Extended Forecast Discussion NWS Weather Prediction Center College Park MD 502 PM 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... ...Pattern Overview and Guidance Evaluation... Guidance remains varied with the progression of a closed upper low tracking 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 general direction, but the GFS is slightly slower with its low than previous runs. A non-GFS consensus also seems to work well for the rest of the country and maintains good WPC product continuity, though with more emphasis on the ECMWF ensemble mean and NAEFS mean into day 6/7 amid growing forecast spread. Out West, there remains a general theme of leading main upper troughing reaching the coast Thursday, with a growing signal and guidance starting to converge on the 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. ...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 into Friday across portions of the Lower Mississippi Valley. Strong storms are also possible into the weekend with slow/steady downstream track of the system. Upper diffluence, ample 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. Above normal temperatures progress from the West on Thursday into the central/midwest states thereafter as the pattern begins to amplify and a strong ridge sets up in between a trough/closed low over the west, and a broad closed low across the western Atlantic. These troughs will support temperatures as much as 10-15 degrees below normal across a large portion of the West and parts of the Mid-Atlantic. Santorelli/Schichtel Hazards: - Heavy precipitation across portions of the Cascades, and northern Idaho, Fri, May 6. - Heavy rain across portions of the northern Plains, Sun-Mon, May 8-9. - Heavy rain across portions of Arkansas into eastern Oklahoma and northeastern Texas, Thu, May 5. - Heavy rain across portions of Arkansas into eastern Oklahoma, northeastern Texas, and Missouri, Mon, May 9. - Heavy rain across the Midwest, Ohio Valley, central Appalachians, and the Mid-Atlantic, Thu-Fri, May 5-May 6. - Severe weather across portions of the lower and mid-Mississippi Valley, the Tennessee Valley, and into southern Plains, Thu, May 5. - Flooding possible across portions of the central Plains, as well as the northern Plains around the Red River Valley. - Flooding occurring or imminent across portions of the Missouri and the Red River Valley. - Flooding likely across portions of the Red River. 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