Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 PM EDT Tue May 03 2022 Valid 12Z Fri May 06 2022 - 12Z Tue May 10 2022 ...Enhanced rainfall threat with closed low track into Friday/Saturday from the Ohio Valley to the Appalachians/Mid-Atlantic... ...Heavy snow threat from the Northwest to the North-Central Great Basin/Rockies Friday into next week... ...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 from the central to eastern U.S. this period, 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. The 06z GFS/GEFS continues a pattern of more progressive and amplified troughing in the central and eastern portion of the country early in the medium range period. A blend of 00z EC/ECE/CMC/UK seems to mitigate the timing and intensity issues caused by the GFS/GEFS through D4 at which point the Midwest-East coast system should have pushed out to sea. A 00z EC/ECE/CMC blend is utilized from D5-D7 due to the continued progressive nature of a western trough in the 06z GFS/GEFS. ...Weather/Threat Highlights... A closed upper trough and well organized surface low/frontal system is expected to track from the south-central Plains/lower Mississippi Valley Friday to the Ohio Valley then Appalachians/Mid-Atlantic over the weekend. Strong storms are possible into the weekend with the 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. Robust digging of a series of dynamic upper systems will lead to a dramactic change over much of the West this period as an amplified mean upper trough and wavy/well defined frontal systems become established over the region Friday into next week. This will support significant cooling and bring a widespread precipitation focus from the Northwest through the north-central Great Basin/Rockies to include a substantial and lingering threat for heavy terrain focusing snows. These troughs will support temperatures as much as 10-20 degrees below normal across a large portion of the West. Upper dynamics and slow wavy 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, albeit with less certain system details at these longer time frames. The Storm Prediction Center has highlighted areas of concern for Severe Weather over portions of the Central Plains and Middle Mississppii Valley between Sunday and Monday. Localized heavy rainfall could lead to runoff issues as the region has experienced quite a bit of rain in April. Kebede/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