A light snow event is currently affecting the area after a week-long break from snow, with up to 1 inch expected. A brief surge of much colder temperatures is expected Thursday night into Friday, falling into the single digits for most locations overnight and reaching the mid 20s for highs. More widespread clouds will build into the region as a widespread storm system affects the region on Sunday and Monday, with a high probability of snow despite the time of the year entering March (Image credit: PSU e-Wall).
12pm Short Term Update
As of 12pm, most of the snow showers have progressed offshore, but with an area of moderate snow squalls over Long Island which will continue to track east through 1-2pm, producing areas of moderate to locally heavy snow and lower visibility. These squalls are expected to produce up to 1 inch of snow, with locally higher totals under the heavier snow squalls. Another back end line of light-moderate snow showers is developing over north central NJ into SE NY, and will continue to progress ESE as well with light to moderate snow over the next hour expected to affect NE NJ, SE NY/southern CT and NYC.
Today – Saturday: Light Snow Today, Cold Ending To Week
Posted above from left to right are the latest surface analysis and radar composite from WPC, and the initialized GFS 500 millibar heights and vorticity from NCEP MAG; both are valid at 12z (7am). After a week-long pattern relaxation, winter has returned into the northeast US, first marked by the return of colder than average temperatures beginning Monday. Focusing on the eastern half of the US, widespread light snow can be seen extending from Washington DC into New Jersey, associated with a relatively weak shortwave trough over Ohio. This shortwave will continue to race eastward, with scattered snow showers over the NYC area tapering off by 1-2pm with up to 1/2 inch expected, locally up to 1 inch east and south of NYC. Clearing skies are expected later today with high temperatures peaking early in the upper 20s to low 30s, falling into the upper 10s-mid 20s by the evening hours.
With a highly amplified ridge over the western US extending up to Alaska supporting a strong northerly flow extending close to the North Pole, a strong piece of the polar vortex has surged southwards over the last two days and is currently positioned near central Canada. With the usage of the term polar vortex emerging again, especially following the early January cold outbreak, it is important to remember that the polar vortex is not a feature which forms and dissipates at random times, nor is it a feature that can be visibly observed, but is rather a strong upper level cyclone associated with cold surface temperatures that always exists in some form, and is typically centered near the north pole region but occasionally splits and/or shifts away from the polar regions. In this case, the upper level low over Canada is a strong piece of the polar vortex which split several days ago from a strong upper level low over Siberia, associated with some of the coldest temperatures in the northern hemisphere.
12z run of the high-resolution 4k NAM at hour 48, for 12z Friday (7am), depicting the modeled overnight low temperatures, which are over 20 degrees below average. This model may be too cold for NYC and coastal locations (image credit: PSU e-Wall).
While the core of the cold will remain over southern Canada, the region will again experience a brief round of well below average temperatures. A strong shortwave southwest of the Hudson Bay, associated with this strong piece of the polar vortex, will continue to rapidly progress south, then southeast, reaching New York state on Thursday, aiding in the development of a relatively strong but moisture starved low pressure near northern NY state on Thursday. While overnight lows tonight will fall into the mid-upper 0s inland and the lower half of the 10s elsewhere due to brief clearing with a period of radiational cooling, the southwesterly flow ahead of this low pressure will lead to Thursday’s high temperatures reaching the upper 20s-low 30s again. With a strong pressure gradient behind this low pressure, a period of strong cold air advection is expected on Thursday evening and night with winds from the west-NW at 15-25 mph, gusting up to 40 mph at times. With frigid temperatures just north of the US/Canada border, very cold temperatures are expected on Thursday night, likely falling into the 0 to -5 degree range in interior NW NJ/SE NY, low 10s in NYC and the immediate coast, and the single digits elsewhere, generally in the upper half of the 0s closer to NYC and lower half further inland. This will be accompanied by wind chill values near to below zero, especially away from the coast. Winds will subside on Friday as a high pressure moves overhead, with mostly sunny skies and highs in the low-mid 20s across the area. This is nearly 20 degrees below the Central Park average of a high of 44 and low of 31 for February 28. Central Park’s record low of 5 degrees, set in 1934, is likely to remain unchallenged, but with other record lows likely to be approached and/or surpassed, including 15 degrees in JFK (1950), 12 degrees in LaGuardia (1980), 12 degrees in Islip, NY (2008), and 10 in Bridgeport, CT (1950). Warmer temperatures will return for Saturday with mostly cloudy skies and highs in the low-mid 30s.