Extended Forecast Discussion NWS Weather Prediction Center College Park MD 311 AM EDT Fri Mar 25 2022 Valid 12Z Mon Mar 28 2022 - 12Z Fri Apr 01 2022 ...Early next week wet pattern for southern California spreads eastward and significantly expands/intensifies over the east-central U.S. mid-later next week to include wrapping northern periphery snow/ice... ...Overview... An amplified upper trough and lingering wintry weather will exit the northeastern U.S. by early next week, leaving a cooled airmass down across the north-central through eastern states. The main weather focus across the nation will shift to the West as a strong upper trough and embedded closed low progress into/through the Southwestern states early next week before lifting across the south-central Rockies/Plains midweek. There is then a growing guidance trend to increase phasing with northern stream trough energies over the east-central U.S. into next Thursday/Friday that would also promote more organized surface low and frontal development and strength. Overall, this will favor rather unsettled and wet pattern from CA and the Southwest to the south-central Rockies early next week (including mountain snows) that will emerge, expand in magnitude and spread from Plains to the east-central and eastern/southeastern U.S. later next week as Gulf moisutre increasing feeds into the system. ...Guidance Evaluation/Predictability Assessment... A composite of reasonably well clustered guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET/Canadian seems to offer a good forecast basis Monday into Wednesday. Forecast spread increases by later Wednesday into next Friday, but has improved a bit from yesterday. Of the ensemble systems, the 12 UTC ECMWF ensemble mean provides the most reasonable midpoint position/phasing solution between more varied models are these longer time frames. The ECMWF ensemble mean also favors more renewed upper trough digging than the GEFS and especially the flatter GFS by then back into the West. This seems reasonable considering upstream flow ampitude and 00 UTC guidance has trended or maintained this scenario. The WPC medium range product suite was primarily derived from preferred guidance along with the 01 UTC National Blend of Models. This solution seems in line with latest guidance trends and maintains good product continuity. ...Weather Highlights/Threats... Model guidance shows the heaviest rain totals for southern California into Monday especially enhanced by higher terrain, which could cause flooding issues if heavy rain falls over burn scar areas. Rain and higher elevation snow will spread across the Intermountain West and Rockies Monday and Tuesday. As surface low pressure strengthens in the Plains and tracks east, more widespread rain and thunderstorms are likely for the southern/eastern Plains and mid-lower Mississippi Valley Tuesday and Wednesday. Meanwhile on the northern side of the precipitation shield, a wintry mix and accumulating wrapping snows are possible for the northern tier, mainly from the Upper Midwest the the Great Lakes and northern tier of the Northeast. Rainfall could remain heavy through the east and especiallly the Southeast later next week. 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