Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 224 PM EST Thu Dec 19 2019 Valid 00Z Fri Dec 20 2019 - 00Z Sun Dec 22 2019 ...Heavy rain and mountain snow for the Pacific Northwest and rain returns to the Gulf Coast region in time for the weekend... Heavy rain and high elevation snow will be making weather headlines from northern California to western Washington as an atmospheric river advects deep Pacific moisture inland across the region. This pattern will be supported by an active jet stream pivoting around a large and slow moving low pressure system over the northeast Pacific, spawning multiple waves of low pressure along a slow moving cold front. Extended periods of moderate to heavy rain could result in rainfall amounts on the order of 5 to 10 inches over portions of western Washington and Oregon through Saturday morning. Over the higher elevations of the Cascades and Olympic Mountains, heavy snow is expected with accumulations potentially exceeding three feet for the highest mountains! An upper level low crossing the southern Plains on Friday is forecast to reach the Gulf Coast region by Saturday night. A strong shortwave impulse associated with this will result in the development of a surface low over the northern Gulf of Mexico by late Saturday. Increasing cloudiness followed by widespread rain is forecast from the central Gulf Coast eastward to the Florida Panhandle as copious moisture surges northward. Further development of this low is expected beyond this forecast period. In terms of temperatures, much of New England will remain colder than average through Friday with conditions gradually moderating through the weekend. In contrast, warmer than normal temperatures are expected across the northern and central Plains, and this should expand eastward to the Great Lakes, Ohio Valley and the Southeast by the weekend. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php