Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1156 AM EDT Fri Nov 02 2018 Valid 12Z Mon Nov 05 2018 - 12Z Fri Nov 09 2018 ...Overview... Broad cyclonic flow will dominate the lower 48 next week in a pattern that will feature below average temperatures for the central US behind a deepening area of low pressure lifting through the Great Lakes on Tuesday. A stalled front along the east coast will keep a chance of rain for many coastal areas early in the week preceding the Great Lakes system. Weaker systems embedded in the northwest flow aloft will dive out of southwestern Canada into the trough which may spread lighter rain/snow from the northwest through the Rockies. ...Guidance/Predictability Assessment... The models and ensembles remain mostly well-clustered through the period with generally timing differences among the guidance. A consensus approach has been the most stable guide and the 06Z GFS and 00Z ECMWF fall near that overlap through most of the period with the 00Z Canadian mostly in line as well. This maintains the central US trough through the end of next week as the downstream Atlantic ridging meanders in place and the upstream Pacific ridge shifts between 130-160W as systems slide up and over it near Alaska. ...Weather Highlights/Threats... 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. Some records highs may be possible ahead of the front across the Southeast/Florida Tue/Wed. Precipitation will be concentrated around two systems: 1) along a stalled front near the east coast Mon-Tue and 2) with the mid-Mississippi Valley/Great Lakes system Tue/Wed. The former has shown the potential for heavy rain along the coast from SC to the mid-Atlantic but this may remain just offshore. The latter system has much stronger forcing behind it from aloft and at the surface and will bring increasingly windy and wet conditions to the middle Mississippi Valley northward into the Great Lakes as the surface low winds up rather quickly. Severe weather will also be possible in the warm sector in the Southeast and the Storm Prediction Center has outlined Mon/Tue as the best chance of organized severe weather. After the system lifts into Canada, colder air will work into the Great Lakes in its wake with 850mb temperatures dropping to -12 to -15C over lake temperatures around +5 to +10C (and surface temperatures in the upper 20s and low 30s F. This could support a significant lake effect snow event for the UP of Michigan and northern lower Michigan late next week though the flow may be variable as weaker systems rotate through. To the south, the front may sink well into the Gulf with cooler/drier air pushing through most of Florida except for perhaps Miami and the Keys. Additional rain may expand through the lower Mississippi Valley later next week well north of the front in a weak overrunning environment with the flow above the surface out of the western Gulf. 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