Extended Forecast Discussion NWS Weather Prediction Center College Park MD 245 AM EDT Sun Oct 06 2019 Valid 12Z Wed Oct 09 2019 - 12Z Sun Oct 13 2019 ...Another round of cold/snow for the Northern Rockies/Plains next Wed/Thu... ...Overview... A positive height anomaly near Labrador/northeastern Quebec will favor deepening 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 lurk just offshore New England. ...Guidance/Uncertainty Assessment... A blend of the 12Z ECMWF/ECMWF ensemble mean and 18Z GEFS mean offered a reasonable starting point to the forecast through the period. The 12Z/18Z GFSs were quicker with the timing of the western trough as it progressed onto the Plains, against the multi-day trends and the vast majority of the ensembles. The 12Z Canadian/UKMET showed a similar slower timing comparable to the ECMWF. Off the New England coast, the 12Z ECMWF was on the southern third of the ensemble spread with the potentially subtropical system while the GFS/Canadian were much farther north. Preferred an ensemble mean consensus with a weight toward the ECMWF ensemble mean by next Sat/Sun which was slower to lift the system northward than the 18Z GEFS mean. ...Weather Highlights/Threats... Strong cold front will push out of the Northern Rockies on Wednesday which will drag down well below average temperatures through the region. Record cold is likely for many areas in its wake for both lows and highs (record cold max temperatures) as readings may be 20-40 deg F below average. Cooler air will spread southward to Texas and eastward to the mid-Mississippi Valley by Friday but with less intensity. Still, a large area of the CONUS will see temperatures below average by about 5-15 deg F. The exception will be east and south of the front, mainly from the Appalachians eastward and into the Southeast/Florida until the front passes. Along with colder temperatures, modest accumulating snowfall is likely for parts of the Northern Rockies and eventually the Northern Plains and Upper Midwest. Ahead of the cold front, 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. Rain threat in general will decrease farther east as the system lifts into Canada. The low off the New England coast will bring a threat for locally heavy rainfall to at least parts of coastal New England next week, but this is dependent on how close the low tracks to the coast. NHC is also monitoring this system for potential tropical or subtropical development. Regardless, stiff easterly onshore flow will be prevalent through southern New England into the coastal Mid-Atlantic around its circulation. 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