Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1137 AM EDT Fri May 17 2019 Valid 12Z Mon May 20 2019 - 12Z Fri May 24 2019 ...A Stormy and Wet Pattern for the Western and Central U.S next week.... ...Overall Weather Pattern... It remains the case that a stormy and unsettled weather pattern is expected across much of the central U.S. during the medium range period with a large scale upper trough becoming established over the Intermountain West and a building upper level ridge over the southeastern states. Three well defined storm systems are expected next week, with the first affecting the northeastern U.S. on Monday. The second storm exits the snowy Rockies Monday to gather strength across the Plains on Tuesday and tracks towards the Great Lakes, and the third well organized system slams into the West Coast Tuesday, develops over the Intermountain West midweek to reach the Plains late next week. ...Guidance/Predictability Assessment... The 06 UTC FV3 and 00 UTC ECMWF forecasts are well clustered with GEFS/ECMWF ensemble solutions through this medium range period, bolstering confidence. The WPC medium range product suite was primarily derived from a seemeingly reasonable composite blend of these guidance pieces. This also maintains good WPC continuity. In contrast, the 00/06 UTC GFS runs offer more outlier solutions that become much more progressive than the WPC composite from the Gulf of Alaska to western Canada and the northwestern U.S. mid-later next week. This does not seem as good a fit with the overall amplifying pattern. ...Weather Highlights and Hazards... Numerous showers and thunderstorms continue to be in the forecast going into next week across the central/southern Plains and extending to the Upper Midwest. Multiple rounds of MCS activity are likely with both of the low pressure systems that are progged to track across the Plains. This will have the potential to produce very heavy rainfall capable of flash flooding, and severe weather is also likely from northern Texas to the Midwest based on recent SPC forecasts. The greatest chance of flooding would be from the Texas Panhandle region to Iowa with the strong low pressure system for the early to middle part of the week. Additional heavy rain is also possible from the next storm system tracking eastward from the Intermountain West later in the week, although details on timing and placement are less certain. There will also be a dichotomy of temperature anomalies given the amplified flow pattern in place. Temperatures are expected to be well above normal across much of the southeastern U.S. owing to the strength of the upper ridge, and this will also serve to keep rainfall chances minimal. The opposite will be the case across much of the western U.S. and also the northern Plains that will be under the influence of the upper level trough and to the north of the low tracks. Heavier late season snows are also likely for the Sierra Nevada to the northern Rockies. D. Hamrick/Schichtel WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml