Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 PM EST Fri Feb 14 2025 Valid 12Z Mon Feb 17 2025 - 12Z Fri Feb 21 2025 ...Intense Arctic Blast for the North-Central U.S. with increasing potential for East Coast winter storm late next week... ...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. At the surface, a massive arctic high will settle southward across the Plains and reach the Gulf Coast by Wednesday. 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 storm for the end of the week. Widespread arctic cold envelops much of the central to eastern U.S. to close out the work week. The 12Z model guidance suite features above average model agreement thorough the entire forecast period, with mainly modest amplitude and timing differences with individual short waves. A multi- deterministic model blend sufficed as a starting point through Wednesday, with ensemble means increased to only 30% by Friday. ...Weather/Hazards Highlights... A closed upper low/trough and deep surface low will work into the Canadian Maritimes by early next week. Trailing upper energies and very cold lower atmospheric flow will combine with lingering wrap- back moisture to fuel Great Lake effect to northern New England snows. The tight pressure gradient may result in a period of strong, gusty winds. Behind this system, elongated upper troughing will linger across the northern tier and 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 record cold temperatures with focus over especially the central U.S. in this pattern. Temperatures are expected to be on the order of 25 to 45 degrees below average through midweek from Montana to Kansas! 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 through the period. A main focus for precipitation will spread to the Central/Southern Plains early next week as a low pressure system moves south across the region towards the Gulf Coast. The existing WPC Day 5 Marginal Risk area on Tuesday has been expanded some to the east to include the western Florida Panhandle, given a larger heavy QPF signal in the 12Z model guidance, with the potential for 1-3 inches of rainfall during this time period. The prospects for an impactful winter storm have increased over the past 12-24 hours, with the new WPC winter weather outlook now up to 50-60% for Thursday across portions of the Mid-Atlantic, and this also holds true for Friday into southern New England. Both the NBM and the majority of the deterministic guidance has trended higher with QPF across this region as the surface low tracks farther north compared to earlier forecasts. With abundant sub-freezing temperatures in place ahead of this storm system, widespread snow is becoming more likely, with a corridor of mixed precipitation farther to the south. 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 (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