Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Tue Oct 08 2019 Valid 12Z Fri Oct 11 2019 - 12Z Tue Oct 15 2019 ...Record cold to gradually relent in the Central Rockies to Northern Plains/Upper Midwest... ...Pattern Overview and Guidance/Uncertainty Assessment... An anonymously deep upper low will very slowly lift through the Upper Midwest/western Great Lakes through the weekend. Near the east coast, a potential subtropical system is forecast to track close to southeastern New England (near the 40/70 benchmark). The National Hurricane Center is monitoring this area for development. Please reference their outlooks for more information. The models and ensembles were in generally good/great agreement on the synoptic pattern with typical timing differences in the west/central CONUS--GFS generally quicker and ECMWF generally slower with the UKMET/Canadian in between. A blended solution was preferred given the deterministic-subset cluster well within the multi-center ensemble cluster. Off the east coast, models were still having trouble resolving the track/intensity and even structure of the hybrid system through the period. Preferred the slower/western solutions given the transient Rex block pattern and separation from the upstream closed/cutoff low which should favor a system west of 70W. Agreement among the 12Z ECMWF/UKMET/Canadian with the 12Z ECMWF ensemble mean was convincingly strong. Ultimately, as the whole pattern unwinds, the Atlantic system will be pushed farther out to sea as the cold front reaches the east coast around Sunday. ...Weather Highlights/Threats... Amplified pattern will bring record cold to the west and central states that will moderate after Friday. Still, temperatures 20-40 degrees below average on Friday should still be below average by about 10-20 degrees by next Tuesday over the Dakotas. Milder than average temperatures will precede the cold front across the eastern states and the South and will stay near to above average along the Gulf Coast. Upper Midwest system will continue to bring wind/snow and pre-frontal/lower-latitude rain to the region Friday. Precipitation will wind down over the weekend but will continue to wrap around the surface low as it moves into western Ontario. Over New England and the coastal Mid-Atlantic, models show large spread in rainfall amounts depending on the proximity and strength of the ocean system. For now, took a modest approach given the uncertainty with 1-1.50" from 12Z Fri onward over eastern MA diminishing to near zero along/west of I-87. In the Pacific Northwest, a cold front will push through the area on Saturday with only light rain and mountain snow Fri/Sat west of the Cascades that will spread into northern Idaho and northwestern Montana next Sun/Mon. By then, Gulf moisture may begin to spread northward as the tail-end of the stationary front may lift back northward ahead of the western front moving through the Plains. 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