Long Range Weather Forecast Discussion
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    Long Range Forecast Discussion February 27-March 11, 2018
    407 EST Sat. Feb. 24, 2018

    Feb. 27-Mar. 3: Models and ensembles are in good agreement on the pattern. A building ridge across the high latitudes of the North Atlantic will result in the development of a rex Block. These positive height anomalies are forecast to gradually shift westward and reach the Labrador Sea late in the week, with the axis of the rex block to shift west as Well. The NAO and the AO will be negative. Models indicate that a cut-off low will be trapped under this highly anomalous ridge. The trough axis will also shift farther west, and with that, the potential for a storm track along the East coast. A negative NAO at this time of year does not guarantee a big coastal event, but chances will be elevated. Positive height anomalies will also build north from the east-central Pacific into the Arctic Ocean.

    Heavy precipitation with higher elevation snow will be possible in portions of the West. Expect below normal temperatures across the West and into the northern Plains through the period. Further east, widespread convection and heavy rains will once again pose a threat of flooding across portions of the lower Mississippi Valley into the Tennessee Valley. A system tracking across the Plains and to the Great Lakes will cause snow in its path. Heavy rain is forecast for the Mid-Atlantic to the Northeast late in the week with snow in New England. Above normal temperatures are forecast in the East.

    Mar. 2-6: Little overall change is expected in the flow. Strong positive height anomalies are forecast over the Aleutians and the high latitudes of the North Atlantic. A trough is forecast in the West and the western Atlantic.

    TEMPERATURES

    Below normal temperatures are forecast for the West and the Northern Plains. Forecast anomalies of 4F are expected. Near to above normal temperatures are forecast for the remainder of the nation. Forecast anomalies of 2F are expected.

    PRECIPITATION

    Above normal temperatures are forecast for the Northwest, the northern Plains, and the upper Mississippi Valley. The probability of occurrence is 35-55 percent. Below normal precipitation is forecast for the Southeast. The probability of occurrence is 40 percent.

    Mar. 7-11: The positive heights over the North Atlantic continues to slide west along with the western Atlantic trough. Positive height anomalies is forecast over the Bering Sea.

    TEMPERATURES

    Below normal temperatures are forecast for most of the nation. Forecast anomalies of at least 4F are expected. Above normal temperatures are forecast for the Four Corners and New England. Forecast anomalies of 4F are expected.

    PRECIPITATION

    Above normal precipitation is forecast for the coastal areas of northern California, Oregon, and Washington. The probability of occurrence is 35 percent. Below normal precipitation is forecast for the four corners and the southeast. The probability of occurrence is 35-55 percent.

    Jim Munley, Jr.
    http://www.jimmunleywx.com



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