Extended Forecast Discussion NWS Weather Prediction Center College Park MD 408 PM EDT Fri Oct 16 2020 Valid 12Z Mon Oct 19 2020 - 12Z Fri Oct 23 2020 ...Guidance Evaluation/Preferences... Model guidance offers a well clustered larger scale forecast evolution through medium range time scales. This pattern will be highlighted by a broad upper trough over much of the lower 48, save lingering ridging over the Southeast. Shortwave energy will periodically traverse the northern Rockies and north-central states. However, there remains high forecast spread with the timing of smaller scale impulses progressing through the flow and weather focusing surface systems. Towards the end of next week, tropical moisture could be drawn northward from the Gulf of Mexico into the central Gulf states as well as brushing the Florida Keys with potential flow amplification across the U.S. The WPC medium range product suite this morning was based on an even blend of the 00Z UTC ECMWF/00Z EC mean with the 06Z GFS/GEFS. ...Weather/Hazard Highlights... A series of wavy frontal systems with modest moisture will focus periods of light to moderate precipitation from the Northwest/Rockies and north-central U.S./Midwest to the Northeast. Post-frontal Canadian cold air surges will dig through the Northwest/Great Basin/central U.S. and into the Great Lakes. Temperature profiles favor periods of snow for the Cascades and northern Rockies to the Dakotas. The highest chance of wintry precipitation is forecast for next Wednesday over the higher elevations of northwestern Montana. Some enhanced rainfall is possible on Monday near a stalled front from the mid-Mississippi Valley to the Ohio Valley. A good chance of rain is forecast for the upper Midwest later next week with mixed rain and snow possible for the northern portion of the area. Meanwhile, tropical moisture may increase across the Florida Keys and the central Gulf states towards the end of next week as a tropical low is forecast to move into the western Caribbean Sea together with gradual amplification of the upper-level pattern over the U.S. Kong/Schichtel Hazards: - Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Central Appalachians, the Ohio Valley, and the Tennessee Valley, Mon, Oct 19. - Heavy snow across portions of the Northern Plains and the Northern Rockies, Wed, Oct 21. - Flooding occurring or imminent across portions of the Lower Mississippi Valley. - Much below normal temperatures across portions of the Upper Mississippi Valley, the Northern Plains, and the Northern Rockies, Mon-Tue, Oct 19-Oct 20 and Thu-Fri, Oct 22-Oct 23. - Much below normal temperatures across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Mon-Tue, Oct 19-Oct 20. 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