Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Fri Aug 27 2021 Valid 12Z Mon Aug 30 2021 - 12Z Fri Sep 03 2021 ...Tropical Storm "Ida" to Intensify to Hurricane with Central Gulf Coast Landfall Monday and a Heavy Rainfall/Runoff threat spread from the South to Mid-Atlantic through Thursday... ...Tropical Storm "Nora" to also become Hurricane with Baja California Landfall Monday with lead moisture to fuel a Southwest U.S. Heavy Rain Threat mid-later next week... ...Guidance Evaluation and Preferences... A composite of increasingly better clustered guidance of the GFS/GEFS and ECMWF/ECENS along with the National Blend of Models now seems to provide a good forecast starting point for the day 3-7 forecast period (Monday-next Friday) for much of the nation, bolstering forecast confidence. In this period, the big story concerns impending high impacts from Ida and Nora that are both forecast to become hurricanes. Please refer to products from the National Hurricane Center and your local offices to obtain the latest information on these dangerous tropical systems. ...Pattern Overview with Weather/Hazard Highlights... Tropical Storm Ida is expected to intensify to a hurricane to landfall into the central Gulf Coast by Monday and provide a Heavy Rainfall threat northeastward with steadily weakening but still deeply moist system track from the South to the southern Appalachians and Mid-Atlantic through Thursday. Ida is likely to bring rainfall totals of 8 to 16 inches with isolated maximum amounts of 20 inches along the central Gulf Coast from southeast Louisiana to coastal Mississippi and Alabama Sunday into Monday. Ida is forecast to turn northeast as it moves inland with rainfall totals of 4 to 8 inches possible across southern and central Mississippi. This is likely to result in considerable flash, urban, small stream, and riverine flooding. Moisture feeding increasingly inland with time may also then interact with a slowing front set to drape over-top the system to offer a lead heavy rainfall focus. Tropical Storm Nora is also forecast to become a Hurricane and make landfall into Baja California with lead moisture to fuel a Southwest U.S. Heavy Rain Threat next week. The latest track from the NHC lift a weakening system northward across Baja to offer a risk for lead associated moisture to enhance rainfall mid-later next week into the Southwest U.S. with max potential over favored Arizona terrain. Elsewhere, northern stream upper trough and lower atmospheric frontal system progression across the Northeast quarter of the country early next week will support a period with locally enhanced rain. Additional upper troughing well upstream will meanwhile dig a wavy but only modestly unsettling/cooling front down from the Northwest. Subsequent system progressions and genesis mid-later next week out across the Rockies to the north-central U.S. will increasingly focus an enhanced convection/rainfall pattern that could focus locally heavy convection/rainfall. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml