Extended Forecast Discussion NWS Weather Prediction Center College Park MD 222 AM EDT Tue Apr 19 2022 Valid 12Z Fri Apr 22 2022 - 12Z Tue Apr 26 2022 ***Threat of winter storm increasing for portions of the Northern Plains this weekend*** ...Weather Pattern Overview... The upper level pattern over the continental U.S. becomes more amplified by the end of the week and into the weekend as a large synoptic scale trough from the Pacific moves inland across the Intermountain West, and this will spur surface cyclogenesis across the High Plains by Friday night. This low will then track across the Upper Midwest through early Sunday, with a trailing front across the Mississippi River Valley that will fuel showers and storms. Meanwhile, a downstream ridge axis builds across the eastern U.S. and results in a considerable warming trend for the weekend. Another Pacific trough approaches the northwestern U.S. by the beginning of next week. ...Model Guidance Evaluation... The 00Z model guidance suite appears to have above average agreement on the main synoptic scale features through early Saturday, with just some minor differences in the timing of the upper trough evolution over the western states. The GFS is not as progressive as earlier runs with the axis of the main trough axis across the central/northern Plains, although the CMC is slower in lifting the trough/closed low out of the region. By early next week, the models are in good agreement on the depiction of another storm system over the northeast Pacific Ocean, but model differences still exist with the degree of upper level ridging ahead of that feature across the Intermountain West. A nearly multi-deterministic model blend was incorporated as a starting point for Friday and Saturday, and then more of the ECMWF/ECENS was used going forward into early next week along with some of the GFS and GEFS mean. ...Sensible Weather/Threats... The threat of a noteworthy winter storm is increasing with time for western North Dakota and portions of eastern Montana for the upcoming weekend on the backside of the intensifying surface low, where a well-defined deformation zone will likely exist. This will likely be coupled with strong northerly winds owing to the tight pressure gradient that will be in place, and this could result in blizzard conditions for some areas if these model trends continue. Moderate to heavy snow is also likely for the northern Rockies through early Saturday, and this will also include the higher terrain of northern Utah and central Colorado. Heavy showers and thunderstorms could also make weather headlines on Sunday and going into early Monday across the central U.S. as a deep surge of Gulf moisture advects northward and interacts with a slow moving surface cold front with multiple shortwave perturbations moving overhead. This will likely be in the form of multiple mesoscale convective complexes with repeating rounds of convection, and some strong to severe storms are also possible. In terms of temperatures, a major warming trend is forecast for much of the eastern half of the nation going into the weekend, along with increasing humidity levels, in response to deep southerly flow ahead of the central U.S. storm system. One of the caveats in the temperature forecast will be the presence of a back door cold front/cold air damming for the Mid-Atlantic and Northeast U.S. this weekend, with potentially a big contrast over a relatively short distance near the front. It will likely remain uncomfortably cold from Montana to North Dakota and northern Minnesota with near-freezing highs running 15 to 25 degrees below normal. 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