Extended Forecast Discussion NWS Weather Prediction Center College Park MD 340 PM EST Mon Jan 23 2023 Valid 12Z Thu Jan 26 2023 - 12Z Mon Jan 30 2023 ...Strong storm to prolong a heavy snow and high wind threat over the interior Northeast into Thursday... ...Guidance/Predictability Assessment... The WPC medium range product suite was primarily derived from a composite blend of well clustered and consistent guidance from the 06 UTC GFS, 00 UTC ECMWF/UKMET/Canadian, the 13 UTC National Blend of Models (NBM) and WPC continuity Thursday into Saturday in an active pattern with seemingly above normal predictability. 12 UTC guidance now also remains in line with this forecast strategy. However, there still are ample concerns by the weekend with the disparate model handling of complex Alaska/Gulf of Alaska system energies set to dig into the Western U.S. to the lee of an amplified eastern Pacific upper ridge. Recent GFS runs have offered the least amplified solution while the ECMWF/Canadian have been the most amplified. Prefer an ensemble mean solution to mitigate some of these differences and run to run variations. Of the ensemble systems, prefer the ECMWF ensemble mean whose more amplified upper trough development than the GEFS down through the West Coast seems to fit best with upstream upper ridge amplitude, recent model trends, WPC continuity and pattern history. This solution is on the more amplified side of the full envelope of solutions, but not as amplified as the ECMWF/Canadian. ...Weather/Hazard Highlights... The latest in a recent series of main storm systems will reach the Northeast U.S. Thursday. Enhanced snows are anticipated to linger from the lee of the lower Great Lakes in cooled flow as well as across interior areas of the windy Northeast as the secondary low develops, with gales up the coast with secondary coastal low development. This will be in response to amplified trough passage aloft that exits the region to the Canadian Maritimes by Friday. Following this system, an Alberta Clipper low will work some snow back into the Great Lakes region Friday. The southward plunge of a trailing cold front will meanwhile begin to drive cold Canadian high pressure down through the north-central U.S. and then into the West. Expect much below normal temperatures across the north-central U.S. for the weekend into early next week, with highs running up to 15-25 degrees below normal potentially across portions of Montana, the Dakotas, and Nebraska. Cold air will also filter into the Northwest/Intermountain West. Upper trough passage/height falls will combine with lower atmospheric upslope fetch to spread a focus for locally heavy terrain enhanced snows down across north-central parts of the Intermountain West/Rockies/High Plains. Energies dug into the West eject downstream to potentially support a new system or systems that may organize over the weekend into early next week over The South. Gulf moisture return may support a moderate to heavy rainfall focus over the central Gulf Coast states and vicinity, with more modest rains spreading northward over the east-central U.S. into/ahead of a wavy front. In this pattern, the pre-frontal airmass warms as upper ridging builds from the Southeast. There is a signal for plowable snows on the northern periphery of the emerging overall precipitation shield more under lead influence from the aforementioned cold Canadian airmass. Campbell/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 Southeast, the Lower Mississippi Valley, and the Southern Plains, Sat-Sun, Jan 28-Jan 29. - Heavy snow across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Fri, Jan 27. - Heavy snow across portions of the Northeast and the Great Lakes, Sun, Jan 29. - Heavy snow across portions of the Northeast, Thu, Jan 26. - Flooding possible across portions of the Central Plains. - Much below normal temperatures across portions of the Central Plains, the Northern Plains, the Great Lakes, the Northern Rockies, the Central Rockies, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Southern Plains, Sat-Mon, Jan 28-Jan 30. 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