Extended Forecast Discussion NWS Weather Prediction Center College Park MD 227 PM EDT Fri Mar 14 2025 Valid 12Z Mon Mar 17 2025 - 12Z Fri Mar 21 2025 ...Guidance/Predictability Assessment... Models and ensembles overall continue to offer reasonable agreement, at least on the large scale, through the medium range period, but some notable differences in the details which would have impacts on sensible weather threats. A trough exiting the East Coast early next week has trended better in terms of timing. The next trough into the Central U.S. looks to spin up a modestly strong surface low next Tuesday-Wednesday, but the models continue to indicate some timing questions on both the shortwave and surface low. The GFS remains on the fast side, with the ECMWF/CMC/UKMET runs today clustered close and slower. WPC favored the slightly slower EC/CMC/UKMET (with the EC Mean) for this, which was also close to WPC continuity. Worth a note that the new 12z CMC today (available after forecast generation time) did trend even slower while the 12z ECMWF trended slightly faster. The next two systems mid to late next week show some timing variability as well, but this was covered well with incorporation of the ensemble means into the blend for the late period. ...Weather/Hazards Highlights... An amplified upper trough and lead/wavy cold front will exit the East Coast by Monday to moderate temperatures briefly and sweep widespread thunderstorms out to sea; with possible low deepening out over the Western Atlantic a possible maritime hazard. Temperatures are forecast to warm back up in the central and then eastern U.S. as the week progresses. This occurs with advent of upper ridging as a next main upper trough moves across the western and central U.S. early-mid next week and onward to the East later next week. Dynamically and terrain enhanced rain and elevation focusing snow is forecast to spread out from the West Coast to through the Interior West Monday- Tuesday. Cyclogenesis over the Plains on Tuesday and subsequent main/windy low track through the Midwest/Great Lakes into Thursday will combine with secondary cold frontal cooling to enhance upslope and wrapback heavy snow potential from the north-central Rockies/Plains through the Upper Midwest Tuesday- Thursday. A wavy trailing cold front will have less moisture than the early week system, but will align showers and thunderstorms across the central U.S. then the East, exiting next Thursday/Friday as new Pacific system energies and late winter precipitation work back into the West/Northwest. Santorelli/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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 https://www.wpc.ncep.noaa.gov/#page=ovw