Extended Forecast Discussion NWS Weather Prediction Center College Park MD 302 PM EDT Sat Apr 01 2023 Valid 12Z Tue Apr 04 2023 - 12Z Sat Apr 08 2023 ...Blizzard continues across the northern Plains and Upper Midwest into Wednesday night... ...Heavy rainfall and severe thunderstorms from the South into the Midwest Tuesday, persisting rest of the week over the South... ...Winter cold for the West and North-central U.S. next week to starkly contrast summer heat that shifts east from the South through the East/Southeast through midweek... ...Synoptic Overview... Energetic closed upper low will move east-northeast over the north-central Rockies and spill over the north-central High Plains Tuesday before further strengthening as it turns northeast and lifts over eastern South Dakota Tuesday night and Minnesota Wednesday. Winter cold, broad/heavy swaths of snow and high winds to the north of the track of the powerful low pressure system make for widespread blizzard conditions. This is in stark contrast to widespread convective warm sector showers/thunderstorms that develop Tuesday afternoon from northeast Texas into the Midwest which includes a threat for severe weather with a Mid-South Tuesday per the Storm Prediction Center (SPC). Upper ridging over the Gulf Coast builds northward over the eastern U.S. through Wednesday and supports anomalous warmth ahead of the cold front from the large Plains storm. This pattern should lead to the stalling of the trailing front near the Gulf Coast at least into the weekend. Frontal wave enhancements with the ejection of southern stream upper energies should focus convergence/convection and potential training/flash flooding issues, especially with the front aligned with the upper flow across the moist and unstable lower Mississippi Valley in the favorable right entrance region of the upper jet. Accordingly, the experimental WPC medium range Excessive Rainfall Outlook (ERO) expands the Slight Risk threat area for Wednesday. ...Model Guidance/Predictability Assessment... Confidence remains well above normal for the main weather threats next week. Forecast clustering is best Tuesday-Thursday with the 06 UTC GFS and 00 UTC ECMWF/UKMET/CMC (with the CMC dropping off on Day 4) provides a good forecast basis that is well supported by ensembles. Forecast spread slowly increases heading into next weekend, particularly with the placement and strength of a reinforcing trough over the Intermountain West Wednesday into Thursday along with potential for a positively-tilted trough late next week off southern California with some possibility on it becoming a cutoff low including with 12 UTC guidance. This lends a gradual transition to a preference for the more run to run consistent GEFS/ECENS ensemble means along with the 13 UTC National Blend of Models (NBM). There continues to be a gradual southward trend in QPF (toward the Gulf Coast) over the south Wednesday to Friday with 12 UTC guidance. ...Weather/Hazards Highlights... Blizzard north-central High Plains through the Upper Midwest peaks Tuesday night and continues into Wednesday. Areas farther east may see brisk to strong winds even if to a less extreme degree. There is also another substantial threat of strong to severe storms in the expansive warm sector, with the Storm Prediction Center highlighting and area over the Mid-South on Tuesday. Numerous showers and thunderstorms are likely from the Gulf Coast to the Midwest Tuesday, continuing next week over the South as reinforcing southern stream trough energies suggest a continued advection of copious Gulf moisture and instability, especially with a wavy/stalling front. Accordingly, the experimental WPC medium range Excessive Rainfall Outlook (ERO) expanded a "Slight Risk" threat area over the lower Mississippi Valley to portions of the Tennessee Valley Wednesday. A pronounced temperature contrast will persists across the nation early-mid week with well below average readings spreading across much of the western U.S. and central/northern Plains, and well above average temperatures shifting from the southern Plains/Gulf Coast through much of the eastern states. Tuesday night-Wednesday night look to be the coldest stretch versus normal over the West/Plains with some areas seeing highs as much as 20-30F below normal. The reverse will hold true over the southern Plains early in the week and farther eastward thereafter, with highs generally 10-20F above normal and lows 15-25F above normal. Daily records mainly for cold highs are expected over the West during the first half of the week. Farther east in the warm sector, Wednesday-Thursday should see some daily records, with warm lows tending to be more numerous than record highs until the cold frontal passage. Jackson 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