Extended Forecast Discussion NWS Weather Prediction Center College Park MD 312 AM EDT Sun Apr 02 2023 Valid 12Z Wed Apr 05 2023 - 12Z Sun Apr 09 2023 ...Blizzard for the Upper Midwest into Wednesday... ...Heavy rainfall and strong thunderstorms over the South this week, especially for the west-central Gulf Coast states... ...Winter cold for the West and North-central U.S. this week to starkly contrast summer heat that shifts from the South through the East/Southeast... ...Model Guidance/Predictability Assessment... Confidence remains well above normal for the main weather threats next week. Forecast clustering is best Wednesday into Friday with the 18 UTC GFS and 12 UTC ECMWF/UKMET/CMC providing a good forecast basis that is well supported by ensembles. Forecast spread slowly increases heading through next weekend with embedded mid-smaller scale features. This lends a transition to a preference for the more run to run consistent GEFS/ECENS/NAEFS ensemble means along with the 01 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 recent guidance and WPC products continue this trend/preference. ...Overview and Weather/Hazards Highlights... An energetic closed upper low will lift over the eastern Dakotas and Minnesota by Wednesday. Winter cold, high winds and broad/heavy swaths of snow to the north of the track of the powerful surface low pressure system make for widespread blizzard conditions. Upper ridging over the Gulf Coast builds northward over the eastern U.S. Wednesday into Thursday that in stark contrast will support anomalous warmth and widespread showers and strong to severe thunderstorms across the east-central to eastern U.S. along/ahead of the trailing cold front from the large storm. Activity and flash flooding issues may focus over the moist and unstable west-central Gulf Coast states. Accordingly, the experimental WPC medium range Excessive Rainfall Outlook (ERO) offers a "Slight Risk" threat area over the lower Mississippi Valley to portions of the Tennessee Valley Wednesday that shifts across the lower Mississippi Valley into Texas by Thursday. The stalling of the front near the Gulf Coast into late week and the weekend along with less certain frontal wave enhancements with the ejection of southern stream upper energies should continue to focus convergence/convection and additonal potential runoff/flash flooding issues. The WPC product suite tends to limit the northern lift of the bulk of later week/weekend activty given overall upper flow amplification, seemingly for much of the upcoming period, embedded feature uncertainty over time and the general southern positioning of the main barolinic zone/front. Out West, expect less organized terrain focusing snows across the north-central Great Basin/Rockies through midweek with passage of flow embedded shortwaves. Lead flow with approach of more energetic Pacific systems should then favor moderate precipitation chances across mainly the Northwest mainly Thursday/Friday that should gradually diminish with ample West Coast upper ridge building over next weekend that also ushers in warmer conditions. 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 especially the Southeast and vicinity with highs generally 10-20F above normal and lows 15-25F above normal. Expect some lingering daily records mainly for cold highs over the West into midweek. 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. 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