Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 309 AM EST Thu Nov 15 2018 Valid 12Z Thu Nov 15 2018 - 12Z Sat Nov 17 2018 ...Ongoing winter storm will impact the Ohio Valley, Appalachians, and Mid-Atlantic today and the Northeast tonight... ...Another area of snow will overspread the Northern Rockies and Northern Plains on Thursday night into Friday... A significant winter storm is developing across parts of the central and eastern U.S. A strong upper-level low will move through the Ohio Valley today, causing the area of snow and freezing rain there to persist and move northeastward. Parts of the Ohio Valley are forecast to receive a few additional inches of snow and a glaze of freezing rain. Additionally, a surface low pressure system will strengthen over the Southeast coast and move northward along the Eastern Seaboard on Thursday and Friday. On the backside of this surface low to the north and west, more wintry weather is expected today. Freezing rain will be the main threat across the Southern and Central Appalachians as warm and moist air overruns the cold air in place at the ground. Ice accumulations could be over a quarter of an inch there. Tonight, the upper-level and surface lows will work more in conjunction with each other to create heavy snowfall in the northern Mid-Atlantic and into the interior Northeast. Snow of over a foot is possible in portions of interior Pennsylvania and New York. Widespread Winter Storm and Ice Storm Warnings as well as Winter Weather Advisories are in effect, with Winter Storm Watches in place in the Northeast. The heaviest of this wintry precipitation will remain west of the major cities of D.C. to New York City, but a wintry mix is possible at the onset of this event on Thursday and could cause travel issues before transitioning to rain. Precipitation due to this low is expected to stay all rain in the Southeast and from the Piedmont eastward in the Carolinas, as well as along the coastal Mid-Atlantic. Locally heavy rainfall is possible today in those areas, and a Marginal Risk of excessive rainfall/flash flooding is in place. A series of cold fronts dropping southward from Canada will lead to snow across the northern tier of the country as well. Light snow is possible in the Upper Midwest today as a surface low pressure system moves through. By Thursday night, a front will approach the Northern Rockies into Northern Plains, and snow will overspread those areas. Snow is forecast to move southward with the cold front into the Central Rockies and Central Plains and into the Middle Mississippi Valley by Friday evening. Altogether, the Northern and Central Rockies could see 6 to 10 inches of snow in higher elevations, and a swath of 2 to 4 inches of snow is expected from the Northern Plains into parts of the Upper and Middle Mississippi Valley by Saturday morning. One more day of fire weather concerns will occur Thursday in Southern California. The Storm Prediction Center has an Elevated Risk delineated in their Fire Weather Outlook, with some brief high winds, low relative humidities, and ongoing drought. Conditions will finally become less favorable for fires in California by Friday. Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php