Extended Forecast Discussion NWS Weather Prediction Center College Park MD 246 PM EDT Fri Oct 21 2022 Valid 12Z Mon Oct 24 2022 - 12Z Fri Oct 28 2022 ...Model and Predictability Assessment and Weather/Hazard Highlights... Model and ensemble solutions have trended towards better agreement since even just 24 hours ago, and now show fairly good agreement on the overall pattern, but plenty of run to run variability and increasing spread on the details next week. WPC leaned on a composite blend of the 00z CMC/ECMWF and 06z GFS the first half of the period, with increasing contributions from the ensemble means the later half amidst increasing spread/uncertainty. This generally maintained good continuity with the previous shift. In this scenario, an exiting upper trough/low and deepened surface low/system over the north-central U.S. Monday offers windy/wrapping precipitation including lead strong to severe convection as per SPC and some wrapping backside snow. Lead early week pre-frontal warmth moderates through the rest of the week over the east-central U.S. Upstream, system energy pushing inland across the Northwest to the Rockies will produce a swath of precipitation including elevation snows enhanced by terrain before reaching the northern Plains. Potent trailing upper trough energies in this stream across an unsettled Southwest Monday may tap modestly with some moisture from Mexican landfalling and decaying Roslyn. The driving upper trough/closed low is slated to then eject from the Southwest and lift northeastward across the central U.S. and Great Lakes/Midwest though midweek. Timing and amplitude issues remain in the guidance. The main outlier at this point is the GFS which is slower and maintains a closed low longer than the rest of the guidance would suggest. The pattern though should focus Gulf moisture and instability into the developing front and WPC has issued an experimental "Slight" risk of excessive rainfall centered over the Southern Plains Monday where multiple inches of convective rains may focus. Subsequent renewed upper trough energy flow into the West Coast into mid-later week was been handled differently by the models, but the latest runs this morning are more in agreement with an overall trend for digging. This should prolong a quite cold period over the West/Rockies and system amplitude should favor a decent and repeatable moderate QPF coverage response to include additional heavy snow threats with focus over favored terrain from the West Coast states through the Great Basin and the Rockies. This system is slated to emerge over the central U.S. late period to renew rain/convection, although uncertainty on placement and amounts are highly variable at this time. Elsewhere, lingering upper troughing over the Mid-Atlantic and offshore troughing focus through at least early next week has proven highly uncertain in guidance from run to run. However, the pattern does offer protracted support for coastal effect with perhaps best flow focus over New England. In terms of QPF across the country compared to the 13z NBM, increased amounts and somewhat the general coverage based on a multi-model ensemble blend, especially early week across the southern/central Plains into the Midwest. Santorelli/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, experimental excessive rainfall outlook, 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/#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