donsutherland1

HRRR for tomorrow morning:

It’s unfortunate that such an accident occurred.

Scranton -2 (tied record from 1960) and Mount Pocono -9 (old record: -6, 1989).

I didn’t.

It was a turboprop.

I believe that reference to a single measurement pertained to the measurement of snow depth for a white Christmas.

The day got off to a frigid start. The low temperature in New York City was 13° while it was 11° in Philadelphia. Outside the cities, widespread single-digit readings were recorded. Low temperatures included: Albany: -4° Allentown:1° Atlantic City: 8° Boston: 10° Bridgeport: 9° Danbury: 2° Farmingdale: 11° Groton: 7° Hartford: 5° Islip: 10° Meriden: 6° Montgomery: -5° Mount Pocono: -9° New Haven: 10° New York City-Central Park: 13° New York City-JFK Airport: 12° New York City-LaGuardia Airport: 12° Newark: 11° Oxford: 0° Philadelphia: 11° Poughkeepsie: -2° Providence: 9° Reading: 8° Trenton: 5° Westhampton: 1° White Plains:6° Wilmington, DE: 9° Worcester: 4° Tomorrow will be variably cloudy. Snow showers are likely as a clipper passes north of the region. Parts of the region could experience a heavier snow shower or snow squall that could briefly create low visibilities and drop a coating to an inch of snow with a few locally higher amounts. The cold will begin to recede late in the week. December will likely close with above normal temperatures. The opening days of January will likely also begin with above normal temperatures, but it will start to turn colder. Snowfall prospects will remain limited through the end of December. However, the pattern could become more favorable for moderate or perhaps larger snowfalls as the cold returns during the first week of January. On account of a lack of snowfall, 2023-2024 will likely set a new records for the lowest snowfall over a two-year period for Boston and New York City. Boston: 2023-2024 Total to Date: 26.7"; Record: 38.2", 1979-1980 New York City: 2023-2024 Total to Date: 11.6"; Record: 17.4", 1997-1998 In past days, an occasional run of the operational GFS showed a significant snowstorm from Washington, DC to New York City. However, the pattern makes such an event very unlikely for this region. Since 1950, there were 5 December snowstorms that brought 6" or more snow to all three of these cities. Four (80%) occurred with a PNA+/NAO- pattern. The NAO is forecast to be positive. In addition, three (60%) occurred when the MJO was in Phase 8, which is not likely over the next 10 days. Only the December 23-25, 1966 event produced 6" or more snow in all three cities with a positive NAO, but the AO was strongly negative (< -2.000), which is not likely during the next 10 days. In sum, the interior sections will be far more favored for an appreciable or perhaps greater snowfall than the Washington-Baltimore-Philadelphia-New York City area over the next 10 days. A smaller snowfall remains plausible, as occurred during December 20-21 and is possible from tomorrow's snow showers or snow squall. The NAO fell to a preliminary -2.751 on September 24th (all-time September record: -2.371, September 12, 1971). That was the 9th lowest value on record. La Niña winters following September cases where the NAO fell to -1.900 or below featured a predominantly positive NAO. The most recent such winters were 2016-2017 and 2022-2023. The mean temperatures for those winters in New York City were 39.3° and 41.0° respectively. The 1991-2020 normal value is 36.2°. A warmer to much warmer than normal outcome is favored by the November run of the ECMWF for Winter 2024-2025. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.8°C for the week centered around December 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.17°C and the ENSO Region 3.4 anomaly has averaged -0.35°C. Neutral ENSO conditions may still evolve into a La Niña event during the winter. Uncertainty as to whether a La Niña will actually develop persists. On the December 19 outlook, 56% of dynamical models but 0% of the statistical models forecast the development of a La Niña. The SOI was -0.73 today. The preliminary Arctic Oscillation (AO) was -0.590 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 96% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.0° (2.1° below normal).

So far, the GEFS continues to suggest that the strongest shots of cold during the evolution of a colder pattern in January will dump into the West. There remain questions about the timing of the onset of the colder pattern in the East. The EPS (through 0z) had remained faster than the GEF (through 12z). Both support the development of a pattern that could become more favorable for moderate (4"+) or, if the PNA+ persists, significant (6"+) snowstorms than has been the case all winter so far. Whether there will be short waves present to produce the storminess remains to be seen. Below are cases for severe multi-day cold shots that reached the East during the first half of January (1980-2024). Finally, the cold start to December and 1.8" snowfall to date in New York City make it unnecessary to post "winter futility charts" at this time. Indeed, out of 156 winters (which includes 2024-25), Winter 2024-25 ranks 65th worst in terms of cold and snow (standardized basis) through December 22nd for New York City.

It would be nice to see a decent snow squall give NYC enough snow to assure the 1" snow cover at 7 am 12/25. Hopefully, the high-res models will provide good insight into the intensity and duration of the possible snow squall line.

JFK: 11/21/1987 LGA: 11/22/2018 NYC: 11/16/1933

Central Park likely had 1" snow cover on December 25, 1998. 2.0" fell on December 24th and the high that day was 32°.

The frequency of New York City's high temperatures of 21° or below:

High or low temperature?

The week was actually colder than normal in the Northeast unlike the ECMWF weekly forecast. Measurable snow fell in Boston, New York City and Philadelphia. Boston's record 1,028-day snow drought without 4" or more snowfall ended on December 20th when 5.2" fell.

Parts of the region saw their coldest temperatures in nearly two years. Overnight low temperatures included: Albany: 2° (coldest since February 4, 2023) Allentown: 7° (coldest since January 18, 2024) Boston: 11° (coldest since February 4, 2023) Bridgeport: 13° (coldest since February 4, 2023) Hartford: 11° (coldest since January 22, 2024) Islip: 17° (coldest since January 22, 2024) New York City: 15° (coldest since February 4, 2023) Newark: 17° (coldest since January 18, 2024) Philadelphia: 17° (coldest since January 22, 2024) Providence: 11° (coldest since February 4, 2023) Today's high temperature in New York City was 21°. That was the coldest high temperature since December 24, 2022 when the temperature topped out at just 15°. It will again be very cold tonight. Low tempertaures tomorrow morning will again be in the teens in Philadelphia and new York City. Many areas outside those cities will likely experience single-digit lows. High temperatures will reach the upper 20s in New York City and upper 20s to near 30° in Philadelphia. Tuesday could see a few snow showers as a clipper passes north of the region. The cold will begin to recede after midweek. December will likely close with above normal temperatures. The opening days of January will likely also begin with above normal temperatures, but it will start to turn colder. Snowfall prospects will remain limited through the end of December. However, the pattern could become more favorable for moderate or perhaps larger snowfalls as the cold returns during the first week of January. On account of a lack of snowfall, 2023-2024 will likely set a new records for the lowest snowfall over a two-year period for Boston and New York City. Boston: 2023-2024 Total to Date: 26.7"; Record: 38.2", 1979-1980 New York City: 2023-2024 Total to Date: 11.6"; Record: 17.4", 1997-1998 In past days, an occasional run of the operational GFS showed a significant snowstorm from Washington, DC to New York City. However, the pattern makes such an event very unlikely for this region. Since 1950, there were 5 December snowstorms that brought 6" or more snow to all three of these cities. Four (80%) occurred with a PNA+/NAO- pattern. The NAO is forecast to be positive. In addition, three (60%) occurred when the MJO was in Phase 8, which is not likely over the next 10 days. Only the December 23-25, 1966 event produced 6" or more snow in all three cities with a positive NAO, but the AO was strongly negative (< -2.000), which is not likely during the next 10 days. In sum, the interior sections will be far more favored for an appreciable or perhaps greater snowfall than the Washington-Baltimore-Philadelphia-New York City area over the next 10 days. A smaller snowfall remains plausible, as occurred during December 20-21. The NAO fell to a preliminary -2.751 on September 24th (all-time September record: -2.371, September 12, 1971). That was the 9th lowest value on record. La Niña winters following September cases where the NAO fell to -1.900 or below featured a predominantly positive NAO. The most recent such winters were 2016-2017 and 2022-2023. The mean temperatures for those winters in New York City were 39.3° and 41.0° respectively. The 1991-2020 normal value is 36.2°. A warmer to much warmer than normal outcome is favored by the November run of the ECMWF for Winter 2024-2025. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.6°C for the week centered around December 11. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.17°C and the ENSO Region 3.4 anomaly has averaged -0.27°C. Neutral ENSO conditions may still evolve into a La Niña event during the winter. Uncertainty as to whether a La Niña will actually develop continues to increase. Currently, 47% of dynamical models and 22% of the statistical models forecast the development of a La Niña. The SOI was -2.70 today. The preliminary Arctic Oscillation (AO) was -0.451 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 92% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.2° (1.9° below normal).

December 7, 2002: -1°

The last time Central Park was below 5° was February 4, 2023 (3°). JFK's last time was February 4, 2023 (4°). LGA's last time was January 31, 2019 (3°).

The probability that a colder pattern could begin evolving during the first week of January has increased. That does not guarantee the rapid onset of severe cold. Below are the composite maps for multi-day periods of severe cold during the first half of January since 1980: Below are the 12/21 6z and 12z runs of the GFS vs. the 12/22 6z and 12z runs: Below are the temperature anomalies for the last six runs of the GFS: Key Points: Even as the probability of an evolution toward a colder pattern during the first week of January has increased, that outcome does not mean that there would be a rapid outbreak of severe cold in the eastern half of the CONUS The timeframe involved is still subject to considerable change (as seen in the recent GFS runs) The GFS briefly showed a 500 mb pattern consistent with multi-day shots of severe cold in the eastern half of the CONUS, but has since backed away. Whether that means any such outbreaks would be delayed or that the cold would dump into the West only to reach the East in modified form remains to be seen (the 12z ECMWF still brings the severe cold early with a pattern that is somewhat similar to Cluster 2) The ECMWF weeklies suggest that there will be a multi-week pattern of below normal temperatures in the East, though the CFS is more muted on the outcome Separately, with January opening with a forecast AO-/PNA+ pattern, the potential of moderate (4" or more) or perhaps significant (6" or more) snowfall could increase in an area including Boston, Chicago, Detroit, New York City, Philadelphia, Toronto, and Washington, DC. A persistent PNA+ pattern would be more important for New York City, Philadelphia, and Washington, DC. Needless to say, short waves that would be candidates for such storms would be needed. Those are details that cannot be forecast reliably on multi-week timeframes.

With prospects for a significant snowfall (6"/15.2 cm or above) in Philadelphia and New York City low for the remainder of December, a look ahead at favorable patterns for January is in order. Since 1950, 16 January storms brought 6"/15.2 cm or more snow to both Philadelphia and NYC. Let’s see if January can deliver.

Week Ahead: A generally cold but quiet week lies ahead. Temperatures will moderate after midweek.

For today's measurable snowfall: JFK: 0.12"; LGA: 0.12"; NYC: 0.15"

Yes. That’s correct for Central Park.

I thought that it would come in at 2” or a little above based on reports in the Bronx and Manhattan. I suspect that the measurements occurred at 7 am and again at 1 pm, which would miss the snow that fell after 7 am.

Unfortunately, a lot of international data is not accessible, so it's difficult to be sure.

Phoenix also recorded 21 consecutive record-tying or record-breaking high temperatures, by far a new national record. Today, Phoenix has tied its record high (so far). This year, it has tied or broken 124 daily record highs, record high lows, or record high means.