Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 504 PM EDT Sun Apr 08 2018 Prelim Day 1, Day 2 and Day 3 QPF Discussion Valid Apr 09/0000 UTC thru Apr 12/0000 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 ...Florida and eastern Carolinas and Georgia... A frontal boundary stalls across central FL, before moving back north as a warm front tonight into Monday. Moisture and instability focused on the front feed convection that produces locally heavy rainfall, both this afternoon in south central FL and Monday afternoon in northern FL. There was enough model agreement to use a multi model blend as a basis for the WPC QPF. This combination placed an axis of 0.50 to 1.00 inches of qpf from Lake Okeechobee to Vero Beach and West Palm Beach this afternoon and again over northeast FL Monday afternoon. Locally higher amounts are possible if training occurs along the the front. Three hour flash flood guidance values are fairly high, so while locally heavy rainfall is possible, flash flooding is not expected. On Monday a ripple of low pressure develop along the front and moves off the southeast coast. The 12z and a few of the high res ARW/ARW2 runs show higher amounts further west onshore in the eastern Carolinas, although the gfs/ecmwf/Canadian regional GEM do not have higher amounts onshore. The latter cluster was given a little more weight given they agree best with the predominant cyclone track. ...Pacific Northwest/Rockies... The upper level wave across the northern Rockies this evening moves quickly southeast across Wyoming and CO with an upper jet streak progressing across ID/UT and CO, providing favorable upper divergence maxima crossing the ranges of western MT/western WY and northern CO. Precip streaks out on to the Plains of CO in tandem with the upper divergence maxima late tonight/early Monday. Rainfall rates taper in the Pacific northwest as a mid-upper level Pacific ridge develops and drifts east towards the region. The ridge has the net effect of reducing the strength of onshore flow and even backing of the south towards the south occurs Mon in WA/OR. With the weakening lift and convergence, coverage should steadily diminish late tonight into Monday in the northwest and northern Rockies. There was generally good model agreement,so the WPC QPF used continuity with a multi-model/HREF Mean blend. ...Mid MS Valley/OH Valley/central Appalachians... Recent radar/surface observations show widespread precip across the mid MS Valley to central Plains as coupled low level convergence and upper divergence combined with low level moisture fluxes to produce the precip. The models still forecast to low-mid level trough and sfc low to weaken, so the strength of low level convergence weakens and precip coverage amounts start to wane. The moisture in the vicinity of the low level warm front moves out of KY into the WV/VA Appalachians tonight into early Monday. Enhancement are expected in windward terrain in these areas. See the winter weather graphics and discussion for potential snow amounts. Days 2/3 ...Pacific Northwest to the northern Rockies... A fetch of Pacific moisture will stream onshore ahead of an approaching low pressure system, which will allow precipitation to overspread the Pacific northwest and expand eastward into the Northern Rockies. There will be a brief lull on Monday before amounts steadily increase west of, and along the coast. 0.75 to 1 inch PW will cause some locally heavy precipitation in preferred western slopes of the Coast Ranges and Cascades. Model consensus keeps the axis of heaviest qpf just offshore the Washington/Oregon coast...which largely comprised of continuity of the previous forecast with trends toward the 12Z GFS/ECWMF ...Central Plains to the Mid Atlantic... Several pieces of weak shortwave forcing will shift east-southeast from the Great Plains and Great Lakes Monday resulting in patches of light precipitation. Remnants of a shortwave trough will shift east from the upper Midwest to PA/NY Monday with QPF generally under a tenth inch expected. ...Far Southeast/Florida... Locally heavy rain is expected to develop along a slow moving cold front across the Southeast. Strong jet support along with 1.75 inch PW will support higher rainfall rates over this region, although model differences on timing and placement are still affecting whether the higher qpf falls on/offshore. An excessive rainfall risk may be needed eventually for north-central Florida, but was not introduced at this time. A general model blend minus the 12Z NAM was preferred. ...South TX... A southward shifting frontal boundary will become convectively active in PW 2 to 2.5 standard deviations above normal Monday night and Tuesday morning across northeast Mexico near the border with south Texas before shifting well south by evening. The latest run of guidance keeps the bulk of the precipitation well south of Texas. Chenard/Campbell Graphics available at www.wpc.ncep.noaa.gov/qpf/qpf2.shtml