Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Mon Feb 28 2022 Valid 12Z Thu Mar 03 2022 - 12Z Mon Mar 07 2022 ...Overview... Latest guidance continues to suggest that a steadily building eastern Pacific upper ridge from late this week into early next week will help to establish mean troughing from central Canada through the western U.S. This general pattern appears likely to persist beyond the medium range period. Ahead of the developing mean trough, eastward progression of an initial Rockies/High Plains upper ridge will eventually displace an eastern North American mean trough. By early next week a broad zone of southwesterly flow should exist downstream from the mean trough axis. Leading energy moving into and through the West will spread precipitation across the region and then bring a broad area of various precip types to the central U.S. as its northeastward ejection supports a Plains through Upper Great Lakes surface system late Friday through the weekend. The trailing front may become a focus for enhanced rainfall over parts of the east-central U.S. late weekend into early next week. Below normal temperatures will spread over an increasing portion of the western/central U.S. with time while above normal temperatures become more focused over the East. ...Guidance Evaluation/Predictability Assessment... From a multi-day mean perspective, guidance continues to show very good agreement and continuity for the expected large scale pattern. The embedded details continue to offer varying degrees of uncertainty though. Recent runs have been nudging a little slower with the leading shortwave entering the West late this week but the past couple UKMET runs appear somewhat extreme with their southwestward elongation as the feature nears the coast. Models continue to show different ideas for how this energy will evolve as it ejects through the Plains during the weekend, with various influences from low-predictability small-scale trailing impulses dropping into the mean trough as well as possibly southern Canada/northern tier U.S. energy. As a result operational models show about a 20 mb spread for surface low pressure by the time the system reaches the Upper Great Lakes by early Sunday, with the 18Z/00Z GFS on the weak side and the 12Z ECMWF deepest. The 00Z CMC has come in almost as strong as the 12Z ECMWF. A curious evolution aloft in the 00Z GFS keeps its weak system stuck over the Great Lakes an extra day, versus the ensemble means that maintain a reasonable northeastward progression. Adding to the intrigue, the new 00Z ECMWF trends much weaker and even replaces it with another system by Monday. Behind the Great Lakes system, confidence is fairly low for shortwave details within the western trough (as demonstrated in consecutive ECMWF runs) but there is reasonable consensus that the front trailing from the aforementioned system should become aligned with flow aloft by early next week. During the first half of the period the 18Z GFS, 12Z CMC, and past two ECMWF runs through 12Z/27 provided the best cluster of guidance with general ensemble mean support. Then the forecast trended to an even model/ensemble mean weight by day 7 Monday given the increasing detail uncertainties. This approach yielded an intermediate solution for the system tracking through the Upper Great Lakes. ...Weather Highlights/Threats... The system moving into the West late this week will spread a broad area of mostly light to moderate (though perhaps locally heavier) rain and high elevation snow across the region. Some scattered precipitation may persist over the West through the rest of the period depending on shortwave details. Toward the end of the week through the weekend precipitation should become more widespread across the central U.S. as low pressure tracks from the central Plains through the Upper Great Lakes. The best potential for wintry precipitation types continues to extend from the northern half of the High Plains into the Upper Great Lakes and eventually New England. Highest probability of significant snowfall currently exists over the Upper Midwest, just to the northwest of the surface low track. There is still considerable uncertainty over the strength of the system so confidence in the precipitation/wind specifics is fairly low. Rainfall of varying intensity will be possible over the rest of the central/east-central U.S. ahead of the trailing cold front. Guidance is signaling the potential for heavier rainfall within an area from the southern Plains into the Ohio/Tennessee Valleys by Saturday night/Sunday into Monday, as the front decelerates while it becomes more aligned with flow aloft and interacts with low level Gulf moisture. The northern fringe of this late-period moisture shield could contain some wintry weather. Late this week expect above normal temperatures from the central/southern Plains through the Southeast, and including back to the Great Basin/Southwest on Thursday. Highest anomalies should be in the plus 15-25F range over the central Plains. On the other hand the northern tier may see readings up to 10-20F below normal. Colder air overspreading the West starting late this week will continue to expand into the Plains during the weekend into early next week, yielding a broad area of temperatures 5-15F below normal by next Monday. Meanwhile the eastern U.S. will see increasing coverage of warmer temperatures Saturday-Monday, generally plus 10-20F anomalies for highs and up to plus 20-25F anomalies for morning lows. Temperatures may challenge record highs over the Southeast. 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