Extended Forecast Discussion NWS Weather Prediction Center College Park MD 318 PM EDT Wed May 25 2022 Valid 12Z Sat May 28 2022 - 12Z Wed Jun 01 2022 ...Weather Pattern Overview... Behind a departing eastern U.S. upper trough and embedded low, guidance is agreeable and consistent with developing a very amplified western trough/eastern ridge pattern whose slow evolution raises the potential for a period of significant precipitation from the northern Rockies into the northern-central Plains and Upper Midwest. A system reaching the Pacific Northwest coast on Saturday may also bring a brief period of locally moderate to heavy precipitation to that part of the country. Scattered rainfall may develop over parts of the South heading toward the middle of next week, depending on uncertain details of upper energy that could try to retrograde underneath the eastern U.S. ridge. This pattern evolution will gradually shift much above normal temperatures from the Plains more into the northern half or two-thirds of the East while it spreads much below normal temperatures (especially for highs) through the West and into the northern Plains. ...Model Guidance and Preferences... Within the agreeable and consistent large scale forecast, individual models and ensembles differ with some important details that will affect sensible weather specifics at some locations. Near the East Coast, guidance continues to have difficulty with handling the weekend upper trough/low. Consensus from the 00Z/06Z package appeared to have nudged somewhat slower than the majority from the prior 12Z cycle. The 06Z GFS was on the extreme slow side but both the 00Z/06Z GFS runs hold it far enough back to result in an ultimate path toward the Southeast coast as upper ridging builds to the west/north. Remaining guidance and the 12Z GFS are more progressive with the main trough/low, with only lingering southern periphery energy serving as any feature that could slide beneath the upper ridge. Meanwhile, the 12Z models are showing a significant consolidation toward a more GFS-like solution (though not as strong as the 06Z run) for the compact but potentially vigorous system expected to reach the Pacific Northwest coast on Saturday. Models generally agree that this and surrounding dynamics should yield a closed low that tracks approximately through the Northwest/Great Basin into northern Rockies during Sunday-Tuesday. However from Monday onward there is enough spread for the exact path/strength/timing of the upper low and shortwave details ahead of it to lower confidence in specifics of the wavy surface boundary setting up over the Rockies/central U.S. along with accompanying significant precipitation. Developing differences upstream over the Pacific may begin to have some influence toward midweek as well. The updated forecast started with a blend of the 00Z/06Z GFS and 00Z ECMWF/UKMET/CMC for about the first half of the period, leading to a conservative forecast for the initial East Coast trough/low and intermediate/consensus forecast across the West, with the amplifying upper trough likely reaching its greatest depth around Monday. Widening detail spread later in the period favored maintaining a blended model/ensemble mean approach by Tuesday-Wednesday. ...Sensible Weather/Threat Highlights... On Saturday a compact but potentially vigorous system should bring a brief episode of locally moderate to heavy precipitation and possibly brisk winds to parts of the Pacific Northwest on Saturday. This system and its moisture will contribute to a larger scale upper low tracking into/through the West during the weekend into next week and reinforce a leading wavy frontal already in place over the central U.S. during the weekend. Some showers and thunderstorms will be possible over the northern Plains/Upper Midwest during the weekend with this leading front, while the combination of the western upper low and developing low level upslope flow could produce a multi-day period of heavy precipitation potential over and just east of the northern Rockies from the weekend into next week. This may include heavy snow at high elevations within the northern Rockies. By the middle of next week rainfall may become heavier along the wavy front over the central Plains. The Storm Prediction Center is monitoring the potential for severe weather with the activity over the northern Plains/Upper Midwest during the weekend, as well as for what reaches the Plains next week but with too much uncertainty in details for the latter to resolve the specifics at this time. Check the latest SPC outlooks for additional information on severe threats. The upper trough/low initially near the East Coast could produce some scattered showers/thunderstorms on Saturday followed by a drier trend over most of the East. Depending on how energy aloft to the south of the building eastern ridge evolves, some showers/storms could develop over parts of the South toward midweek. The Florida Peninsula should see episodes of showers and thunderstorms through the period. Temperatures will be quite warm across the central and southern Plains during the weekend into the start of next week with highs reaching well into the 90s from southern Nebraska to the Gulf Coast, and on Saturday-Sunday some low-mid 100s across western Texas which could challenge some daily records. The heat will then build eastward/northeastward as upper ridging strengthens over the East, with plus 10-20F anomalies becoming increasingly entrenched over the Great Lakes/Ohio Valley/Northeast. Well below normal temperatures will gradually progress from west to east across the West and into the northern Plains as upper troughing deepens and then persists over the western U.S. Expect one or more days with highs 10-20F below normal and possibly localized colder readings over parts of the northern Rockies/High Plains. Rausch/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