Extended Forecast Discussion NWS Weather Prediction Center College Park MD 212 AM EDT Sun Oct 02 2022 Valid 12Z Wed Oct 05 2022 - 12Z Sun Oct 09 2022 ...Overview... A wavy pattern should be in place by the start of the medium range period on Wednesday, with a compact upper low shifting off the Mid-Atlantic coast and a shortwave moving into the Upper Midwest. By Thursday-Friday, energy diving southward across Canada combining with the latter shortwave will act to amplify upper troughing across the East while ridging builds over the West, with this pattern remaining generally stagnant into next weekend. Relatively quiet weather conditions are expected across the CONUS besides some monsoonal moisture and weak energy over the Southwest leading to showers and storms and perhaps extending into portions of the Plains. The large-scale trough should push a potent cold front across the central and eastern U.S., with potential for some rain particularly in the Upper Great Lakes and considerably cooler temperatures behind the front. ...Guidance Evaluation/Predictability Assessment... Model guidance remains in good enough agreement through Friday to warrant a general model blend. By next weekend though, models begin to diverge some regarding details and timing of individual pieces of energy into the larger scale Eastern U.S. trough. There isn't a lot of run to run consistency and these systems are small scale that it's tough to choose one solution or pattern evolution over another. The 01/18Z GFS and 01/12Z CMC were a little more consistent with each other over the ECMWF which showed a bit more amplification. Preferred a solution weighted more towards the GFS/CMC and ensemble means for 6 into 7. This also worked well out west where individual ensemble members show quite a bit of spread regarding energy rounding the top of the ridge into the Rockies and how much influence this might have on ridge breakdown. The QPF forecast was based largely on the 02/01Z National Blend of Models but with a wider footprint for light amounts added across much of the country as this under forecast of low amounts from the NBM is a known bias. ...Weather/Hazards Highlights... Rainfall and gusty winds associated with a compact upper low exiting the Mid-Atlantic coast on Wednesday should be offshore by the start of the medium range period, with only some lingering showers along coastal locations expected. Meanwhile, monsoonal moisture into the Southwest will continue to drive some diurnal showers and thunderstorms, with locally heavy rainfall possible. Rainfall intensity should wane after Wednesday, but showers could linger through the rest of the week across the Four Corners states. To the north, a cold front shifting from the Northern Plains to the Upper Midwest and Great Lakes should result in scattered showers as the front moves through. Temperatures out West will trend much warmer by Wednesday underneath a blocky upper ridge with daytime highs over the Northwest 10 to 15 degrees above normal through next weekend. Despite the anomalies, the resulting temperatures peaking in the 70s and 80s (90s for parts of California) are unlikely to create any heat related hazards. Canadian high pressure spilling into the north-central U.S. and expanding eastward behind the cold front will result in much below normal temperatures shifting from the northern Plains into the Midwest and the Northeast Thursday-Sunday. Daytime highs in some locations could be 15 to 20 degrees below average with overnight temperatures dropping into the 30s for many, and even 20s for far northern areas of North Dakota/Minnesota particularly Friday morning. Santorelli 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