Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 342 AM EDT Sun Mar 25 2018 Prelim Day 1 QPF Discussion Valid Mar 25/1200 UTC thru Mar 26/1200 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 ...Western CONUS... Shortwave energy over the eastern Pacific, pivoting on the backside of the longwave western U.S. trough, will allow the trough to further amplify with more pronounced height falls into southern CA and the Southwest by the end of the period (12Z Mon). As this occurs, broad-scale, deep-layer ridging and northerly flow behind the trough will expand across the eastern Pacific, thereby preventing any subtropical moisture infusion into the system as it crosses into the Great Basin. Therefore despite the broad upper level forcing and expansive warm conveyor belt (wcb) ahead of the trough, the lackluster moisture profiles (PW anomalies actually negative over most areas per the SREF and GEFS) will restrict the potential for anything more than light-moderate precipitation across the western U.S. this period. Late in the period (toward 12Z Mon), strengthening low-mid layer westerly flow will boost PWs to near 0.75" toward the PAC NW coast, which along with the favorable orographic component (moist onshore flow largely orthogonal to the terrain), will generate localized totals between 0.50-0.75" overnight across the WA Coastal ranges (Olympics) and northern Cascades. Elsewhere, per a multi-model blend composed of the ECMWF and high-res means including the HREF and NBM, highest 24 hour areal-average totals of 0.50-1.00" are expected over the eastern slopes of the WY Rockies (aided by the easterly upslope flow). ...Central CONUS... Broadening warm advection behind the departing large surface high and the lee cyclone migrating slowly east of the southern-central Rockies will foster a fairly elongated s-n ribbon of moist isentropic ascent and generally light pcpn across the central U.S. during day 1. WPC continued to focus on two main areas where enhanced large-scale forcing (stronger lift/deeper moisture) will aid in higher QPF totals. First across eastern OK-KS and into western MO where the models continue to depict more pronounced 850 mb moisture transport overnight via 40+ kts of southwesterly inflow. Meanwhile, PWs climb to 1.25+ inches and elevated CAPES approach ~500 j/kg by 12Z Mon over this region ahead of the amplifying upper trough (increased upper difluence) and surface warm front. Model QPF spread during this period remains considerable, particularly with the location of heaviest totals. GFS and ARW are farthest south with highest areal-average QPF Sunday night, while the rest of the guidance were north of the surface warm front/warm sector where the combination of elevated instability and deep-layer forcing would be more conducive for widespread coverage. Opting for a non-GFS mutli-model blend, QPF amounts were generally capped under 1" through 12Z Monday, with certainly more on the way thereafter at the large-scale pattern continues to amplify and additional shortwave energy is fed into the southern Plains-mid MS Valley. Hurley