Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Wed May 25 2022 Valid 12Z Sat May 28 2022 - 12Z Wed Jun 1 2022 ...Weather Pattern Overview... An upper trough with possible embedded closed low will be crossing the eastern U.S. late this week into the weekend, with some uncertainty over how quickly it and the associated surface wave/frontal system exits the East Coast. Meanwhile, a shortwave reaching the northwestern U.S. by Friday will be at the leading edge of a larger scale trough that should amplify over the West during the weekend and into early next week. A strong ridge will build over an increasing portion of the eastern half of the country going into the beginning of June as the western trough deepens, with the potential for a blocky pattern to develop. ...Model Guidance and Preferences... The 00Z model guidance suite is now favoring a more amplified trough solution across the East Coast region for Saturday, with both the GFS and CMC favoring a bit of a closed low. Out West, the guidance shows good timing agreement on the initial shortwave into the West late this week, and the CMC is slightly slower with the second impulse, which will reinforce the overall synoptic scale trough that develops across the western U.S. by Sunday and beyond. Going into Tuesday, the GFS gets stronger and faster with the trough over the Rockies and lifting it out across the western High Plains. There is very good model agreement on the building upper ridge over the Ohio Valley. The WPC forecast trended more towards the ensemble means for the second half of the period to account for this uncertainty, whilst still maintaining some of the deterministic CMC/ECMWF/GFS, and generally shows good continuity with the previous WPC forecast as well. ...Sensible Weather/Threat Highlights... With rainfall diminishing in coverage/intensity over the East by the weekend, the main focus for precipitation will extend from the Northwest through the northern-central Plains into the western Great Lakes. Showers and storms will initially develop across the Northern Plains and Upper Midwest in response to a developing low pressure and frontal boundary over the north-central U.S., while some precipitation extends back into the northern Rockies and vicinity. Another shortwave reaching the Pacific Northwest around Saturday could bring an episode of enhanced precipitation to parts of the region, followed by this moisture streaming across the Rockies and interacting with the wavy frontal system set up over the Plains. Late season snow for the higher terrain of the Northern Rockies is looking increasingly likely, with potentially over a foot of accumulation above 8000 feet elevation. There is also the potential for heavy rainfall across portions of the Dakotas by early next week behind the front with moist upslope flow, with perhaps 1 to 3 inches for some areas. Temperatures will be quite warm across the central and southern Plains for the weekend with highs reaching well into the 90s from southern Nebraska to the Gulf Coast, and some low-mid 100s across western Texas which could challenge some daily records. The heat then builds eastward to include the Ohio Valley and eventually the East Coast going into early next week, compliments of the building upper ridge and southerly flow ahead of the storm system over the Plains. Well below normal temperatures will likely encompass areas from the Pacific Northwest to the Northern Rockies and Northern Plains as the upper trough moves in behind the cold front, with highs up to 20 degrees below late May averages. 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