305 FXUS02 KWBC 072002 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 402 PM EDT Wed Oct 7 2026 Valid 12Z Sat Oct 10 2026 - 12Z Wed Oct 14 2026 ...Isaias will bring heavy rainfall and potential flash flooding across parts of the Southeast into the Mid-Atlantic through the weekend... ...Remnants of Rachel to increase heavy rainfall potential across the Southwest and Intermountain West this weekend into early next week... ...Pattern Overview... Isaias and its remnants will produce heavy rain and the potential for flash flooding as it tracks into the Tennessee and Ohio Valleys this weekend before being swept eastward across the Mid-Atlantic by Monday. An amplified western trough will interact with Rachel and its remnants, bringing widespread rain across the Southwest and Intermountain West/Rockies Sunday into Monday. Meanwhile, the first widespread snow of the season arrives for the high elevations of the northern Rockies this weekend and continues into early next week. ...Guidance/Predictability Assessment... The latest available guidance continues to have a fairly decent handle on the large scale pattern through the medium range period, though uncertainties remain with the smaller scale details. Overall, the machine learning guidance (AI-GFS/EC-AIFS) along with (to a lesser degree) the deterministic runs of the GFS and UKMET seem to have the best depiction of both the upper and surface patterns, especially with respect to the temporal and spatial distributions of both tropical systems (Isaias and Rachel). These guidance sources were heavily utilized for QPF and other gridded elements, along with fronts and pressure. Towards the end of the period, more weighting was placed on the ensemble means of the EC and GEFS, which helped to smooth larger differences. ...Weather/Hazards Highlights... The primary concern for the upcoming weekend will be the ongoing heavy rain and potential flash flooding as Isaias tracks northward into the Tennessee and Ohio Valleys. Even after Isaias becomes extratropical and weakens not long after pushing inland, a deep plume of Gulf moisture and a broad circulation will support periods of moderate to heavy rainfall across portions of Southeast. Flash flooding will be the most likely where training occurs and/or where the remnant circulation interacts with frontal boundaries. Antecedent wet soils from previous rainfall will also increase the potential for renewed flooding concerns. The system will quickly track north and then sharply eastward Sunday into Monday, bringing periods of steady moderate to locally heavy rainfall to portions of the Ohio Valley, Mid-Atlantic, and Northeast. Any leftover rain likely ends by Tuesday with drier air filtering into the region in the system's wake. Over the western U.S., an amplifying upper trough will bring periods of rain to portions of the Pacific Northwest and Intermountain West this weekend, with rain spreading into the northern/central Rockies as the trough digs southeastward. Colder air surging in behind a cold front will quickly lower snow levels and change any rain to snow across the higher elevations of the northern Rockies. Accumulating snow will continue in the high country through the weekend into early next week, with some snow possible in the lower elevations as well. The snow will likely be wet and heavy at times, which could weigh down trees and power lines. The latest WSSI-P continues to highlight >50 percent probabilities for at least minor winter weather impacts across the higher terrain of Montana and northwest Wyoming, with 10-20 percent probabilities for moderate impacts. As the western trough continues to deepen, it will likely draw Rachel and its post-tropical remnants in the eastern Pacific northward before sweeping it sharply eastward towards the Southwest U.S. Increasing dynamic forcing from the trough combined with the tropical moisture from the remnants of Rachel will likely lead to widespread heavy rainfall and localized flooding over parts of the Southwest and Intermountain West/Rockies Sunday into Monday. Burn scars, slot canyons, urban areas, and poor drainage/low-lying areas are likely to be most at risk. Temperatures should trend downward behind the advancing western trough over the Northwest into the north/central Plains through Wednesday. Periods of rain will spread into the Plains and Upper Midwest along a frontal boundary Monday through Tuesday. Miller/Oudit 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$