Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 153 PM EDT Sat Mar 17 2018 Prelim Day 1 QPF Discussion Valid Mar 18/0000 UTC thru Mar 19/0000 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 Southern Appalachians into the southern Mid-Atlantic The relatively small closed low initially over the upper MS valley region expected to continue to weaken day 1 as it presses east southeastward from the upper OH valley into the central Appalachians and southern Mid Atlantic tonight into early Sunday. The model consensus is for precipitation ahead of this closed low to refocus across the southern Appalachians this evening and move fairly quickly east southeast across the southern Mid Atlantic tonight. The quick movement likely to be a detriment to any widespread heavy totals with model consensus for areal average moderate to possibly isolated heavy amounts across these areas. Southern Plains---lower MS Valley---central Gulf coast Height falls in the southern stream flow expected to push east northeastward out of northern Mexico into the southern Plains this evening---eastward toward the lower MS valley by early Sunday. There is a fairly consistent signal in the hi res guidance for convection to develop late this afternoon over portions of north central TX and move fairly quickly downstream. Despite the expected fast movement---intense rainfall rates over a short period will support locally heavy to isolated excessive rainfall amounts---especially in the first 6 to 9 hours of the upcoming day 1 time period---with rainfall intensities and amounts expected to decrease after this as the initial activity moves toward the lower MS valley/central Gulf coast region. The marginal risk area on the latest excessive rainfall potential outlook over portions of northeast TX was not changed with runoff issues possible in the most intense heavy rain cores---especially if they occur over any urban areas in the vicinity of Dallas to Waco. Late Sunday morning into Sunday afternoon---another round of precip expected to break out over portions of the Southern Plains in an increasingly diffluent pattern ahead of additional southern stream height falls moving northeastward from northern Mexico and stronger upstream height pushing east from the southwest into the southern high plains. This next area of precip looks like it will form farther to the north than the lead area---from north TX into eastern OK Sunday afternoon---pushing into the lower AR river valley toward the end of the day 1 period---with model consensus for .25-50" amounts. Western U.S. The broad mean upper trof initially over the large portions of the western U.S. will become increasingly separated into distinct circulations day 1. The northern portion of this trof will be comprised of three fairly slowly moving circulations. One moving very slowly southward off the Pacific Northwest coast---while one over the northern Rockies and another over southern Alberta/southern Sask combine near the MT/Alberta/Sask border region. Meanwhile---stronger and faster moving height falls will eject out of the base of the trof tonight---pushing from southern California---through the Southwest and emerging into the southern high plains Sunday afternoon. Overall---there is good model agreement on what will be a large region of precip associated with each circulation center. Model consensus is for areal average moderate totals---with locally heavy amounts possible in the favored terrain regions from the Mogollon Rim of AZ---the central Rockies of CO---through the Wasatch of UT and into the northern Rockies of north central ID into western MT. Oravec