March 1-15: Wintry Start then Moderation

[donsutherland1]

The first half of March is likely to be characterized by the slow retrogression to the Hudson Bay region of a moderate block (an NAO that peaks in the -1.000 to -2.000 range). This period of blocking commenced on February 22 and should continue until sometime in the 3/5-12 timeframe based on the historical experience with moderate blocks that developed in a similar timeframe:

∙ Median duration: 14 days
∙ Mean duration: 15.4 days
∙ Shortest: 7 days (2/26-3/4/1998)
∙ Longest: 23 days (2/26-3/20/1954)

The NCEP ensemble mean 500 mb height anomalies have continued to show this situation quite well, though the overwhelming share of individual ensemble members keep the NAO < 0 through at least 3/10. Based on the historical experience with moderate blocks around this time of year, the current situation should lead to cooler then normal readings for the first 7-10 days of the month, on average, and then moderation afterward. The warming could be most pronounced in the Mid-Atlantic region and southward.

In addition, there should be multiple storm opportunities. Such storms could bring snow to at least parts of the East and Ohio Valley areas. New England will probably see the greatest snows. While moderate storms might be the rule, something along the lines of the February 22-28, 1969 storm, in terms of the area in which snows accumulate with the risk of significant snows there, can’t be ruled out. The best timing would be in the 3/6-8 period and a suppressed solution is less likely than either a mainly New England-focused storm or more widespread moderate to heavy snowfall given the block’s forecast location near the Hudson Bay.

Conclusion:
With the retrograding moderate block being the dominant synoptic element during the first 7-10 days of March, I expect the following:

∙ The 3/1-7 period will likely see readings in the Mid-Atlantic/New England/eastern Great Lakes region average below normal.
∙ The 3/8-15 period should see moderating temperatures with readings averaging out near normal in New England and somewhat above normal in Washington, DC and Richmond and possibly as far north as Philadelphia and New York City.
∙ Accumulating snow is likely during the 3/1-10 period in Boston, Detroit, New York City, and Philadelphia, and Washington, DC. One or more of these cities could pick up 4” or more, with odds favoring the Philadelphia to Boston region.
∙ The 3/3-8 period could feature a significant storm for parts of the East Coast.
∙ With the block having faded, the storm track shift to a Great Lakes trajectory near mid-month (probably in the 3/10-15 timeframe). During this timeframe, readings could surpass 60° on at least one day in Washington, DC and Richmond and perhaps 50° in Detroit.

March Snowfall:
In my view, March snowfall will likely reach:
Boston: 10” or more
Detroit: 7” or more
New York City: 6” or more
Philadelphia: 6” or more
Washington, DC (DCA): 4” or more

Temperatures should average 1°-2° below normal in Philadelphia, New York City, and Boston and 0°-1° below normal in Washington, DC and Detroit.

The current MEI and ENSO anomalies + PDO suggest that March will likely see above normal snowfall for the northern Mid-Atlantic and New England regions.

Similar MEI situations and March Snowfall:
Boston: Mean snowfall: 13.1”; 15” or above: 50% cases; 10” or above: 50% cases; 6” or above: 80% cases; 2” or above: 100% cases

New York City: Mean snowfall: 7.4”; 15” or above: 20% cases; 10” or above: 40% cases; 6” or above: 50% cases; 2” or above: 60% cases

Washington, DC (DCA): Mean snowfall: 2.8”; 15” or above: 10% cases; 10” or above: 10% cases; 6” or above: 10% cases; 2” or above: 30% cases

Similar ENSO Region Anomalies and PDO + Situations and March Snowfall:
Boston: Mean snowfall: 11.2”; 15” or above: 36% cases; 10” or above: 45% cases; 6” or above: 64% cases; 2” or above: 100% cases

New York City: Mean snowfall: 6.4”; 15” or above: 9% cases; 10” or above: 27% cases; 6” or above: 45% cases; 2” or above: 64% cases

Washington, DC (DCA): Mean snowfall: 2.6”; 15” or above: 9% cases; 10” or above: 9% cases; 6” or above: 9% cases; 2” or above: 27% cases

It should also be noted that the two analogs per the ENSO regional anomalies and MEI that saw February snowfall of 8" or more in Washington, DC (DCA) and 15" or more at both New York City and Boston were 1966-67 and 1995-96. The small sample size suggests a measure of caution is in order. However, the larger historical patterns (based on seasonal snowfall to date) and La Niña-PDO+ winters suggest a good possibility for above normal snowfall in March.

The Impact of Moderate Blocking (March 1-10):
The first 7-10 days of March will likely be dominated by a moderate block that will slowly retrograde to the Hudson Bay region. In general, such blocks result in cooler temperatures in the eastern third of the United States. The Mid-Atlantic region and Great Lakes areas are most responsive to moderate blocks in terms of temperatures. The Mid-Atlantic region is most responsive to stronger blocks.

Change in Mean Temperatures with an NAO of -1.000 to -1.999 vs. an NAO of 0.000 to +0.999:
Boston: -1.5°
Detroit: -5.2°
New York City: -2.5°
Philadelphia: -2.5°
Washington, DC (DCA): -3.6°

Change in Mean Temperatures with an NAO of -2.000 to -2.999 vs. an NAO of 0.000 to +0.999:
Boston: -2.0°
Detroit: -4.5°
New York City: -4.3°
Philadelphia: -4.6°
Washington, DC (DCA): -6.4°

Mean Temperatures at Select Levels of the NAO:
Boston:
-2.000 to -2.999: 34.7°
- 1.000 to -1.999: 35.2°
0.000 to -0.999: 35.0°
0.000 to +0.999: 36.7°

Detroit:
-2.000 to -2.999: 29.4°
- 1.000 to -1.999: 28.7°
0.000 to -0.999: 31.9°
0.000 to +0.999: 33.9°

New York City:
-2.000 to -2.999: 36.8°
- 1.000 to -1.999: 38.6°
0.000 to -0.999: 38.9°
0.000 to +0.999: 41.1°

Philadelphia:
-2.000 to -2.999: 37.1°
- 1.000 to -1.999: 39.2°
0.000 to -0.999: 39.5°
0.000 to +0.999: 41.7°

Washington, DC (DCA):
-2.000 to -2.999: 39.8°
- 1.000 to -1.999: 42.9°
0.000 to -0.999: 44.0°
0.000 to +0.999: 46.2°

Percentage of days with Highs of 50° or above vs. days with highs below 40°:

-2.000 to -2.999: 14% vs. 41%
- 1.000 to -1.999: 17% vs. 41%
0.000 to -0.999: 15% vs. 42%
0.000 to +0.999: 26% vs. 39%

Detroit:
-2.000 to -2.999: 6% vs. 65%
- 1.000 to -1.999: 13% vs. 70%
0.000 to -0.999: 14% vs. 52%
0.000 to +0.999: 29% vs. 45%

New York City:
-2.000 to -2.999: 22% vs. 54%
- 1.000 to -1.999: 34% vs. 25%
0.000 to -0.999: 32% vs. 23%
0.000 to +0.999: 40% vs. 18%

Philadelphia:
-2.000 to -2.999: 24% vs. 31%
- 1.000 to -1.999: 42% vs. 22%
0.000 to -0.999: 41% vs. 19%
0.000 to +0.999: 49% vs. 17%

Washington, DC (DCA):
-2.000 to -2.999: 39% vs. 23%
- 1.000 to -1.999: 58% vs. 14%
0.000 to -0.999: 60% vs. 12%
0.000 to +0.999: 64% vs. 6%

It should also be noted that as the blocking weakens, the risk of a blowtorch (readings at or above 60°) increases in the 3/1-10 period. The following is a comparison of the percentage of days with high temperatures of 60° or above for situations when the NAO ranges between -1.000 and -1.999 vs. those when the NAO ranges between 0.000 and +1.999:

Boston: 1% vs. 13%
Detroit: 0% vs. 15%
New York City: 5% vs. 19%
Philadelphia: 10% vs. 25%
Washington, DC (DCA): 27% vs. 38%

[sprites]

DonSutherland, while your analysis is very diligent and detailed, it fails to mention any other parts of the country. I would assume you are only mentioning the upper eastern seaboard in your analysis only. Have you analyzed the western portion of the United States or are we to look somwhere else for that info? I am not trying to be hard on you, but I would think if you are going to post something like this that it would include an analysis for everyone. Thanks for the info though.

[sprites]

Also, I am reading that the "blowtorch" effect would only occur in the lower southern plains and the cold would stiffen some in the upper eastern portion of the conus. Also, the Tornado season which is upon us would become exacerbated by this "blowtorch", which meets Mr. Winter up by the mid-planes. However, the some of the models are showing a deepening trough that is suppose to intrude down south deep into Florida, how well do the models show this? Also, we are getting clobbered here in California, but will the rain end and the heat turn on for us soon? I don't think we will get much more rain in the future soon.

[wxmann_91]

Also, I am reading that the "blowtorch" effect would only occur in the lower southern plains and the cold would stiffen some in the upper eastern portion of the conus. Also, the Tornado season which is upon us would become exacerbated by this "blowtorch", which meets Mr. Winter up by the mid-planes. However, the some of the models are showing a deepening trough that is suppose to intrude down south deep into Florida, how well do the models show this? Also, we are getting clobbered here in California, but will the rain end and the heat turn on for us soon? I don't think we will get much more rain in the future soon.

For us, many of the models paint a long range picture of multiple storms continuing to impact our area. Needless to say, the models aren't always right

[sprites]

Also, I am reading that the "blowtorch" effect would only occur in the lower southern plains and the cold would stiffen some in the upper eastern portion of the conus. Also, the Tornado season which is upon us would become exacerbated by this "blowtorch", which meets Mr. Winter up by the mid-planes. However, the some of the models are showing a deepening trough that is suppose to intrude down south deep into Florida, how well do the models show this? Also, we are getting clobbered here in California, but will the rain end and the heat turn on for us soon? I don't think we will get much more rain in the future soon.

For us, many of the models paint a long range picture of multiple storms continuing to impact our area. Needless to say, the models aren't always right

If the models hold true wouldn't this be indicative of an "EL NINO" type set up a la "Pineapple Express"?

[donsutherland1]

Earlier, I had noted my March snowfall estimates, as follows for select cities:

Boston: 10” or more
New York City: 6” or more
Washington, DC (DCA): 4” or more

This would be a fairly uncommon occurrence. Since 1891-92, just 13 (11%) seasons have seen such an occurrence. The following are March snowfall amounts for such seasons.

Boston:
1892 20.3
1896 14.5
1906 21.9
1923 10.6
1934 10.5
1941 13.1
1956 31.2
1958 12.0
1960 22.3
1978 16.1
1993 38.9
1994 14.8
1996 16.8

New York City:
1892 12.0
1896 30.5
1906 11.5
1923 8.1
1934 8.6
1941 19.2
1956 21.1
1958 15.9
1960 18.5
1978 6.8
1993 11.9
1994 8.1
1996 13.2

Washington, DC (DCA):
1892 11.2
1896 7.7
1906 7.3
1923 6.5
1934 9.1
1941 11.2
1956 4.0
1958 10.6
1960 17.1
1978 8.3
1993 6.6
1994 4.0
1996 5.2

In 7/13 (54%) cases, there was at least one snowstorm that brought 12" or more snow to one of these cities. So, overall, employing the combination of historic experience, moderate block to start March, and ENSO analogs, one might well have a chance at seeing such a storm affect some part of the East Coast.

[LarryWx]

Don,
Excellent, well-organized easy to read post as usual. In addition to having a gentleman's attitude when dealing with others, your writing skills are among the best I've seen on the internet, not to mention your vast wx knowledge and good forecasting abilities. Even though I don't live anywhere close to your area, I still find your posts quite interesting and sometimes even useful for my area such as when you talk about the climo of blocks.

[donsutherland1]

Thanks very much for the kind words, Larry.

Very best wishes.

[hcaeb]

Don,
I read your posting everyday and thank you for your expertise. You keep mentioning the East Coast. I am in NC and we reached 75 today and looking for 82 tomorrow. Are we going to get any of this cold air or snow showers in the upcoming weeks?

[donsutherland1]

Hcaeb,

Saturday through Tuesday looks to be cooler than normal in NC. Monday and Tuesday could be especially cool, particularly if a storm develops and drives colder air down into the Southeast. Late next week it could again be warmer to perhaps much warmer than normal.

[boca]

Here in Florida we had a shot of colder air just to be replaced by normal to above normal temps all next week. The trough along the East coast they were forecasting is supposed to be in the Western Atlantic so minimal effects here in Florida. Winter is over in Florida until next December or a fall version of winter.

[AnthonyC]

Don,

Any thoughts on the PNW regarding this deep trough expected in the coming days? Could Seattle see one more bout with snow? Awesome analysis BTW!

Anthony

[bob rulz]

How about the Intermountain West? They say we could see "significant" snowfall late next week in Salt Lake City, but it's hard to judge what they consider "significant" here.

[donsutherland1]

Anthony,

I'm not yet sure that Seattle will see snow even as much or all of the first half of March should see below normal readings, on average. It seems that even as the cold has performed up to expectations (e.g., 23° low on one day in late February and 4 consecutive days with lows < 30°), the timing has not coincided with available moisture.

[donsutherland1]

Bob,

Right now, there does appear the possibility for accumulating snow at Salt Lake City around Thursday. There is some division in the models and some offer warmer solutions than others. It's too soon for me to speculate on amounts, but the potential for several inches does exist. Whether or not it is realized will depend on how much warming occurs.

[bob rulz]

Thanks for the info! My local news stations have been unusually consistent and in good agreement with each other for the past 5 days or so that we may see the "biggest storm of the season" on Thursday with a chance for snow for several days afterward. This could be a big one.

[bob rulz]

Damn, it seems that all of the weather forecasts have calmed down significantly on this storm for Salt Lake City. The snow advisory is only for 2-4 inches (locally 6 on the benches), which is a huge dissapointment for me. Guess I got my hopes up too much.

Don, is this what you see for the snow tomorrow? What about any storms in the next few days? I'm interested to know what you get out of it.

[donsutherland1]

Bob,

I'm thinking 2"-5" falls in Salt Lake City (probably around 3.5") on Thursday.

Best wishes.

[bob rulz]

Yep, that's about how much ended up falling (at least at my house). About 3 inches on the ground. Looks like I'm going to have to wait at least until next year to see another big snowstorm.

[donsutherland1]

Verification:

In general, total snowfall around the Salt Lake City area proved quite light. The City received less than I had expected.

My estimate: 2"-5"; Actual: 1.4"; Error: 0.6"