Extended Forecast Discussion NWS Weather Prediction Center College Park MD 246 AM EDT Sat Oct 17 2020 Valid 12Z Tue Oct 20 2020 - 12Z Sat Oct 24 2020 ...Guidance Evaluation/Preferences... Guidance continues to offer 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. However, there is above normal forecast spread with the timing of smaller scale impulses progressing through the flow and associated weather focusing surface systems. Towards the end of next week, moisture may be drawn northward from the Gulf of Mexico into the east-central Gulf states/Florida consistent with potential flow amplification over the nation. This would be well to the north of a potential Caribbean tropical low as per NHC. The WPC medium range product suite was based on a blend of the most compatible 12 UTC GEFS/ECMWF ensemble means along with the 01 UTC National Blend of Models. This maintained good WPC continuity. ...Weather/Hazard Highlights... A series of wavy frontal systems with modest moisture will focus periods of 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, the northern Rockies and the Dakotas. The highest chance of enhanced snows is over the northern Rockies. The heaviest rains may focus over the Midwest/Great Lakes. Meanwhile, moisture may increase into Florida and the east-central Gulf states late next week as a tropical low is forecast to move into the western Caribbean Sea together with expected gradual amplification of the upper-level pattern over the U.S.. 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