Extended Forecast Discussion NWS Weather Prediction Center College Park MD 301 AM EDT Mon Sep 30 2019 Valid 12Z Thu Oct 03 2019 - 12Z Mon Oct 07 2019 ...Heavy rain threat diminishes over the central Plains late this week but could return by next Sunday into Monday... ...Record warmth continues for the Southeast into Thursday... ...Overview and Guidance/Uncertainty Assessment... Relatively zonal/progressive flow is expected to be in place across the CONUS to start the medium range period as an upper trough initially across the Rockies lifts out into the central U.S. The heavy rain threat should be diminishing along a wavy surface front across the central Plains. Meanwhile, a less vigorous upper trough is forecast to move through the Pacific Northwest and the northern Rockies late this week before moving into the Plains by this weekend and into next Monday. There are some indications for heavy rain to develop over the central Plains these couple of days as a low pressure system could form. Global models show fairly good agreement on the synoptic pattern evolution across the U.S. through Day 5 (Sat). There is a trend toward a more robust development of a frontal wave over the Northeast on Thursday and Friday, especially the GFS. By Sunday and Monday, potential exists for another frontal wave to develop in the Midwest. Therefore, more of the ensemble means are used to handle the uncertainty for this system. The WPC medium range forecast was a general consensus of the 12Z ECMWF and the 18Z GFS together with their ensemble means. Only a small percentage of the 18Z GFS is used for days 6 and 7 since the frontal wave appears to be too strong. ...Weather Highlights/Threats... The heavy rain threat near a frontal boundary across the central Plains should begin to diminish on Thursday as the main dynamics of the system shifts further northeast into New England ahead of a developing frontal wave. Localized heavy rain is possible across portions of New England on Thursday into early on Friday as the frontal wave could strengthen before it moves offshore. Meanwhile, a vigorous upper trough is expected to bring scattered mixed precipitation across the northern Rockies on Friday. By the weekend, the upper trough should begin to inject moisture from the Gulf and increase the threat of heavy over the central Plains ahead of a frontal system. Record warmth over the Southeast is expected to continue into Thursday before a gradual cooling trend sets in. Overall, temperatures will become less extreme across the country as we head toward the weekend. Meanwhile, deep-layer easterly flow will bring an influx of tropical moisture across southern Florida and into the Gulf of Mexico this week north of a tropical low. 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