Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 252 PM EDT Tue May 15 2018 Prelim Day 1 QPF Discussion Valid May 16/0000 UTC thru May 17/0000 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1... ...Upper Ohio Valley---Central Appalachians into the Mid-Atlantic... Much above average pw values 1.5 to 2.5+ standard deviations above the mean expected to persist day 1 along the west to east oriented stationary front forecast to lie from the Ohio Valley---through the Central Appalachians and into the Mid-Atlantic. Persistent low level southerly flow into this front and enhanced large scale accent from shortwave energy moving parallel to this boundary will support a good chance of widespread moderate to heavy precip totals across these areas. Lower confidence with some of the shorter term qpf details---but overall higher confidence on the widespread moderate to heavy totals given the overall favorable pattern. No changes made to the previous marginal to slight risk area aligned parallel to the front across these areas. ...Southern Mid-Atlantic---Southern Appalachians---Southeast into Florida... To the south of the above mentioned west to east front---pw values will also remain much above average through the southern Mid-Atlantic---Southern Appalachians--Southeast and across Florida. The slow moving closed low over the northeast Gulf of Mexico off the northwest Florida coast will continue to provide a broadly diffluent pattern to its northeast in this anomalous pw axis across Florida---the Southeast---Southern Appalachians and into the southern Mid-Atlantic. While there are the typical smaller scale qpf differences among the models---overall there is very good agreement on widespread moderate to heavy totals. The Southern Appalachians in the vicinity of northeast Georgia---the Upstate of South Carolina and into western North Carolina likely will have the greatest precipitation potential ahead of this upper low as uvvs will be enhanced by southerly upslope flow. ...Southern Plains toward the Lower MS Valley... The western portion of the stationary front across the Ohio Valley will remain across the Southern Plains into the Lower MS Valley. Shortwave energy rounding the top of the shortwave ridge over the Southern Plains tonight will push southeast toward the Lower MS Valley on Wednesday. Organized convection is possible along and north of this front---with model consensus of the qpf axis from the TX/OK panhandle region---eastward across much of OK and into western Arkansas. Moderate to heavy precip totals possible in this qpf axis---with the expected progressive nature of the convection being a limiting factor on very heavy totals---although no changes planned for the marginal flash flood risk area across this area. ...Northern Sierra---Oregon---Northern Sierra into the Northern Rockies... The closed low off the central California coast will be kicking northward the lead upper low over the Great Basin northward into the Northern Rockies day 1 as it presses inland into northern California Wednesday. A broad area of upper difluence ahead of each of these features will support a widespread area of scattered precipitation from the Northern Sierra---across much of Oregon---the Great Basin and into the Northern Rockies. Model consensus for the greatest totals is from the northern Sierra---northern California into the Cascades of Oregon to the north of the closed low moving into northern California Wednesday. No changes made to the marginal risk area to the north of this closed low where pw values will remain much above average. Oravec