Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Sun Mar 27 2022 Valid 12Z Wed Mar 30 2022 - 12Z Sun Apr 03 2022 ...A rapidly deepening low pressure system presents a mid-late next week heavy rain/severe weather threat focus across the South while heavy snow/ice and high wind threat focus across the Upper Midwest/Great Lakes... ...Guidance Evaluation/Predictability Assessment... Model guidance this morning continues to indicate the likelihood of a rapidly deepening cyclone to track from the central Plains through the Great Lakes Wednesday-Thursday. Model consensus appears to trend toward a faster progression of the cyclone center through the Great Lakes in better agreement with earlier GFS runs. In addition, there has been a gradual eastward shift in the rainfall maximum across the Deep South with a slightly faster eastward motion of the southern stream low. This eastward shift might have ceased in the most recent couple of model cycles. The faster southern stream low also resulted in a faster progression of the cold front through the eastern U.S. Thursday-Friday. Meanwhile, the next upper trough from the Pacific will come into play by midweek as it reaches the Pacific Northwest. Models have been showing difficulties in handling and resolving the timing and evolution of this system as it heads downstream. It appears that the consensus is for the system to generally glide southeastward across the western U.S. late this week as the ECMWF and CMC have adopted a less amplified solution compared with earlier runs. This would favor frontal wave development by the weekend over the central Plains as supported by the ECMWF. The timing of the progression of the upper trough downstream is subject to large uncertainty however. At present, the consensus supports a frontal wave to move across the Southeast late this weekend after a potential resurgence of Gulf moisture late next week across the central and eastern Gulf Coast states north of a stationary boundary. A composite blend of 40% 00Z ECMWF/EC mean, 40% 06Z GFS/GEFS and 20% from the 00Z CMC/CMC mean was used to compose the Days 3-5 forecasts, transitioning to mostly a consensus of the ensemble means by Day 7. The results compare well with WPC continuity. The timing of the upper trough/frontal wave across the mid-section of the country is the most uncertain part of the forecasts. ...Overview and Weather Highlights/Threats... As a main surface low pressure system over the Plains strengthens and tracks northeast, increasingly widespread rain with heavy downpours and a threat for severe weather are forecast across the South into Wednesday before spreading over the Southeast/Mid-Atlantic Thursday. A "slight" risk area remains depicted on the WPC experimental medium range excessive rainfall outlook (ERO) for Wednesday given favorable system ingredients and antecedent conditions. Meanwhile, rain and thunderstorms are also expected farther north from the central Plains through the East with wavy frontal progression across the region. On the northern side of the precipitation shield, expect a swath of heavy wintry mix and accumulating snows from the Upper Midwest to the Great Lakes into Wednesday-Thursday given continued excellent model consensus on developing a rather intense cyclone. In addition, high winds appear likely near and well to the west of the low track given the impressive rate of cyclogenesis. Some wintry precipitation is also forecast for northern New England ahead of and on the back side of this system. Late week, additional upper trough energies forecast to dig with some uncertainty southeastward from the Pacific Northwest through the West could provide another opportunity for an enhanced round of wintry weather, mainly for the northern to central Intermountain West/Rockies to the High Plains. Potential system amplitude and progression into next weekend would favor return moisture flow into an increasingly wavy/lifting front. This may support renewed heavy rainfall potential across the central/eastern Gulf Coast states and Southeast next weekend. Kong/Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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