Extended Forecast Discussion NWS Weather Prediction Center College Park MD 249 AM EDT Tue Sep 29 2020 Valid 12Z Fri Oct 02 2020 - 12Z Tue Oct 06 2020 ...Hot and dry conditions return for the West... ...Heavy Rainfall Threat for South Florida... ...Overview and Guidance/Predictability Assessment... Models and ensembles agree to develop and maintain a highly amplified upper level flow pattern featuring a western U.S. ridge and east-central U.S. trough will become well-established throughout the medium range period. This will support above normal temperatures across the West and generally below normal readings for the central/eastern U.S.. The WPC medium range product suite was primarily derived from a blend of the quite compatible GEFS/ECMWF ensemble means. This seems prudent given high confidence in the larger scale flow, but less than stellar recent model continuity issues with embedded smaller scale features (even into short range time frames). ...Weather/Hazard Highlights... . An amplified upper ridge over the West offers hot and dry conditions and a renewed fire risk. Expect temperatures to reach 5-15 degrees F above normal (isolated higher values) from California/Arizona/Nevada through the Pacific Northwest. Some record-breaking values will be possible, mainly over parts of California but perhaps into Oregon/Washington as well. A front with multiple but uncertain waves will reach the East Coast later in the week and may provide another focus for rainfall over the Mid-Atlantic/Northeast along with unsettled maritime conditions. Rain with this front should be lighter due to less moisture being available than with the first system. Fronts will tend to decelerate and possibly stall near southern Florida Peninsula and the Keys where periods of heavy rain are possible through the period. The amplification of the east-central upper trough favors deep tropical moisture influx into south Florida associated with a western Caribbean wave/disturbance could fuel lingering heavy downpours. Cold air aloft will meanwhile provide instability for scattered showers across the Midwest/Great Lakes/Appalachians under the upper trough, including some Great Lake enhancement. A wave expected to drop into the central then east-central U.S. Sat-Mon may produce light to locally moderate rain from the Plains to the Great Lakes and Ohio Valley. Cold air surges will support temperatures of 5-15 degrees F below normal for much of the central to eastern U.S.. There is a chance for a first frost/freeze of the season for the Northern Plains and Upper Mississippi Valley late week. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards 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