Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 PM EST Fri Feb 18 2022 Valid 12Z Mon Feb 21 2022 - 12Z Fri Feb 25 2022 ...Heavy to excessive rain threat from the Lower Mississippi/Tennessee Valley to the Mid-Atlantic Monday-Friday... ...Heavy snow/ice threats across from northern Plains to northern Maine Monday-Tuesday and southern Plains to Northeast Wednesday-Friday... ...Pattern Overview... A very active weather pattern is expected to develop by early next week as an upper level trough digs across the Western U.S. with ejecting energies and induced frontal waves progressing downstream. The upper trough should shift eastward into the Central Plains and Midwest by later next week as amplified ridging builds over the East Pacific and West Coast. This very amplified pattern results in a renewed heavy rain and flooding threat from roughly the lower Mississippi/Tennessee Valley to the Mid-Atlantic through most of next week, with a double dose of winter storm potential -- first across the northern tier to far northern Maine Monday and Tuesday, and again from the southern Plains to the Northeast the second half of the week. ...Guidance Evaluation/Predictability Assessment... Models and ensembles continue to show very good agreement on the overall large scale pattern described above through most of the period. The amplifying trough during the early part of next week over the West is showing better agreement in terms of timing compared to previous days, though timing becomes a little more uncertain later in the week as the shortwave energy slides into the central Plains and the Midwest next Thursday-Friday. Despite above average large scale agreement, the latest guidance continues to offer plenty of uncertainty in the details, which will have more significant impacts to heavy snow/rainfall potential across much of the eastern half of the nation. Nothing notable stands out at this time, as most of these differences are the typical extended range model run to run variations anyways. By later next week, there's indications an amplified ridge should be located over the eastern Pacific, and possibly into parts of the West, but quite a bit of disagreement on individual systems rounding the top/eastern part of the ridge into western Canada and the Northwest U.S.. WPCs blend for today used a majority deterministic model blend for days 3-5. After this, increased the ensemble means to help mitigate the smaller scale, harder to resolve, detail differences. This approach maintains good continuity with the overnight WPC package as well. ...Weather Highlights/Threats... Moderate to heavy mountain snows are likely to focus early to mid next week across the cooling West/Rockies as potent trough energies dig into an amplified western U.S. upper trough position. A wavy front on the leading edge of a cold surge set to dig into the central U.S. early-mid next week will have upper support to favor a swath of heavy snow from the northern plains/Upper Midwest to northern Maine next Monday-Tuesday with some ice accumulations possible along the southern edge. Meanwhile, ample upper energies working downstream from the West next week will also act to induce waves along a lead front and tap deepening moisture from the Gulf of Mexico. This is expected to fuel a heavy rain and flood threat from the Lower Mississippi/Tennessee Valleys to the Mid-Atlantic starting early next week along with potential for re-development along the wavy/slowed trailing front later next week. This second wave may also support a heavy snow/ice threat from parts of the southern plains and Mid-Mississippi/Ohio Valleys to a cold air dammed Northeast Wednesday-Friday. Given detail uncertainties in the guidance, confidence on exact snow/ice amounts and locations remains very low at these longer lead times, but the potential is there and the pattern certaintly supports a threat somewhere. Arctic high pressure surging southward into the Central U.S. during the first half of next week will support much below temperatures from the Northwest into much of the Central U.S. as far south as Texas. Especially from the northern High Plains to the northern/central Plains, daytime highs and overnight lows could be 30-40 below normal, which could approach to exceed record low mins and max values. Daytime highs across the northern part of this region could struggle to get above 0F Monday and Tuesday. This cold should moderate somewhat by later next week and spread eastward into the Mississippi Valley and parts of the Midwest. Meanwhile, much above normal temperatures are expected across the South and East early in the period (with some records possible, especially overnight mins) as upper level ridging builds over the region. Temperatures should moderate back to normal for the Northeast next Thursday-Friday, but remain above normal for the Southeast. Santorelli 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