Long Range Weather Forecast Discussion May 8-22
James Munley
Long Range Weather Forecast Discussion May 8-22
252 PM EDT Tue. May 5, 2026
May 8-12: An upper-level low over eastern Canada will continue to send multiple shortwaves across the East. This will keep conditions cool and wet. A ridge is forecast in the West with a trough in the East.
An upper-level low over eastern Canada will continue to send multiple shortwaves across the East. This will cause cool and unsettled weather across the central and eastern states. Frontal passages will cause showers and storms across the eastern and central states through Monday. A lingering frontal boundary across the lower Mississippi Valley into the Southeast will cause rain across the area. Below-normal temperatures will continue across the Great Lakes into the Northeast through the weekend. A warming trend will occur across much of the western and central states.
May 13-17: The eastern trough will lift out and be replaced by brief ridging with another trough sinking into the north-central states. The GFS ensembles depict a ridge, trough, and ridge pattern from the West Coast to the East.
A system develops in the Plains early next week with rain and thunderstorms. The system progresses east to the Midwest and the East Coast by Thursday, spreading rain and storms in its path from the southern Plains to the Northeast. The next system moves across the northern states into the Northeast by Sunday. This will push a front east. Rain will be possible by the end of the period.
Above-normal temperatures are forecast for most of the Plains to the Pacific Coast. Anomalies could be near or greater than 8°F in parts of the Northwest and the northern Rockies. Below-normal temperatures are forecast across the eastern U.S. Anomalies could be near 6°F across New England.
Below-normal precipitation is forecast for northern California, the Northwest, the northern and parts of the central Rockies, the Plains, and the Mississippi Valley, parts of the Gulf Coast, and the Midwest. The probability of occurrence is 35 percent. Above-normal precipitation is forecast for parts of the northern Plains to the Northeast. The probability of occurrence is nearly 43 percent.
May 18-22: There is expected to be a gradual flattening of the flow during this period. The ECMWF is faster at bringing above-normal heights across the country. The ensembles exhibit a trough-ridge-trough pattern across the country. The ECMWF AI has a split flow in the West with a trough from Canada into the Plains and Mississippi Valley. The GFS AI has an upper low in the West and the western Atlantic.
A front will bring rain from the middle Mississippi Valley to the Mid-Atlantic. Rain is expected across the Rockies with snow in the higher elevations.
Above normal temperatures are forecast from the Mississippi Valley to the Pacific Coast. Anomalies are expected to be near or greater than 8°F.
Little change is expected in the precipitation anomaly forecast from the previous period.
Jim Munley
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