Discussion: The upper (250mb) jet is expected to remain over or just N of New Jersey for the immediate forecasting period (through first few days of 2020). 500mb geopotential height anomalies will correlate with above-average values through Dec 31 until a closed-off upper-level low passes through just to the N of New Jersey. This could take our temps down a bit from New Years eve through about January 3. Then a small moderation of mostly average upper-level heights Jan 4-5 followed by a hard injection of cold air ~Jan 5-6 (full trough spill). The data beyond the Jan 5-6 cold shot arrival is outside of the confidence period. Therefore it is uncertain how long the cold will stay around. At the very least a few days in the result of a transient cold shot. Possibly longer if any sort of blocking sets up. Regardless the chance of a winter storm until the Jan 5-6 cold shot is low. Some snow showers are possible in the New Years Eve/Day period but nothing serious. Mostly likely lake effect streamers with NW flow. There’s a weak signal on Jan 3 but would likely be an elevation snow shower event with little-to-no accumulations (rain for most of NJ). On Sunday, when I do the Monday-Friday outlook, we should be able to gain a few days further of confidence regarding the duration of the Jan 5-6 cold arrival.
Friday (Dec 27) high temperatures should range from near-50 to mid-50s NNJ to SNJ. Skies should be mostly cloudy during the day with a chance for passing light rain showers. Skies should clear into overnight hours. Winds should be light out of the SW. Overnight lows should fall into the mid-to-upper 30s for most areas.
Saturday (Dec 28) high temperatures should reach near-50 for most areas. Skies should be mixed with sun and clouds. Winds should be light out of the NW. Overnight lows should range from mid-20s to mid-30s NNJ to SNJ.
Sunday (Dec 29) high temperatures should range from near-40 to near-50 NNJ to SNJ. Skies should transition from partly sunny to mostly cloudy throughout the day with rain showers possible afternoon through evening. Winds should be light out of the E. Overnight lows should range from mid-30s to mid-40s NNJ to SNJ.
An early look at next week indicates the mild and benign (for winter) pattern lasting through New Years and into next weekend. The only chance for snow at the moment are light snow showers around the New Years Eve period. The next expected cold shot is around the ~January 5-6th period and its duration is uncertain from this range.
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