Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sat Apr 01 2023 Valid 12Z Tue Apr 04 2023 - 12Z Sat Apr 08 2023 ...Blizzard threat across the northern Plains and Upper Midwest into Tuesday/Wednesday... ...Heavy rainfall and severe thunderstorms from the South into the Midwest Tuesday, lingering 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 to the East/Southeast next week... ...Synoptic Overview... Energetic closed upper trough ejection out from thr West/Rockies will foster deep storm genesis and track from the central Plains to the Upper Midwest Tuesday into Wednesday. Winter cold, heavy snow and high winds to the north of the track of the powerful low presure system offer a threat for blizzard conditions. This is in stark contrast to widespread convective warm sector showers/thunderstorms to develop and spread across the eastern half of the country that includes a threat for severe weather with a Mid-South focus Tuesday as per the Storm Prediction Center (SPC). Upper ridging over the Gulf Coast should build northward over the eastern U.S. and support anomalous warmth ahead of the storm's associated cold front. This pattern may lead to the stalling of the trailing front into later next week across the U.S. southern tier. Frontal wave enhancements with the ejection of southern stream upper energies may 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 experiental WPC medium range Excessive Rainfall Outlook (ERO) plans to introduce a "Slight Risk" threat area by next midweek. ...Model Guidance/Predictability Assessment... Confidence remains above normal for the main weather threats next week. Forecast clustering is best Tuesday-Thursday with the 18 UTC GFS and 12 UTC ECMWF/UKMET and a composite blend seems to provide 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 reinforcing trough energies chaotically into/out from the West. This lends a gradual transition to a preference for the more run to run consistent GEFS/ECENS ensemble means along with the 01 UTC National Blend of Models (NBM). WPC product continuity is well maintained in this manner and the latest 00 UTC models and ensembles are in line overall. ...Weather/Hazards Highlights... The big headline is the deepening Plains low that tracks from the central Plains through the Upper Midwest Tuesday/Wednesday. Probabilities for heavy snow have steadily increased from the north-central Plains through the northern Plains and Upper Midwest. This storm will also produce strong winds so blizzard conditions are likely. Other 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. 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 expanding from the southern Plains/Gulf Coast through much of the eastern U.S. Tuesday-Wednesday look to be the coldest days 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 will be possible over the West during the first half of the week. Farther east in the warm sector, Tuesday-Thursday will offer the best potential for 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