Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Tue Jan 24 2023 Valid 12Z Fri Jan 27 2023 - 12Z Tue Jan 31 2023 ***Coldest weather so far this month expected across the Dakotas and the Upper Midwest starting this weekend*** ...Synoptic Overview... The departure of the strong low pressure system from New England late Thursday will yield an upper level pattern with broad cyclonic flow with an Alberta clipper system tracking eastward across the Great Lakes on Friday. This will herald the arrival of an arctic airmass settling southward from Canada. The strong cold front will likely spur surface cyclogenesis across the southern Plains by the weekend, but it currently appears this low should be weaker than the one that will be in place over the next couple of days. The southeast ridge is expected to remain rather strong over the Bahamas/southwestern Atlantic, and this will tend to limit the southward extent of the arctic airmass. ...Guidance/Predictability Assessment... The 12Z model guidance suite agrees very well on the main pattern evolution going through Friday and Saturday. Going ahead into Sunday, a trough settling southward from British Columbia will introduce more uncertainties across the West Coast region and this would have an effect on the degree of surface low development over California going into the beginning of next week. The GFS has trended more in the direction of the ECMWF/CMC/UKMET in terms of amplitude and westward extension of the West Coast trough, but is on the slower side of the guidance. The UKMET is on the faster side of the guidance, so a CMC/ECMWF blend works well for a starting point in the forecast here. Looking ahead to Monday/Tuesday, models are in closest agreement across the Eastern U.S. and the upper ridge over the Bahamas/Cuba, and more spread across the West and the northern tier states. The CMC remains more pronounced with the trough across the West Coast whereas the GFS/ECMWF are weaker and more inland. The fronts/pressures forecast was primarily based on a multi-deterministic blend through Saturday, and then less of the 18Z GFS (it had a weaker western trough) and more of the ensemble means going into the Sunday to Tuesday time period. ...Weather/Hazard Highlights... In the wake of the departing Northeast U.S. storm, an Alberta Clipper low will produce mainly light snow across portions of the Great Lakes region Friday and northern New England Saturday. The southward plunge of a trailing cold front will advect an arctic surface high pressure down across the north-central U.S. and then into the northern Rockies/western High Plains. 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 across portions of Montana, the Dakotas, and Nebraska. This would be the coldest weather since Christmas for this region, with some locations remaining subzero for daytime highs by Sunday. This cold weather will also be expected to reach into the Northwest/northern Intermountain West. Upper trough passage combined with lower atmospheric upslope flow will produce moderate to locally heavy terrain enhanced snows down across north-central parts of the Intermountain West/northern Rockies/western High Plains. The shortwave energy initially from the southwestern U.S. is expected to eject eastward across the Plains and support a new low pressure system over the weekend into early next week over Texas and the central Gulf Coast region. Gulf moisture return may support a corridor of moderate to heavy rainfall over portions of 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. 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