Extended Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EDT Tue Oct 27 2020 Valid 12Z Fri Oct 30 2020 - 12Z Tue Nov 03 2020 ...Wintry weather in New England Friday... ...Overview and Guidance Evaluation/Preferences... After an active short range period weather-wise and a spate of wintry weather across parts of the Northeast Friday, the weather appears to calm down for the medium range. An upper trough is forecast to push offshore of the East for the end of the week, while another shortwave develops across the Northwest before moving east as ridging forms over the West for the beginning of next week. There was fairly good model clustering early on, though the UKMET may be just a bit aggressive with keeping the upper low closed in the East Fri. Nevertheless, a multi-model deterministic blend, somewhat favoring the 00Z ECMWF, was used for the first half of the forecast period. This also worked for the shortwave tracking across the northwestern to north-central U.S. Fri/Sat and deepening into a more potent/longer wave trough by Sun with its axis over the Great Lakes. That trough evolution and its associated surface low become a little more questionable by Mon as the 06Z GFS created a separate upper low and surface low near the Northeast, and the 12Z GFS has followed in its footsteps. Increasing spread among the deterministic models and ensemble members led toward favoring the 06Z GEFS and 00Z EC ensemble means for the Mon/Tue forecast. ...Weather/Hazard Highlights... A low pressure/frontal system offshore of the Mid-Atlantic/Northeast is expected to join up with Zeta, and wraparound precipitation is possible for the Northeast Fri. Precipitation should take the form of accumulating snow especially in higher elevations of New York and New England, including parts of the Catskills, Berkshires, and the southern Green Mountains through Friday. Exact precipitation amounts will depend on elevation and the low track. The CONUS is forecast to dry out substantially after this event, with only light precipitation possible across the Great Lakes to Northeast given the flow pattern underneath the trough early next week, southern Florida near a stalled front, and the Northwest by Tue as a trough could approach. In terms of temperatures, a couple of rounds of cooler than average temperatures are expected in the central and eastern U.S. behind the aforementioned frontal system as well as a second reinforcing front. Temperatures of 5 to 15 degrees below normal are forecast periodically from the Plains to the Eastern Seaboard. Meanwhile, underneath the ridge in the West, temperatures around 5 to 15 degrees above normal can be expected for parts of the Pacific Northwest, California and into the Great Basin, spilling into the Northern/Central Plains by Mon/Tue. Tate 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 Hazards: - Heavy precipitation across portions of the Mid-Atlantic, the Northeast, and the Great Lakes, Fri, Oct 30. - Much below normal temperatures across portions of the Southern Rockies, and the Southern Plains, Fri, Oct 30. 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