Extended Forecast Discussion NWS Weather Prediction Center College Park MD 242 PM EDT Tue Oct 13 2020 Valid 12Z Fri Oct 16 2020 - 12Z Tue Oct 20 2020 ...Overview... A broad upper-level trough around a deep low centered just west of Hudson Bay will remain the dominant feature across inland North America through at least this weekend. Confidence continues to increase for moderate to heavy rainfall across the Northeast this weekend as a surface low develops there. ...Guidance Evaluation/Preferences... A reinforcing shortwave trough currently crossing Vancouver Island will amplify into a deep trough over the Plains/Midwest through the midweek before sending an associated surface low up the Eastern Seaboard as a heavy rain maker Friday/Saturday. Uncertainty increases after this feature with the next shortwave pushing south from BC on Friday. The 06Z GFS/00Z CMC were much more amplified with this trough than the 00Z ECMWF/UKMET. Preference was given to the ECMWF/UKMET solution, though by Day 5 much of the blend was given to the 00Z ECENS and 06Z GEFS means due to great timing differences with the shorter wave features. The general pattern of a dominant trough over the central CONUS remains in all guidance with a leading surface low crossing the northern Plains/western Great Lakes this weekend and the next wave moving along the stalling front over the Midwest early next week. ...Weather/Hazard Highlights... A low pressure system is expected to develop over the Northeast late in the week, and bring the potential for moderate to heavy rainfall along with thunderstorms to the region. This could help with drought conditions across much of the Northeast. The highest elevations of New England/Adirondacks could see some snow as well. A cool high pressure system coming in behind the cold front associated with that Northeast low will spread below normal temperatures by 5 to 15 degrees across the Plains to the eastern Seaboard through Saturday. A potent low and cold front with an even more anomalous cold surface high trailing will cross the northern Plains to Lake Superior this weekend which will reinforce even colder temperatures to the central CONUS. Max temps of 30s and 40s will spread east across the Northern Plains to the Upper Mississippi Valley Sat-Mon which is 15 to 25 degrees below normal. Min temps in the teens and 20s are 10 to 20 degrees below normal. This cold air banked up against the northern Rockies will cause a round of precipitation over the northern Rockies this weekend. Notable wintry precipitation is likely in the mountains and possibly onto the adjacent northern High Plains. Meanwhile, the Southwest from far west Texas to California and the Central Great Basin will remain under an upper ridge through this weekend. Warmer than average temperatures are forecast there, and upper 90s to low 100s are forecast for the lower deserts of Arizona and California, which could be near high temperature records at some locations. The upper ridge shifts farther west late this weekend, making for more moderate temperatures by early next week. Meanwhile, tropical showers are expected across southern Florida into Saturday until a cold front passes. Jackson 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