donsutherland1

EPS ensembles:

When 2022-23 is added, its numbers impact the means and standard deviations.

Roger, Please find below: 1. The final rankings 2. Rankings through March 10th, excluding 2022-2023 3. Rankings through March 22nd (to reflect the impact of 1997-1998's 5.0" snowfall) 4. Rankings through March 10th, including 2022-2023

A cooler regime is now developing. The March 13-20 timeframe could be the month's coldest week with temperatures averaging 4°- 7° below normal for the week. Nevertheless, severe late-season cold is unlikely. The colder regime will gradually fade afterward, but will likely persist through the closing week of March. A storm will likely bring rain to the coastal plain on this evening into tomorrow. As the storm moves away tomorrow, the rain could end as a period of snow from Philadelphia to New York City. Well north and west of New York City and Newark, 1"-3" of snow could fall. Generally 0.5" or less appears likely in Philadelphia, Newark, and New York City. Another larger storm could affect the region during the March 13-15 timeframe. The coastal plain again risks seeing more rain than snow. Cities including Albany, Binghamton, and Concord, along with higher elevations could be in line for a substantial snowfall. Parts of central New York State, upstate New York, and central New England have a chance to see 1-2 foot amounts. Historic experience with very low snowfall totals through February argues that a very snowy March or big snowstorm during March or April are unlikely. There were 16 winters that had less than 8" of snowfall through February in New York City. Just two (13%) had a 6" or greater snowstorm during March or April: 1889-1890: 6.0" on March 19th and 1991-1992: 6.2" on March 19th. With just 2.3" snowfall through March 10, New York City is at growing risk of seeing winter 2022-2023 finish with less than 10" of snow. Since 1869-70, 82% of winters with less than 8" of snow through March 10 wound up with less than 10" seasonal snowfall. All such winters wound up with less than 20" of seasonal snowfall. The ENSO Region 1+2 anomaly was +1.1°C and the Region 3.4 anomaly was -0.2°C for the week centered around March 1. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.48°C and the ENSO Region 3.4 anomaly has averaged -0.43°C. La Niña conditions have now given way to neutral ENSO conditions. Neutral ENSO conditions will likely prevail through at least mid-spring. The SOI was +5.17 today. The preliminary Arctic Oscillation (AO) was -1.297 today. On March 8 the MJO was in Phase 8 at an amplitude of 4.281 (RMM). The March 7-adjusted amplitude was 3.913 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a colder than normal March (1991-2020 normal). March will likely finish with a mean temperature near 42.0° (0.8° below normal).

Latest NWS forecast:

I’m just referring to the timeframe of the storm. For NYC and nearby areas, Tuesday could be the better bet. We should get a lot of precipitation and strong winds, even if the snow disappoints.

For now, it seems reasonable for Monday-Tuesday.

Select EPS Data:

Latest EPS ensemble members for NYC:

With the temperature likely to remain at or above 35° throughout the precipitation event tonight and tomorrow in New York City, historical odds support growing model support for less than 1" of snow in Central Park. Almost three-quarters of events with a minimum temperature of 35° or above (n=23 from 1869-present), saw less than 1" of snow. My thinking remains 0.5" or less for New York City and Newark with a risk that either or both cities could see no measurable snowfall whatsoever.

The NBM comes out hourly.

The UKMET has, unfortunately, backed off from big snows around the NYC area.

12z HREF:

Yes. I agree that there will probably be 24" amounts in some inland areas. Central and Upstate New York into parts of adjacent New England might be plausible candidates right now. There could still be changes.

It's possible that further cutbacks will be coming with this afternoon's package, especially for the coastal plain. The ensembles were never really on board (low agreement). The National Blend of Models was very persistent in showing low amounts. The most aggressive NBM numbers were 1.0" for Allentown and 0.6" for NYC (now 0.2" and 0.0" respectively on the 14z run). The Norlun trough was a wildcard, but they are very difficult to predict.

EPS ensemble members for NYC: This storm has a lot more potential and there is sufficient time for things to change significantly. At this point in time, the ensemble guidance is suggesting this could be a potentially massive snowstorm well inland (i.e., Albany, Binghamton, Concord, Scranton) and at higher elevations (Catskills, Poconos, etc.). About one-in-four ensemble members shows Boston with 10" or more. The operational ECMWF is sort of an outlier for the coastal plain in depicting around 10" for NYC. That's where the ensembles stand now. Things remain subject to significant change.

Latest EPS members for NYC for the upcoming system: My thinking at this time is 0.5" or less in NYC and 1"-3" 25-30 miles north and west of the City.

March 1997 and March 2015 also had extreme amplitudes in Phase 8.

A colder regime is poised to develop in coming days, even as no severe March cold appears likely. The March 13-20 timeframe could be the month's coldest week with temperatures averaging 4°- 7° below normal for the week. The colder regime will gradually fade afterward, but could persist through the closing week of March. A storm will likely bring rain to the coastal plain on Friday into Satuday. As the storm moves away on Saturday, the rain could end as a period of snow from Philadelphia to New York City. Well north and west of New York City and Newark, 1"-3" of snow could fall. Generally 0.5" or less appears likely in Philadelphia, Newark, and New York City. However, there remains a degree of uncertainty. Another larger storm could affect the region during the March 13-15 timeframe. Although this storm appears capable of bringing more snow to the region, the coastal plain again risks more rain than snow. There is a larger degree of uncertainty concerning this potential event. The picture should become clearer by the weekend. Historic experience with very low snowfall totals through February argues that a very snowy March or big snowstorm during March or April are unlikely. Despite attractive 500 mb patterns, the base case is that at least through March 10th, snowfall will likely be below normal from Philadelphia to New York City. For further historical perspective, there were 16 winters that had less than 8" of snowfall through February in New York City. Just two (13%) had a 6" or greater snowstorm during March or April: 1889-1890: 6.0" on March 19th and 1991-1992: 6.2" on March 19th. Historical perspective argues for caution when the operational models are popping big snowstorms into and out of existence like quantum particles in the extended range. The ENSO Region 1+2 anomaly was +1.1°C and the Region 3.4 anomaly was -0.2°C for the week centered around March 1. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.48°C and the ENSO Region 3.4 anomaly has averaged -0.43°C. La Niña conditions have now given way to neutral ENSO conditions. Neutral ENSO conditions will likely prevail through at least mid-spring. The SOI was +5.93 today. The preliminary Arctic Oscillation (AO) was -1.533 today. On March 7 the MJO was in Phase 8 at an amplitude of 3.856 (RMM). The March 6-adjusted amplitude was 3.659 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 56% probability that New York City will have a colder than normal March (1991-2020 normal). March will likely finish with a mean temperature near 42.0° (0.8° below normal).

When it comes to each storm, using the soundings is far better. My point was to illustrate that in March, one should be cautious about using 10:1 maps. To illustrate my point about winters and somewhat higher ratios, for January, 10:1 or above ratios for 32° or below temperatures in NYC occurred 46% of the time and 12:1 or above ratios occurred 25% of the time. 15:1 or above ratios occurred 13.5% of the time, just slightly below the frequency of 12:1 ratios for March.

No. This approximation doesn’t consider conditions in the snow growth zone. Winter snow growth is usually better resulting in higher ratios.

Snow:Rain Ratios for New York City for March (1950-2022):

On Twitter, there has been a proliferation of 10:1 snow maps. During March, ratios tend to be lower than 10:1. As a very rough approximation, below is some data for Philadelphia's March snowfalls (precipitation of 0.10" or above) from 1950-2022 based on daily mean temperature. The kind of hourly data needed for a finer analysis is not available. Smaller precipitation amounts e.g., 0.01", can lead to skewed outcomes.

Morning thoughts… It will be partly sunny and pleasant. High temperatures will reach the upper 40s and lower 50s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 50° Newark: 53° Philadelphia: 53° Somewhat cooler than normal to near seasonable readings will likely prevail through the remainder of the week. Normals: New York City: 30-Year: 47.5°; 15-Year: 48.1° Newark: 30-Year: 48.5°; 15-Year: 49.3 Philadelphia: 30-Year: 50.3°; 15-Year: 50.6°

EPS members for NYC for Friday into Saturday: Ensemble support for a big snowfall in NYC, Newark, and their suburbs early next week is low on the ensembles. The 0z ECMWF is an outlier for the suburbs. For example, the ECMWF shows 11" for White Plains. However, just 3 of 51 (6%) of ensemble members show 10" or more. Even Binghamton, for which the ECMWF showed 29", had just 6 of 51 (12%) of ensemble members with 10" or more. While the storm can't be written off just yet, a lot more support will be needed to have confidence in a big snowfall idea.