Extended Forecast Discussion NWS Weather Prediction Center College Park MD 132 PM EST Sat Feb 26 2022 Valid 12Z Tue Mar 01 2022 - 12Z Sat Mar 05 2022 ...Overview... Latest guidance continues to show an upper pattern consisting of a western ridge and broad eastern mean trough through midweek, followed by a transition toward a mean trough settling into the western U.S. while upper heights rise farther to the east. The primary precipitation focus early in the period will be over the Pacific Northwest and northern Rockies ahead of the eastern Pacific trough that eventually moves into the West. Progression of this trough later in the week into next weekend will spread precipitation over other parts of the West and then bring a variety of precipitation types to the central U.S. as low pressure emerges over the Plains. Ahead of this system, expect most precipitation east of the Rockies to be confined to a couple episodes of snow across northern areas with associated surface waves. The pattern evolution will favor above normal temperatures over a majority of the western/central U.S. through Wednesday or Thursday and then a cooler trend over the West and warmer readings over the East. ...Guidance Evaluation/Predictability Assessment... Overall, the latest 00z/06z suite of models and ensembles continued to be relatively agreeable on the large scale flow evolution during the medium range period. There remains some questions on timing of a few clipper systems within the broader Eastern U.S. trough. Bigger uncertainties lie with a couple of incoming shortwaves into the West and then how that trough opens and broadens over the West late period. The 00z ECMWF is a hair faster with an initial shortwave into the Pacific Northwest on Thursday (and also late period with developing low pressure over the Plains), while the CMC is more amplified. More uncertainty upstream from this initial wave arise, mainly in the details of possible compact and embedded closed lows and timing. In general, the 06z GFS seemed to be the most stable and agreeable to the ensemble means as the mean trough comes into play across the West. The WPC blend for todays updated progs used a multi-model deterministic blend for days 3-4, slowly increasing contribution from the ensemble means later in the period. Was able to maintain 60 percent deterministic even out to day 7, though with more weighting on the GFS compared to the ECMWF and CMC. This approach helps to mitigate the harder to resolve small scale differences and maintains good continuity from the previous WPC forecast. ...Weather Highlights/Threats... Moist flow ahead of the upper trough initially over the eastern Pacific should continue a Pacific Northwest atmospheric river event already in progress at the start of the period early Tuesday. Amounts during Tuesday-Wednesday should be somewhat lower than in the short range at the start of the week but could still be meaningful at some locations. Some of this moisture will extend into the northern Rockies. Progression of the upper trough into the West after midweek should lead to a lighter trend along the West Coast and spread precipitation into central California and some other parts of the West, mostly with light to moderate amounts of rain and higher elevation snow. Expect precipitation to expand across the central U.S. late week into the weekend as western trough energy reaches far enough east to support Plains low pressure. Best potential for some wintry weather will be over the northern third of the Plains into the Upper Midwest. Areas from the Upper Midwest into Northeast may see a couple periods of snow Tuesday-Thursday in association with clipper systems, the first one fairly well forecast but the second having much greater uncertainty for strength/track details. Thus confidence is a lot lower for coverage and amounts of snow with the second system. Above normal temperatures will prevail over a majority of the western and central U.S. Tuesday-Wednesday. Progression of the initial eastern Pacific upper trough will promote a cooler trend over the West after midweek and then favor northward expansion of above normal temperatures (plus 10-15F or so anomalies) from the South across a greater portion of the eastern U.S. Plus 10-20F anomalies will be possible for max and/or min temperatures for one or more days over the Great Basin/Southwest through midweek and parts of the Rockies/Plains into later in the week. Central Plains locations could exceed plus 20F anomalies for highs. Areas from the Upper Midwest to the Northeast will tend to be moderately below normal and colder air filtering into Montana/North Dakota could bring highs down to 10-20F below normal by next Saturday. Santorelli/Rausch 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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml