Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Fri Feb 09 2024 Valid 12Z Mon Feb 12 2024 - 12Z Fri Feb 16 2024 ...Deep coastal storm genesis threat early next week may produce impactful wrap-back snows and gusty winds over the Northeastern U.S.... ...General Overview... An active weather pattern will initially be in place across the southeastern U.S. and the Mid-Atlantic/Northeast and maritime concerns as a potent upper trough sustains a well developed inland surface low with widespread precipitation. The low should exit the East Coast and re-develop as a deepening Atlantic coastal storm into Tuesday. This offers a threat for impactful wrap-back snows and gusty winds from the Appalachians/northern Mid-Atlantic through south-central areas of the Northeast, especially inland from coastal areas given likely storm track, but considering a relative lack of cold air over and set to feed into the area with system development and passage. Elsewhere, a quasi-zonal mean flow pattern develops across much of the nation in the wake of this storm system, with a modified arctic airmass likely digging into the north-central U.S. later next week, but nothing too extreme or wintry at this point. Meanwhile, an upper level mean ridge is likely to become established over the West Coast states and this will tend to limit the progression of offshore Pacific storm systems, but near coastal areas from Pacific Northwest to northern California may gradually see an uptick in precipitation into later next week that may be leading into a wetter Week 2 forecast as per CPC. In this pattern, some light snow showers are possible downstream from the northern Rockies to the Upper Midwest/Great Lakes with weak shortwave passages. Later period, there is a growing guidance signal for an emerging rain areas over the southern Rockies/Plains in about a week contingent of the extent of return flow in southeasterly lower level flow up from the Gulf of Mexico in advance of uncertain approach of southern stream system energies. ...Guidance/Predictability Assessment... Model and ensemble solutions seem reasonably clustered Monday and a composite along with input from the National Blend of Models (NBM) and WPC continuity seems to mitigate lingering small scale variance. The broader story still seems decently showed by guidance into later next week, but local focus/forecast spread increases by Tuesday both with development of the deepening coastal storm up/off the East Coast and with subsequent and uncertain shortwaves with expected development of flatter upstream flow across much of the rest of the lower 48 through later next week, albeit in a much less active weather pattern. The WPC product suite was mainly based on GEFS/ECMWF ensemble mean guidance and the NBM at these longer time frames. Latest 12 UTC guidance remains generally in line with earlier guidance, but has trended a tad less progressive/deeper with coastal storm development. This needs to be monitored, but seems consistent with standard bias with a separated southern stream flow system, pending uncertain phasing. ...Overview and Weather/Hazards Highlights... Upper support and deepened moisture with the main low frontal system working across the East Monday may fuel an axis of heavy rainfall in the warm sector of the low and with the trailing cold front over the Southeast/Carolinas. A WPC Excessive Rainfall Outlook Marginal Risk area was maintained. 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/Northern Mid-Atlantic through south-central areas of the Northeast Monday night and Tuesday into early Wednesday as the whole system exits the coast as a continued maritime hazard. Behind this system, conditions across much of the continental U.S. should overall dry out mid week besides periodic intrusions from the Pacific into the West Coast/Northwest. No excessive rainfall areas are currently necessary for the Day 5 period on Tuesday-Tuesday night. There is a growing guidance signal for an emerging rain areas over the southern Rockies/Plains in about a week contingent of the extent of return flow in southeasterly lower level flow up from the Gulf of Mexico in advance of uncertain approach of southern stream system energies. 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, high pressure and leading edge cold front digging south from western Canada is expected to bring a return to below average temperatures down through the north-central U.S. where a modified arctic airmass is expected to move into the region, but there is certainly 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/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, 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