Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Fri Feb 24 2023 Valid 12Z Mon Feb 27 2023 - 12Z Fri Mar 3 2023 ***Significant storm system to track across the Plains and Midwest to the Northeast U.S. early next week with strong storms and heavy snow*** ...Synoptic Overview... The weather pattern is forecast to remain quite active going into much of next week. The 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, the upper trough rebuilds across the western U.S. and this will support the development of a second surface low that will likely track from the West Coast to the Plains and eventually the Great Lakes region for the Wednesday to Thursday time period, and could easily result in another round of widespread precipitation and thunderstorms. ...Guidance/Predictability Assessment... The 00Z model guidance has an excellent overall depiction of the overall weather pattern for the beginning of the week, including the expected evolution of the winter storm tracking from the Midwest to the Northeast. Going into Tuesday, the CMC becomes slightly more displaced with the original surface low over southern Ontario, and that trend continues into Wednesday. For the next storm system emerging over the Plains mid-week, the CMC becomes displaced to the southeast with the axis of the front and the main surface low, whilst the UKMET is to the northwest of the model consensus. With the deep upper trough reaching the southern Plains by the end of the week, the ECMWF is more progressive, and the GFS is between it and the slower CMC solution. Even greater model differences exist with the next Pacific Northwest storm system arriving on Friday. The WPC fronts/pressures forecast was primarily derived from a nearly multi-deterministic model blend through Tuesday, and then transitioning to about 60% ensemble means by Friday to account for the increasing mesoscale uncertainty. ...Weather/Hazard Highlights... The upper low initially ejecting out of the Southwest will produce a strong storm system over the Plains/Midwest into Great Lakes with a broad area of precipitation. The most favorable conditions for heavy rainfall should exist over the Central Plains and the Midwest, where copious amounts of moisture and some instability may combine to produce potentially heavy short-term rainfall rates. Most of the precipitation will likely fall in liquid form as the airmass will not be as chilly as the previous system. There will be at least a potential transition among precipitation types in the Upper Midwest/Great Lakes, with possible issues for locations receiving snow from the previous system and rain from this one. Meanwhile probabilities for significant snow are somewhat higher over New England, with the most favored axis depending on the details of secondary coastal/offshore low development around next Tuesday. Current model trends support an offshore low and with a track in the southern part of earlier guidance spread. This would hold colder air/snow over New England with enough suppression to keep most snow to the south of far northern 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. The next storm system approaches the West Coast late Sunday into next week, and it will likely bring heavier precipitation to the West Coast region, with highest totals expected along the central West Coast and the Sierra Nevada. The Day 4 Excessive Rainfall Outlook (12Z Monday-12Z Tuesday) has a Marginal Risk area along the central West Coast, mainly due to the combination of the approaching upper trough/front providing enhanced focus for locally heavy rain early in the outlook period. 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 Gulf moisture into the eastern half of the country, with rainfall beginning to expand in coverage and intensity at that time. Specifics will be resolved in coming days. The strong upper high over Cuba/northwestern Caribbean will maintain warmer temperatures over the South with some record highs possibly lingering into next week. A broad area of the southern two-thirds of the central/eastern U.S. should see one or more days of temperatures 10-20F above normal with some days featuring 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 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