Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 500 AM EDT Sun Jun 03 2018 Prelim Day 1, Day 2 and Day 3 QPF Discussion Valid Jun 03/1200 UTC thru Jun 06/1200 UTC Reference AWIPS Graphics under...Precip Accum - 24hr ...Eastern U.S.... The stubborn, compact mid-upper level trough across the mid Atlantic region will finally push offshore later Sun and Sunday night. The moist cyclonic flow along with the continued anomalous PWs (1.75-2.00") will maintain a threat for excessive rainfall, especially early in the period with the better forcing and greater instability south of the surface frontal boundary. By mid-late afternoon, the surface front will slide south to near the VA/NC border, as will the highest 1-3 hour rainfall rates per the HREF probabilities. WPC will maintain a small slight risk area across portions of central and south-central VA into eastern VA and southern MD based on the higher potential for heavy additional rainfall amounts (per the multi CAM consensus), along with the low FFG values (1 hour FFGs of 1" or less). WPC QPF comprised a blend of a 00Z multi-model consensus (including HREF mean and NBM) along with continuity (previous forecast). ...Great Lakes/Ohio Valley into the Northeast... A negatively-tilted upper trough will continue to push showers and embedded thunderstorms eastward across the Great Lakes and Ohio Valley today, with the activity then spreading into the Northeast overnight ahead of the occluded surface front. The progressive nature of the system along with limited/negligible instability should limit the potential for heavy amounts, however the ridge of higher (anomalous) PWs ahead of the upper trough and surface occlusion remains rather impressive, and as such even without much if any CAPE well in this region well north of the warm sector, moderate totals averaging 0.25-0.50+ inch are likely per the multi-model consensus. ...Southern Rockies/High Plains... Guidance continues to show a good signal for developing precipitation, with locally heavy amounts possible across much of NM into southwest and south-central CO (especially during the afternoon and evening). Increasing southeasterly low-level inflow ahead of a well defined, compact mid-upper level shortwave moving across the Four Corners region is expected to support developing showers and storms during the afternoon and evening hours, with a multi-CAM signal for moderate to locally heavy amounts across the southern Colorado and the New Mexico ranges. Day 2 ...Northeast... A closing low in the negatively tilted mid to upper level trough deepens Monday over the Ontario/Quebec border. Model differences persist with timing and strength of shortwave impulses rounding the low. The most notable effect of these shortwave differences is position of the surface low to the coast and associated QPF max. The 00Z NAM is the closest to the coast, while the 00Z GFS/ECMWF are more offshore with the max (with the ECMWF spreading moderate precip farthest inland). A blend of the 00Z GFS/ECMWF/NAM with preference to the GFS was the basis for QPF. ...Southern Plains... A shortwave trough rounding the broad subtropical ridge centered over northwest Mexico will push across KS Monday. Organized convection is possible ahead of this through as height falls occur over Gulf moisture (1.5 inch PW is 1.5 standard deviations above normal). One limiting factor is a preference to forward propagation and progression. A Marginal Risk of excessive rainfall was maintained along the OK/TX border. QPF was mainly a blend of the 00Z GFS and NAM. ...Gulf coast of TX to FL... Scattered convection likely along a cold front pressing southward off the central Gulf coast---into North Florida and east Texas. Light flow aloft will make for scattered convection...often heavy with 1.75 inch PW. ...Northern Plains... A shortwave trough over Alberta Monday night will tap Gulf-sourced moisture over MT/ND with locally heavy rain particularly near the border. QPF based mainly on the 00Z GFS/NAM. Day 3 ...The East... The deepened low over Ontario/Quebec ejects east to New England Tuesday. Strong southeast low level flow will continue ahead of the surface low moving from off the southeast New England coast to the south coast of Nova Scotia. Timing and amplification differences issues continue. WPC QPF is based on a blend of the 00Z GFS/NAM/ECMWF. Moderate to heavy precip potential is greatest across central to eastern Maine in the region of strongest onshore flow. ...Lower Great Lakes into the Northern Mid-Atlantic... Additional height falls rotating southeast into the mean trough position across southeast Canada will help push a cold front south to the Mid-Atlantic. The 00Z GFS was a southern outlier with the axis of precip associated with this front. WPC favored a blend of the 00Z GFS/NAM/ECMWF. ..Southern Plains to Lower MS Valley... Convection may fire in the northwesterly mid to upper level flow parallel to the surface front over the Southern Plains or the lower MS Valley Tuesday. The 00Z ECMWF came in much wetter and farther east than any other guidance while the 00Z GFS and NAM were similar with the potential moderate to heavy qpf axis from western to central OK into northeast TX and western LA. WPC QPF favored the western solutions with a note to future shifts to monitor this closely given PW approaching 2 inches. Hurley/Jackson Graphics available at www.wpc.ncep.noaa.gov/qpf/qpf2.shtml