Extended Forecast Discussion NWS Weather Prediction Center College Park MD 247 PM EDT Mon Sep 28 2020 Valid 12Z Thu Oct 01 2020 - 12Z Mon Oct 05 2020 ...Hot and dry conditions return for the West... ...Overview and Guidance/Predictability Assessment... The evolution toward an upper level flow pattern featuring western U.S. ridging and eastern U.S. troughing will become well-established throughout the medium range period, as the system affecting the East Coast departs. The latest model guidance shows very good agreement at least through day 5 and generally keeps the amplified pattern in place. This will support above normal temperatures across the West and generally below normal readings for the central/eastern US. Heading into the later portions of the medium range period, another reinforcing shortwave trough may drop through the flow across the central US and this could spawn a surface low over portions of the southern Plains to Mid-MS River Valley. The depth/strength of this feature differs in the deterministic guidance, with the ECMWF showing a more developed low near the Great Lakes on Day 7 compared to the other models. The ensemble means support some sort of feature coming through during that time, so the WPC blend did favor the ECMWF day 6/7 with some inclusion of the GFS/GEFS to maintain continuity and show some of the uncertainty in place. ...Weather/Hazard Highlights... The West will see increasing fire danger once again this week as the amplified upper ridge over the region brings a return of hot and dry conditions. 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 western Oregon/Washington as well. By next weekend modest weakening of the upper ridge could allow for some moderation of the heat close to the West Coast. A trailing front with one or more weak waves, reaching the East Coast later in the week 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. Both fronts will tend to decelerate and possibly stall near/south of the southern Florida Peninsula and Keys where periods of rain are possible through the period. Tropical moisture influx there could fuel some 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/Taylor 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