Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 543 AM EDT Fri Mar 30 2018 Final Day 1, Day 2 and Day 3 QPF Discussion Valid Mar 30/1200 UTC thru Apr 02/1200 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 Eastern seaboard into northern to central Florida The elongated mid to upper level trof initially stretching through the mid to lower MS Valley will be pressing steadily eastward day 1---pushing the associated surface frontal boundary eastward off the eastern seaboard and southward through northern to central FL. Given the overall progressive nature of this boundary---the model consensus is for generally light to moderate precip totals despite the above average pw values expected ahead of the front. The best chances for any heavy precip totals appears to be over north Florida where convection may remain defined in a region of favorable right entrance region jet dynamics early in the day 1 time period. Northern Plains into the Upper MS Valley and upper Great Lakes A well defined surface wave expected to move east southeastward from the northern high plains into the Upper MS Valley day 1 along the strong arctic frontal boundary draped across these regions. This low will support strong isentropic lift ahead of it and the potential for a stripe of heavy snows from central to northern ND into north-central MN---northern WI and the western U.P. of MI. There is fairly good model qpf agreement with the above described axis---leading to a fairly high confidence forecast. See the latest QPFHSD for additional winter weather information across this area. Northern Rockies In the wake of the area of low pressure moving eastward from the Northern Plains into the Upper MS Valley---the arctic front will push southward Friday and become banked up against the Northern Rockies. Post frontal upslope flow will support moderate to locally heavy snows across portions of the Northern Rockies from north-central to northwest MT into south central to northwest MT. Days 2 & 3 ...Pacific Northwest/Northern and Central Rockies/Central Plains... One piece of short wave energy tracking across the northern Rockies early on Day 2 will provide synoptic scale lift over an arctic front stretching from western MT into eastern CO. The approach of a second upper level jet core and mid level circulation center will help start a second round of precipitation over the Pacific Northwest and the Northern Rockies on Day 3. The NAM and UKMET looked to be outliers in how quickly they amplify the flow out in this part of the country on Day 3. Considering this is not an ideal position for that magnitude of amplification, we will favor the GFS/ECMWF There was generally good model agreement with the overall synoptic setup, so the WPC QPF was based on a blend of the 12z ECMWF/GFS. ...Upper Great Lakes/OH Valley/Northeast... Short wave energy tracking across the northern tier of states and the Upper Great Lakes at the beginning of Day 2 will push a surface low and an axis of heavier QPF north of the surface low. Precipitation in this part of the system will gradually taper off over the Great Lakes early on day 2 as the surface low heads north of the international border. Precipitation should then begin to develop over parts of the Northeast U.S. as the surface low approaches from the west. To the south of low pressure center, a frontal boundary will provide the focus for a separate area of precipitation. WPC tended to place the heaviest QPF across portions of the OH Valley where the axis of 125 to 140 kt upper level jet sweeps over the frontal boundary and provides additional upper level support. ...FL... Weak short wave riding over an inverted surface trough provides synoptic scale lift for convection on Days 2 and 3. There was good model agreement with the placement of the inverted trough and maximum QPF, so the WPC QPF was based on a multi model blend. Oravec/Bann Graphics available at www.wpc.ncep.noaa.gov/qpf/qpf2.shtml