through Thursday night where catastrophic flash flooding and landslides are expected... ...Above average temperatures and summer-like warmth forecast to stretch from the Southwest to northern Plains... Hurricane Helene is currently entering the southeastern Gulf of Mexico this afternoon and is forecast to become a major hurricane on Thursday before making landfall over the Florida Panhandle sometime Thursday evening. A Hurricane Warning is in effect over the Florida Big Bend and extending inland into southwest Georgia for damaging hurricane-force winds. The damaging wind threat is also expected to stretch even further inland towards the southern Appalachians and much of Georgia as the storm races northward through Friday, with Tropical Storm Watches posted. Helene will grow in size as it strengthens, spreading its impacts to much of Florida and the Southeast. There is a danger of life-threatening storm surge along the entire west coast of the Florida Peninsula, central and eastern sections of the Florida Panhandle (including the Florida Big Bend). The highest inundation levels are expected along the coast of the Florida Big Bend. Prepare now and heed instructions from local officials about evacuations in these areas. Please refer to the National Hurricane Center for the latest updates on the track and timing of Helene. Helene will also cause significant rainfall and flooding threats. Even ahead of Helene itself, tropical moisture will be pulled north into the Southeast to southern Appalachians through tonight ahead of a slow-moving upper trough/low. This moisture will pool along and ahead of a stalling front at the surface and lead to excessive rainfall. A rare High Risk (level 4/4) is in place in WPC's Excessive Rainfall Outlook (ERO) across portions of Georgia into the southern Appalachians tonight, in addition Slight Risks (level 2/4) of flash flooding have been issued in parts of the Florida Peninsula and west coast of Florida as Helene approaches. Today's rainfall is forecast to create numerous instances of flash flooding while also leading to wet antecedent conditions that should likely overlap heavy rain along Helene's track Thursday-Friday. Thus a High Risk of excessive rainfall is also delineated on Thursday across the southern Appalachians where upslope flow should increase rain totals and varying terrain could lead to landslides. Additionally, a separate area of extreme rainfall is also likely near the core of the storm as it passes over the Florida Panhandle, where a separate High Risk of Excessive Rainfall is in effect. Overall, 6 to 12 inches of rain with isolated totals around 18 inches is forecast over the Southeast and southern Appalachians. Catastrophic and life-threatening flash and urban flooding, including landslides, is expected across portions of the southern Appalachians through Friday. Considerable to locally catastrophic flash and urban flooding is likely for northwestern and northern Florida and the Southeast through Friday. Widespread minor to moderate river flooding is likely, and isolated major river flooding is possible. Another weather hazard associated with Helene to monitor is the tornado threat, especially on the eastern side of the track. The Storm Prediction Center is indicating a Slight to Enhanced Risk of severe weather, primarily for tornadoes, on Thursday into Thursday night for parts of northern Florida into Georgia and South Carolina. Elsewhere, showers and storms are also possible farther north in the eastern U.S. along the northern part of the frontal system over the next couple of days. A couple of fronts passing through the Northwest should lead to some precipitation there and gusty winds. Meanwhile the rest of the western U.S. stretching into the north-central U.S. can expect dry conditions with warmer than average temperatures. The Desert Southwest will see highs well into the 100s and low 110s, which has prompted Excessive Heat Warnings from south-central Arizona into the high deserts of southern California. High into the 90s are possible in the northern High Plains, with 80s stretching into the Upper Midwest through the end of the week. Some record warm temperatures are possible for both morning lows and afternoon highs. Snell Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php