Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Thu Mar 03 2022 Valid 12Z Sun Mar 06 2022 - 12Z Thu Mar 10 2022 ...Heavy rain potential across the Mid-Mississippi Valley into Ohio Valley late Sunday into Monday... ...Overview with Weather Highlights/Threats... An upper-level trough forecast to move through the southwestern U.S. this weekend and then lift across the Plains early next week will likely support the development of an elongated low pressure system along a polar front to promote a heavy rain event across the Mid-Mississippi Valley into Ohio Valley into Monday. A winter weather event should be ending across the upper Great Lakes Sunday morning as the medium-range period begins. The system will possibly bring some snow/freezing rain across northern New England Sunday morning and some snow Monday morning. A swath of wintry precipitation is forecast to quickly develop in its wake from the central Plains through the lower Great Lakes and interior Northeast Monday into Tuesday as the elongated low pressure system tracks across. Thereafter, a familiar pattern will tend to re-establish across the U.S. as northern stream clippers tend to slide east-southeast toward an eastern U.S. broad trough while a subtropical jet tends to linger across the northern Gulf. An increasing chance of heavier rainfall appears to emerge across the Deep South to the Gulf Coast toward the latter portion of next week with a stationary front across the northern Gulf of Mexico while a tropical low lingers into the southern Gulf. Another surge of arctic air appears in store for the northern Plains through midweek behind the clipper systems. The eastern and southern U.S. will be much warmer than normal at the start of the medium-range period but progressively cooler air will work its way across these areas through midweek. The central and southern Rockies into the nearby High Plains will begin the medium-range period with the passage of the upper low interacting with an arctic front. The snow in these areas will gradually taper off early next week as the upper trough exits the region. The focus of mountain snow will then shift northward across the northern Rockies and the foothills by Tuesday through midweek as the next surge of arctic air arrives from Canada. For the rest of the western U.S., dry and near normal temperatures are expected to return behind the exiting upper trough. ...Guidance Evaluation/Predictability Assessment... Model guidance appears in reasonably good agreement with one another in predicting the synoptic pattern evolution across the U.S. through the medium-range period. The GFS, especially the 18Z run, was among the slowest guidance in placing the low pressure center of the ongoing winter storm moving across the upper Midwest/upper Great Lakes as medium-range starts Sunday morning. The timing of the elongated low pressure system in its wake also presented some more issues for the GFS with the 18Z run being much slower than its ensemble mean as well as the ECMWF/EC mean. By midweek next week, the largest model spread appears to be across the Northeast into eastern Canada where the timing of the various clipper systems and their potential interactions presented a challenge. The WPC medium-range package was derived based on a multi-model consensus with 40% from the 12Z ECMWF/EC mean, 40% 12Z+18Z GFS/18Z GEFS, and 20% from the 12Z CMC/CMC mean. Excellent WPC continuity was maintained. Kong 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, 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