Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 PM EST Sat Feb 15 2025 Valid 12Z Tue Feb 18 2025 - 12Z Sat Feb 22 2025 ...Intense Arctic Blast for the Central to Eastern U.S. next week with an impactful South-Central U.S. to East Coast Winter Storm... 19Z Update: The 12Z model guidance suite is generally in above average agreement through about Thursday on the overall synoptic scale pattern, with a multi-deterministic model blend working well as a starting point in the forecast process. However, the 12Z UKMET stands out slower and farther west with the East Coast low compared to the model consensus, so the preference here is for a CMC/GFS/ECMWF/ECENS blend. For QPF, the NBM is likely a little on the low side for the storm system tracking from the Deep South to the East Coast through Thursday, so this was blended with about half NBM and half of the CMC/GFS/ECMWF. This yielded some heavier QPF across inland portions of the Mid-Atlantic and the Northeast U.S. compared to the prior forecast, and therefore probabilities in the winter weather outlook have increased some for the Day 5 and 6 periods. There is also a good chance of impactful freezing rain across portions of central North Carolina that will continue to be monitored. The previous forecast discussion is appended below for reference. /Hamrick ------------------ ...General Overview and Guidance/Predictability Assessment... An elongated upper trough stretched from south-central Canada to Quebec will pivot south across the north-central U.S. for the beginning of the week as shortwave troughs upstream dig into the West. At the surface, a massive arctic high will settle southward across the Plains and reach the Gulf Coast by Wednesday to envelop much of the central to eastern U.S. next week. This cold front will then form a low along it, which should then track to near the Mid- Atlantic Coast by Thursday and support a winter coastal storm for the end of the week off the Northeast. The 00/06 UTC guidance suite still features above average model agreement thorough the entire forecast period, with modest amplitude and timing differences with individual short waves. A broad model and ensemble mean composite seemed to provide a quite reasonable forecast basis generally in line with the National Blend of Models and WPC product continuity. Latest 12 UTC model guidance still seems in line. ...Weather/Hazards Highlights... Elongated upper troughing will linger across the northern tier of the nation as an impressive Arctic airmass takes hold over the central and eastern U.S. next week. Entrenched cold air will maintain lake effect snows and also offer a widespread threat of numerous record cold temperatures with focus over especially the north-central U.S. in this pattern. Temperatures may be 25 to 45 degrees below average for Tuesday and Wednesday for portions of the central and northern Plains. Upstream, several organized shortwaves/frontal systems will dig southeastward through the West. These systems will bring rounds of low elevation rain and mountain snow to the Pacific Northwest, Northern California, and the Northern/Central Intermountain West/Rockies. Fortified upslope fetch with the aforementioned Arctic frontal surge trough the central U.S. will favor snow and wind into the High Plains/Rockies, earnestly spreading across the Central Plains and Big South Tuesday. As for heavy rainfall potential, the WPC Excessive Rainfall Outlook (ERO) for Day 4/Tuesday and Day 5/Wednesday maintain the Marginal Risk areas with little in the way of any changes, extending from the central Gulf Coast through the Carolinas to show the potential for 1-3 inches of rainfall during this time period as an organizing frontal wave track enhances moisture inflow into the region. Downstream, an impactful winter coastal storm offers a threat for heavy snow from the Mid-Atlantic through New England Wednesday and Thursday as depicted in the WPC Winter Weather Outlook (WWO). With abundant sub-freezing temperatures in place ahead of this storm system, widespread snow is expected, with a corridor of mixed precipitation farther to the south. Guidance however continues to adjust the inland extent of the bulk of precipitation. Schichtel/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 (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