Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Thu Oct 6 2022 Valid 12Z Sun Oct 9 2022 - 12Z Thu Oct 13 2022 ...Synoptic Overview... A rather amplified upper level flow pattern is expected to be in place for the upcoming weekend and extending into the middle portion of next week. For the eastern U.S., a big Canadian surface high settling in from the Plains to the East Coast will bring a pristine fall-like airmass after the passage of a strong cold front. The next cold front arrives across the central and northern Plains by Tuesday with some showers and a few storms ahead of it. For the western U.S., the persistent weak upper low/trough over northwestern Mexico is expected to evolve into an open trough, although shower and storms will likely remain. By Tuesday, a more impressive upper trough begins building across the western U.S. which will likely bring much cooler conditions for much of this region by the middle of next week. ...Guidance Evaluation/Predictability Assessment... Overall, the 00Z deterministic guidance is in good overall agreement on most features for Sunday, with the main difference at this time being a slower and stronger solution with the UKMET across the Upper Midwest and Great Lakes with the trough dropping southward from Canada. The models also agree well on the upper low that evolves into a trough near the Desert Southwest through the weekend. Looking ahead, the deterministic guidance still suggests a cut-off low will develop across the Intermountain West by Wednesday, albeit weaker than the 12Z guidance. The CMC still maintains a stronger solution regarding that low. The main trough axis is forecast to be over the northern tier states, accompanied with another strong cold front. A mainly CMC/GFS/ECMWF model blend suffices early in the period, followed by increasing the weighting of the ensemble means for Tuesday-Thursday and maintaining some previous WPC continuity. For the QPF, the NBM combined with some of the operational GFS/ECMWF was used as a baseline through about Tuesday, and then mainly went with NBM for Wednesday. ...Weather/Hazards Highlights... The combination of persistent monsoonal moisture and an upper low over northwest Mexico will continue to fuel diurnal showers and thunderstorms over parts of the Desert Southwest/southern Rockies through Sunday, with the greatest rainfall totals expected for central and southern New Mexico based on latest model guidance. The upper low should evolve into an open trough by Monday, but isolated to scattered convection will likely persist across the Intermountain West as the next disturbance enters the region. An amplifying upper trough and a strong cold front reaching the Northwest/northern Rockies by next Tuesday will likely produce showers and even high elevation snow for portions of the northern Rockies for the Tuesday and Wednesday time period. Elsewhere, light to locally moderate rainfall will likely spread northward over the Florida Peninsula as easterly low level flow strengthens behind a front, and scattered showers and some storms are likely from the Central Plains to the Great Lakes ahead of the next front. Much of the northwestern U.S. should have above normal temperatures at least through Monday, followed by a noticeable cooling trend commencing by Tuesday as the strong cold front drops southeastward, and then temperatures more typical of November are expected across the Rockies and Intermountain West by next Wednesday with highs generally 5-15 degrees below average. Farther east, temperatures should be moderating going into early in the week after a relatively chilly weekend for most locations. Readings should still be mild across most of the Plains states through Wednesday before the front passes through the region. Hamrick 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