March 20: Rainstorm Approaching

Jonathan Carr
By Jonathan Carr March 20, 2019 12:24

March 20: Rainstorm Approaching

Discussion: A few pieces of upper-level energy will come together (phase) and produce a rain & wind storm for the Mid-Atlantic and NorthEast US. Overall timing impact for New Jersey is between late-tonight (Wednesday) and early Friday AM with the meat and potatoes of the rain and wind expected between late Thursday morning and Thursday evening. In general the data and observations are indicating about a half-inch to 1.5 inches of total rainfall. I wouldn’t be surprised to see some localized amounts of near or slightly-above 2 inches.

The coastal surface low’s center of circulation should take a track along the I-95 corridor. This puts many areas to the S and E of the low during it’s movement. Therefore NJ should simply be too warm for snow. There is more of a concern for flooding either in the form of flash flooding statewide from heavy rainfall or coastal flooding from wind-driven storm surge. It’s impossible to determine where the heaviest bands of rain will set up but again, since we have the passing low in close-proximity,  flash flooding is possible under any such mesoscale convective bands. Most of the SNJ/SENJ coasts should experience mild, possibly moderate, levels of coastal flooding but nothing major/catastrophic. The highest risk for coastal flooding appears to be the back/furthest inland parts of the Raritan Bay and Long Island Sound.

Winds should be very volatile as the cyclone moves a few different air masses around. High pressure out in the ocean is moving away and already generating a weak SE onshore flow. This onshore flow should gradually pick up tonight through tomorrow as the low approaches from the S. These kind of systems produce higher winds along the immediate coast when compared to inland. Therefore let’s break inland vs coastal winds down. Inland areas should expect sustained winds of 10-15mph with gusts of 25-30mph possible. Immediate coastal areas should expect sustained winds of 15-20mph with gusts to 30-40mph possible. Peak wind conditions should occur between late-Thursday morning through Thursday afternoon and into Thursday evening. While the wind is off the ocean temperatures should be in the 50s statewide with coastal areas possibly hanging in the 40s. Once the low gets N of NJ latitude then winds will switch to the N/NW and rush much colder air in for the Friday-Saturday period. We can’t rule out snow flurries on Friday with the strong N/NW flow behind the departing low.

The low should then strengthen for coastal New England and SE Canada. Looks like a pretty solid cyclone wrap-up after essentially sparing NJ with the worst conditions. Once again the back-side N/NW flow will keep us cold Friday and Saturday but some good spring weather is on-tap for Sunday. I see more volatile ups and downs for next week. Anything but a sustained warmth look. We can’t be that much further from such however.

In English: Rain should move in tonight (Wednesday) from S to N and reach all of NJ by early Thursday AM. Rainfall should intensify through Thursday late-AM and PM hours before tapering off by either late-Thursday PM or early-Friday AM. Winds should also intensify off the ocean tonight through tomorrow. A minor-to-moderate risk of flash and coastal flooding exists especially surrounding the two Thursday high tides (just before noon and just before midnight). Can’t rule out an embedded thunderstorm during peak storm conditions (Thursday PM). We then turn back to cold for Friday and Saturday before moderating back to mild for Sunday. Everyone have a great rest of your Wednesday and please be safe! JC

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Jonathan Carr
By Jonathan Carr March 20, 2019 12:24