Extended Forecast Discussion NWS Weather Prediction Center College Park MD 410 PM EDT Thu Mar 26 2020 Valid 12Z Sun Mar 29 2020 - 12Z Thu Apr 02 2020 ...Great Lakes to Northeast storm threat Sun-Mon... ...Heavy rain for the South Mon-Tue then coastal low development up the East Coast Wed-Thu... ...Periodic wet flow into the Pacific Northwest next week... ...Guidance/Predictability Assessment and Weather/Hazard Highlights... The medium range forecast is characterized by average forecast confidence initially but quickly drops to below average from day 5 onward. At the start of the period, model guidance has converged on a similar evolution for the lead deepening low near the Great Lakes and as it tracks through the Northeast by Monday morning. A secondary low is forecast to develop off the Northeast coast, which is well agreed upon by the most recent deterministic models. A secondary positively tilted trough then moves across the Southwest U.S. early next week and through the southern/central U.S. by mid-week. Here, model differences increase considerably. The ECWMF phases more northern stream energy over the central U.S. resulting in a deeper, closed low over the eastern U.S. by the end of the period. Conversely, the GFS suggests a faster southern stream shortwave and therefore less interaction with approaching PacNW shortwave. The sensible weather impacts range from a deepening area of low up the East Coast (ECMWF solution) to a weaker/suppressed system (GFS). Along/ahead of the projected surface low over the Deep South / Southeast U.S. could result in heavy rainfall though details are less than certain at this time given the model differences. The WPC model blend and progs were derived from a deterministic blend on Day 3 but quickly transitioned to a blend heavily focused on the ECENS ensemble mean with some component of the 00Z ECMWF. Taylor 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 - Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great Basin, Sun-Mon, Mar 29-Mar 30. - Heavy rain across portions of the Lower/Middle Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Mon-Wed, Mar 30-Apr 1. - Heavy snow across portions of the Northeast, Sun-Mon, Mar 29-Mar 30. - Flooding possible across portions of the Middle Mississippi Valley and the Upper Mississippi Valley. - Flooding occurring or imminent across portions of the Lower/Middle Mississippi Valley, the Northern Plains, the Tennessee Valley, the Southeast, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Middle/Upper Mississippi Valley, the Northern Plains, and the Ohio Valley. - Much above normal temperatures across portions of the Upper Mississippi Valley and the Northern Plains, Mon, Mar 30. - Much above normal temperatures across portions of the Southeast, Sun-Tue, Mar 29-Mar 31. 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