Extended Forecast Discussion NWS Weather Prediction Center College Park MD 302 PM EDT Mon Sep 25 2023 Valid 12Z Thu Sep 28 2023 - 12Z Mon Oct 02 2023 ...Overview... A trough digging south from the Pacific Northwest becomes a cutoff low over the Great Basin Sunday as ridging over the east-central CONUS amplifies. Prolonged precipitation, with high elevation snow, is expected to develop across the Intermountain West, northern Rockies, and northern High Plains this weekend. Meanwhile, a slow moving cold front will bring continued rain for the Florida Peninsula into this weekend. Warm conditions can be expected over the Great Plains through Great Lakes. ...Guidance Evaluation/Predictability Assessment... Deterministic guidance shows very good agreement with the expected flow pattern of a closing/cut off low over the West and ridging over the east-central CONUS. Blending the 00Z ECMWF/CMC/UKMET and the 06Z GFS worked well through Day 5 with inclusion of the 00Z ECENS and 06Z GEFS means for Days 6/7. QPF grids were generally a blend of the 13Z NBM with mainly 06Z GFS and 00Z ECMWF through Day 5, then the GFS was used to temper/reduce QPF coverage from the 13Z NBM for Days 6/7. ...Weather/Hazards Highlights... A stalled front over the Florida should progress southward as a frontal wave forms to their east, progressing past Bermuda ahead of a progressive and positively tilted upper level trough. The ERO for Day 4/Thursday into Friday morning, the signal for a cool season heavy rainfall setup into northeast FL remains, so does the Marginal Risk. For day 5/Friday into Saturday morning, the Marginal Risk was trimmed a bit to the south for both cool season, post-frontal heavy rainfall setting up a bit farther south than prior guidance. This is off the very warm western subtropical North Atlantic and for the central and southern peninsula closer to the front, which have been a bit wetter than average this past week. A digging western trough will close into a cut off low centered over the Great Basin this weekend and will focus moderate precip over the Intermountain West through northern Rockies, and northern High Plains. No excessive rainfall areas appear needed. Snow at higher elevation becomes increasingly favored with time across the Northern Rockies as the upper level low develops. Increased ridging over the center of the country and troughing across the West, will slowly shift temperatures of 10 to 15 degrees above normal east across the Central Plains through the Great Lakes with temperatures below normal expanding from the Northwest to across the West. Below normal temperatures over the Mid-Atlantic States can be expected into Friday before moderating on approach of the ridge axis. Jackson/Roth 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