Long Range Weather Forecast Discussion December 7-21
James Munley
Long Range Weather Forecast Discussion December 7-21
412 PM EST Mon. Dec. 4, 2023
Dec. 7-11: Heights remain above normal across Greenland with a trough and below normal heights from Siberia into the eastern Pacific. A ridge builds into the West with a zonal flow with below-normal heights across the east-central states.
Pacific energy will reach the West Coast at the start of the period (Thursday) and will aid in the development of an upper trough across the West. The trough will push eastward and result in cyclogenesis in the Plains. The system will track northeast towards the Ohio Valley and Great Lakes and spread precipitation east. Snow will be possible northwest of the low.
Dec. 12-16: Above normal heights are forecast across most of the nation. A trough sinks into the central states.
Above normal temperatures are forecast from the Midwest, Plains to the Pacific Coast. Anomalies are expected to be near 6°F.
Above-normal precipitation is forecast for the Northwest, a portion of the Great Lakes, a portion of the Ohio and Tennessee Valleys, the Southeast, the Mid-Atlantic, and the Northeast. The probability of occurrence is 35-40 percent. Below-normal precipitation is forecast for central and southern California, the southern Rockies, and the central and southern Plains. The probability of occurrence is 35 percent.
Dec, 17-21: A zonal flow is forecast across the nation with below-normal heights in the West and above-normal heights across the remainder of the country. The ECMWF ensembles depict above-normal heights across the nation.
The change in the temperature anomalies forecast from the previous period is to include New York and New England in the 2-4°F above normal anomalies.
Below-normal precipitation is forecast for the northern Rockies, the extreme northern Plains, and the upper Mississippi Valley. The probability of occurrence is near 35 percent. Above normal precipitation is forecast for California, the southern Rockies eastward across the Gulf Coast States, the Southeast, the Mid-Atlantic, and the Northeast. The probability of occurrence is 35 percent.
Jim Munley
Youtube: Jimmunleywx
Twitter: @jimmunley
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