Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Mon Mar 28 2022 Valid 12Z Thu Mar 31 2022 - 12Z Mon Apr 04 2022 ...A deep cyclone will likely move across the Great Lakes with high winds, gradually departing wrap-around snows, areas of heavy rain and possibly severe weather along the East Coast on Thursday... ...Guidance Evaluation/Predictability Assessment... Latest model guidance this morning continues with the recent trend of lifting a deep cyclone faster across the Great Lakes as the medium-range period starts on Thursday morning. This northward trend not only resulted in a faster passage of the cyclone center across the Great Lakes but also lifted the heavy rainfall axis in the warm sector farther north from northern Florida into the coastal plains of the Southeast. There is also a continued model tendency to push the cold front slightly faster off the East Coast on Friday. Behind the departing cyclone, the next upper trough over the Pacific is forecast to penetrate farther inland through the Pacific Northwest. Models have generally abandoned the previous idea of deepening this trough over the Southwest but rather, glide it steadily east-southeast through the western U.S. into the central/southern Plains by the weekend. This pattern would favor the formation of a frontal wave/clipper system over the central Plains by the weekend. Models have generally shown better agreement today regarding the timing of this clipper system, with a tendency to converge toward the ECMWF, which is in between the slower CMC and the faster GFS. By late in the weekend, model consensus continues to suggest that the clipper will move across the Southeast and then exit into the Atlantic. There was a faster trend in the models to push the clipper off the coast, which resulted in a potentially heavy rainfall axis to be nudged farther south along the central and eastern Gulf Coast earlier during the weekend. Meanwhile, models have shown very good agreement on a steady increase of moisture to reach the Pacific Northwest late this weekend. The WPC medium-range forecasts were composed based on a composite blend of 40% 00Z ECMWF/EC mean, 40% 06Z GFS/GEFS and 20% from the 00Z CMC/CMC mean. Less of the GFS was used on Day 5 to allow a slower progression of the clipper system. The blend then transition to mostly a consensus of the ensemble means by Day 7. The results compare well with WPC continuity, with reasonable timing discrepancy on frontal positions on Day 7. ...Overview and Weather Highlights/Threats... A deep cyclone is set to lift from the Great Lakes to eastern Canada Thursday into Friday, offering a threat for wrapping heavy snows north of the low track. High winds appear likely on the backside of the cyclone on Thursday across the upper Midwest, especially along the south shore of Lake Superior. In the warm sector, pre-frontal convection will likely sweep across the Eastern Seaboard on Thursday along with a severe weather threat focus over the Mid-Atlantic as per SPC while a heavy rainfall threat should extend from northern Florida through the coastal plains of Georgia and the Carolinas. A protracted series of more modest upstream upper trough energies and frontal systems forecast to dig with some uncertainty through the West later week into next week could each provide an opportunity for enhanced rounds of wintry weather, mainly for the north-central Intermountain West/Rockies. Potential system amplitude and progression into next weekend/early next week would favor return moisture into a wavy frontal pattern off the Gulf Coast. This may support a heavy rainfall focus from the Gulf Coast states to the Southeast/Mid-Atlantic. By early next week there is also a guidance signal to bring more energetic Pacific flow toward the West Coast in two streams to be monitored. 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 WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml