Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Thu Sep 26 2024 Valid 00Z Fri Sep 27 2024 - 00Z Sun Sep 29 2024 ...Helene is forecast to make landfall as a major hurricane later Thursday evening and bring life-threatening impacts to Florida and the Southeast through early Saturday... ...Rare High Risks of excessive rainfall are in place for parts of the Florida Panhandle where Helene will make landfall, and for the southern Appalachians 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, now a major hurricane, is moving northward through the Gulf of Mexico this afternoon and forecast to make landfall later this (Thursday) evening in the Florida Big Bend Region. Because Helene is a large system and will initially move inland quickly, damaging and life-threatening hurricane-force winds, especially in gusts, will penetrate well inland over portions of the Florida Panhandle/Big Bend region and into southwestern Georgia late Thursday and Thursday night where Hurricane Warnings are in effect. Strong, tropical-storm force wind gusts are also likely farther north across portions of northern Georgia and the Carolinas late Thursday and into the day Friday, particularly over the higher terrain of the southern Appalachians. Additionally, catastrophic and deadly storm surge is expected along portions of the Florida Big Bend coast, where inundation could reach as high as 20 feet above ground level, along with destructive waves. There is also a danger of life-threatening storm surge along the remainder of the west coast of the Florida Peninsula. 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 bring catastrophic and life-threatening extreme rainfall and flooding threats. Beginning ahead of Helene itself, tropical moisture is being pulled north into the Southeast to southern Appalachians ahead of a slow-moving upper trough/low and surface front, currently causing rainfall and flooding that will continue through the next couple of days as Helene moves inland. Heavy to extreme rainfall from yesterday has already led to wet antecedent conditions in places where Helene will track, contributing to the significance of the flooding threat with this system. A rare High Risk (level 4/4) is in place in WPC's Excessive Rainfall Outlook (ERO) through Friday morning across portions of the Florida Panhandle/Big Bend Region, Georgia, and into the southern Appalachians. This threat will extend into at least mid-day Friday for the southern Appalachians where upslope flow should increase rain totals and varying terrain is likely to lead to landslides. Catastrophic and life-threatening flash and urban flooding, including numerous significant landslides in the Appalachians, is expected. A much broader Slight Risk (level 2/4) is in effect over much of the Southeast and extending northward into the central Appalachians and west through the Tennessee and Ohio Valleys into the Mid-South where more scattered flash flooding is expected through Friday. A more targeted Slight Risk continues into Saturday over the Ohio Valley where areas of heavier rainfall and scattered flash flooding may continue as the forecast extratropical Helene and the upper-low interact over the region. Overall, Helene is forecast to produce total rain accumulations of 6 to 12 inches over portions of the Southeast, with isolated totals of 20 inches or more into the southern Appalachians. Widespread significant river flooding and isolated major river flooding are likely. 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, from the Florida Peninsula north into the Carolinas through early Friday, continuing in the Carolinas through early Saturday. Elsewhere, showers and storms are also possible farther north in the eastern U.S. along the northern part of the frontal system for portions of New England though Friday, and as tropical moisture interacts with the front over the Mid-Atlantic through Saturday. 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. Much of the interior West including the central California Valleys and Great Basin will see highs into the low 90s. Highs into the mid- to upper 80s and even the low 90s are forecast for the northern Plains, with low 80s stretching into the Upper Midwest. Record warm temperatures are possible for both morning lows and afternoon highs. Putnam/Tate Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php