Extended Forecast Discussion NWS Weather Prediction Center College Park MD 134 AM EST Tue Feb 25 2020 Valid 12Z Fri Feb 28 2020 - 12Z Tue Mar 03 2020 ...Overview... Upper pattern on Friday will feature a western ridge and eastern trough that will flip as the longwave pattern progresses downstream. Building ridging to the north/northeast of Hawai'i and south of the Gulf of Alaska late this week favors the development of a sharp/digging trough through California Sun/Mon that may close off over the deserts. Northern stream will continue across the northern tier or southern Canada, trending northward in time east of 100W as subtropical ridging again builds through the western Caribbean. ...Guidance/Predictability Assessment... The 12Z/18Z models/ensembles generally showed good agreement on the longwave evolution through the period. The GFS and UKMET were displaced a bit with a couple features that made their forecasts less desirable. For the former, both the 12Z/18Z runs were quite aggressive with a sfc low Sat/Sun offshore OR/CA that was not supported by the ensembles, resulting in a slower speed of the longwave upper trough by Mon compared to the 12Z ECMWF ensemble mean and NAEFS mean. For the latter, it has had trouble resolving incoming Pacific systems (too strong and/or displaced) in recent days compared to the ensembles but was considered acceptable elsewhere. The 12Z Canadian may be too strong with a sfc low off SE New England late Sat into early Sun as well. Overall the 12Z ECMWF offered the most reasonable solution through the period. Trended toward the ensemble consensus by next Mon/Tue with the developing system over the Southern Plains as the upper trough lifts out of the Southwest. ...Weather/Hazard Highlights... Lake-effect snow will continue late this week into the start of the weekend with broad cyclonic flow around the departed system. Some record cold max temperatures may be approached in the East, even into south Florida where some areas may not reach 70F. By contrast, the West will see a couple more mild/warm days Fri-Sat with some potential record highs in California on Friday. Pacific system will bring an increasing coverage of light to modest terrain-enhanced rain/snow as the upper trough digs in. Temperatures will trend much cooler by Sun/Mon but only about 5 degrees below average overall. Milder air will get pushed to the east of the Rockies next week, with readings about 5-10 degrees above average (moreso overnight) in advance of the exiting Southwest system. Fracasso Additional 3-7 Day Hazards information can be found on the WPC medium range hazards 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