421 FXUS02 KWBC 191924 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 324 PM EDT Sun Apr 19 2026 Valid 12Z Wed Apr 22 2026 - 12Z Sun Apr 26 2026 ...Overview... Unsettled weather will persist through the period as a Pacific mid/upper-level trough pushes across the Great Basin, Intermountain West and northern Rockies before ejecting eastward into the Northern Plains mid to late week. This system will bring very strong winds and widespread precipitation, including low elevation rain and heavy mountain snow. As the trough and its associated surface low interacts with surging Gulf moisture over the central U.S., episodes of heavy rain and severe weather will become more likely Thursday and Friday. Cooler than normal temperatures will expand from the western U.S. to the central U.S. behind a strong eastward advancing cold front. ...Guidance/Predictability Assessment... The latest model guidance continues to have a fairly decent grasp of the large scale pattern through the medium range period. That being said, uncertainty remains relatively high within the smaller scale details of a dynamic mid/upper-level Pacific low/trough, especially for Day 5 and beyond. Given the uncertainty, the WPC forecast leaned more heavily into the ECMWF and GEFS ensemble means to smooth out the small scale differences, with weighting of the means increasing to 40% by Day 5 and 60% by Day 7. Additionally, the weighting of deterministic models leaned more on the 00Z EC and the 06Z GFS, with less weighting on the 00Z CMC and 00Z EC-AIFS given more emphasis on the development of the lead wave vs the kicker wave. Despite these preferences, solutions involving multiple shortwaves rotating within and around the parent low are notoriously volatile, so continue to expect run-to-run changes in the near term before solutions stabilize. ...Weather/Hazards Highlights... The Pacific system and amplified trough lifting across the western U.S. will support unsettled conditions from California into the Great Basin and central/northern Rockies on Wednesday. Multiple embedded shortwaves rotating within and around the base of the trough will bring periods of widespread low elevation rain and mountain snow, with locally heavy precipitation possible along favored terrain. Accumulating snow will primary be confined to higher elevations, with impacts limited to high mountain passes and mountain towns. In addition, strong gusty winds are expected as the system moves across the Intermountain West into the Plains and Mississippi Valley through the week. By Thursday, the deepening Pacific system ejects eastward into the Plains, setting the stage for late week heavy rain and severe weather threats as rich Gulf moisture surges northward. Large scale forcing combined with increasing instability along and ahead of a strengthening surface low and strong cold front will likely result in the development of widespread clusters of strong to severe thunderstorms capable of producing heavy rainfall and isolated flash flooding. This flooding threat is highlighted by a Marginal Risk in the Day 5/Thursday ERO, which has been expanded in areal extent with the afternoon update given a larger QPF footprint. Given increasing soil moisture from previous bouts of convection, an upgrade to a Slight Risk is not out of the question in future updates. Farther south, scattered to numerous showers and thunderstorms are possible across parts of southeast Texas and southwest Louisiana on Wednesday. Sufficient instability and above normal moisture will support another risk for localized flash flooding concerns, continuing from Day 3/Tuesday. As a result, decided to introduce a Marginal Risk in the Day 4/Wednesday ERO to account for this isolated threat. Elsewhere, a relatively weak cold front will continue to push through the Ohio Valley, Mid-Atlantic, and Northeast Wednesday into Thursday, bringing chances for isolated to scattered showers. Otherwise, much of the Desert Southwest and Southeast will be mainly dry next week, before the cold front drops into the Southern Plains/Mississippi Valley by Friday. As the front pushes eastward, showers and thunderstorms may develop Friday into the weekend. Below normal temperatures over the western U.S. will continue through the period with temperatures dropping 10-15 degrees below average across California on Wednesday behind the cold front. Ahead of the system, temperatures 20-30 degrees above average will persist over the central U.S. on Wednesday. As the cold front pushes into the Plains by Friday, above normal temperatures gradually move eastward by the end of the week, while below normal temperatures will spread into northern/central Plains and Midwest by the weekend. Over into the West, temperatures will begin to moderate late in the period. Miller/Oudit 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 $$