012 FXUS02 KWBC 021956 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 356 PM EDT Sat May 2 2026 Valid 12Z Tue May 5 2026 - 12Z Sat May 9 2026 ...General Overview... A slightly blocky upper level pattern is expected to be in place for this forecast period, featuring a southern stream upper trough/closed low near the Desert Southwest, a ridge axis extending across the Pacific Northwest and northern Rockies, and broad cyclonic flow with a general trough over the eastern half of the country. A cold front will cross the eastern U.S. and exit the coast Thursday night, with moderate to heavy rainfall ahead of it from the Lower Mississippi River Valley to the central Appalachians, and a return to colder weather behind it to close out the work week. ...Guidance/Predictability Assessment... The 12Z model guidance suite is in great synoptic scale agreement across the country through the middle of the week, with a general deterministic model blend working well for frontal placements and pressures. There is also decent agreement on a corridor of enhanced QPF from the Deep South to the Ohio Valley and central Appalachians, but differ on latitudinal placement, with the ECMWF and AIFS guidance to the south of the GFS/UKMET/NBM. Model guidance remains in good agreement going into the Friday/Saturday time period as well, with some normal mesoscale differences. The GFS is a little to the west with the upper low over the Desert Southwest compared to the ECMWF/CMC, and the CMC is more broad with the upper ridge off the Oregon/Washington coast by Saturday, but in both instances these models are all able to be incorporated into the blend, with the ensemble means increased to about 30-40% by this time. ...Weather/Hazards Highlights... The upper-level low will continue to meander over central to southeastern Canada through the medium-range period, bringing a series of shortwaves rotating around the base of the mean trough. This will support multiple frontal passages and waves of precipitation across Central/Eastern U.S. The associated cold air behind the front and cyclonic flow will bring below normal temperatures across the northern/central Plains into much of the eastern U.S., with frost/freeze conditions from the Upper Midwest to the Great Lakes. Ahead of the cold front, expect showers and thunderstorms across Upper Midwest/Mississippi Valley, Ohio/Tennessee Valley, Great Lakes and Northeast on Tuesday, with gusty winds across from the Southern Plains to the Ohio Valley and into the Northeast. As the front slowly moves southward and interacts with warm Gulf moisture, showers and thunderstorms will expand into the Mid-South, Mid-Atlantic, and Southeast by Wednesday. With the combination of upper-level forcing and organized thunderstorms producing heavy rainfall along the front, localized flooding may be possible across the mid/lower Mississippi Valley into the Ohio/Tennessee Valley Wednesday into Thursday. This flood threat is represented by the Marginal Risk on the Day 4/Tuesday ERO. Going into Wednesday, the front slows down some, allowing for an influx of moisture along the boundary over the Southeast and the Tennessee Valley, supporting locally heavy rainfall. With flooding concerns over the area, the Marginal Risk has been expanded for the Day 5/Wednesday ERO for parts of the Ohio/Tennessee Valley, lower Mississippi Valley, and the Southeast. There is a good possibility that a Slight Risk could eventually be needed over portions of the outlook area in later updates. As cold air pushes into the Northern U.S., there is a slight chance for some mixed precipitation over some isolated higher- elevation areas/northern areas near the U.S. Canada border, but impacts will be minimal. In addition, colder air behind the upper low ejecting from the Southwest U.S. will also bring below normal temperatures into California and the Desert Southwest, where temperatures will drop 5-15 degrees below average into midweek before moderating late in the week. Over the western U.S., the Pacific upper low/trough will move into the Southwest early in the period, then gradually ejects into the Plains by late week. This will bring sufficient moisture and instability to support widespread low elevation showers and possible thunderstorms, as well as some high elevation snow across parts of California and Great Basin. The cold front associated with the leading edge of the cold air intrusion into the High Plains will drop into the Rockies/Plains on Tuesday, expanding the chance for showers and thunderstorms, with a cold rain for the Front Range of Colorado to southern Wyoming through Wednesday and heavy snow for the Colorado Rockies. Over the Pacific Northwest, a ridge will push inland, bringing a warming trend. As the ridge continues to move eastward, above normal temperatures will return across much of western U.S. later next week. Oudit/Hamrick 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw $$