While skies are clear now, there is
enough low-level moisture to create a challenging sky cover and therefore low
temperature forecast tonight. Low clouds are already approaching from southern
Ontario and are somewhat more expansive than most models show. Winds will be
light (though out of the south), and there is fresh snow cover after yesterday’s
heavy lake effect snow, so temperatures will fall rapidly during any period of
clear skies. KART experiences very pronounced radiational cooling, much more
than model guidance, in these conditions. (As an example, it reached -7F last
night!) However, if the clouds are persistent, it will stay much warmer all
night. I am betting on at least some breaks in the clouds to cause brief quick
temperature dips, especially at the beginning (Tuesday 06z) or perhaps more
likely around sunrise, but not enough to cool down to its full potential. There
is a wide range of possible low temperatures. The high is somewhat less
uncertain, with clouds dissipating and almost full sunshine with a bit of southerly
winds starting to come in leading to a rapid warmup, though the snow cover
could prevent it from racing past model guidance.
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