Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Wed Mar 16 2022 Valid 12Z Sat Mar 19 2022 - 12Z Wed Mar 23 2022 ***Strong low pressure system will likely produce heavy rain and severe storms across portions of the southern U.S. by early next week*** ...Overview... A rather active weather pattern will be developing across much of the nation beginning this weekend, and particularly into the beginning of next week as a deep upper level trough develops over the Intermountain West as Pacific shortwave energy moves inland. This will likely evolve into a closed upper low by Monday along with an intensifying surface low over the central/southern Plains that will eventually result in heavy rain and severe storms from Texas to the Deep South by the end of the forecast period. There will also be a well organized storm system across the Northeast U.S. this weekend ahead of the central U.S. event. ...Guidance Evaluation/Predictability Assessment... The 00Z model guidance suite is generally in above average agreement through Monday night with the overall synoptic scale pattern and the evolution of the main upper level trough/closed low over the Rockies and Southern Plains. The GFS is stronger with the closed low but still within the realm of possibility. By Tuesday, the GFS and its ensemble mean are farther north across Kansas, whereas the CMC/ECMWF solutions are favoring a position over the Texas panhandle with the closed low. By the end of the forecast period Wednesday, the 00Z ECMWF is out of phase across the Pacific Northwest with a much stronger trough passage, whereas the ensemble means are favored more of a ridge axis. Taking these factors into account, the WPC forecast was primarily based on a multi-deterministic model blend as a starting point through about Monday, and then incorporated more of the ensemble means whilst still maintaining smaller contributions from the ECMWF/GFS/CMC. ...Weather Highlights/Threats... The surface low tracking from the Ohio Valley to the Northeast on Saturday will likely be accompanied by a swath of moderate to locally heavy snow across northern portions of New England, particularly central and northern Maine. Elsewhere, moderate rain is expected from the northern Mid-Atlantic to central/southern New England for the first half of the weekend. Attention then turns to the Plains and Gulf Coast region as a surface low becomes better organized by early Monday and taps into a surge of Gulf moisture across Texas and the central Gulf Coast region. The prospects for heavy rainfall and severe weather have increased since yesterday, mainly later in the day Monday and especially into Tuesday. Flooding rain could also be an issue as multiple rounds of convection develop over the same general areas. The Storm Prediction Center has additional information pertaining to the severe weather potential. In terms of temperatures, the East Coast should continue to have above normal readings this weekend and into the middle of next week as upper level ridging develops ahead of the deep trough over the Plains. Even greater positive anomalies are likely across the central and northern Plains by Sunday ahead of the storm system, with highs up to 25 degrees above average, whereas a return to slightly below average temperatures is expected across the Rockies and the western High Plains under the upper level trough for Monday and Tuesday. No major surges of arctic air are expected. Hamrick 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