Extended Forecast Discussion NWS Weather Prediction Center College Park MD 301 PM EST Fri Feb 24 2023 Valid 12Z Mon Feb 27 2023 - 12Z Fri Mar 03 2023 ...Significant storm system to track across the Plains and Midwest to the Northeast U.S. early to mid next week with strong storms and heavy snow... ...A series of active storms for the West through the period also may lead to emerging late next week storm development across The South... ...Synoptic Overview... The weather pattern is forecast to remain quite active going into much of next week. The highly anomalous and intense low pressure system that will initially affect California and the Desert Southwest will eventually eject eastward across the central Plains and then to the Midwest states by early Monday. Secondary coastal cyclogenesis is likely off the southeast New England coast by early Tuesday and this will continue to develop further as it drifts away from shore. Surface high pressure briefly settles in across the eastern U.S. in the wake of this storm for the middle of the week. Meanwhile, a persistent and cold/amplified upper trough position will repeatly rebuild sharply across the cold and wet/unsettled West. Midweek and late next week ejection of these energies downstream will support development of additional surface waves. One will likely track from the West Coast to the Plains and eventually the Great Lakes region and Mid-Atlantic/Northeast for the Wednesday to Thursday time period, and could easily result in another round of widespread precipitation and thunderstorms. Additionally, yet another storm may be on tap to emerge across The South late next week along with a threat for heavy rain and again for potentially enhanced northern periphery snow/ice. ...Guidance/Predictability Assessment... Recent runs of the GFS/ECMWF/Canadian model solutions seem clustered better than normal through medium range time scales and have good GEFS/ECMWF ensemble support for the larger scale pattern evolution and the main flow embedded weather focusing systems in very active and stormy split flow over the lower 48 and vicinity. A guidance composite offers a good forecast basis and tends to mitigate consistent with individual system predictability much of the still evident smaller scale variances. This solution is reasonably consistent with the National Blend of Models and WPC product continuity. ...Weather/Hazard Highlights... The upper low initially ejecting out of the Southwest will evolve into a potent storm system over the Plains/Midwest and then into Great Lakes with a broad area of precipitation. There will likely be a potential transition among precipitation types across portions of the Upper Midwest/Great Lakes, with possible issues for northern areas receiving heavy wrap-around snows. Meanwhile probabilities for significant snow are increasing over the Northeast, with the most likely axis depending on the details of secondary coastal/offshore low development later Monday into Tuesday. This would keep colder air/snow over New England. This system may produce some very strong and gusty winds through its existence, and in particular over the southern High Plains and from parts of the Midwest/Ohio-Tennessee Valley into Lower Great Lakes owing to the strong pressure gradient that will be in place. The next storm system approaches the West Coast late Sunday into next week, and it will likely bring additional rounds of heavier precipitation to the West Coast region, with highest totals expected along the central West Coast and the Sierra Nevada. Expect some enhanced precipitation for the coastal areas of northwestern California, mainly due to the combination of the approaching upper trough/front providing enhanced focus. A broader area of precipitation should spread farther south and inland across the West. By next Thursday the upper trough may reach just far enough east to start drawing up deeper Gulf moisture into the eastern half of the country, with rainfall beginning to expand in coverage and intensity at that time. There is an emerging guidance signal for potentially well organized southern stream low development and track across The South later next week along with an expanding precipitation shield that could then affect the East Coast. In terms of temperatures, much of the central/eastern U.S. should see one or more days of readings 10-20F above normal, and potentially even warmer morning lows. The West will see a persistent cool pattern from the weekend through Thursday with central/southern areas most consistently seeing highs up to 10-20F below normal. Some daily records for cold temperatures are possible over/near parts of California. Hamrick/Schichtel 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 Hazards: - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Ohio Valley, Thu-Fri, Mar 2-Mar 3. - Heavy rain across portions of the Great Lakes, the Central Appalachians, and the Ohio Valley, Mon, Feb 27. - Heavy snow across portions of the Pacific Northwest and the Northern Great Basin, Thu-Fri, Mar 2-Mar 3. - Heavy snow across portions of the Northeast, the Central Great Basin, the Mid-Atlantic, California, the Great Lakes, and the Southwest, Mon-Tue, Feb 27-Feb 28. - Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Mon, Feb 27. - Severe weather across portions of the Southern Appalachians, the Ohio Valley, and the Tennessee Valley, Mon, Feb 27. - Flooding possible across portions of the Central Plains, the Middle Mississippi Valley, the Great Lakes, the Ohio Valley, and the Upper Mississippi Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley. - Flooding likely across portions of the Great Lakes. - High winds across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Northern Rockies, the Southern Rockies, the Northern Great Basin, the Southern Plains, and the Southwest, Tue, Feb 28. - High winds across portions of the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Great Lakes, and the Ohio Valley, Mon, Feb 27. 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