Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EST Tue Dec 15 2020 Valid 00Z Wed Dec 16 2020 - 00Z Fri Dec 18 2020 ...Major winter storm poised to bring heavy snow and areas of freezing rain to the Mid-Atlantic and Northeast beginning on Wednesday... ...Snow over the central Plains expected to taper off tonight... ...More unsettled weather will impact the Pacific Northwest over the next couple of days... An area of low pressure currently developing under an energetic upper trough over Texas will take center stage as it is forecast to track across the East Coast and evolve into a significant nor'easter. The developing system is expected to produce moderate snowfall across portions of the central Plains into this evening. Slick road conditions and reduced visibility at times could make travel difficult across the region where Winter Storm Warnings and Winter Weather advisories are in effect into this evening. As this low pressure system moves generally eastward, moisture from the Gulf of Mexico and eventually from the Atlantic Ocean will interact with the upper trough and result in a swath of rain to quick expand across the Deep South, the Southeast and into the Mid-Atlantic on Wednesday. Meanwhile, a strong area of high pressure located over southern Quebec, Canada will help filter colder air down along of the Appalachian Mountains into the Mid-Atlantic. This will result in an expanding area of snow to overspread the Ohio Valley and into the central Appalachians on Wednesday. In between the snow in the north and the rain in the south, a wintry mix is forecast to stretch across the southern Appalachians and the interior Mid-Atlantic roughly along the I-95 corridor. Freezing rain is the main concern across this region, as upwards of a quarter inch of ice accretion is possible. This could lead to scattered tree damage and power outages. As the precipitation shield advances north throughout the day on Wednesday, heavy snow will overtake areas northwest of I-95 in the Mid-Atlantic. This means major cities, such as Washington D.C. and Philadelphia, will likely see a wintry mix and potentially plain rain for areas just to the southeast. Further northeast, heavy snow will also encroach upon northern New Jersey southern New York State by Wednesday evening, this includes the greater New York City metro region with strengthening winds from the northeast. By Wednesday night, snow will also impact southern New England as the storm will likely near peak intensity while moving off the coast south of Long Island. The heaviest snowfall amounts are currently forecast across south-central Pennsylvania, where as much as two feet of snow is possible. This would likely lead to very dangerous travel conditions and isolated power outages. Many locations from eastern West Virginia to southeast Massachusetts to forecast to see a foot of snowfall accumulation. Snowfall amounts are expected to drop off dramatically to the south and east as sleet and rain are expected to mix in. There is still uncertainty regarding exact alignment of the rain/snow line. A very slight adjustment to the north or south could mean for vastly different outcomes in local areas from central Maryland to Long Island. Be sure to check your local forecast for the latest updates and more specific details. Meanwhile, the Pacific Northwest will see their own unsettled weather through the next couple of days as two separate systems swing across the region. The current wave of moisture associated with a frontal system will quickly penetrate well inland into the northern and central Rockies by Wednesday morning before a stronger storm brings the next wave of coastal rain and mountain snow by Wednesday evening. Rainfall amounts of 1 to 2 inches are likely during this time frame along the immediate coastline. Across the Cascade Mountains and higher elevations of Idaho and northwest Montana, 1 to 2 feet of snow could fall. Kong/Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php