Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Mon May 02 2022 Valid 12Z Thu May 05 2022 - 12Z Mon May 09 2022 ...Severe weather and enhanced rainfall threat with southern stream closed low track Thursday into Saturday... ...Heavy snow threat from the Northwest to the North-Central Great Basin/Rockies Friday-next Monday... ...Active pattern set to transition to Omega-style blocky pattern by early next week... ...Model Guidance Evaluation... Guidance remains varied with the progression of a closed upper low tracking out of the West into the Plains and eastward, with the GFS/GEFS mean still on the fast side compared to the better clustered and slower recent ECMWF/UKMET/Canadian and ECMWF ensemble mean solutions. The WPC forecast continues to lean towards the slower side of the forecast envelope, given continuity, but also the general nature of a separated southern stream flow with an embedded closed system. Latest 12 UTC models and ensembles continue to trend in this direction. This combination seems to work well for much of the rest of the country and maintains good WPC product continuity, albeit with more emphasis on the ECMWF ensemble mean into day 6/7 amid growing forecast spread. Out West, there remains a general theme of leading main upper troughing to reaching the coast Thursday, with guidance converging on depiction of a more digging system over the weekend into early next week as part of a developing Omega style block over the lower 48 to also include downstream development of an amplified and warming east-central U.S. upper ridge and stormy western Atlantic closed low/trough. ...Pattern Overview and Weather/Threat Highlights... A closed upper trough and well organized surface low/frontal system is expected to track from the south-central Plains to the Mississppi Valley/Midwest to the Mid-Atlantic Thursday-Saturday. The Storm Prediction Center shows a threat for severe weather Thursday/Friday from the southern Plains to the Mid-South. Strong storms are also possible into the weekend with slow/steady downstream track of the system. Upper diffluence, moisture inflow and instability will also offer a threat for enhanced comma head and wavy lead/trailing frontal rainfall focus from the mid-lower Mississippi and Ohio valleys to the Appalachians/Mid-Atlantic Thursday-Saturday. The digging of a moderately amplified/dynamic upper trough and frontal system energies across the West Coast and subsequent inland progress Thursday through the weekend will bring a widespread precipitation focus from the Northwest through the north-central Great Basin/Rockies and height falls/cooling will favor a threat for heavy terrain focusing snows. Upper dynamics/frontal translation should also support an emerging convection/rainfall pattern with local runoff concerns across the north-central U.S. by later weekend/early next week. Upstream, the guidance signal is growing for yet another frontal surge into the West for ther weekend into early next week as unsettling upper trough energies seem set to dig more earnestly into the region that may lead to closed low/trough development over the south-central Great Basin/Southwest as part of a large scale Omega style block to also include downstream development of an amplified and warming east-central U.S. upper ridge and stormy western Atlantic closed low/trough. 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