Transition day today leads to a nice end to the week

The cold front that had helped to cause the thunderstorms and heavy downpours over the past couple of days is finally working its way through the area, which will gradually clear our skies as the day goes on. However, the front will be slow to move through the area, given the strong western Atlantic ridging. Combining this with an extremely powerful mid and upper level disturbance, placing us in the right-entrance region of the jet stream, there will still be plenty of clouds around and some showers, with locally heavy downpours. That being said, considering the cold front has shifted to the east, the biggest threat for heavy rain should stay to the east of NYC.

4-panel plot of this morning's NAM run, valid for 10:00am. Precipitation still hangs around the coast, with a cooler airmass behind it (top-left), a closed 850mb low in SE Canada leads to very chilly readings in the upper Midwest (top-right), a powerful 500mb low with strong vorticity that helped provide our messy weather still lingers (bottom-left), and a powerful jet streak at 300mb leads to upward vertical motion for clouds and rain (bottom-right). (New York Metro Weather Models)

4-panel plot of this morning’s NAM run, valid for 11:00am. Precipitation still hangs around the coast, with a cooler airmass behind it (top-left), a closed 850mb low in SE Canada leads to very chilly readings in the upper Midwest (top-right), a powerful 500mb low with strong vorticity that helped provide our messy weather still lingers (bottom-left), and a powerful jet streak at 300mb leads to upward vertical motion for clouds and rain (bottom-right). (New York Metro Weather Models)

The powerful 500mb low is actually a piece of the Polar Vortex, which explains why it is so strong and is bringing chilly temperatures to the Midwest, where temperatures even fell into the 30s this morning! Out ahead of it, strong southwest flow persisted for days, providing a conveyor belt of moisture and instability for thunderstorms. Now that the cold front is finally moving eastward, the conveyor belt also shifts eastward, which puts a limit to the coverage of rain. Most of New Jersey should stay rain-free, but clouds will remain for most of the day, thanks to the 100 + knot jet streak shown in the bottom-right panel. Long Island may have to deal with some rain and locally heavy downpours as we head through the morning.

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