Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Sat Feb 19 2022 Valid 12Z Tue Feb 22 2022 - 12Z Sat Feb 26 2022 ...Heavy to excessive rainfall threat from the Lower Mississippi/Tennessee Valley to the Mid-Atlantic Tuesday-Friday... ...Heavy snow/ice threats from the Upper Midwest to Maine Tuesday and southern Plains to Northeast Wednesday-Saturday... ...Pattern Overview... A very active weather pattern is expected to develop by early next week over our fine nation 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 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. There is also a double dose of winter storm potential with a leading swath from the Upper Midwest to Maine Tuesday, then broadly from the Southern Plains to the Northeast Wednesday into Saturday. ...Guidance Evaluation/Predictability Assessment... The latest models and ensembles continue an ongoing recent trend to offer quite similar mid-larger scale flow evolutions in a medium range pattern with average predictability. A composite of generally well clustered guidance from the GFS/ECMWF/UKMET/Canadian along with the National Blend of Models (NBM) seemingly provides a good forecast basis for days 3-5 (Tuesday-Thursday). This solution is well supported by GEFS/ECMWF ensembles. The last few GFS runs were slower than the rest with the other guidance, therefore it was utilized less in our product blend. The WPC product suite was then mainly derived from the GEFS/ECMWF ensemble means and NBM into days 6/7 in a period with gradulaly growing model forecast spread. This broad strategy tends to mitigate lingering smaller scale system variances while maintaining good WPC product continuity. ...Weather Highlights/Threats... Moderate to heavy mountain snows are likely to focus early-mid next week across the cooling West/Rockies as potent upper trough energies, enhanced by post-frontal upslope fetch, dig into the West. The 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 Upper Midwest to Maine 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 experimental "slight" ERO flood threat from the Lower Mississippi/Tennessee Valleys to the Mid-Atlantic starting early next week along with potential for periodic re-development and training along the wavy/slowed trailing front through later next week. A main second wave evolution may also support the spread of a heavy snow/ice threat from parts of the southern plains and Mid-Mississippi/Ohio Valleys and into a cold air dammed northern Mid-Atlantic and Northeast Wednesday into Saturday. Given lingering detail uncertainties in the guidance, confidence on exact snow/ice amounts and locations remains less certain at these longer lead times, but the potential is there in this favorable pattern. 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 or even 50 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 Tuesday. This very cold air will spread, but gradually modify later next week across the Midwest/East. Meanwhile, much above normal pre-frontal temperatures are expected across the Southeast/East early in the period (with some records possible, especially overnight mins) with upper level ridging over the region. Kebede/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 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