Extended Forecast Discussion NWS Weather Prediction Center College Park MD 228 PM EDT Mon Apr 18 2022 Valid 12Z Thu Apr 21 2022 - 12Z Mon Apr 25 2022 ...Additional snow and cold weather anticipated for portions of the Northern Plains Friday night into Saturday night... ...Weather Pattern Overview... A quasi-zonal flow pattern aloft becomes more amplified Thursday night as a large low off the Pacific Northwest opens and digs southeast over California before crossing the Intermountain West Friday and slowing as it closes again as it drifts over the northern Plains late Friday night through Saturday night. Surface cyclogenesis over the central High Plains is expected by Friday evening before tracking up through the north-central Plains into Sunday. Showers and thunderstorms will develop ahead of the low on both on the warm and cold fronts with substantial rain for the Mid-South likely in the Sunday timeframe. Meanwhile, a downstream ridge axis builds across the eastern U.S. and results in a considerable warming trend for the weekend continuing into next week. ...Model Guidance Evaluation... Above average agreement on the main synoptic scale features are apparent among the latest global guidance into this weekend. Similar to recent days, the 06Z GFS was more progressive with the axis of the main trough across the central/northern Plains, and definitely stronger by 12Z Saturday compared to the 00Z ECMWF/CMC/UKMET which were in close agreement with their depiction of the closed low evolving over the Dakotas by early Sunday. So far among 12Z guidance, the 12Z GFS/CMC/UKMET have slowed, likely leaving the 12Z GFS still the most progressive deterministic solution with the deepest northern Plains low. By Sunday, deterministic guidance are in decent agreement on the depiction of the next storm system near the Gulf of Alaska, but considerable model spread is apparent with the timing of the surface low over the north-central U.S. with the 12Z CMC the slowest. A multi-deterministic model blend was used for Days 3-5 with minor inclusions of the 06Z GEFS/00Z ECENS beyond the 144hr forecast period of the UKMET (Days 6/7). ...Sensible Weather/Threats... Moderate to heavy precipitation with snow levels generally 5500ft to 6500ft will continue to spread down the Sierra Nevada Thursday before easing Thursday night as the digging upper trough moves inland. This spring event will deliver some highly beneficial precipitation to drought-stricken areas of California, with the potential for 1-2+ inches of rain in some areas of central and northern California, and 1-3 feet of snow for the High Sierra. Moderate to locally heavy rain/mountain snow (snow levels generally about 7000ft) then progresses ahead of the upper trough across the Intermountain West Thursday night through Friday. Organized showers and thunderstorm are expected to develop across the central Plains/Midwest and north Thursday night through this weekend as Gulf moisture is advected northward ahead of the western trough. Additional moderate to heavy snow is expected for portions of the northern Rockies Friday, spilling onto the northern High Plains Friday night into Saturday night. The threat for heavy snow remains across the western Dakotas and eastern Montana/Wyoming, likely affecting the similar areas to the recent blizzard and subsequent storms. 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 wedge front. It will likely remain uncomfortably cold from Montana to North Dakota and northern Minnesota with near-freezing highs running 20 to 25 degrees below normal. Jackson 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