Extended Forecast Discussion NWS Weather Prediction Center College Park MD 243 AM EDT Sat Oct 05 2019 Valid 12Z Tue Oct 08 2019 - 12Z Sat Oct 12 2019 ...Another round of cold/snow for the Northern Rockies next Tue/Wed... ...Overview... A positive height anomaly near Labrador will favor troughing in the western to central states and increased precipitation for the Mississippi Valley. Western Atlantic ridging is forecast to compress into the subtropics, allowing a cutoff upper low to linger just offshore New England and Nova Scotia. ...Guidance/Uncertainty Assessment... For Tue-Thu, a blend of the 12Z/18Z GFS, 12Z ECMWF/Canadian, and 18Z GEFS mean/12Z ECMWF ensemble mean offered a reasonable starting point as the western system sinks through the region. By next Fri/Sat, ensemble spread increases quite markedly with respect to how quickly (or slowly) the trough moves eastward. The Canadian represented the slower solutions while the GFSs represented the quicker/quickest solutions. 12Z ECMWF fell mostly in line with the ensemble means and this grouping was preferred for the end of the period. The multi-day trend has been slower and more amplified but upstream flow may be progressive enough to prevent a cutoff solution in the central Rockies. To the east, upper low and surface occluded front are forecast to stay just offshore enough to prevent any direct impacts to New England, but a slower/deeper western trough would likely mean that offshore system could come much closer to the Northeast. ...Weather Highlights/Threats... Cold front will bring well below average temperatures to the West Wednesday onward--as much as 30-35 deg F anomalies (temperatures in the 30s). Montana will be the focus for the cold on Wednesday, followed by Wyoming on Thursday and the High Plains Fri/Sat. Precipitation will accompany the front with widespread modest elevation snow in western Montana spreading eastward even to many valley locations and eventually to parts of the Plains. Cooler air will spread southward to Texas and eastward to the mid-Mississippi Valley by Friday but with less intensity. Rainfall will expand and offers a risk to become locally heavy from the south-central Plains to the mid-MS Valley/Midwest later in the period with moisture inflow return from the Gulf. Fracasso 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