A few updates will be posted below on the rain and thunderstorm event affecting the area today. Radar images are from the Pennsylvania State University e-Wall.
Links: Yesterday’s forecast | Twitter | Facebook
Final storm rain totals in NYC: (Updated 8am)
Central Park – 0.35″ | LaGuardia – 0.35″ | JFK Airport – 0.15″
9:00 AM: Light Snow In LI, CT
Since the previous update, the narrow line of rain moved through the area in the evening, producing generally less than 1/2 inch of rain, followed by a quick drop in temperatures late in the evening, with temperatures in a 2-hour span falling from 54 to 36 degrees in Newark, NJ and from 47 to 31 degrees in Somerville, NJ. Temperatures have continued to fall into the mid 10s-low 20s, and will slowly rise today into the mid to upper 20s with a NW wind at 20-30 mph, gusting up to 45 mph, with wind chill values in the single digits to low 10s. These temperatures are nearly 20 degrees below average.
The area stayed dry following the passage of the cold front, although an extended band of snow is developing over eastern New England, brushing central-eastern CT and the eastern half of Long Island. Light snow showers will continue through the next 2 hours before winding down, with isolated flurries possible through the remainder of the morning.
The next forecast update will be posted late tonight, focusing on the continued temperature swings through the weekend and next week.
5:45 PM: Light Rain Spreading In
As of 5pm, the low pressure was near east central Pennsylvania. Minimum pressure is near 984 mb, and the low continues to slowly deepen while tracking ENE. The low is expected to pass close to NYC later this evening before continuing into coastal New England and just south of Maine tonight.
The area has generally been dry so far, but with a broad area of light to moderate rain currently affecting New Jersey into NYC and Long Island. Rainfall rates are generally light, but with steadier moderate rain observed towards NW NJ and southeast NY. The warmest temperatures remain just south of the area, peaking in the 60s as far north as Trenton, NJ, while generally steady in the low-mid 50s in NYC and northeast NJ and the 40s further inland, falling down to the upper 30s-low 40s in Orange county.
The latest estimated temperatures from the RTMA analysis from the NCEP Model Analysis and Guidance, posted to the left, depicts the placement of the warmest temperatures south of about southern PA into central NJ. These locations may observe locally strong to severe storms with the passage of the cold front this evening, with strong wind gusts the primary concern. Further north into the area, the squall line is expected to move through between about 7:30-9pm, extending into 10pm towards Long Island and CT, with a period of moderate to locally heavy rain, occasional thunder, and strong wind gusts.
Further north, the strengthening temperature gradient can be seen over northern PA into northern NY, with strong cold air advection occurring in these locations in the lower levels. As this occurs, the sharp temperature gradient will continue to gradually shift southeast closer to the area. This will also result in an axis of heavy freezing rain and sleet stretching from the northern Hudson Valley into southern NH/VT and coastal Maine, which can already be seen developing in the precipitation type radar above, as surface temperatures rapidly cool down while southwesterly winds continue in the mid levels as the mid level low is still well to the north of the surface low pressure, tracking over NY state. The strong temperature gradient will move through between 11pm-1am from NW to SE, with temperatures sharply falling from the upper 40s-low 50s into the mid-upper 20s in as little as 2 hours, and continuing to fall from there into the 10s for most locations and low 20s near NYC, coastal CT and Long Island as a strong northwesterly wind develops up to 15-30 mph, gusting up to/over 40 mph, leading to wind chill values in the single digits later tonight into Thursday morning. The anticipated flash freeze will also lead to a risk of black ice tonight into Thursday’s morning commute.