Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 PM EST Thu Nov 07 2019 Valid 12Z Sun Nov 10 2019 - 12Z Thu Nov 14 2019 ...East of Rockies Arctic Outbreak Includes a Heavy Snow/Ice Threat... ...Pattern Overview and Guidance/Predictability Assessment... The large scale flow pattern will reamplify early next week with a northeastern Pacific to Alaska ridge drifting east allowing a deep downstream trough to dig down the Rockies and spread across the central/eastern CONUS. Confidence is high with the overall large scale pattern with smaller scale features which affect low positions still uncertain through the middle of next week. The 00Z UKMET was again too sharp with the leading shortwave on the digging trough entering the CONUS on Day 3 and slower trough motion over the Great Lakes from the 00Z CMC starting on Day 4 results in an outlier stronger and slower storm over the northeast CONUS by Day 6. Also, the 00Z GFS was the fastest solution ejecting a trough over northwest Mexico, so the 06Z GFS/GEFS was preferred there. The 00Z ECMWF/06Z GFS dominates the blend for Days 3/4 with 00Z ECENS/06Z GEFS increasingly used for Days 5-7. ...Weather Highlights/Threats... Arctic-sourced high pressure and a leading cold front will surge south down the Great Plains Saturday night through Sunday night to produce much colder than normal temperatures over the eastern 3/4 of the lower 48 states this weekend into next week. The surface high pressure center will track from the Canadian Prairies southeastward to the central Plains by Monday night before turning east through the midweek. Expect a broad coverage of maximum temperatures 15-25F below normal and a risk of widespread record cold temperatures will spread across the central and eastern U.S Monday through Wednesday night. The positively tilted upper trough trailing the cold front will promote snow in the back side of the frontal zone across the north-central Plains into the Midwest through Monday night. Upslope snow on the eastern slopes of the northern-central Rockies (MT to CO) will occur from easterly flow on west side of the high center into Monday. Organized waves of low pressure along the front are expected to track along a profound baroclinic zone from the southern Plains to off the East Coast Mon-Wed. These will produce a swath of moderate rainfall along/south of the boundary from across the South and Southeast/Mid-Atlantic, but also a threat of snow/ice north of the front in the cold air from the s-central Plains northeastward from the Mid-South to the OH Valley/Appalachians/Mid-Atlantic/Northeast. Snows may be additionally enhanced over the Northeast by coastal storm development as the trough tilts negatively, although there remains uncertainty with coastal proximity and full extent of wintry onshore impacts. This risk is depicted in the WPC Winter Weather Outlook probabilities. There is better agreement with guidance of a trough pushing through the ridge and into BC/the Pacific Northwest Tuesday which should bring higher elevation snow to the Northwest CONUS into Wednesday. Jackson 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 - Heavy precipitation across portions of the Northeast, Mon-Tue, Nov 11-Nov 12. - Heavy snow across portions of the Great Lakes, Mon, Nov 11. - Heavy snow across portions of the Northeast and the Great Lakes, Mon-Tue, Nov 11-Nov 12. - Flooding possible across portions of the Southern Plains. - Flooding occurring or imminent across portions of the Middle Mississippi Valley and the Northern Plains. - Flooding likely across portions of the Southern Plains and the Northern Plains. - Much below normal temperatures across much of the Central and Eastern U.S., Mon-Thu, Nov 11-Nov 14. 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