March Medium Range Discussion

[IsentropicLift]

What we got last week is a typical march snow. If you expect snow pack and covered roadways in march, you will have better luck just waiting until December.

And please it's the nam at 84 hrs stop

You're kidding me right?

 

Nothing of what you wrote adds any value to the discussion.

 

The 12z NAM has the support from every single other model.

[JERSEYSNOWROB]

In case you missed this from HM in the Philly banter thread:

The last few springs have been awesome and maybe even a little too summer-like. It certainly was nice and I'm definitely looking forward to convective season. Unfortunately, it looks like this is the kind of spring that starts off with a nor'easter or two.

The "return to a blocking state around astronomical spring" idea is looking better and better. While we always get brief bouts of warmth (like earlier this week) this time of year, it seems like cold temperatures will be able to plow southward through mid-April.

[pazzo83]

Posts like this add nothing to the discussion and belittle great input from don s, earthlight, and Doug

Please, I've been on these boards for almost a decade and a half, I think the discussions around the 240+ hr models are the laughable posts.  The two "threats" that we were looking at over the next week have all but dried up.  If you look at meaningful accumulating snow (>5") past March 25th in NYC, it is virtually unheard of, especially in recent times.  In the past 70 years it has happened TWICE: once on April 5, 1944 (6.5") and once on April 6, 1982 (9.6").  In fact, it only happened 6 times during the entire 20th Century.

 

Some on here look poorly on probability analysis with this, but when it is derived from past events, it reflects what the climate of a particular area supports.  And we can see clearly here that 5" or greater snowfall from the last week of March onward is excessively rare in NYC.

[IsentropicLift]

In case you missed this from HM in the Philly banter thread:

The last few springs have been awesome and maybe even a little too summer-like. It certainly was nice and I'm definitely looking forward to convective season. Unfortunately, it looks like this is the kind of spring that starts off with a nor'easter or two.

The "return to a blocking state around astronomical spring" idea is looking better and better. While we always get brief bouts of warmth (like earlier this week) this time of year, it seems like cold temperatures will be able to plow southward through mid-April.

I've been saying this for awhile, this month might end up a lot like March 2010 with several very rainy noreasters and a renewed river flooding threat.

[MJO812]

The only ones hallucinating are those saying winter is over. Will we have another snow event? Who knows, and of course it is unlikely as it is already mid march. But this march it is a whole lot

more likely than an "average" march. And btw those saying people that there are no threats, they tend to be the same people who naysay every event and some who have already called winter off.

 

 

The pattern coming up is a great one for March. The chance of snow in the upcoming pattern will all depend on where the blocking sets up.

[Allsnow]

Please, I've been on these boards for almost a decade and a half, I think the discussions around the 240+ hr models are the laughable posts. The two "threats" that we were looking at over the next week have all but dried up. If you look at meaningful accumulating snow (>5") past March 25th in NYC, it is virtually unheard of, especially in recent times. In the past 70 years it has happened TWICE: once on April 5, 1944 (6.5") and once on April 6, 1982 (9.6"). In fact, it only happened 6 times during the entire 20th Century.

Some on here look poorly on probability analysis with this, but when it is derived from past events, it reflects what the climate of a particular area supports. And we can see clearly here that 5" or greater snowfall from the last week of March onward is excessively rare in NYC.

I posted how I agreed with the stats you posted. Most anyone was talking about in here was the up coming pattern, which supported a late winter accumulating snowfall. It's not often we get this type of pattern post march 15, hence why the stats don't support it. If anything spring is not around the corner

[IsentropicLift]

Please, I've been on these boards for almost a decade and a half, I think the discussions around the 240+ hr models are the laughable posts.  The two "threats" that we were looking at over the next week have all but dried up.  If you look at meaningful accumulating snow (>5") past March 25th in NYC, it is virtually unheard of, especially in recent times.  In the past 70 years it has happened TWICE: once on April 5, 1944 (6.5") and once on April 6, 1982 (9.6").  In fact, it only happened 6 times during the entire 20th Century.

 

Some on here look poorly on probability analysis with this, but when it is derived from past events, it reflects what the climate of a particular area supports.  And we can see clearly here that 5" or greater snowfall from the last week of March onward is excessively rare in NYC.

While I would agree that climo has to be taken into account regarding the chances of significant accumulating snows the upcoming blocking pattern as advertised would be something special. I also feel the need to remind you that this sub-forum covers more than just Central Park and New York City.

[pazzo83]

I posted how I agreed with the stats you posted. Most anyone was talking about in here was the up coming pattern, which supported a late winter accumulating snowfall. It's not often we get this type of pattern post march 15, hence why the stats don't support it. If anything spring is not around the corner

It definitely is an anomalous pattern, and I'm sure some areas on the edge of the metro will see something.  I just think the chances of widespread accumulating snow in the area, despite the favorable pattern, are quite slim.

[uncle W]

great post Don...March 29th is the last date on the calendar that had multiple snowstorms...April 5-9 is another period that produced some late season snowfalls...

March 29th..............

1.1"... 28-29th, 1959...was snow and sleet for my tenth birthday...I remember it well...

3.0"... 1885...

4.1"... 28-29th 1996...started as wet snow...changed to rain/sleet...Changed back to heavy wet snow...

3.3"... 28-29th 1984...major storm...started as wet snow...changed to rain and sleet...back to snow and sleet...ends as mix...26" in the Poconos...

3.2"... 1974...Starts as rain...changed to snow in the afternoon...ended as rain...10" in the Poconos...

4.0"... 1970...Started as rain...Changed to snow in the afternoon...Got very cold at the end of the storm...

April 5-9th.........

4.0"...4/7/2003...7" on Staten Island...stayed cold after the storm...

9.6"...4/6/1982...13" in the Poconos...record cold followed...

4.2"...4/8/1956...started as heavy rain...

6.5"...4/5/1944

6.4"...4/7/1938

6.5"...4/9/1917

5.0"...4/9/1907

If the AO falls to record levels later this month it will snow or get cold for the season...2001 had a little snow and one last cold spell when the ao was that low...i expect at least that this year if the stronger blocking develops...

I don't give up until May...even then it snowed in the past near the city...The forecast blocking could lead to at least prolonging the cold here...

[IsentropicLift]

The GFS is pretty far north with the over running but warm at the surface.

[Snow_Miser]

After the cutting storm system an extremely cold airmass moves into the region. Very very cold.

[IsentropicLift]

I thought everything agreed with the 84 hr nam?

I'm not even sure why I'm entertaining this post but whatever....

 

My earlier post referred mostly to the clipper system which is well before 84 hours.

 

As far as the over running is concerned, the GFS shifted north, which of course was run after the NAM.

[Allsnow]

Ggem way north with over running

[earthlight]

Just some thoughts this afternoon.

 

It seems to be like there is a bit of an underlying passiveness on the forum towards March snowfall events. I guess this comes somewhat naturally due to the past several years, which have offered very little hope by this time of year. In fact, last year a few days ago much of the area saw temperatures soar into the 70's for highs. Lets face it, March has been a nonexistent winter month in our area with the exception of a storm in 2009 (which coincidentally dramatically underperformed in my area).

 

But the point of this post, essentially, is to discuss the developing blocking and put to rest the fallacy that March snow is impossible or incredibly unlikely. Yes, it becomes much more difficult towards the last week of the month. But it is important to remember that forecast guidance has been strongly pointing towards the potential for a significant blocking episode -- not just a run of the mill Greenland block or positive height anomaly. Just glancing at the Arctic Oscillation forecasts, we can see remarkable ensemble agreement with the AO readings falling literally off the cliff. Almost every ensemble member brings the Arctic Oscillation below -4 and some of them to -5 -- this is not your run of the mill - AO development. A word of caution though, we should carefully watch the AO over the next several days as it has outrun the 7 day ensembles forecast in a positive direction recently.

 

 

The high latitude blocking teleconnection response is also extremely impressive. In this situation, there are blocking signals (robust, impressive ones at that) on both sides of Central Canada. One over the NAO region which builds into Greenland, and another over the EPO region north of Alaska with a strong 552+dm ridge. This essentially helps dislodge the core of the Polar Vortex into Central Eastern Canada and it will elongate there. This is important because we are now dealing with polar cold air not just on our side of the globe, but hanging out just to our north over Canada.

 

 

That being said, the timing of the individual disturbances remains somewhat up in the air and forecast models are going to struggle with them as we move forward. This is important, because it seems like there is some concern here about the forecast models not showing any major snowstorms are we move forward. I say to give it some time. There are several which catch my eye -- none of which are in the short to medium range at the moment. One of the better seems to be around the 20th-22nd of the month (credit to ag3 who texted me about this two weeks ago). We're starting to see this threat appear on the GFS, GEFS and ECMWF over the past few model cycles. With the aforementioned blocking, favorable MJO state and mid and upper level height field across not only the CONUS but Canada and the high latitudes, this storm system has the potential to produce significant wintry weather across much of the Northern 1/3 of the US from the North-Central Plains, through the Ohio Valley and into the Northeast.

 

[SnoSki14]

I would think the post 20th storm shown on the gfs would not cut as shown given the favorable MJO, an intense and favorable blocking pattern and it coincides with the major -ao although for some reason models keep amplifying and cutting these systems well to the north and west.

I'm guessing it probably has to do with the mid to late March wave lengths and a lack of a PNA to help with digging but I'd imagine these systems would be much further south if the same pattern was shown from dec to feb.

[MJO812]

GGEM at 102

[Kaner587]

That's a good looking ggem panel right there. Mod snow ongoing at 1pm Monday

[Storm At Sea]

Nice post! I like the idea of the AO tanking and the blocking and all, but I feel like some on here are forcing the idea of March snow down our throats. We get it. The blocking is there, but the orientation is off and the STJ is not cooperating (I suspect that may be due to the tendency for the MJO to be leaving phase 8...I'm certainly no MJO expert). Most northern stream S/W's that do develop are a New England issue and not a PHL/NYC corridor issue. This has not been a good year for the Miller A, which is what I think we would need in order to get a good snow for NYC.

Just some thoughts this afternoon.

 

It seems to be like there is a bit of an underlying passiveness on the forum towards March snowfall events. I guess this comes somewhat naturally due to the past several years, which have offered very little hope by this time of year. In fact, last year a few days ago much of the area saw temperatures soar into the 70's for highs. Lets face it, March has been a nonexistent winter month in our area with the exception of a storm in 2009 (which coincidentally dramatically underperformed in my area).

 

But the point of this post, essentially, is to discuss the developing blocking and put to rest the fallacy that March snow is impossible or incredibly unlikely. Yes, it becomes much more difficult towards the last week of the month. But it is important to remember that forecast guidance has been strongly pointing towards the potential for a significant blocking episode -- not just a run of the mill Greenland block or positive height anomaly. Just glancing at the Arctic Oscillation forecasts, we can see remarkable ensemble agreement with the AO readings falling literally off the cliff. Almost every ensemble member brings the Arctic Oscillation below -4 and some of them to -5 -- this is not your run of the mill - AO development. A word of caution though, we should carefully watch the AO over the next several days as it has outrun the 7 day ensembles forecast in a positive direction recently.

 

ao.png

 

The high latitude blocking teleconnection response is also extremely impressive. In this situation, there are blocking signals (robust, impressive ones at that) on both sides of Central Canada. One over the NAO region which builds into Greenland, and another over the EPO region north of Alaska with a strong 552+dm ridge. This essentially helps dislodge the core of the Polar Vortex into Central Eastern Canada and it will elongate there. This is important because we are now dealing with polar cold air not just on our side of the globe, but hanging out just to our north over Canada.

 

block.png

 

That being said, the timing of the individual disturbances remains somewhat up in the air and forecast models are going to struggle with them as we move forward. This is important, because it seems like there is some concern here about the forecast models not showing any major snowstorms are we move forward. I say to give it some time. There are several which catch my eye -- none of which are in the short to medium range at the moment. One of the better seems to be around the 20th-22nd of the month (credit to ag3 who texted me about this two weeks ago). We're starting to see this threat appear on the GFS, GEFS and ECMWF over the past few model cycles. With the aforementioned blocking, favorable MJO state and mid and upper level height field across not only the CONUS but Canada and the high latitudes, this storm system has the potential to produce significant wintry weather across much of the Northern 1/3 of the US from the North-Central Plains, through the Ohio Valley and into the Northeast.

 

gfs.png

[SR Airglow]

GGEM looks like nine hours of moderate snow, followed by 2-3 hours of mixed precip(sleet or freezing rain) and then it goes over to rain(I assume the cutter/miller B takes over by then). No way of knowing total QPF, it's anywhere from one to three mm per hour, assuming on average 2 mm per hour, that's 18 mm snow, or around .71" liquid. That seems sort of high, so assume that each panel is the minimum 1 mm, so 9mm of QPF which is around .35 liquid, still a 2-4" event. It's the farthest north model at the moment, although the GFS which was the southern outlier came significantly north. I think the EURO might find the overunning again at 12z, it lost it at 0z, but, nothing else lost it completley at 6 or 12, so it's probably going to be back. The question is if it comes north enough, somilar to its earlier runs, or if it goes to the GFS, in which case we get an inch or two on the grass at best.

-skisheep

EDIT: also remember that those panels run slightly warm, so if it is borderline, go colder.

[Allsnow]

Euro has some light snow at hr 54 from clipper

[NEG NAO]

12z GFS ensembles has us in the .25 - .50 precip saturday night and WPC gives us a chance of accumulating snow saturday night into sunday

http://www.hpc.ncep.noaa.gov/pwpf/wwd_accum_probs.php?fpd=24&ptype=snow&amt=1&day=3&ftype=probabilities

[earthlight]

Nice post! I like the idea of the AO tanking and the blocking and all, but I feel like some on here are forcing the idea of March snow down our throats. We get it. The blocking is there, but the orientation is off and the STJ is not cooperating (I suspect that may be due to the tendency for the MJO to be leaving phase 8...I'm certainly no MJO expert). Most northern stream S/W's that do develop are a New England issue and not a PHL/NYC corridor issue. This has not been a good year for the Miller A, which is what I think we would need in order to get a good snow for NYC.

 

I think there's a point-counterpoint in every argument. So I can see how one could argue that it's less likely to get snow this time of year than it is in the middle of winter. That would be 100% correct. But what I'm arguing is that the chances are much higher than normal for this time of year given the blocking development. And this becomes especially true if the block develops to the degree which the model guidance is predicting that it will. It becomes an atypical situation for late March with a very cold airmass and a very favorable pattern for storm systems.

[Allsnow]

Euro is nothing like Ggem for next week meh

[Allsnow]

Hr 108 light snow/ over running. Primary is much farther nw.

[Allsnow]

By 114 it's rain city south. Nice run for sne

[MJO812]

Hr 108 light snow/ over running. Primary is much farther nw.

 

Euro still gives the area some snow. 850's are -5 at the start of the event. Good run for SNE northward.

[Allsnow]

Secondary takes over under Long Island hr 120

[Allsnow]

The blocking helps sne a lot. Great hit for them

[ag3]

GGEM looks like nine hours of moderate snow, followed by 2-3 hours of mixed precip(sleet or freezing rain) and then it goes over to rain(I assume the cutter/miller B takes over by then). No way of knowing total QPF, it's anywhere from one to three mm per hour, assuming on average 2 mm per hour, that's 18 mm snow, or around .71" liquid. That seems sort of high, so assume that each panel is the minimum 1 mm, so 9mm of QPF which is around .35 liquid, still a 2-4" event. It's the farthest north model at the moment, although the GFS which was the southern outlier came significantly north. I think the EURO might find the overunning again at 12z, it lost it at 0z, but, nothing else lost it completley at 6 or 12, so it's probably going to be back. The question is if it comes north enough, somilar to its earlier runs, or if it goes to the GFS, in which case we get an inch or two on the grass at best.

-skisheep

EDIT: also remember that those panels run slightly warm, so if it is borderline, go colder.

 

 

You can see the ggem total precip on meteocentre:

 

Total precip through hour 108:

 

 

 

Total snow through hour 108:

 

[ag3]

Euro gives NYC about .40" of precip with <540 thicknesses and <0 850s.

Surface is iffy though. Hovers 34-35 degrees the entire time.