Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 344 PM EST Sun Dec 24 2017 Valid 00Z Mon Dec 25 2017 - 00Z Wed Dec 27 2017 ...Heavy snow possible over parts of the Northeast, the Great Lakes, and Central Rockies... ...Freezing rain possible over parts of the Pacific Northwest... ...Snow possible for part of the Cascades and the Northern Rockies... ...A slight risk of freezing rain over parts of Southern New England... Upper-level energy over the Ohio Valley will move northeastward into Southeastern Canada overnight Christmas, Monday night, that will combine with low pressure off the Southern Mid-Atlantic Coast that is moving northeastward to off of Cape Cod by Christmas morning, Monday. The system will produce snow over the Great Lakes/Ohio Valley that will move northeastward into the Northeast while merging with an area of rain moving northward along the Mid-Atlantic Coast into Southern New England by Monday morning, Christmas. The area will changed over to mostly snow by Monday afternoon over the Northeast that will move into Southeastern Canada by early Tuesday morning. In addition, along the rain/snow line pockets of rain/freezing rain will develop over parts of Southern New England overnight Christmas Eve, Sunday evening ending by Monday morning. In the wake of the system, upper-level energy will move over the Great Lakes into the Northeast through Tuesday. The energy will aid in producing lake effect snow downwind from the Great Lakes from Christmas, Monday, into Tuesday. Meanwhile, weakening upper-level energy will move onshore over the Pacific Northwest and continue eastward to parts of the Middle Mississippi Valley by Tuesday. An area of cold high pressure over West-Central Canada will move southeastward to the Northern High Plains by Tuesday. The system will produce coastal rain and higher elevation snow over parts of the Pacific Northwest with snow streaming into part of the Northern Intermountain Region/Great Basin overnight Christmas Eve, Sunday night, continuing over the Northwest through late Christmas evening, Monday evening. Additionally, pockets of rain/freezing rain will develop over parts of the Pacific Northwest ending overnight Monday a long with the rest of the precipitation. The snow will expand into parts of the Northern/Central Rockies by Christmas morning, Monday, that will continue to expand eastward into the Central/Northern High Plains Monday evening into Tuesday. Elsewhere, on Christmas, Monday, moisture from the Western Gulf of Mexico will start to flow northward over the Southern Plains into parts of the Lower Mississippi Valley by Tuesday. The moisture will aid in developing rain over parts of the Western Gulf Coast by Tuesday morning. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php