Extended Forecast Discussion NWS Weather Prediction Center College Park MD 330 AM EDT Sun Sep 29 2019 Valid 12Z Wed Oct 02 2019 - 12Z Sun Oct 06 2019 ...Heavy rainfall possible midweek from the southern/central Plains to the lower Great Lakes... ...Anomalous warmth culminates over the eastern and southeastern U.S. on Wednesday, while very chilly conditions moderate in the northern and northwestern states... ...Overview and Guidance/Uncertainty Assessment... Model guidance continues to indicate that the upper-level pattern will be generally more zonal and less amplified during the medium-range period following the ejection of a low pressure system moving toward the Great Lakes and New England. The trailing cold front is expected to move more slowly across the Plains under the more zonal upper-level flow. There is a strong consensus that moisture drawn northward from Tropical Storm Narda in the eastern Pacific will interact with the front and result in a band of heavy rain midweek from northern Texas across the central Plains and into the lower Great Lakes. Meanwhile, another upper trough is forecast to move through the Pacific Northwest and the northern Rockies late this week. The upper trough should be out into the northern Plains where a low pressure center may develop during the weekend. The WPC medium-range grid package is basically a consensus of the 12Z ECMWF and the 12Z/18Z GFS, trending more toward their ensemble means for Days 6 and 7. The CMC ensemble also agrees well with the EC and GEFS for Days 6 and 7. Thus, a small percentage of the 12Z NAFES is included as well. ...Weather Highlights/Threats... Confidence is increasing for a band of heavy rain to impact portions of the central Plains on Wednesday into early Thursday as moisture drawn northward from Tropical Storm Narda interacts with a frontal boundary. A few inches of rain is possible within this band, which could result in flash flooding in parts of the area. There is some potential for heavy rain to develop over New England on Thursday ahead of a developing low pressure wave along the front. Meanwhile, deep-layer easterly flow will bring an influx of tropical moisture across southern Florida and into the Gulf of Mexico later this week, and could approach the lower Texas coast during the weekend. Very chilly conditions over the western U.S. into Northern Plains are expected to moderate through this week. On the other hand, many locations from the Gulf Coast to New England will see daily record high temperatures on Wednesday. As the strong upper ridge retreats, the heat will gradually abate as we head into the weekend. Although uncertainty is high at this point, there is some potential for heavy rain to develop during the weekend over the central Plains where a low pressure system may form. Kong 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