Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 405 PM EST Fri Mar 02 2018 Final Day 1, Day 2 and Day 3 QPF Discussion Valid Mar 03/0000 UTC thru Mar 06/0000 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 ...Western U.S... A closed mid/upper level low will remain nearly stationary over the pacific northwest through Saturday. Waves rotating around the southern periphery of this low, combined with easterly onshore upslope flow and persistent right entrance region jet dynamics...will all support a continuation of rain and snow over much of the west coast into the central Great Basin. Overall not the strongest moisture transport or PWATs...so precipitation rates will not be all that impressive. With that said, still looking at a long duration of upslope flow and favored synoptics, especially over the Sierras. Thus QPF through the day 1 period should end up in the 1-2" range over much of the Sierras. Lighter amounts can be expected elsewhere...with localized 1" amounts in the southern California Transverse Ranges where orographic factors will also be maximized. Models were in pretty good agreement, with WPC thus utilizing a blend of the latest HREF and global model means, with greater weighting to the higher res guidance to capture orographic effects. ...Northeast... Precipitation will be winding down after 0z across the northeast as the area of low pressure moves off to the east. Additional QPF after 0z should generally be within the 0.5"-1" range over southeast MA. Generally followed close to a blend of the 12z HREF and recent HRRR runs to derive QPF for this area into the evening hours. Days 2/3... ...West... Rare zonal movement of low pressure systems (over the western CONUS and off the eastern CONUS) is expected Saturday night through Monday. The low over the western CONUS will lose its connection with deep Pacific moisture. Between decent height falls and difluent upper level flow, there will still be enough forcing to produce a quarter to a half inch of liquid precipitation Saturday night through Sunday across the Intermountain West. Also...an inverted trough extending north from UT to MT will enable moderate wintry precip to develop and spread onto the high plains of MT late in Day 2. ...along with locally higher amounts where the flow is perpendicular to the terrain. Please refer to WPC's Heavy Snow Discussion (QPFHSD) for more details on winter weather. Also...a lot level trough crossing southern CA Saturday evening may enable locally moderate rain. However...rates do not look strong enough at this time to warrant a Day 2 excessive rainfall outlook even over burn scar areas. WPC QPF for Day 2 was based on a blend of the 12Z GFS/ECMWF/NAM. ...Northern Plains into the Midwest... Low pressure shifts east from the north-central Rockies tot he central plains Sunday with a low level jet advecting gulf moisture to the northern plains - to the north side of the developing surface low. A deformation zone is expected to develop on the north side of the low Sunday night with locally moderate to heavy wintry precip. Please refer to WPC's Heavy Snow Discussion (QPFHSD) for more details on winter weather. Inflow east of the system will bring rain into the upper Midwest Sunday night through Monday. However...limited instability and PW generally only two standard deviations above normal does not warrant an excessive rainfall outlook as of this time. The Day 3 WPC QPF forecast was based on a non-Canadian general model consensus. ...Southern Plains/Lower MS Valley... A low level jet ahead of low pressure shifting east from the north-central Rockies will bring PW around 1.5 inches over east TX into the lower MS Valley Sunday through Monday. This is 2 to 2.5 standard deviations above normal and locally heavy rainfall is expected as the associated cold front crosses the southern plains Day 3. However...areal average QPF up to 1.25 inches does not warrant an excessive outlook at this time. Chenard/Jackson Graphics available at www.wpc.ncep.noaa.gov/qpf/qpf2.shtml