Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Wed Mar 6 2019 Valid 12Z Sat Mar 9 2019 - 12Z Wed Mar 13 2019 ...Weather Pattern Overview... An active weather pattern is expected during much of the medium range period as two large scale troughs originating from the Pacific lead to surface low development across the central U.S. and Midwest states. The first storm system develops and intensifies across the central plains and Upper Midwest this weekend with surface high pressure exiting the East Coast region. The second Pacific disturbance crosses the Desert Southwest on Monday and then undergoes secondary cyclogenesis over the western High Plains by the end of the forecast period next Wednesday. ...Model Guidance Evaluation and Preferences... The agreement among the models and ensembles has continued to improve on the synoptic scale for the entire forecast period with the more amplified pattern that will be in place, and forecast confidence is above average for this time period. The ECMWF, GFS, FV3, and the EC and GEFS mean indicate rather impressive consensus for a day 7 forecast regarding the second low to affect the central part of the nation, with the CMC being the exception to this by having the low well to the south across Texas. The CMC is also to the west of the model consensus with the weekend storm across the Upper Midwest. There has been a slightly faster trend in the ensemble means for the weekend storm and slightly more amplified with the storm system early-mid next week. Taking all of these factors into account, the forecast was primarily derived from the 12Z ECMWF/18Z FV3 and GFS/12Z UKMET for the first three days, and then slightly higher percentages of the EC and GEFS means while still keeping a significant percentage of the deterministic GFS and ECMWF for the second half of the forecast period. The WPC forecast is very similar to the previous forecast. ...Weather Highlights and Hazards... Widespread rain and thunderstorms are expected to develop from the Gulf Coast to the Ohio Valley and southern Appalachians on Saturday and into early Sunday as a rich supply of Gulf moisture surges northward ahead of a strong cold front from the Midwest surface low. The heaviest rainfall is likely from eastern Texas to the southern Appalachians, where a general 1 to 2 inches of rain is likely that may lead to some local flooding issues based on the current forecast. However, the progressive nature of the event should limit the duration of the heaviest rain. Depending on where the surface low tracks, a corridor of blizzard conditions is becoming increasingly likely across parts of the Upper Midwest, including parts of the Dakotas. Another facet to this low pressure system will be the potential for severe thunderstorms to develop in the warm sector, and this is something that the Storm Prediction Center is currently monitoring. Upstream, the pattern again favors an amplified mid-upper level trough developing off the West Coast this weekend. This will support another round of precipitation over the southwestern U.S. as the trough moves inland on Monday. Additional widespread rain may then develop across the central and southern plains by the end of the forecast period as the trough induces another surface low east of the Rockies. There is also the potential for severe weather with this storm system, and details on this will become more evident in the upcoming days. D. Hamrick Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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