Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1157 AM EDT Sat Nov 03 2018 Valid 12Z Tue Nov 06 2018 - 12Z Sat Nov 10 2018 ...Overview... Broad cyclonic flow will remain anchored over most of the lower 48 next week as embedded systems pass through the trough. A lead system on Tuesday will exit through the central Great Lakes while another will dive through the west and spin up late Thursday into Friday through the eastern Great Lakes. This may spread some wintry weather across the central Plains and to the north of the surface low track. ...Guidance/Predictability Assessment and Preferences... A multi-model blend offered a reasonable starting point for the lead system in the east Tue/Wed as the cold front pushes offshore. By next Thursday, the models and ensembles have now shown for two consecutive runs (but much unlike 24 hrs ago) a stronger northern stream shortwave through the west on Wednesday that will likely amplify into the Plains Thursday and spin up a surface low over the lower Mississippi Valley that will lift northeastward Friday and out through the St. Lawrence Valley Saturday. This was a significant change from the 00Z/02 ensembles as only a few members showed such a solution but the consensus is strong in the 00Z/03 ensembles. However, timing/amplitude differences are evident with the 00Z/06Z GFS quicker/weaker and the 00Z ECMWF slower/stronger. Their respective ensemble means were a bit slower/quicker than their deterministic counterparts, respectively, to offer a bit better agreement. The 00Z parallel GFS (FV3-GFS) was close to the preferred speed near the ensembles as was the 00Z Canadian to a lesser degree. ...Weather Highlights/Threats... Dynamic system in the east on Tuesday will spread rain/storms (possibly severe along the I-81 to I-95 corridor between Georgia and Pennsylvania) through the east with another shot of cooler air behind it through the High Plains. Later week more modest precipitation may renew over the southern Plains as the western shortwave taps available western Gulf of Mexico moisture atop a stationary boundary. With marginally cold air to the north, wintry precipitation is possible along and east of the central Rockies through the central Plains. Isolated but potentially heavier rains in the warm sector may spread northeastward out of the lower Mississippi Valley Friday into the Northeast and central Appalachians as the surface low deepens and heads toward the eastern Great Lakes. Northwest flow around the western Great Lakes may support on and off lake effect snows with cold air aloft and still mild lake temperatures. Temperatures will be below average from the northern Rockies through the Plains into the Great Lakes and Ohio Valley as reinforcing cold fronts drag cool/cold Canadian air through the region. The west will see near to above average temperatures thanks to upper ridging while the east will be a bit variable -- warming up ahead of the Great Lakes system Tue/Wed then cooling off after the front passes. Fracasso WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found 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