Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 AM EST Fri Feb 9 2024 Valid 12Z Mon Feb 12 2024 - 12Z Fri Feb 16 2024 ...General Overview... An active weather pattern will initially be in place across the southeastern U.S. and the Mid-Atlantic/Northeast as a potent upper trough sustains a well developed surface low, and this should exit the East Coast Tuesday morning with widespread rain and interior Northeast snowfall. A quasi-zonal flow pattern develops across much of the nation in the wake of this storm system, with a modified arctic airmass likely reaching Montana and the Dakotas later in the week but nothing too extreme. Meanwhile, an upper level ridge is likely to become established over the West Coast states and this will tend to limit the progression of offshore Pacific storm systems. Elsewhere, some light snow showers are possible from the northern Rockies to the Upper Midwest with weak shortwave passages. ...Guidance/Predictability Assessment... The models and ensembles are in relatively good overall agreement across most of the U.S. on Monday, with the exception of the Southeast states. At the time of fronts/pressures compilation, the 18Z GFS was considerably slower with the track of the surface low across the Mid-Atlantic region for the early week storm system. The 18Z ICON model indicated a solution more in line with the 12Z UKMET/ECMWF/CMC consensus for the Monday through Tuesday night time period, so a non-GFS blend was used for the first half of the forecast period to account for this. The 00Z GFS continues to be slower than the other guidance with this event. However, the GFS was more in line with the ensemble means for the Wednesday through Friday time period, so it was a part of the model blend by this time after the low exited the East Coast. Model spread for the Thursday-Friday time is worse than normal owing to complicated flow interactions and timing differences, and the best agreement is across the West Coast region with the upper ridge axis, and more weighting was applied to the ensemble means during this time. ...Overview and Weather/Hazards Highlights... The low pressure system crossing the Mid-Atlantic Monday night into early Tuesday will likely have enough moisture to fuel an axis of heavy rainfall in the warm sector of the low across the eastern Carolinas. There has been a slight increase in model QPF during the new Day 4 period across eastern NC and central/eastern SC, and therefore the Marginal Risk area inherited from the previous Day 5 was extended north to the NC/VA border. Farther to the north, there is an increasing potential for the spread of wrap-around accumulating snows and windy conditions across the marginally cool Appalachians/interior Northeast Monday night and into Tuesday before the whole system exits the coast as a continued maritime hazard. Behind this system, conditions across much of the continental U.S. should dry out mid next week besides periodic intrusions from the Pacific to bring some modest precipitation to parts of the Northwest and north-central Plains. No excessive rainfall areas are currently necessary for the Day 5 period on Tuesday-Tuesday night. Temperatures are expected to be generally 5 to 15 degrees above mid-February averages across much of the Midwest and the Southeast U.S. on Monday with slightly below average readings over the Desert Southwest to the southern Plains. Going into Wednesday, a cold front dropping south from western Canada is expected to bring a return to below average temperatures across Montana and North Dakota where a modified arctic airmass is expected to move into the region. There is certainly the potential for things to trend colder in future forecasts. Meanwhile, much of the remainder of the U.S. should have temperatures generally within 5 degrees of climatological averages. 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw