FXUS02 KWBC 040700 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Wed Dec 4 2024 Valid 12Z Sat Dec 07 2024 - 12Z Wed Dec 11 2024 ...Return flow to fuel emerging rainfall from the west-central Gulf Coast to the Appalachians this weekend to early next week... ...Guidance/Predictability Assessment... The WPC medium range product suite was mainly derived from a composite of reasonably clustered guidance from the latest guidance GFS/ECMWF/UKMET/Canadian models that have good ensemble support and continuity. Pivoted to the most compatible solutions of the ECMWF/ECMWF ensemble mean and Canadian/Canadian ensemble mean at longer time frame to maintain best continuity amid otherwise growing forecast spread. ...Weather/Hazards Highlights... Arctic air that has persisted over the east-central U.S. will moderate by this weekend as amplified upper troughing finally lifts out after a prolonged time period. Nevertheless, lake effect snow is likely to be ongoing into early Saturday in the wake of a strong clipper-type system. By early next week, temperatures should be near to a little above average across much of the Eastern U.S.. Meanwhile, emerging moist return flow from the Gulf of Mexico as ambient high pressure over the South retreats to the east will support increasing coverage of showers and thunderstorms, some of which could be heavy, from the west-central Gulf Coast states up through the southern Appalachians this weekend through early next week. In terms of the WPC Excessive rainfall outlook, maintained a Day 4/Saturday Marginal Risk area centered over Southeast Texas to cover event genesis. Introduced Marginal and Slight Risk areas for Day 5/Sunday into Monday centered over the Lower Mississippi Valley as convection erupts in a favored right entrance region of the upper jet pattern to favor training/repeat cells as strong moisture flux from the central Gulf continues ahead of an approaching main cold front. Upstream, moderatly heavy terrain enhanced precipitation is expected to develop this weekend over the Pacific Northwest with energetic upper trough passage and long lead moisture feed. Terrain enhanced snows will then spread increasingly inland across the Northwest to the north-central Rockies with cold frontal passage over the West into early next week. Expect a nice warming trend in advance of this front out from the West through over the central U.S. this weekend/early next week prior to cooling passage. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$