Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 350 AM EDT Thu Sep 26 2024 Valid 12Z Thu Sep 26 2024 - 12Z Sat Sep 28 2024 ...Helene is forecast to rapidly intensify to a major hurricane in the Gulf today and bring life-threatening impacts to Florida and the Southeast through Friday... ...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 is moving northward through the Gulf of Mexico this morning and is forecast to become a major hurricane before making landfall. Potentially catastrophic hurricane-force winds are expected within the eyewall of Helene when it makes landfall in the Florida Big Bend region this evening. Because Helene is becoming 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 northern Florida and southern Georgia late Thursday and Thursday night where Hurricane Warnings are in effect. Strong wind gusts are also likely farther north across portions of northern Georgia and the Carolinas, particularly over the higher terrain of the southern Appalachians. Additionally, catastrophic and deadly storm surge is likely 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 cause significant rainfall and flooding threats. Even ahead of Helene itself, tropical moisture continues to be 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 last through the day. Heavy to extreme rainfall from yesterday has also led to wet antecedent conditions in places where Helene will track. A rare High Risk (level 4/4) remains in place in WPC's Excessive Rainfall Outlook (ERO) across portions of Georgia into the southern Appalachians where upslope flow should increase rain totals and varying terrain is likely to 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 is in effect in the Day 1 ERO. A broad Slight Risk (level 2/4) with an embedded Moderate Risk (level 3/4) over the Appalachians is in place for Friday for continued rainfall. Overall, Helene is forecast to produce total rain accumulations of 6 to 12 inches, with isolated totals around 20 inches, over portions of the Southeast into southern Appalachians. Catastrophic and life-threatening flash and urban flooding, including numerous significant 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 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, today into tonight for parts of Florida into Georgia and South Carolina/southeastern North 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 likely in the northern High Plains today, with 80s stretching into the Upper Midwest through the end of the week. Record warm temperatures are possible for both morning lows and afternoon highs. Tate Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php